NOTE:- Jan 2013 - UK MOT testing
requirments state for a tricycle - only 1 wheel required to have mechaincal
parking brake - this can be either front or Rear.
Trike builders guide JP7 builders guide trike design build
JP7 builders guide trike design build Although these are guides, the
author does not advise anyone to actually build or even consider building
such devices. Read, but do not act upon this information. Everyone should
just live a quiet, pastoral life because the dogs of law lie around
every corner. I have no wish to be closed down like other useful websites
from threats by parasitic lawyers. (As lawyers get rich, society gets
Always try to improve society rather than just take from it. Until
then, lawyer stuff. Copying, duplication or transmission of this material
whole or in part is not permitted without the written permission of
the author. The contents of this text are for illustrative purposes
only, and available here to view, for those who wish to buy a copy and
support the research. Those using this information do so entirely at
their own risk. Errors and omissions excepted. Contents subject to change
without notice. All material herein is subject to copyright, patent
and other intellectual property rights. All rights reserved. Copyright
(C) J.Partridge. 1999. 2003.
Have a nice (lawyer free) day.
In March 2006, this web page has been copied and printed, then sold
on E bay without my permission. Such is the modern world, at least I
know that this web page as a book is worth 20 quid plus a fiver for
postage, so perhaps I should start publishing it for a tenner, plus
a fiver for postage - any takers ? - Of course not, why pay for something
that's free. If someone tries to sell my work again, I'll may get annoyed
and even consider putting one of those awful parasitic lawyers on the
If you are going to print this out, (for personal use only !) then at
least check out 'Printers' on my web site for cost effective inkjet
printing, so it need only cost you a few quid to print out. On my word
processor it works out to 150 pages, or 100,000 words and that's without
the piccies, so you may wish to set the browser text to small or smaller
and test with a few pages before printing from a web page. It takes
all sorts I suppose. Have a nice, lawyer free day. :)
This text is available to view as there are not enough high quality
trikes out there. If you like the text, please offer feedback as this
helps me to refine the contents.
Lots of other bike and trike stuff via the website at www.btinternet.com/~jhpart./index.htm.
Being long term unemployed motorcycle mechanic, technology and science
teacher, marine and nuclear engineer, B.Sc, B.Ed. and draughtsman, I'd
like a job please.
Please consider this monograph a bit of a C.V.
Feel free to email. email@example.com
A Builders Guide To Trike Design.
J.Partridge. B.Sc., B.Ed. Gizzajob.
Version 1j. April 2006.
Because of a plague of litigious lawyers in Britain today, nobody should
nor ever attempt to act upon the following information.
Index for trikes.
The engine I.
Frame design I.
Frame design II.
Building the frame.
A build sequence.
Radiators and aerodynamics.
Keeping it tidy.
Non destructive testing.
Basic tool kit.
Basic materials check list.
Useful info sources.
This monograph is a bit long. Don't try reading it all in one go, (I
I'd recommend a skim through, then properly read each section when you
I've kept it down to just the basic stuff, plus some of the more interesting
bits and bobs. There is almost no arithmetic and certainly no maths,
leaving you to gauge trike structural and handling requirements by using
common sense and non arithmetic geometry assessments and other ways
to make your trike handle better from the design stage onwards and also
make it safer. If anyone wants the maths, physics and geometry stuff
to be added, just ask !
For the wiring, well that's another (42,000 word) story, also freely
available on my website.
I help design and build trikes, from mini's to V12 fuel injected trikes.
These trikes can out-handle rally cars on corners, and Jags on the straight.
I build custom trikes and trike modification kits to order, if local,
see appendix. If you want to build the worlds ultimate trike and do
it on a sensible budget, just ask. I'm unemployed, so feel free to employ
NOTE: The following is based upon personal experience and is for guidance
only. No-one should try building such machines without reasonable abilities
and know that injuries can ensue from the materials, tools and from
riding of machines. Those using this information do so entirely at their
own risk. Fully understand the implications and dangers before building,
testing and riding.
This monograph is aimed at those who wish to learn from a hands-on
approach using commonly available technology. The intention is to make
trike design and manufacture available for all.
This is not a 'stick part A to part B' type of guide, neither is it
a 'how I built a trike' guide.
It is exactly what it's called. -
A Builders Guide To Trike Design.
Attention is drawn to the fact that there are a few other reference
works explaining the technical and theoretical application of similar
machines, mainly regarding on single front wheel - dual rear wheel stability.
This monograph is how to design and build a trike is a full process,
from initial idea to final testing and beyond. You will be expected
to use YOUR brains to design and build and test YOUR dream trike. This
monograph should hopefully keep you on the right path, and hopefully
help you build a much better trike. If you are prepared to learn, and
want a better trike, welcome.
When building a trike, remember that it's all been done before, from
children's trikes, through VW trike's to V12 monsters and beyond. What
is important is getting it right.
Getting it right is not simple, but neither is it unduly difficult,
as many home builders can manage excellent machines without expense.
Yet far too many trikes start off as a good idea, but often suffer with
poor design if any, with bits bodged on as and when needed. Some trikes
that are road legal simply frighten most people; we all know what we
are talking about.
I often get people emailing me asking for advice after an expert has
built them a trike and it handles appallingly because it is of such
In some of these photos I see excellent welding, new tubing and a big
workshop, but although the mechanic is working to their best, it simply
is not enough. A good mechanic is all to often not a chassis designer,
the ability to design a trike is desperately in need of more than just
simple mechanic work.
I realise that most who build trikes are not engineers nor perfectionists,
but usually know that a better trike is possible, hence this monograph,
to help them look a little further towards a better trike.
It is the common failure to develop the fundamental machine in the initial
stages is usually the main reason why so many potentially good trike
concepts remain less than perfect. Read on.
Designing a trike is not just a case of building the nearest idea that
will work. Anyone can design a simple cardboard box, and many trikes
look like they are thrown together rather then designed. Take your time
to think first, only then can you build.
This monograph does not want the reader to follow like a sheep, as this
simply limits the readers boundaries. This monograph is a means to help
develop the initial idea for a dream machine, and then to build and
". . . you won't have a future if you don't make one for yourself.
It is as simple as that.
If you accept the forms that be, then you are doomed,
to your own ultimate blandness."
- John Lydon. (Sex Pistols.)
It is possible to make a simple trike such as welding a Austin Metro
subframe to a bike frame or a couple of scaffold poles, or fixing forks
on the front of a VW with a bit of box-section, but a triker's life
should be far more exciting. To make life more interesting and to highlight
what this can involve, the following is based on a car engined trike
with a frame designed from scratch, with bike framed trikes also considered.
This describes a path through the design stage, the building jungle
and traps, to testing a working machine. From this, the sculpting and
other options are then discussed.
This monograph is aimed mainly at designing the larger, car-engined
trike and is based on first hand experience building trikes which out-handle
sports cars in the bendy bits of the road. The processes are not expensive.
Many excellent machines are built on a small budget and good wits.
Each trike will be different to what is described herein, but the guides
and suggestions will be applicable to all. It's assumed that the reader
is able to rebuild an engine and know the basics of transmission and
suspensions. If not, the workshop manual of the donor machine will help.
For first timers, it's best to build to a budget at first, then to
decide if to modify, elaborate or simply try again.
A budget trike can also be a work of art without compromise, if based
on a fairly sensible (and surprisingly cheap) car engine. The cost of
creating a well-built trike need not be expensive, thereby allowing
for a few tries or major modifications before the final form is acceptable.
The processes described herein are all fairly cheap and can enable a
good working trike to a sensible budget.
Even if the first attempt does not work well, rebuilding a frame is
not as bad as it may seem, as a total rebuild does not require making
new steering head, gearchange nor a host of other re-usable components,
leaving just the frame tubes to be re-designed.
Flourishes can be added later, such as a full engine rebuild, better
wheels, seats and paint. This should be done preferably once the basics
are refined to a level where it stonks around corners, stops on a sixpence
and performs reliably.
The basic costs are a decent welder or paying for the services of a
professional welder, the cost of an almost complete donor vehicle, usually
a car and also the steel tubing. See check list at end. Tools are minimal,
but an angle grinder and a good engineers vice mounted on a strong workbench
make for a much easier life and are always worth the cost.
The only high costs are having the steering head, spindle and slab yokes
made professionally, although even these can be circumvented as described
Both the donor vehicle and stock metal tubing are surprisingly cheap.
The biggest cost is time and effort. Time and effort lead to good design,
accuracy and good handling.
This monograph is long and I doubt if anyone will follow all the possibilities,
but even if just a few aspects mentioned herein are of use, then I hope
it can lead to a better trike.
Getting your ideas together.
When ideas grow, they rarely stop and they will give a vast choice of
ways to do things, from the simplest nut and bolt to the overall look
of the machine.
Some people may find drawing difficult, so begin by copying pics from
magazines to start the ideas rolling. Buy an A3 sketch book, a decent
2B pencil and eraser. The reader will be surprised just how fast the
pages will fill up with ideas, usually rough sketches at first. Well
considered ideas are the difference between a second rate machine and
a trike to be proud of.
If your drawings are terrible, do them anyway and if, like many of us
who failed play school hand painting, and you're embarrassed, then keep
them to yourself. Your ideas are what you need, not good art.
Your ideas will change, perhaps as your wife and kids hassle you for
better seating, while you prefer sleeker styling, meaner look. There
are a thousand and one other needs, such as where to put the shopping.
Yes, trikes are often used as day to day transport for shopping and
to take the kids to school.
When the rough outline gets close, follow up with simple plan and side
sketches to decide how the engine, kids, shopping and macho image will
eventually fit into your design. This takes time and many a good cuppa
or beer, usually over many weeks or months.
A trike by it's very nature is a lifestyle statement, but this alone
should not be seen as justification for a second rate machine. If making
a lifestyle statement, be it high tech, post-apocalyptic in style, or
a sculptured art form on wheels in the Italian style, then make it a
superb example. Do not accept second rate.
All good trikes start with a clean sheet of A4 paper and a pencil.
After dozens of sheets, the design will flourish and evolve far beyond
the original concept.
For those with garage or other floor space and enthusiasm, buy a roll
of pain wall paper, often known as lining paper. Join two ten foot lengths
together with a little glue to give a large sheet to draw the machine
full size in side view, which can be rolled up when not in use or pinned
to a dry garage wall. A full-size side view is important. This will
greatly help getting much of the design right, including the weight
balance, centre of gravity, rider seating, deciding the vertical forces
and the frame design. A full-size side drawing is also very important
to ensure the side view styling will be as good as possible.
The other side of the paper can contain most of half a plan view. As
lining paper is cheap, simply use more paper for the plan. For those
with dedicated garage space, then the basic machine can be drawn roughly
full size in chalk upon the floor, modified with a damp cloth as the
Drawing full size gives the best chance for the fundamental design and
overall styling to be refined. This saves time and money, by allowing
the engine layout and seating to be thought through and refined before
purchasing anything. Always note that full size drawing do not always
look the same as what you imagine. Stand next to an ordinary car and
imagine that if you drew this on the wall, it would look to small to
get into. For this reason you will also be drawing full size shapes
of the rider and passengers. If drawing on the lining paper or on floor,
then time to sit down and draw some outlines. Welcome to ergonomics.
Decent centre lines can be painted on the most level part of the garage
floor, allowing the chalk ideas to be regularly re-developed. A taught
string accompanied by two strips of masking tape each side followed
by a narrow line of paint. For those who seek total accuracy in poorly
painted lines, accurate scribe lines can be made in the paint with a
Eventually an idealised layout must be decided. If deciding to build
around a specific engine, then that is OK. Trikes can be built engine
first, or style first. But there is no need to decide on a specific
engine before designing the trike, as there is a vast choice of engine
layouts available for fitting into almost any trike design.
The next step is to draw a trike and a stick man on your sketch pad.
It does not have to be accurate, simply measure the probable wheel diameters,
relative to the stick man, e.g, wheels up to the knee. Check by standing
next to the potential choices of donor car, to find how far up the leg
the wheel is, then place the feet toe to heel across the front or back
to get the overall width across the wheels. Welcome to research.
To make a scale drawing, measure your height, divide by four or whatever
is usable to get a scale drawing of the wheel arrangement and a man
which roughly fits the page. Make a note of the scale on the page.
Then measure the outside width of the driven wheels of the potential
donor vehicle and make a basic plan view using this wheel width and
centre line. (Plan view is looking down from above.)
If a scale drawing is too much hassle, simply use approximate drawings.
Before buying a donor vehicle, buy the workshop manual and sketch or
trace the engine and wheels onto the pad first. Do this in side and
plan views. The intention is to get a general shape of the engine to
see where any awkward problems may arise. Once these drawings are reasonable,
draw the lines much bolder. Now use this general arrangement of engine
and wheels to slide under the pages to help make many more drawings.
With side and plan views of the engine and wheels, then this easy drawing
system will allow a large number of designs to be easily created. It
is not unknown for two or three different engines to be drawn allowing
a better range of options for the final design.
It is now much easier to make many drawings of the machine in various
forms, styles and passenger layouts. Usually done at work or while watching
TV, and may probably become more interesting for all the family. If
the kiddies want a parasol top or twin rocket launchers, then at least
they are becoming part of the design process and may soon grow up to
learn a lot faster about design, technology and style than other kids.
The design associate involved with taking the kids to school and the
shopping will be much more dedicated in certain concerns, such as a
cool luggage compartment so the ice cream does not melt above the exhaust
on the way home from shopping.
Even a family friendly trike can still be an intimidating machine to
other road users, or an art form, often both.
Design many times, to build the best once.
Study the workshop manuals or actual machines.
Many engines in the front of cars can be moved rearwards in a trike.
This applies to both in line and transverse engines. Decide how much
further to the rear the engine can be moved to give better overall trike
balance. The typical front wheel drive transverse engine, wheels and
transmission can be positioned to the rear as one lump. A traditional
in-line car engine can shorten the prop shaft.
Draw the various options to slide under the sheet until the engine can
be repositioned until ideal, or to see where it can and cannot go. The
stick man rider and passengers will compete with the engine for room,
but a good accommodation of all should ensue.
As time progresses, there will gradually develop a need to have an engine
with perhaps a specific shape, layout, mounting, gearchange or braking
system. The range of possible proportions and layout is priceless knowledge.
As the ideas gradually fall into place like a jigsaw puzzle, the choice
of engine will become more defined. This is where paper simply saves
so much hassle later - the process of creating a better design from
the start. There are many trikes which suffer from the outset from using
less than ideal layouts. Only the reader will know whether the choices
will work well and also look good later.
By having a basic drawing of the engine and rear wheel layouts over
which to trace, it is possible to draw up many different chassis designs.
The front wheel can now be positioned wherever it will give good style
and balance with a decent turning circle. The stick man will give overall
scale, which is very important to get the ergonomics and all-round proportions
and the styling close to the real thing.
When building any trike, get the basics right and many of the details
well-sorted before the hard work starts, so there will be fewer hassles,
possibly none. Make sure it's fun, a trike made with loads of hassles
from the outset will always be second best. The best way to eliminate
most hassles is to get it right before starting the hard work or spending
money. The reader may not know the problems, so drawing will help highlight
the many ways a dream trike can become a nightmare, and so prevent problems
later. Brain work done in the first few months will save more than three
times the effort later - guaranteed.
By taking time in the early stages and constantly refining the design,
the builder will enjoy watching the original ideas grow and flourish
on the paper. By gradually working though the design, finding better
or easier alternatives or work-arounds for major problems, the processes
will develop fewer hassles, and finally design an effective machine,
perhaps the trike to beat all other trikes. Engine choices may change
and refine, seating will get better, and overall profile will gradually
evolve towards the perfect shape and form.
Should your kids one day point at an Italian sports car and decide
the cut lines are 'totally incongruous', then smirk quietly and consider
becoming a design and technology teacher.
I have received many requests, from email land. Here is a typical example
from across the pond. We all learn from our mistakes.
So while reading this, do not just make something different, but also
take plenty of time to understand the fundamental design needs so that
your designs will not cause problems.
This is where paper and pencil come into their own.
The pen is always mightier than the welder.
Time and a cuppa tea cost nothing - so use it to your advantage.
Here is a Yamaha 1100 V twin modified into a trike. The owner had many
problems with it and emailed me as the mechanic seemed less than happy
to solve them.
I suspect this builder had no pipe bender, and although this is not
vital, it does help produce a nicer machine.
So please, please, please use the paper and pencil before anything else,
as it solves so many problems and always makes for a happier trike and
a happier mechanic.
There are superb welds, but some classic potential trike problems.
The arrow points towards the white mark on the rear wheel showing that
accuracy is probably good and that the basics are understood, needing
just a little initial thought prior to making a much better design.
The Yamaha 1100 front end was standard right back to the swing arm.
Because it was a shaft drive, a ford rear end was used and there is
nothing wrong with this. Both very reasonable choices.
What was wrong was the serious lack of forethought.
The propeller shaft from the engine to the diff was left at its original
length, and therefore the rear end was too far to the rear that it put
nearly the weight over the front wheel and it became atrociously heavy
and possibly dangerous.
A possible solution: As this is a fixed rear differential, then there
is no need whatsoever for a long propeller shaft, and even a sliding
spline link need only slide a millimetre or so, to allow for chassis
flexing and engine fitting play.
Therefore cutting down a prop shaft needs only the grinding of the weld
and sawing the tube much shorter, then welding the end accurately with
a set square and file. Then spin and balance between a couple of spikes,
or with the wheels off. Prop shaft end pieces are usually fitted in
the tube with a stepped machined face, so are fairly easy to fit. Because
the prop shaft is much shorter, balancing it is also easier.
I suspect the prop shaft length and inability to solve it from the outset
led to most of the heavy front end problems.
With the short prop shaft, the overall balance of the machine is far
better, much less weight is placed over the front wheel, preferably
a similar load to that of the original machine, although now having
a purely vertical alignment, the steering will of course be harder,
- as leaning a bike, and with round profile tyres, makes bikes easier
Nevertheless, this trike with a very short prop shaft would be far closer
to a good trike.
But there is much more to be done before I could live with this trike
The width at the rear was atrocious, and although used in lard land
across the pond, I still believe that lithe trikes are better. Therefore
I would shorten the left shaft from the diff to the wheel axles, buy
cutting, shortening then sleeveing and balancing, to bring the rear
wheels in about 20 percent closer. I would also check if there were
any mass dampers on the original wheel prop shafts.
This would also align the diff to line up with the bike shaft output.
Then make sure both wishbones are identical, but the diff offset to
one side in the frame a little to optimise the diff alignment, and reduce
overall width of the machine. The wishbones would be a little narrower,
and would allow a stronger central frame. The minor offset of this fixed
mass could be offset by placing the battery appropriately so the axle
loadings are well balanced.
The ford diff has fine set of six bolts on the output of the diff,
and to this I would contemplate fitting motorcycle discs outboard of
the diff, so that I could use wire or there spoke wheels with a very
light, clean and open look.
There is also no cross piece between the lower rear wishbone mounts,
so this part of the frame is prone to spread dangerously under load
and will cause steering problems but welding one would permanently prevent
the diff being removed, while a bolted version would place undue stress
on bolts unless well designed. I would weld the lower tubes and employ
an upper, bolted tube in compression for easier removal of the differential.
The wishbones could be a lot sexier, and they also looked identical
in length for upper and lower, units, which is another wasted opportunity.
The wishbones have no triangulation, so under power, they will want
to bend forward along the horizontal plane as an unstable four bar linkage.
For this reason, wishbones are usually triangular. These will need a
triangulation tube to change them from a rectangle to a rectangle made
of two triangles. as the main forces are accelerating, then I'd place
the triangulation tubes from outer rest to inner front as compression
is always the best way to resolve force in short tubes which do not
have large welds.
I would have made the lower wishbone extended triangular, with the extended
front tube to take the acceleration and braking loads, thus making the
upper wishbone lighter and leaner for easier passenger room.
The shocks in this example are poorly placed and offset. The vertical
shocks, just under the arrow are not the happiest of items.
If needing a low profile for perhaps a top rack or seats, then two lighter
shocks on each side is preferable to maintain balance, although it would
look much nicer to take the opportunity to use Formula one technology
and fit compression struts to shocks mounted horizontally above the
differential. This would also allow the shocks to be adjusted in leverage
to match the rear axle loadings and also allow the horrible upper structure
to be removed to leave clean lines.
The superstructure is also most likely to push up and bend if not supported
with a stay tube from the present upper shock mount to a point on the
lower tubes, preferably near the diff to prevent bending.
The best solution is to mount two small motorcycle shocks either side
of the lower wishbone outer pivot and have these shocks either side
of the prop shaft to a low upper mounting. Such shocks are often available
from 125 and 250cc bikes, - so choose a commonly scrapped bike for donor
parts. A simple rear end would be to place the shocks on the upper of
the axle housings and fit a small triangular arrangement to the frame
over the differential should it be needed.
(I have shown this picture a second time, to save the reader from having
to scroll up and down, and takes no extra room on my website.)
First, shorten the prop shaft as much as possible. Then cut the frame
tubes beside the original bike frame and move the whole forward to the
optimum new prop shaft length and alignment. The width of the bike frame
will allow a slightly offset differential. Then shorten one shaft and
build this side wishbone first, then make a symmetrical copy for the
Then position the shocks close to the prop shafts to decide the shock
loading, and mount accordingly, to allow supple suspension.
Because the new frame tubes do not reach up far onto the frame, then
there is a natural tendency for the upper rear tubes to bend the frame
tubes inwards, This would be reduced with a shorter frame, but must
be checked nevertheless. This should be checked under a load of sandbags,
and see if the rear engine bolts are tight. If so, then I'd recommend
that the upper tubes are welded higher, by making a bend in them - and
then at the bends, adding a triangulating tube down to the bottom tubes
where they meet the lower bike frame.
Although this trike is not finished, there is no lateral triangulation
in this frame. As a trike does not lean, there is a far higher lateral,
sideways loading on the frame, and this frame most definitely needs
a triangulation in the horizontal plane. Therefore a tube on both the
upper and lower sections between bike and diff will be needed. By making
them the same looking downwards, the side loads will be even, but if
placing one as a X cross to the other, then there is a chance for a
torsion twisting if the vertical load is too large. So keep it simple
and symmetrical for best handling.
Here is a nice example of a trike rear end.
The axles took MacPherson struts, but have been beautifully crafted
to take adjustable upper wishbones.
This is a nicely done rear end, although a little heavily built because
it's a chain drive GSX, it also has adjustable inner links to adjust
the camber and resolve the acceleration and braking forces well. The
shocks just miss the prop shaft for a neat arrangement with an almost
central shock force resolution under compression, thus improving handling
when cornering. I would implore all trike builders to contemplate a
few similarly neat arrangements, and even the simple 3D graphic below,
shows what is possible with sketching before turning to metal.
Apart from the whole assembly being closer ands mentioned, the bottom
wishbones would be pivoted from the front of the frame to assist acceleration
and braking forces more safely into the frame. I would use rubber bushes
here, either from a small car or from a 250cc bike swing arm.
The rear shocks are neater and far more strongly supported and may be
closer to the original Yamaha shock angles, but if not, then I would
simply use car shocks from the donor rear end if the rear was a little
soft in compliance. The triangulation would be done to enable the differential
to be removed, probably by using a few spacers on the through bolts
holding it in place, so the rear end is well triangulated for resistance
Adding an anti roll bar would be simple, with just a couple of U brackets
and rubber sleeves to take a standard car anti roll bar, and bolt the
ends in rubber, in U clamps near the base of the axles, near the shocks.
This is not complex and is a typical and just plain 'old standard arrangement
found in trikes and kit cars. - Just look and learn.
The original car rear end uses discs, so parking brake may be a pain.
I'd consider adding a parking brake by fitting a small motorcycle disc
on the propshaft flange where it enters the ford diff and mounting a
simple mechanical or hydraulic brake calliper onto this, restrained
by a bracket on the frame such that any excessive braking forced are
resolved parallel to the disc to prevent distortion. A drum brake is
also possible for an easier life, - but make sure it is a bike rear
brake, as this allows the brake to be applied forward and in reverse,
whereas some brakes have twin leading shoes and only work well in one
In this particular case, the owner said the trike handles very poorly
and pulled to one side. After emails, it transpired the forks were out
of alignment, and presumably need straightening or the front end was
not aligned accurately in the vertical plane. Many people use a tape
measure between the centres of the wheels and the steering head, but
fail to check the steering head is vertical relative to the rear wheels.
Other potential problems could have been sticking rear brakes or uneven
wishbones, or incorrectly aligned rear wheels with perhaps toe out or
non symmetrical alignment.
The owner also said the trike was hard to steer. I recommended shortening
the prop shaft and rear frame first, to take some of the load off the
front wheel. Then if this was not enough, the trying a little toe -
in to see how it feels, and if this was not enough, then slotting the
upper yoke central hole slightly then shimming it forwards slightly
to reduce the amount of trail, which should make the handling more skittery,
but as it was too heavy, then this should eventually reach a happy medium,-
but ONLY after careful high speed tests and possible use of a steering
damper if any signs of potential problems occur.
This trike rear end could be totally rebuilt over a weekend using the
same items, plus a hacksaw, welder, tape measure and some thought.
If the mechanic is reading this, please do not be offended, as I have
seen much worse. - You will find that shortening prop shafts is quite
straightforward, and then much of the rest should fall into place. I
would also consider using the donor Ford rear suspension wishbones and
also the ford handbrake and hydraulic linkages for an easier life.
From the outset it is necessary to get the handling right. This is theoretically
imperfect for a single front wheel. But all the theory and science to
the contrary has not managed to make itself apparent on many a good
handling trike - so it can be done. The theory and trike riders who
like power drifts do not always agree. The main problems are weight
balance, decent rake and trail, good wheel alignment and overall set-up.
Chassis design will always be dependant upon the engine, causing the
design to require certain engine mounts and the way the transmission
and wheels were manufactured relative to the engine.
Weight balance is a moot point on trikes, but for general awareness,
the following can be considered.
With equal weight on each of the three identical wheels, basically,
neither wheel will want to break away first, for ideal grip. Unfortunately
most trikes have wider rear tyres and a narrower tyre at the front.
Worse still, when cornering, the outside wheel will become loaded, while
the inner gets light. Worse still, such rear tyres have a flat profile,
while the front is probably a partially rounded section because of action
of the use of forks, with their large rake angle compared to cars. On
a heavy loaded front wheel, the traditional motorcycle fork leg suspension
may often be close to its limits (unless specially designed). When cornering,
the inside rear wheel unweights dependant upon cornering forces, and
will allow the inside wheel to break away first, causing slippage in
the differential. Never rely on rear wheel break-away before the front
as a good idea. It is not.
From this you will realise that too many trike tyre choices have more
to do with style than engineering. But good style can still include
responsible or even superb engineering choices. The engineering choices
of balance and traction while cornering or braking are notorious on
trikes, so always do yourself a favour; consider the better choices
from the outset. If worried bout imbalanced wheel sizes and loads and
footprints, then just consider how much weight is on each while stationary,
then decide if it is ridiculous or adequate or good. While cornering,
consider the wheel loads and how they will or will not help the tyres
in doing their job. Also while braking, the loads on the tyres will
need some reasonable choice. As this part of the design process is likely
to cause worry, the process is described in more detail later, but please
do not worry too much at this stage, just make sure it looks reasonable
and not too stupid, unless a purely show trike. For road use then simple
common sense is usually acceptable.
Ride as many trikes as possible. If not, ask all owners how they handle,
especially around corners. Always take the opportunity to study the
way the various trikes handle to check what is happening at the boundaries
of the ride envelope, then ride within a safety margin. Get to know
the break away signs and refine the riding reactions necessary to control
them. See testing later. Unless the trike balance is based on another
good handling trike, then take care and consider the weight distribution
I have yet to ride a truly decent trike, or at least one that comes
up to my standards of handling, although I have ridden a few that are
very close. (Thanks Spike !) But these are rare and most trikes are
just plain appalling. - I just had to write this monograph.
Do not get overly worried, as many trikes have terrible weight balance
yet are quite adequate for most purposes of daily transport. If building
a better machine, consider that, although most cars, including factory
rally cars, they often have the engine in the front and the driver too,
with a lightly loaded rear, yet they still handle fairly well. For a
much better approach, formula one cars usually prefer a mid engined
design, with weight distribution between 45/55 to 40/60 percent front/rear.
This is not possible on trikes, but a mid mounted engine greatly helps.
For a single front tyre, aim for around equal load on each wheel, giving
about a third of the weight on each wheel. Then adjust to match the
front wheel size. If it's a light, custom front wheel, then reduce the
weight on the wheel more than if the front wheel is a car wheel. In
the worst case such as a VW trike, with the engine hanging out the rear,
this may even require front weights. At the other extreme, this may
not be possible with a Jag V12 trike without serious modifications and
a strong front end.
Sensible engine choice and overall layout of engine, wheels and riders
is going to pay dividends later. Aiming close to a sensible weight balance
is unlikely to do any harm.
Making trikes with bike engines and frames is a doddle.
If you want to use a bike engine but make a new frame, then car chassis
But the bottom line is that using car engines is the best way for maximum
stonk for minimum pennies, and is the main way described in this monograph,
as there are many more variations with car engines than with motorcycle
engines. The only hassle with motorcycle engines and frames is fitting
a differential and rear axle(s), as described later.
Note: Do not use a car engine with a narrow power band, as changing
gear on a trike is not so well controlled as in a car. Choose an engine
with a wide power band, so you don't have to change gear while diving
in to a fast corner, where removing your hand from the handlebars can
lead to poor control.
Only use fiery engines if they have an automatic transmission or have
electronic 'paddle' gear changes.
When it comes to car engines, most trike builders begin knowing little
about car engines. This is not surprising, as nearly all trikers are
bikers and most car engines are boring.
Welcome to the wide and wonderful world of the infernal combustion
Car engines are a wide world of inline fours and sixes (mainly boring
cars, with a few exceptions), transverse fours and fives, yes, fives!,
V6 and V12's. (Transverse Lambo V12s are rare.) Flat fours and sixes
(VW's Porches, Subaru, Alfa Romeo), Vee and flat twelves, inline V6,
V8's, V12's and a whole lot more.
If it's not there, then bikes can furnish V twins, fours, transverse,
2,3,4's and sixes. If looking long enough, the builder will be spoilt
The local newspaper adverts and scrapyards are ready to offer some serious
metal. Start by looking at the cheap cars section in papers, as many
excellent donor vehicles, usually with rusted chassis, are available
for spares or for next to nothing.
When starting your hunt for the engine, go for the whole package, in
both design and in building. The prime concern for a trike is overall
layout of engine and transmission relative to the wheels and overall
Scrapyardin' used to be a traditional British hunting sport. Today,
due burEUocracy, there are few old-style scrap yards which will allow
builders to scramble over their stock. This is a great shame, for inspiration
always comes from looking. When up to the ears in rusty, bent and twisted
metal, one always spots a new idea, a little jem, a new concept or design
possibility. Occasionally one will spot a worthy machine, from which
inspiration can flow in torrents.
Before going to the local scrapyards, stroll off to your local library,
if there is still one. Sit close to the workshop manuals and similar
vehicle publications. Work through them, study the layouts, their possible
options etc. Always take the sketch pad for notes, tracing paper or
some cash for the photocopier. If you have a digital camera, then use
it to good effect. The author is occasionally found in various sections
of libraries reading and often clicking away. Even if the ideal engine
is not found, at least what to avoid will be learnt the easier way.
Most trikes can be built on a tight budget, so knowing the basics with
simple research is a good way to save money, time and effort it works
There are two main forms of car engines as used in trikes, either with
the engine between the riders legs at the front, or hidden at the rear,
between the rear wheels.
Once a general idea is created using your preferred form and layout
of engine and transmission, check out and find the local friendly scrap
yards. If scrap yards are not local, or are less than their normal friendly
type, then get to know engines by simply looking under as many bonnets
(hoods) as possible, as there is no substitute for seeing the real thing
first. This will lead to a working knowledge of what engines are good,
bad or indifferent. The best alternative is to help out in a garage,
or preferably a large scrapyard for a few days, especially if unemployed,
ideally in exchange for a donor machine. Just ask, you may be pleasantly
surprised. Make sure you turn up in tough clothes and boots, be honest
with them and leave your phone number, they may get a rush of vehicles
and need some help soon, possibly during the new car registration season.
Not only will you get a cheap motor, you will also know how machines
are actually held together and work. If you get this lucky, take notes
and always stroll around during your lunch break.
In whatever way is available, helping out always helps to understand
the underlying engineering and makes for a good, short and very effective
Although weight balance is poor, engines like old VW's are easy for
trikes, as the engine, gears, final drive and suspension are all in
one lump and set up ready for use. Even the gearchange is a doddle.
Never take the easy option - you will have to ride it.
Some engines can be very difficult. What looks simple may have major
design flaws. Look, think, then buy. Be prepared to scrap the engine
if a better design is found, as there will be a lot of time and effort
put into building a good trike. When done properly, the trike may be
kept for decades, so if a better design of engine turns up, be prepared
to go for gold. The best is to spend time getting the ideal 'generic'
engine and transmission from the outset, so time and effort spent choosing
the best donor vehicle is never wasted. It need not be an expensive
version donor vehicle at this stage, as the better engine can be fitted
later, possibly the later turbocharged version if the trike handles
If buying a V8 off a friend because it's going cheap, you may be going
about this the wrong way.
Heavy engines at the front tend to understeer.
Engines at the rear tend to oversteer.
Engines with too much weight behind the rear wheels such as VW's can
have you pulling wheelies in second gear every time you pull away. Great
the first few times, but when you get annoyed doing it every day, you
may think differently. Engines with iron cylinder blocks are heavy.
Engines with dubious reliability or poor spares backup should always
be steered clear of.
Here is the crankcase of a Porsche V8 engine, from the front engined
versions which have a terrible reputation for reliability, (Because
the yuppies drive them in to the ground without bothering with servicing)
and so often get sold for pennies. A car for spares for 500 quid and
a runner for 1,000 to 1,500 quid. This includes matched transmission,
serious brakes and all the other bits, including the badge and key fob.
Such machines give the trike builder many excellent starting points,
not only in engine, but transmission and most important of all, a low
slung engine and plenty of serious stonk.
Note the engine is unlike some V8's; It is perfectly balanced, eight
cylinders in 90 degree format, just like having 4 Ducatis,- that'll
do nicely !
For this engine, a low, all alloy and more racing character would be
inherent in the design, more than any aftermarket custom catalogue could
ever hope to achieve. Built properly, it can also be very reliable.
See also sketch of Porsche V8 transmission for a complete, well balanced,
and nicely overpowered trike design.
I am not advocating the Porsche as the only choice, far from it, but
for bang per buck you can not only get excellent power, handling, but
also a posing key fob too, simply by careful choices from the outset.
It all boils down to choosing the best donor car or bike for you.
You simply cannot buy the fundamentals of a real custom machine from
catalogues, no matter how much you spend. You may end up with an overpriced
Harley motor and semi cute frame, but they all eventually look the same
from a distance.
So please think about going for gold, not spending cash like a drug
dealer looking for another Hardly Maybesome.
Another good choice is the Citroen 2CV, 600 twin engine. This is at
the economy end of the engine world, but is a superb example of having
an almost ideal trike engine. The weight is forward of the rear axle
and very low, with inboard rear brakes and can be built with a rear
suspension design similar to formula one. Only the upwards exhausts
are a minor problem. This makes a superb two or three seat trike for
general use at normal speeds. I see these motors being relentlessly
thrashed across France and they are simply indestructible and I consoider
them far more reliable than Porches.
For most of us, the classic choice is the bog-standard transverse front
wheel drive, four cylinder water-cooled car engine and transmission.
These are often available for free.
The whole engine and transmission and wheels can be moved to the rear
of a trike design for minimal hassle. Only the gearchange and rear passenger
seating may be problematic, so check first for the best design choices.
These are just three of many very different yet good possibilities:
Always decide what you want as your trike.
To repeat; Do lots of homework, then enjoy the pleasure of knowing
you have the best design route towards your version of perfection. Take
your time and use some imagination to get the engine, transmission and
wheels with the perfect shape and layout. Searching library, scrapyards,
garages and workshops is the best way to see how engines, transmissions
and suspensions are arranged. Take your time - as the more you know,
the more you will understand how to build your ideal machine, and the
fewer the hassles.
When a good choice is made, search the local ads for a suitable and
cheap test failure, and always get a receipt and the documentation.
Don't get fobbed off with excuses.
No documentation - no purchase.
It may be necessary to place an advert for an unusual machine. If all
else fails, then it's the scrapyard again. With a little common sense,
you may wish to search for a specific machine in a special way, such
as old four wheel drive Subarus which are often left neglected by farmers,
so go a huntin' and ask around. I know of two Subarus in North Wales.
They just need me and a customer needing a trike, to make them happy
Wherever possible, ensure the engine, suspension and ancillaries are
all from a single donor machine so it all fits together and works properly.
Ideally the donor machine should have failed for something which is
not needed on a trike, such as rusty bodywork. Ideally the engine should
run and the whole machine may often be driven back.
An ideal trike would have the engine, transmission and final drive
in one unit to minimise alignment problems and with the weight forward
of the rear wheels. There are quite a few almost perfect engines out
there, but in the real world, no engine will be perfect for every aspect
of trike design.
In an ideal world, a donor vehicle will be a serious crunch job, preferably
with no blood or body parts in the driver area, with only 10 miles on
the clock and no real damage to the parts required. As these types of
machines are soon stripped for spares, keep your wits about you and
carry cash when visiting.
For beginners, it is far better to build with an older version at first,
then keep an eye out for a pristine engine later.
Decide how these strange engine and transmission shapes will fit into
Have a good long look at anything promising, then chat to the guys in
the garage trade and scrapyards. Tell them what you want and they will
tell you if it's a dog or a doozie. If you don't see your dream machine,
they can often tell you where to start looking, and what at engines
are going to be close to what you need.
For example, if intending to use an Alfa, ask the Alfa garage what problems
are common. Don't ask the salesman. If you want the truth, go around
the back and ask the mechanic. A good scrap yard should be able to advise
you if you know what to ask. Do your homework first, and think up just
three best questions to ask them. Any more then three and like most
mechanics, they will want to get back to work, unless it's a ciggie
You may not be buying the donor machine from the scrap yard, but you
will probably find them very useful later on, for larger wheels, exhaust
bits, special tail lights, and a host of other componentry. Scrap yards
are often required to write off vehicles, you may not be able to get
the paperwork from them, requiring the builder to get a new identity
for the machine, so receipts are a must.
So always preferably privately buy a rough but legal donor vehicle for
Your ideal engine and suspension layout is out there somewhere, you
just have to hunt it down.
For example, an Alfa Romeo engine unit lay in a corner of a local
scrapyard. I had never noticed these engines before, but it had promise,
the 1500 OHC flat four engine lay forward of the rear wheels, with the
engine, gearbox and final drive in one unit. It even had the luxury
of inboard ventilated discs on the gearbox output shafts, to allow wire
wheels for a very clean look. A few faults would need working around
including the total lack of carbs, gear linkage and engine mountings.
As the bulk of the problems will be in design and preparation, this
is a good example for designing and making a trike.
As the machine did not have a body shell around it, a search for a second
donor machine was immediately begun. This was eventually found, so that
by the time the chassis was built around the first engine, a second,
running engine was ready for transplant, complete with all the ancillaries
- no need for an engine rebuild, or excessive new wiring etc. As the
Alfa is popular with junkyard racing, a totalled, barely running but
'complete' machine was almost free, but needed a few spares to look
nice, and a very serious service.
The Alfa unit is in many ways similar to a VW, except it points the
right way, forward, with the engine weight forward of the rear axles.
In style, the Alfa is a poor man's Ferrari, as the rocker covers will
polish up nicely and sit either side of the rider, with the Alfa Romeo
logo in resplendent polished alloy. In ease of build, it is similar
to a VW, because the engine, gearbox and differential are one piece,
even better as the brakes are inboard ventilated discs. Being water
cooled it was quieter and would allow a lower body shell and allow alternative
To make life easy, make sure you get any subframes, suspension, gear
linkages, clutch and brake cylinders, wheels, propshafts, carbs, water
gauge, electric ignition, and everything else you need. Buy it all the
same time as one car, so they work properly, it's also much cheaper
than buying separately.
Where possible, fire up the engine and check for a good motor. A crash
damaged or badly rusted vehicle is the best bet for a good engine, as
its unlikely that the engine has caused the machine to be scrapped.
For rust, Italian cars are excellent, as they have alloy, fiery, twin
cam engines, but may be atrocious for spares - so check.
Don't choose an engine you cannot get or afford parts for.
Before paying out a large amount of money for a donor vehicle, first
try buying a cheap, but unusual new spare part for the engine. If you
can't get or afford it, think twice.
If it's your dream engine, be prepared to build up your own spares supply
from scrap donor vehicles.
A friend has a Citroen SM car, with its Maserati V6 engine with everything
polished, even the con rods, a superb classic car, but a totally irresponsible
choice for a trike.
If, like most sensible builders, you choose a common donor car, you
will enjoy buying a new set of brake discs and pads for less than the
cost of a set of motorcycle brake pads. Even a new set of four alloy
wheels with new tyres can cost less than a big bike tyre, and the scrap
yards are full of excellent items at exceptionally happy prices. It
can truly be surprisingly cheap to build a very good trike to a high
spec, when based on a typical donor car.
Clean, check and run the engine, if you find any serious damage or
noises, forget it.
For a front wheel drive, where possible, get the scrap dealer to grind
out the engine complete with engine mounting brackets and such like.
Preferably get the whole engine bay, right back to include the dashboard
and steering, you will then have all the necessary wiring and mountings.
If rear wheel drive, get the whole machine.
The better choice is to buy the whole machine, run the engine and fettle
it, then preserve it carefully. Most scrap yards will deliver a wreck
to your door. (An unusual experience, it's usually the other way around.)
Such machines can be found locally for pennies, usually MOT failures
with mostly rust problems.
The best way is to search the papers for a cheap car and drive it home.
If there is no paperwork, or you cannot drive it, don't buy it.
Once you have got it all back home, there is often only room in a garage
or garden for either the donor vehicle or the trike. Do not worry. In
such cases, metamorphosis gradually removes the unnecessary parts until
the core remains still intact - engine, transmission and suspension.
Then the trike begins to grows in it's place.
First of all, give the whole donor vehicle a good clean, scrub the
engine and hose off the crud. Check the engine and transmission works
again and to dry it out thoroughly.
The machine will gradually transform until the engine and transmission
sits precariously on the core donor chassis, supported on wood blocks
and wedges. The wiring loom ends up hanging up in the roof space held
loosely in place wrapped around the attached dashboard like a demented
python. Likewise brake plumbing and other bits.
Do not throw anything remotely relevant away.
If in doubt, keep it in poly bags in the garden (not next to the trash)
or tucked away in the garage roof space.
At all stages, you will be prone to loosing an important lug, bracket,
clip or other component. It always happens and will always happen, so
protect yourself from such annoying hassles from the outset. Refit all
nuts, bolts and brackets back where they came immediately after disassembly
and carefully bag all the rest.
Some of the things which can be easily lost are important dimensions.
Before touching a spanner, (wrench), make a permanent note of the outside
width of the driven wheels of a transverse engine. This allows the transmission
shafts to be properly aligned later. It is also important to measure
the distance of the engine / clutch housing face to the nearest wheel.
To prevent later drive shaft and suspension inaccuracies, do not replace
these wheels until the chassis is built. Also measure the ground clearance
of the sump, so the engine will be blocked and positioned correctly
for standard suspension set-ups.
Keep the original car speedo that probably works off the gearbox to
calibrate any new speedo. Same goes for the tacho. Keep the seats for
foam and complete seats for total passenger retainment systems. Seat
belts too. Consider flowery pattern seat coverings as patterns for remaking
any passenger seats in vinyl or leather. Tail lights, side lights, boot
(trunk) lid and its lock, ignition switch, steering linkage, handbrake
lever and all the brake bits, both front and rear, all into polythene
bags and free from dust, rain or from getting lost.
If you use an automatic transmission, check if setting up the system
will need special access to certain parts of the transmission housing.
If in doubt, keep it intact as much as possible.
Never use an angle grinder until having removed all the wiring and hydraulics,
as it is possible to cut through something useful such as a brake pipe
or tail light wiring.
The traditional way to compact a car shell is to remove the roof, and
use it to stow all the parts as the shell is gradually cut into chunks.
Either by use of a traditional two handed battle axe and heavy boots,
(Viking heritage of real bikers) or the newer method of angle grinder
The petrol 8 inch angle grinder is now affordable for those who are
not afraid to loose their arms and legs.
But if on a very serious budget, or suffering wallet attack, then buy
a cheap 4.5 inch angle grinder and a few cutting discs. ALWAYS buy goggles
and gloves at the same time. Then use them.
I hang my safety equipment on the grinder, so I have to remove them
before use, - it works for me - it can work for you.
Continue until just the floor pan is left, into which all else can be
dumped and tied down for transport by trailer to the local recycling
It is extremely common to have to change a few bits as the design is
refined. So keep friendly with the scrap dealers, they will probably
have a later model, possibly with turbocharger, as these are harder
to find in local adverts, often having been wrapped around a lamp post.
Car electrics are simple, as the modern alternator is self contained,
with a regulated DC 13.8 volt output to charge the 12 volt battery and
even a warning light connection which can be ignored if you feel lucky.
The rest can be just as simple as you wish.
If you don't like electronic ignition, or if it fails, you can often
replace it with the older contact breaker system of earlier models if
you know their history. Choose your engine carefully, as many car engines
have surprisingly long pedigrees. Again, talk to the trade to make life
easier. Always buy the workshop manual before buying a donor vehicle,
as money spent on this may save you much money later. Read fully and
if all is OK, you have the manual. If not what you want, you have only
lost the cost of a manual.
If the engine does not have electronic ignition, then you can make your
own, using old bike pulsers and CDI units with integral electronic advance
curves, which use the standard motorcycle dual HT lead coils, which
work just as well with 4 cylinder car engines. alternatively you can
use parts from other car engines with a similar basic layout, as they
are nearly all the same in their basic formats. See making your own
CDI systems on my website.
The final engine choice will be narrowed down to an ideal, specific
engine during the design process. Often, part way into a project, a
completely different engine may be chosen which may improve the design
by leaps and bounds.
Considerations for types of trike frame layouts.
As most car engines are ugly, expect to hide them. Notable exceptions,
most early V12's. Later V12's are over-sanitised and 'plasticised' into
amorphous corporate blobs without a soul, ideal for accountants, but
not for bikers.
The standard VW engine will give an unwanted rear overhang, but is easy
to weld up a frame.
The Austin Mini gives a very nice handling machine and is quite easy,
just an engine on a sub frame. It doesn't get much easier to get the
basics right, except in plastic model kits. It's only hassle is a parking
brake and for some, the gearchange. If you have been paying attention,
then I've already mentioned earlier, three good choices.
The transverse engine. (Across the frame).
From (real) Minis to Lamborghini Miura V12.
The basic engine is the mid engine transverse four, plus the occasional
five and six cylinders and the vast range of clones. Transverse V12s
are very rare.
Often a good, well balanced, honest set-up, such as exemplified by the
European classic later Ford Escorts. Some engines have the transmission
exiting to the rear if the engine unit, while a few others have the
engine behind the transmission output. The latter is better for trikes
if carrying passengers very low.
Most of these usually employ McPherson struts which may need widely
placed tubing over the top of the engine. Therefore it may be preferable
to design for the engine to be removed from rear. The top of these suspension
struts can be resolved without upsetting passenger room, as most of
the braking and accelerating forces are taken by the bottom radius arm
/ anti roll bar, which should be kept as is. This set-up applies to
most common machines.
The McPherson strut can be cut down into a more traditional suspension
setting, made using the bottom parts of the McPherson strut, to allow
a much neater and lower design, more in common with formula one.
Like the mini, the gearchange and parking brake will be the biggest
hassles, so do your homework. (See gearchange and brakes later.)
The transverse engine is good for weight balance, allowing the trike
to have most of the weight just forward or to the rear of the rear wheels,
and an open book for the front end. If choosing a transverse engine
layout as used on most front wheel drive cars, then for ease of adaptation,
always choose a design with the gear linkage on the top of the gearbox.
Unlike the real mini, the engine and transmission is not usually on
a sub frame, so it may be preferable to keep some relevant parts of
the chassis interface to weld to the trike frame tubes.
The front engine in-line. From Moggie Thou (A series) to Jag V12.
There are always problems with heavy front ends, so always expect to
design with a shortened prop shaft to move the engine to the rear to
improve axle loadings. Always keep the prop shaft sliding spline. Do
not allow dangerous angles on the universal joints at each end of the
prop shaft. Check the differential movement of a solid rear axle and
use a Panhard rod where needed. Radius arms will usually be needed and
are part of the donor machine.
Independent rear suspensions are usually far better.
The larger engines will cause a heavy front end, and may demand a car
front wheel, so expect to build a heavyweight front end.
The frame will need to support the engine and will probably need to
be a variation of four heavy tubes. Two over the top of the engine to
the steering head, the other from the steering head, around or below
the engine to take the engine mountings. A massive version of the Norton
Featherbed works well if a tube bender is hired. Box section tubing
makes an alternative and is very strong per unit weight but square section
tubing is rarely stylish unless it's done well. If suitable rectangular
section tubing is available, a wrap around design is possible using
single box beams, or variations on multiple tubing.
The rear axle from a donor van may use leaf springs, so the trike will
require longer lower main frame tubes, but simply replace with alternatives
from the saloon variant. If the prop shaft is very short, it is better
to discard leaf spring set-up and use radius arms to maintain good angles
on the prop shaft as the rear axle moves up and down, and to reduce
excessive frame overhang at the rear.
There are a few decent rear ends, with notable mention in dispatches
for Jaguar's definitive limited slip differential / independent drive
shaft set-up. As rear ends are rarely seen, standard components usually
suffice. Solid rear axles are not as good as independent rear suspensions,
so choose carefully and be prepared to mix engine and transmission.
Check the gearing. As most cars use very similar diameter wheels and
fourth gear is usually direct drive and if engine revs are similar,
then gearing hassles will often be minimal. Adjust gearing with van,
saloon, or other gearbox and differential ratios, or other rear axle
units, or more simply with smaller or larger diameter wheels and tyres.
Always check first gear is sensible and will not cause clutch slip.
As most cars are similar, gearing may not be much of a problem, but
always check first.
If using a jet engine, (extreme show customs only), ensure the exhaust
is deflected for zero back pressure and with even, positive down forces.
(Vent exhaust to the sky.) Do not allow the exhaust to be deflected
such that wheelies are produced, (unless for show) so keep the rear
wheels just behind any acting point of exhaust pressure.
For 'general' use or close to crowds, do not expect pure thrust for
power, as other road users do not like scorched front grilles. In such
cases, use helicopter transmission set-ups, to use the power take off
turbine and gearing to drive a modified car transmission. Gears may
not be needed, but a clutch is important. You may need an intermediate
gearbox with oil cooler. You will most definitely need large fuel tanks
and also damn good brakes, as reverse thrust is not acceptable nor practical.
The exhaust may need decent heat and sound shielding.
The intake will need a large screen air filter for road use, which is
impractical, so the intake area may need to be enclosed in a large box,
covered with coarse cloth as a basic filter. This will help prevent
large particle debris from entering, which is much more common on surface
machines. (Most jet engines work in clean air away from the ground,
and can handle a bird strike or two.) Alternatively, the intakes could
be designed to take 'clean' air from ahead of any wheel turbulence.
A large concertina stack of many car air filters may help, but is normally
unnecessary except in sandy or gritty countries.
Gas turbines are very light and powerful, so don't go stupid and get
something totally unmanageable. Gas turbines are designed to burn fuel
like paraffin, so don't expect to fill up at petrol stations on the
way to the shows. Do not choose turbines which need excessive start
up procedures or equipment. Get all ancillary equipment including any
necessary ground crew support kit and installation and service manuals.
Choose an engine with a low number of hours since its last rebuild or
expect to have expensive services by officially approved turbine engineers.
Turbines like to work for hours when up to working temperature, so any
stop-start use is likely to reduce the hours between services. Ensure
access is good enough for regular visual checks of blades. Always retain
and use the number of hours run counter and keep all documentation,
especially the maintenance log. Spares will need to be via specialist
dealers. Be prepared to use 24 volt and exotic electric starting systems.
When a car engine goes bang, usually just the con rod appears out of
the sump. When a jet engine goes bang, there can be a massive amount
of turbine flying in all directions, so inspect and maintain regularly,
and build a serious steel or aramid guard around the areas of the most
vulnerable blade paths, especially near passengers. These are not toys.
A sensible alternative to a jet engine is a multiple rotor wankel.
They are small, powerful, light, uncomplex and very smooth. Do not expect
to tune or modify the engine. Exhausts will get very hot. They drink
fuel and will need larger fuel tanks, an oil tank and need better brakes,
but well worth the effort for an extremely low, extremely serious trike.
The RX8 offers 200+HP from a very small package.
Whatever the donor vehicle choice, always keep the receipts for the
parts and get all documentation. This will show the official inspector
that it's not stolen. It may even still have a 'valid' road legal status.
Other aspects of engines includes noise.
Anyone who has heard a large Detroit lump fire up, will never forget
the sheer thrill of burbling excess of cubic inches. A V12 on song is
sheer poetry of engineering, while a wankel rotary makes its own strange
music. Playing with noises requires getting the exhaust correct and
tuned in and may not always be legal, so always make sure there is also
room for a legal exhaust system or a butterfly valve in the pipe.
Style of engine is very dependant upon two main facts. Status and aesthetics.
For some, it may be possible to get away with an amorphous blob or ugly
engine if it has the right badge. Many high status engines are ugly,
but to be truly perfect, an engine must look good.
Looking good for a front engined trike, the engine must be alloy, at
least a V six, so the pipes look good, and with decent rocker covers.
This must then be backed up with crankcases and heads which will also
look the part. An iron block with oil and fuel pumps sticking out is
not perfect. A sleek alloy lump, clean, neat and devoid of plumbing
and wires will always polish up and look the part - light and powerful.
There is a Rolls Royce Merlin engine in the Imperial War museum in London
in a glass case. It has style, clean looks, perfectly detailed and finished
components, a magnificent number of oval exhausts and a superb name
resplendent on the rocker covers. It is also nice to know that these
engines are still thrashed regularly in the USA in air days and spare
parts are still easy to get. If you ever get the chance to look inside
one of these engines, the highly polished camshafts and other components
will leave a lasting memory. Trikes too, can choose from a similar array
of much more appropriate, yet equally resplendent engines. In the real
world, there is still an excellent range of engines for day to day triking.
Unfortunately, engines also require air filters and other items, if
only to reduce the intake roar and prevent excess wear. Therefore make
ancillary items either hidden as much as possible by mounting the air
filter under the seat and using subtle ducting, or a rethink to make
them part of the overall style.
Here's a few pointers to engines of note.
Please note that the engine descriptions in this monograph are as used
in a trike, not as used in the donor vehicle.
No apologies for aiming high. No apologies for leaving out many also-rans.
No apologies for comments. When choosing an engine, only the builder
can call the shots.
Rear engine in line. (Engine behind the wheels.)
Older VW's and 'real' Porsches - don't bother unless you like wheelies.
Mid engine inline. (Engine just in front of rear wheels.)
Subaru flat fours, good trike material and ideal for powered trailers.
Citroen SM with dated V6 Maserati engine, be prepared to get lost in
Ferrari flat twelve's, - mmmm, nice, but perhaps just a little too pretentious?
For low budgets Citroen 2CV and '4CV'. If disabled, get the version
with automatic clutch. 2CV's are thrashed mercilessly across France
on a daily basis and seem to last forever.
Front engine in line. (All must have a suitable prop shaft to shorten.)
Model T Ford - don't even think it, or I will personally perform your
Porsche water cooled V8. A fine piece of metal, low and light for the
power. Well worth a look, but don't expect to get a genuine workshop
manual. A surprising number of automatics available, and very cheap
Jaguar V12's. Sheer music, but how far will a tankful get you? (It still
works every time for me.)
Rover and American V8's - join the clan.
Mazda wankels. Surprise yourself - get really low for stonkin' around
corners. For high power, compact engines, the latest RX8 Wankel (1300cc)
Gas turbine jets. (Usually from helicopters. You will have serious hassles
becoming road legal, but Frank Bell and Spen King at Rover Cars managed
it - see UK registration number JET1! and others too, including G.M.)
Best kept for show use only.
Mid engine transverse.
Honda and other micro vans and cars, 550cc, 'er, well guv, it's a trainer
trike for the kiddies'.
Ferrari transverse V sixes - its just gotta be done. Rich punters please
call the author.
Lamborghini Miura V12 - prepare to be lynched by owners club.
Front engine transverse.
The ubiquitous and all round favourite - Alex Issigoniss's most excellent
Mini. (Not the lardy Brazilian BMW motor)
Ford Escorts and almost every common car - It will get you to work every
V sixes from various manufacturers now available and coming to a scrap
yard near you soon.
Front engine transverse. - Bikes.
Bike based trikes: Mopeds to Harleys to 'busas upwards. Engines and
frames as supplied. Mopeds only suitable for kiddies.
Honda Gold wings seem a waste of time when equally large car engines
are available for much less cash and already have the dual rear wheel
drive totally sorted. Cars also offer turbo options, tuning mods and
such like for much more affordable pennies.
Although mainly for show use, there is no reason not to use a dual
engined machine. This will require an extra wide double differential
set-up, but quite feasible and usable with limited slip differentials.
Consider differential mods or differential locks should one engine fail.
Other set-ups also possible.
For reliability and ease of build, keep the engine and transmission
as standard as possible.
Having chosen your dream engine, time to design a trike to fit around
It is assumed that if wishing to build a particular type of machine,
the reader will have hopefully ridden a number of similar trikes and
also thought seriously about the engine.
The first thing that may come to mind when riding the average trike
is the awful control, especially the clutch and gearchange. For some,
the experience may end abruptly as reverse is found to be hiding yet
again. This is often soon followed by the awful wallowing around corners
as passengers and luggage struggle to remain with the machine.
When designing trikes, especially those requiring the subjective needs
of usability and good handling, then the designer should begin with
a fierce approach to the prime purpose, only ameliorating the form to
fit the real world.
Sukoi's Fulcrum, possibly the worlds finest air superiority aircraft,
began with the Russian designers just creating the most perfect wing.
Only then were added engines, nose and controls to see how much the
ideal wing was compromised. (The Americans still cannot do a 360 loop
while travelling forwards like the Sukoi's. Perfection does not equate
This is an excellent way to build a trike, beginning with perfect weight
distribution and a low centre of gravity. Then compromise the design
with the best engine layout to fit, plus rider and secondary components
which will minimise any compromise of the potential ride envelope.
Finally, the testing and refining the fundamental structure will help
ensure the best overall design is possible.
Know and understand exactly what is wanted: Good handling, good control,
safe and comfortable passengers, reliability. A trike that truly can
be enjoyed every day.
The first step is to know the dimensions with which to work. Dimensions
are in three forms, the fixed, the dependant and the free. Knowing the
difference enables the process to develop in a fairly logical manner.
Fixed. The fixed dimensions are those which due to their nature cannot
be changed: The sizes, shapes and weights of the rider and standard
components such as engine, wheels and transmission. Even these may need
modification before a final design is made. (I often modify engines).
Decide if the machine is for various rider sizes and which size of wheels
etc. It is the fixed dimensions which give us generic forms. Once these
'unchangeable' dimensions are decided, they become the starting point
of the design process.
Dependant. These semi-variables are decided by the design as it forms,
rather than by a totally free path. This includes the wheelbase and
ground clearance which can change within specific limits set by engineering
constraints. Spend much time thinking about the variables, as this is
where the underlying parameters of a good design are created. For trikes,
such as the possible propshaft shortening for adjusting overall weight
Free. The free variables which must be created in the mind are the
overall shape, colour, seat style and form and the many small styling
options which make a machine a whole and competent device, a complete
mess, or a work of art.
The best way to design a machine is to tie down all possible fixed
dimensions and optimise their arrangement to create the best basic form.
It's often referred to as 'juggling the bits'. Initially rough sketches
on paper at first to assess the overall style before buying anything,
then subsequently more accurately to scale or full size on paper once
the main contenders are chosen, then finally in full size on the garage
floor. Once the fixed dimensions are sorted, (usually engine transmission
and rear wheels) the dependant variables will often fall naturally into
place. Finally the builder can begin to mould them together to create
the best possible design, as seen in the eyes of the designer. The reader
may not consider themself a designer, but this is a genuine hands on
Computers. (It had to happen. If galled or vexed, then skip to 'The
most important design skill is being able to use paper and pencil.')
If preferring to use a drawing package on computer, then simulate the
paper process. Although computers are superb for refinement, they cannot
replace the paper and pencil stage. Neither is there a substitute to
handling full size components and the true feedback they always give.
Computers have the advantage of allowing the designer to model the design
and view it from all angles, to see faults and places of refinement.
Both paper and computers have their uses, and both should be used where
A note before buying expensive CAD packages. Although dimensionally
based drafting packages are the seemingly natural choice for designers
of engineering projects, they do not have the flexibility of 3D packages
such as Newtek's superb Lightwave, which has enabled many fine machines
to be developed and refined. Two industry standard CAD drafting packages
with university training were rarely used by the author in preference
to Lightwave. As the trike is basic engineering, the design can be seen
primarily as an art form.
Fundamental engineering is easily accomplished with or without a computer,
but the overall final form, shape, style, colours and final detailing
of the trike are usually more important, and more easily accomplished
is it can be studied on a 3D software, or on a clay model.
The last paragraph may be controversial, as many designers will offer
the standard reply that building a mechanical design requires mechanical
drawing software. This is often a trap, as the actual design is never
done on the computer, but with common sense.
Computers do not design trikes, - people do.
Sketching a frame tube on a full size or scale drawing on paper or screen
is quite good enough for most purposes.
A trike is not an oil rig or aircraft and therefore does not need a
set of working drawings. Even if a design is to be mass produced, a
simple jig from the original machine often suffices at this level of
engineering. Therefore do not get sidetracked by having to spend many
hours making technical drawings. As a draughtsman from the marine, military,
nuclear and electrical industry, the author does not see any need to
waste time where true design should be done more productively elsewhere
in the design process. Trikes are a fairly basic engineering structure,
aiming, in most cases, to be an art form. Treat them as such.
Art forms develop nicely with 3D visualisations from all aspects and
Lightwave does this extremely well. Understand what is being created
and use the tools available in an appropriate and useful manner. Do
not waste time on computing if it's not needed.
3D modelling (computer or clay) can greatly help refine an idea, especially
overall styling or where components may come into conflict, such as
exhaust runs through frame tubing, steering linkages or items which
move relative to each other. Inverse kinematics is useful for refining
complex steering and suspension systems or particularly evil gearchange
If very keen, exporting work between various packages such as drafting
and finite element analysis should also be checked prior to purchase.
Data transfer is particularly important due to the steep learning curves
of some packages, should the reader wish to become deeply involved in
the design process. Therefore always carry floppy with a test piece,
to see if it transfers easily and correctly. The test piece can be generated
on the first item to be tested.
The most important skill is being able to use paper and pencil.
This works perfectly well for most people and it still remains the definitive
design process for innovation.
If using a computer or on a good 'ole paper sketch pad, begin by roughly
modelling the three best choices of engines, transmission, wheels, front
end plus riders. The engine, wheels and rider can then be positioned
relative to each other, until a refined layout is accomplished. This
is the same as laying parts out in the garage with chalk, or sketching
on paper. The advantage of using a 3D package is that the various virtual
engines can be easily tested and adjusted for looks and fitment, then
seen from all angles for the best possible layout. For basic assessment,
the virtual 3D components need not be much more than a dimensionally
accurate box for the engine, and simple extruded cylinders for clutch
and gearbox, wheels and such like. Then the overall weight distribution
can be calculated on paper once the basic design is optimised.
Designing a frame.
A frame does not appear from nowhere. It grows from the requirements
placed upon it.
The requirements are many, from the fixed dimensions of engine mounts
and suspension set-ups, to the overall structural shape and its styling
requirements. This means understanding the way the frame must work,
and the many parts it has to contain and control.
A good frame is not designed overnight. If you take this seriously you
will (must) be constantly changing the design and refining it.
Every second spent refining the design will reduce the amount of grief
This will also save you from having to ride a less than perfect trike
in the years to come.
At this stage, you will have begun drawing sketches to get your head
tuned in to what you want, and have a good idea of where you are going.
If you get stuck, email your ideas and no more than two small, jpeg
compressed sketches to me for a free assessment and a few hints. I do
not expect works of art.
The structural part of the frame is the most important and is designed
first. This will decide how you will mount the suspension, wheels and
steering. The engine mounting will also demand certain requirements
of the chassis.
The non-stuctural parts will be added later, such as the seats and radiator
The following is what you need to understand your design more closely.
It is assumed the drawing stage will have helped decide the best engine
and the other main components such as rear axle.
Start off with a rough assembling of the engine, wheels etc. on the
garage floor or perhaps on a garden patio, or simply on three levelled
concrete slabs in the garden. This will highlight any possible problems
and to help get your ideas growing.
Clear the scene and block the basic engine, transmission and rear wheels
in a working position using wooden blocks etc. Use original dimensions,
so the assembly is as it was for the original donor machine, to ensure
maximum accuracy and reliability.
Then juggle the bits around to find the best layout. Measure the static
ride height of the engine (ground to sump) before removing the car bits
or wheels. Wherever possible, keep all the transmission and other heavy
stuff intact as one.
For front engined trikes, do not modify the prop shaft to the rear
differential until after deciding the final positions of the components.
The prop-shaft need not be positioned in place at this stage, just leave
sufficient room. Most other parts should be arranged as the manufacturer
intended and has been tested for many years. Use of standard parts and
dimensions are central to long term reliability. Get plenty of scrap
wood or other packing and use simple wooden wedges where necessary for
perfect positioning. Likewise wheel blocks. Do not unnecessarily compromise
the ideal positions of the items. Position the front wheel if possible,
resting the forks against an old chair or strung from the roof.
On transverse engines, there is often little to do. On front engined
trikes, the engine should be moved backwards enough to give good weight
balance and ensure a shortened propshaft works well, yet still allow
room for the riders. It may take days or weeks to decide the best weight
Take your time laying out the bits.
Adjust, look, contemplate.
Then repeat many times, then cover with a cloth and walk away for a
week while you do some styling and detail design. When you look at your
last layout after a week, you may get a better feel for its overall
layout and balance with fresh eyes.
Check what can be rearranged to improve your options, both for aesthetics
and for engineering purposes.
Engine parts which stick out or look ugly should come under closer scrutiny.
An alternator can be repositioned using longer or shorter V belts, or
an awkwardly positioned mechanical fuel pump which could be replaced
with an electric fuel pump somewhere else. See fuel later. On front
engined machines, the radiator can be removed from the front of the
engine to clean up this area and make the machine look leaner. See Cooling
Carbs can be shuffled around, perhaps by simply cutting and re-positioning
their inlet tract. If very lucky, simply bolting back to front or from
side to side on flat fours may suffice, perhaps with just a little re-porting
of the inlet tract to ensure a smooth flow. Keep the carbs level as
intended and ensure all linkages are retained.
Some engines use an iron exhaust header. This can often be replaced
for cosmetic purposes by the four into two into one from the sports
version. Leave the rear half of the exhaust system for later.
If the shocks are not mounted on a sub frame or similar, allow for
ground clearance by measuring the movement of the suspension. Do not
trust the amount of dirt wiped off the suspension chromed central shaft.
The trike should have reasonable ground clearance on full compression.
A basic comparison with the shock movement and the ground clearance
will often suffice. For simplicity and reliability, or if in doubt,
use the same ground clearance as the donor machine.
For a low, better handling machine, you may wish to go for stiffer
suspension, lower the ground clearance a little and add a little more
rubber to the bump stops, but first check the local roads for speed
For very low trikes, consider a sump guard with a firm rubber block
interface between guard and sump. The sump guard should be both curved
up and strongly supported at the front. This should allow a little high
speed skiing with bottomed suspension on less than perfect roads and
hump back bridges, (the ones with sump marks on the road either side
of the brow) such as Postbridge, Devon.
For a nice, low, forward mounted engined trike, consider the 2CV for
a well balanced design with excellent economy. Or perhaps a V8 water
cooled Porches and similar designs which have a nice low engine, with
a 90 degree vee bank for perfect engine balance and many being available
in automatic versions. The five litres of stonk should do quite nicely.
The Porsche engine can be repositioned nicely much closer to the rear
by minimising the high speed prop shaft between clutch and rear mounted
gearbox. Seating may be problematic and require a little juggling.
In some cases where the gearbox is on the differential, a high speed
prop shaft similar to a water cooled Porsche is used. The drawing shows
that the distance between engine and transmission is up to the builder
and a little imagination. From a couple of feet to a couple of inches
or as one lump. Likewise the gearchange is an open book.
If you can match the shaft gearbox splines in a safe manner to a suitable
clutch plate and match the flywheel starter ring to the starter motor,
(by machining the flywheel to take the correct starter ring) then it
is often possible to use an intermediate mounting plate between the
back of the engine and the transmission bell housing. A classic example
is fitting a Ford Pinto engine to a VW transmission unit.
This is a Ford Pinto motor using a large sheet of steel to mount the
VW transmission, a very popular arrangement for dune buggies.
If you want such an engine extremely close to the rear diff of a design
with independent rear suspension, then you can mount the diff on the
back of the engine, using intermediate struts or brackets, but make
sure the engine and diff are rubber mounted. The engine mounted to allow
torsional rotation and any vertical and sideways vibration, and also
allow the diff to take and resolve the torsion from driving the wheels.
For those who want to get rid of the seating problems associated with
upright shock units, consider the suspension of some smaller, older
Renaults which use suspension arms in conjunction with torsion bars
to give a very low mounted suspension set-up. The torsion bar mountings
can be tweaked to get adjustable spring forces with minimal hassle.
Alternative top ends to the tall McPherson struts are mentioned later
for very nice chassis.
5,000cc Porsche engines are not compatible with small car suspension
components. Never apply the power of large engines through ordinary
components. Always use parts that are appropriate for the purpose.
If making an open design of trike without a covering or shell, then
try not to use large sections of the cars chassis, such as the areas
around the shock supports or around the engine mounts which will usually
look ugly. These areas may be kept until the frame is aligned, and then
removed, possibly keeping just a small part of the old mountings and
brackets for ease of manufacture of some important fittings.
Most modern cars have the same layout as the Real Mini which started
it all back in 1959. On the mini, the whole engine, drive and wheels
can be assembled as one system as found on the original vehicle, using
Alex Issigonis's most excellent sub frame.
Today, the extremely common suspension mounting on front wheel drive
transverse engines is the McPherson strut. These often mount directly
into the cars body shell, so upper mountings will have to be built into
the trike frame. An alternative is to chop off the top of the strut
and use the mounting hole in the axle to mount an upper wishbone. Note
that in the picture, the upper suspension pivot bush joint is threaded
into the upper wishbone, allowing the vertical alignment of the wheel
to be adjusted for optimum handling during testing.
Either side of the transverse engine's differential exit the propshafts,
with their appropriate spline positions. Some splines are part of the
wheel axle unit. Splines are the way the shafts allow for the changing
distance between the differential housing and the wheel axle. At rest,
splines should be positioned so they can be slid in, to shorten the
shaft as the wheel goes over a bump. They are usually hidden under a
rubber concertina boot and must be correctly positioned. If an anti-roll
bar is used, then this often statically aligns the width of the items
correctly, but make sure the centre line of the engine and the roll
bar are marked prior to removal, so all will align correctly. Again,
use original dimensions if in doubt. If a crunchy donor car, then be
careful. This is best done by measuring the gap between the inside of
each wheel to a datum point on the engine, such as the clutch housing
to engine face. If the wheels are to be changed, then align with standard
wheels first, or else measure to a retained component such as the hub
carrier bottom pivot. Then remove the shocks and physically move the
wheels up and down to check the prop shaft splines work as intended
and do not suffer from tight spots.
The radius arms will need to mount to strong parts of the frame, forward
from the hubs to a point on the intended chassis and in a manner that
allows them to control the rear suspension. In many cases, radius arms
are often the same item as the anti roll bar.
The wheels will also be positioned either side of the vehicle by a bottom
wishbone or arm, which is there to take the sideways loads from the
wheel into the frame. Again the position will be dependant upon the
correct position of the prop shaft splines. Where these bottom support
arms will eventually mount on the trike, the frame will want to flex
out, so cross support will be required between the trikes lower frame
rails to prevent spreading.
The wheels are positioned to lie vertically. Allow the position of
the upper cross member to support the tops of the two suspension units.
The whole weight of the rear of the trike will be supported on the tops
of the spring units, so distortion of the shock unit springs depends
upon the weight placed upon them at this major structural part of the
chassis. If used, the top of McPherson struts must also be constrained
from slight fore and aft movement. Triangulation is a nice word.
Where torsion bar suspension springs are used, (Renault 4 etc) the fixed
ends must be clamped securely, as the whole weight of the rear of the
trike is acting at these very highly stressed points. Make these mountings
strong, as a lot of torque is developed at the ends. The trike frame
torque arm mountings can be adjustable to allow for slight adjustment
in the amount of torsion used, to give slightly heavier or softer suspension
spring rate. Although torsion bars don't look like springs, they are
indeed springs, they just happen to look like bars. They support the
whole load of the machine. Read the manual to check the amount of preload
required. See also primary testing, later.
McPherson struts. Double check the prop shaft splines are in the correct
position relative to the engine and wheels with the machine at rest.
Then temporarily brace the tops of McPherson struts using a plank and
blocks of wood across the engine etc. The McPherson strut spring rates
are normally set to take the weight of the engine plus half the weight
of two car occupants, so the spring rates are fairly close to ideal
for a two or three seat trike.
Trikes tend to have a poor time with differentials. This is because
they were never designed to use chain drives and too many trike riders
fail to spend enough time designing the differential and its many problem
You can build the worlds nicest trike, but if the differential is not
sorted, neither is the trike.
The differential takes the power from the prop shaft or rear sprocket,
and turns it through a right angle to drive the wheels on each side.
It also modifies the gearing by about 3:1.
Differentials also allow both wheels to rotate at different speeds when
cornering, hence their name.
For trikes with bike engines at the front which have to adapt differentials,
then there are usually two types of rear axles available: The basic,
old style is a one piece differential / axle unit. The other uses independent
rear suspension with a differential fixed on the chassis and separate
drive shafts to the wheels.
The solid rear axle is not a superb solution, as it is heavy and offers
poor suspension movement. But it is much easier to fit, often needing
just radius arms, spring mountings and a Panhard rod.
The independent form of rear drive from the differential is far superior,
but more complex. The radius arms in the picture keeps the fore and
aft position correct, especially under acceleration and braking.
The Panhard rod on the top of the solid axle prevents it from moving
left or right, while still being able to move vertically.
With a front car - engined trike, the propshaft between the gearbox
and differential must first be laid out and the engine then adjusted
for best position allowing for prop shaft mods. For solid rear diff
/ axle units, the propshaft gearbox output should be level with mid
point of the rear axle up and down movement, to ensure the prop shaft
splines will suffer minimal sliding. This is controlled by the radius
Once piece rear axles.
If the one piece axle unit with the differential, it may use leaf springs
as standard and these are usually replaced with radius arms for styling
purposes. Leaf springs require longer and lower main frame tubes. If
the prop shaft is very short, it is better to discard leaf spring set-up
and use radius arms and coil springs to maintain good angles on the
prop shaft as the rear axle moves up and down. The leaf springs act
as radius arms, so build or use radius arms which are similar to this
movement and which pivot at the front either side of the front of the
central prop shaft. This will require minor modifications of the mounting
brackets on the axle, although the shock units can remain essentially
as fitted. Leaf springs are not a good idea for trikes, and is often
easily replaced by using the saloon version of the donor vehicle which
often uses radius arms.
For basic trike designs, there is not always a need to change anything
unless necessary, as most suspension designs are specific to the donor
machine and are often used as the manufacturer intended.
When using front mounted engines it is common to cut down the prop
shaft to get the engine weight more to the rear. With once piece diff
/ axle units, this will require positioning or modifying the radius
arms to closely follow the arc of the prop shaft. Ideally, the front
of the radius arms will be pivot approximately either side of the gearbox
output universal joint. The prop shaft spline will allow the radius
arm pivots to be positioned aft of the universal joint, so overall accuracy
can be reasonable rather than perfect.
Independent rear suspension.
Independent suspension offers better handling, better control over some
adjustments during building but is more complex to fit. Because the
central diff housing is on the frame, the frame also requires suspension
arm pivots and spring mountings to be positioned relative to the differential
housing and it's drive shafts.
For independent rear suspension, the differential housing is fixed on
the frame, so the prop shaft only needs a little flexibility in alignment
and length for the movement in the engine mountings, and thus can be
a lot shorter if required.
Chain drive and differentials.
If the engine has a chain drive, such as for many motorcycle engines,
then fitting a rear sprocket to the differential will be the biggest
Sprocket ratios must be adjusted to match the diameter of the new rear
wheels. If the new wheels are the same outside diameter as the original
bike tyre, then the standard sprockets will often suffice.
The rear sprocket should be mounted onto the differential crownwheel,
in place of the original gear ring. This usually requires a sprocket
with a fairly large hole in the centre, which can be machined or ground
away by powered hand tools. It is always better to choose the sprocket
nearest to the proposed requirements; Some aftermartket suppliers have
excellent sprocket guides in their catalogues, complete with dimensions.
If a standard is close, then preferably machine the crown wheel mounting
to match the sprocket for easy replacement of this high-wear component.
Always get a few spare sprockets.
If there is not enough room in the housing of a solid rear axle unit
to clear the chain and sprocket, simply build up a set of at least four
wrap-around cross braces to support the outside of the differential
housing, which will then allow the differential housing to be gently
trimmed back to clear the chain and sprocket without loosing shaft alignment.
These could be strong, long, curved tubes to support both sides of the
differential unit. Before cuting the diff hosing, fit and weld up the
bearings, and when cross braced, remove just enough to clear the chain
and sprocket. The open area can now be built up with a light sheet metal
or fibreglass GRP shell to help protect the differential bearings and
the chain entry and exit points. Make sure the chain and the sprocket
can be easily replaced.
If replacing the sprocket is particularly difficult, and if it is not
transmitting too much power, and if it is mounted on at least four bolts,
then the sprocket can be bisected with a hacksaw and mounted as two
halves to fit into the standard axle housing.
If you think that running a rear differential without its hypoid gear
oil is likely to lead to extreme wear, fear not. The gear oil is to
overcome the high shear force between the prop shaft pinion gear and
the crownwheel. the rest of the differential does not need this and
the main axle bearings holding the core of the diff do less work than
the wheel axles which run in grease, so greasing these is plenty enough
in most cases. The central star gears do very little work and then only
in corners and at relatively low revs, so can be lubricated by chain
lube or drip feed.
If using a one-piece, solid rear axle, then the sprocket alignment
will be badly offset from the centreline: One side of the rear axle
may need to be cut and shortened using high class engineering techniques.
Alternatively the bike engine can be moved slightly to one side, or
the sprocket on the diff can be spaced out by half an inch and also
one of the road wheels spaced out to give a reasonably even rear wheel
spacing or usually a mixture of all three to get the wheels evenly spaced.
It is for this reason that it is recommend to use independent rear suspension
for chain driven bike engines.
With independent rear suspension, the differential is mounted as part
of the frame, with the independent drive shafts exiting to left and
right. Because the differential is mounted to the frame, then much of
the unit can be rebuilt for trike use.
A design example.
This is just one example of making your own engineering solutions.
It is not simple DIY, but needs a reasonably high degree of engineering
skill, rather than expensive engineering machine shop solutions. Done
badly, it can be very dangerous.
First of all, the differential can be removed from a modern car such
as an Escort Mk 3 or 4 and mounted into its own metal cradle sub- frame
supported from the bike swing arm pivots and shock mounts.
The Escort diff is mounted on taper rollers which are preloaded axially
by large belville washers, so a simplified housing is possible, without
any need for shimming the bearings.
Start by machining the diff centre to take a standard bike sprocket
of the same size as the original, if the bike rear wheel and the trike
rear wheels are of a very similar outside diameter. Adjust the sprocket
ratios if the rear wheel diameters are different.
To mount the bare differential assembly in the fixed sub frame, make
shouldered steel rings or cups to take the diff bearings. These can
be mounted on the left and right sub frames, such that the halves can
be bolted together to make a well mounted differential unit on the bike
Such bearing cups can be made by steel tube, split to fit and welded
to be a snug fit. Then an end plate added which has a hole just big
enough for the prop shaft to fit through.
Measure the width of the assembled diff and bearings, then add two thirds
of the width of the belville washers, so that some compression is available
when the left and right sub frames are bolted together. This will give
the final width of the differential housing in the sub frame. As such
a sub frame is usually a symmetrical pair of left and right hand brackets,
then the differential can be positioned between them and these are easily
bolted together with spacers to ensure the correct width for the differential
to about 1 mm tolerance in width. This will compress the belville washers
enough to hold the main bearings in place. This makes for a very simple
and easy design.
It is then possible to add extra support for rubber seals on the outsides
of the taper rollers to prevent oil loss.
The sprocket is mounted in the place of the large crown wheel and the
sub frame is then adjusted for prefect chain alignment and cross braces
used for final alignment.
Chain adjustment will be needed, and the whole diff assembly can be
slid backwards on slotted mounting bolt holes and kept with adjusting
bolts , similar to those used for a bike rear axle. An alternative is
to use a rigid sub frame on the bike frame, and to use a slipper tensioner
on the bottom run of the chain. The slipper tensioner is the easier
option, as the chain does not need much slack, (unlike bikes with swung
arms or if using solid rear axles). Always set up the engine and rear
sprockets alignment with a NEW chain.
The diff will be open to the rain, but snug fitting plastic bearing
covers, possibly with felt seals will allow grease nipples to be used
to maintain reliable bearings.
The spinning differential body which holds the sun gears can be easily
covered in fibreglass and a small screw hole used to fill this with
about half a pint of hypoid gear oil.
The donor car drive shafts are not the same length, so the designer
can decide which to use, perhaps choosing the shorter props shafts if
living in a congested city, or the longer ones if living in the wide
open plains. If the diff is heavily offset, then use the prop shafts
The Escort wheel axles can then be mounted using their bottom radius
arms. The standard Mac Pherson strut is either mounted to a upper bike
frame assembly, or cut flush with the cast axle unit and a mounting
built to take an upper wishbone with separate shock absorber. See later.
Fully enclosed chains are possible.
A few larger machines use rubber tubes for the purpose which can be
modified to fit. By using a fully enclosed chain, the differential oil
will reduce chain wear, although it may be messy at the front sprocket
area. If too messy, simply allow room to regularly use spray-on chain
lube on the differential and chain, possibly with aftermarket automatic
chain oilers to lubricate the differential bearings and another automatic
oiler for the chain.
Alternatively fit a pan to catch the oil as it flings off the front
sprocket and include a small return pipe back to the diff housing.
Differentials are not pressurised, so a simple fibreglass covering
is that's needed to retain most of the oil. Where the sprocket reaches
the lowest part of the differential, splashing is guaranteed and the
oil level will not last very long unless well sealed. Scrapers and splash
deflectors will help retain oil. The best compromise is to enclose as
much as possible and use dual automatic oilers: one for the chain and
one for the differential.
For long term reliability of solid full width rear axle units, the outer
wheel bearings should be given a metal shield and well greased via a
The chain can run easily in rubber tubes or nylon lined alloy or steel
tubes bolted to the differential. This will keep much of the lubrication
in place. If a lot of oil is carried along the upper run, then an oil
drain cup arrangement can be incorporated into the lower front of the
lower chain tube around the sprocket to drain excess back to the differential
via lower run. This is not perfect, but every little bit helps. For
those who cover many miles but don't want to keep toping up the differential,
the ideal is to fully seal the whole, including the front sprocket.
The heavy oil used in differentials is there for the hypoid gears, which
are replaced by chain and sprocket, so a lighter oil is possible for
splash lubrication. The inner sun gears of the differential unit may
wear a little more, so always ensure any oil drip feed is to these as
well, should oil loss be a problem.
Engines with chain drive will need to align the engine sprocket to
the differential, wheels and the suspension to match the final drive
alignment. On some rare occasions, this may require shortening of one
side of the axle unit, or offsetting the engine in a custom trike frame.
Shortening one side of the rear axle unit will help position an axle
into reasonable alignment to the centreline of the machine. Independent
suspension rear ends make this a little easier.
Fewer problems apply to a prop shaft between engine and differential,
as the shaft will allow the engine and the rear wheels to be retained
centrally in the frame, with the misalignment taken up by the prop shaft
To stop a one piece differential / axle unit from moving left or right,
a Panhard rod is often used which is about two thirds the length of
the axle - or preferably longer. The rod is positioned on one end of
the differential unit, the other end mounted on the frame and kept as
horizontal as possible at mid point of movement. The Panhard rod is
usually on rubber bushed to allow the axle to move up and down without
leaving the centre line of the trike. The Panhard rod should be taken
from a similar car, as it must not buckle under severe cornering forces.
The fixed pivot on the frame should be positioned at mid point of the
suspension movement, so it will keep the rear axle centrally positioned
across its whole movement.
Leaf springs and other types of suspension have been used in the past,
but the standard concentric damper/spring unit seems here to stay. They
can be separated for ease of development, but are not usually worth
the extra effort. Leaf springs can keep spring height really low, eliminate
panhard rods and also prevent one piece rear axle/differential units
from rotating, but will need a wide, lower frame with more rear extension
which can compromise a clean design.
When used merely as a spring, leaf springs need not be positioned fore
and aft, but a single, evenly balanced leaf spring mounted across the
frame can spread the load to both rear wheels. It can be further refined
if an adaptable mounting is used.
There are many types of rear drives and axles which are indirectly
joined to the frame using a variety of methods, so check you know how
your choice of axle works and whether it will fit and integrate well
in the design of trike.
A rigid rear end is not worth considering.
Independent rear suspension is the better design for trikes, as the
system has lighter unsprung mass, should handle much better, allows
constant chain tension with easier full enclosure. The wheel bearings
of independent suspension are sealed and the differential unit can be
modified to fit within the removed swing arm area for standard bike
frames. It must still be capable of adjusting the distance between the
sprockets for chain wear, but suspension movement need not be considered
between the sprockets, so perfect chain tension is possible.
With many front mounted car engines, the drive is usually a prop shaft.
When shortening propshafts, always mark the alignment of the ends first
and only modify just one end, preferably where there are most balance
weights. Please note that the positions of the universal coupling pivots
are symmetrically aligned, so note and check it is replaced in the same
alignment. Then cut and check the end is accurate by a set square so
the end piece fits accurately. Reassemble using the marks and tack weld,
then make sure the shaft runs true initially, by rotating them between
centres. Nothing fancy is needed to make a basic check, just two thin
spikes to fit into the central centring pilot drill holes usually machined
in the ends of each unit. Adjust for minimum friction, then spin and
adjust the bare shaft until it balances. To spin fast, place a spike
in an electric drill and use a rubber flange on the spike to turn the
shaft. If the shaft is not balanced, vibration may trash the couplings.
For the final test, block the axles, remove the wheels and run the engine
in top gear to check the propshaft in situ. Very gently applying a marker
pen to a clean, rotating shaft may show up the high spots requiring
modification. Weld on sheet steel weights opposite, then grind down
the weights until vibration is eliminated. When true, fully weld the
weights in position and check again.
At this stage the machine is not being built, simply working through
the many requirements before figuring out where all the frame tubes
will go to best effect: It's called refining the engineering layout.
Careful consideration of the intended design will reduce the frame
tube count. A common example is a cross-tube doubling as the seat backrest.
If a McPherson strut cross-tube is positioned just a little behind and
below the strut mounting plates, then this will allow the passengers
to recline more comfortably. Not all suspensions will allow this, whereas
a few unusual suspensions will allow almost anything, and triangulation
can overcome most problems.
If something gets in the way, consider redesigning or using a different
component, so the trike will be as uncompromised as is sensibly suitable.
The classic Jaguar differential and suspension rear end is a classic
example which allows almost total design freedom.
Once the general structure for the frame is decided, start designing
how the parts will fit in, on and around the frame. The suspension,
engine and transmission mountings are often fixed, so how the frame
must fit to these is a first priority. Having the donor components in
place will always help, especially with the old engine and suspension
lugs, brackets etc.
Carefully sit between the bits to finalise where the rider and passengers
can sit, and where the frame can and cannot go. This in turn will decide
the position of the gearchange, footrests etc. Adding riders will increase
the load on each wheel, so make sure the axle loadings will be sensible
and fairly even when the trike is eventually ready to roll. Begin to
get a feel of where is the best place for the front wheel. - Just because
you have placed a concrete paving slab in the front of the assembly
for the front wheel, does not mean this is where the wheel will eventually
go, so place two or three pacing slabs to allow you to vary the front
wheel position as you refine the overall balance of the machine.
The frame itself will be most important, but must also take into account
the purpose of the machine when building a trike for people. Far too
many trike passenger seats are 'sit up and beg' designs.
Do not accept a second rate design. Trikes should be fun for all. A
frail 85 yr old lady found some trikes to be extremely comfortable;
easy to get in and out, and very comfy too.
Always take the occasional ten minutes to think of the weight on the
whole machine. Stand back and simply look, then contemplate the weights
and loads. Just stand and look, with a cuppa or a beer, not just for
a few seconds, but as long as it takes to grasp the overall feel of
the machine as it develops in the early stages.
Ensure approximately a quarter to a third of the weight is on the front
wheel, with one rider. Preferably the same with passengers, which requires
they should sit over the centre of gravity of the machine. If you have
the car seats, simply sit, relax, look at the bits laid out. Allow the
mind to do what great artists have been enjoying for hundreds of years
- free thought - nothing forced, nothing directed. This should take
at least one hot cup of tea to contemplate, or a beer etc. Preferably
a long, relaxing afternoon.
Keep the notepad handy and make notes before the best thoughts are forgotten.
When loaded with passengers, try not to have too much extra load on
the front wheel, as the rear end is invariably the main load carrying
area. On heavy front ends, keeping the extra loads to the rear will
help with the steering and manoeuvring in car parks etc.
By mounting the passengers just in front of the rear wheels, the overall
load on the three wheels will remain optimised for better handling with
and without passengers. This also allows the passengers to sit low and
more comfortably, nestled between suspension and frame. Being lower,
the centre of gravity will be less prone to roll the trike, so the machine
will handle much better, improving handling and comfort, especially
around corners. Another major advantage with low riders, is that aerodynamic
drag can be reduced, allowing a higher top speed and the passengers
will get less wind and rain buffeting, - very important on long journeys.
For those with many kids, consider the old USA design, where the boot
(trunk) would open to become an extra pair of seats, with the boot lid
folding backwards to become the backrest. Occasionally referred to as
a 'rumble seat'. Many modern versions of this are possible. A couple
of recessed foot steps, aircraft style, will assist their entry and
add a little extra style.
It may be necessary to take the design process a stage further.
Although most trikes will be quite good using standard components as
intended by the manufacturer, and some atrocious machines still get
used daily, it is nice to be able to see the underlying design when
looking at the machine laid out before ones eyes. Therefore, a little
theory will help develop the plot and improve the possibilities.
As a general rule, it is often advised that the centre of gravity of
a three wheeler should not exceed thirty five prevent of the distance
from the two rear wheels towards the front wheel. That is to say, the
overall weight of trike and rider(s) should be closer to the two rear
If making or modifying engine layout or suspension, consider the following.
Steering and Balance.
I have ridden various trikes and hate those that don't handle, as there
are far too many out there which are absolutely appalling.
Some trikes have out performed sports cars in the twisty bits.
That's not to say all trikes can be superb handling machines, but there
really is no excuse for a poor handling trike.
Trikes can turn better than some cars - if well designed. This is for
many reasons, mainly lower mass and how this mass is positioned relative
to the wheels.
With good balance, a traditional single front wheeled vehicle will tend
to oversteer; that is to say, it tends to turn further into the corner
than required. If the single wheel was at the rear, it would tend to
understeer, which is usually considered safer for ordinary drivers and
for example, usually the safe set-up when handed LeMans car to try if
new to the racing game.
When cornering with a single front wheel, where oversteer is a problem,
then accelerating out of a corner tends to work better, but braking
into a corner tends to de-stabalise a trike. This is reversed for a
rear single wheel.
This is not a perfect description, as it also depends upon whether the
weight of the engine is at the front or at the rear of the trike.
Unfortunately for a single front wheel, the forces involved in braking
are higher than accelerating, so making sure the ability for a trike
to brake when in a corner must be very carefully considered. When further
compromised with a narrow front tyre, with a round profile which tends
to limit braking ability, then problems can accrue. Hence, like a bike,
brake in a straight line before the bend and accelerate out, unless
it is poorly balanced.
When cornering, the designer must realise that if sufficient traction
so the wheels do not slide, then the weight distribution of the trike
will determine how it handles. When turning a corner, you are moving
heavy loads such as the engine and riders around a corner. The heavy
bits will either tend towards the rear or front of the trike. Making
them go around corners happily will depend how they relate to the wheel
The more the centre of gravity is towards the front of the machine,
the greater the tendency to understeer; it will tend to move towards
the outside kerb.
The greater the centre of gravity is to the rear, the greater the tendency
to overtseer; it will want to tuck into the turn and is usually the
more dangerous option. (If you are ever offered a test ride of a very
high performance machine such as a race Ferrari, then the mechanics
will usually set up the steering to understeer, so you don't get into
too many problems on the test track.)
When considering the overall way your machine will behave, it is not
the way the steering works, but the way the masses act in relation to
the wheels. Getting the mass central to the wheels will help the trike
handle well in corners, even when accelerating and braking heavily.
If making a stonking brute for serious thrashing, then it will be difficult
to minimise understeer if using a V12 at the front, unless a long wheelbase
can keep the engine unbelievably close to the rear.
With a poorly handling trike, perhaps for show use, then there are
suspension and geometry tricks to ameliorate the suspension and steering
to reduce the effects of imperfect weight distribution.
Now a short guide to what you should be looking at when considering
the overall layout of your trike.
Heave up and down.
Stiffer suspension makes handling better, but gives a harsher ride.
Therefore trike comfort is dependant upon many factors. If standard
components are retained and are in good condition, most problems from
suspension bounce and rebound etc will be fairly acceptable. When changing
to different wheels or suspension arms and links, the dynamics may alter,
but the natural frequencies of most standard and slightly modified suspension
systems are usually within acceptable limits.
Most acceptable systems allow the springs to compress about ten to fifteen
percent in normal riding conditions. If the springs do not do so, choose
lighter springs, or re-position these items until they act so. This
slight initial compression is to allow the suspension to already be
in an active state, allowing both up and down movement so the wheels
can comply with all normal road irregularities. If the springs did not
compress slightly under normal conditions, they may act as a stiff block
until a large bump is encountered, and this means a very harsh ride
and far inferior handling.
For a lightly loaded rear end of a front engined trike, the weight of
a couple of passengers will compress the suspension further, which may
cause problems of a light rear end, such as a trike with the engine
at the front. For this problem, use springs and dampers from a similar
situation, such as from the rear a light family car which also has a
When using a front engined car engine and suspension, placed to the
rear of a trike, the load is fairly close to standard. In practice,
this rarely needs much, if any adjustment.
Next time you are beside a car, push down on a front wing, and also
on a rear wing, to see how it reacts and behaves and try to get your
trike to be in the same ball park. Decide if the engine mass affects
the movement appreciably. Get to know what is happening, so you can
also check this against your trike as it's being built. If possible,
do the same on a real sports car.
The amount of sprung to unsprung mass is more important on a lightweight
trike. On a heavy machine, the greater mass usually absorbs the forces
of maintaining the wheels in contact with the road. Trikes are usually
much lighter. The unsprung mass of the wheel, tyre and half the suspension
is going to have a larger, negative effect on a lighter chassis. It
is best to keep such weight low, such as inboard discs, alloy wheels
and such like wherever possible. This is especially important if aiming
for a good handling, comfortable, lightweight machine. This is further
refined by adjusting the damping rates to suit. Where the shock unit
is rebuildable, this may require changing the damper fluid to get better
Do not get overly cautious as the spring rates often do not need to
be changed if they compress a little at normal static road loadings.
Pitch fore and aft.
Fore and aft pitching is a problem for many trikes, especially those
with tall, front engines while braking, where the nose of the trike
dips down. This causes minor problems with geometry and suspension.
Antidive is a secondary solution, but it is better not to have the problem,
or at least to ameliorate it from the outset.
Therefore it is important to keep the centre of gravity low and nicely
positioned between the front and rear wheels to reduce most pitching
problems. Poorly designed trikes with this problem can be greatly improved
with leading link suspension systems or hub centre steering.
It is not just the suspension which causes comfort problems. The classic
VW engine hanging out the rear will give rise to wheeling tendencies,
especially if a fierce clutch linkage is used.
Yaw side to side.
The ability to quickly set a trike up into a turn from a straight line
is much faster than most cars. The ability for the heading to change,
- that is to point to left or right faster, is called the yaw response
time. With lower mass and reasonable road holding, the trike can have
a great advantage. As steering involves the front wheel, a single front
wheel trike is not as good as the two wheels front, one wheel back version,
but the conventional trike still remains a good contender in the cornering
The trikes lower mass enables the forces available to redirect a trike
to be more responsive. The polar moment of inertia (force to move a
mass through an arc) can be lower on a trike than a car, hence cornering
is greater fun. Polar moment of inertia can be considered as a 'dumb
bell', as used in weight lifting. If the weights (mass) are at the ends,
turning it is difficult. If the mass was in the middle, if would be
easier to turn.
The best polar moment of inertia is if the centre of gravity of the
whole mass is positioned fairly central with the wheels relative to
a sensible wheelbase. A front engined trike such as a V12, will have
more of a dumb bell action: Whereas a mid engined trike with the engine
and passengers just forward of the rear wheels will be very nicely balanced
and allow the steering forces to turn the machine much easier and will
be a lot more fun on twisty Dartmoor roads.
When cornering, there will be a rolling action towards the outside of
the turn. The mass of the trike further above the ground will cause
greater roll. Roll works in harmony with the suspension set-up, but
the lower the mass is to the ground, (low centre of gravity) the less
the roll and the more effective and subtle the suspension can be.
From a safety aspect, there is less chance to roll-over if the centre
of gravity is low. In plan view (looking down from above), draw a triangle
between front and rear wheels. The closer the centre of gravity is to
the centre of this triangle when seen in plan view, the less the roll
effect. Unfortunately this can be improved by moving the centre of centre
of gravity rearwards, by positioning the heavy bits to the rear, but
not always at the expense of poor weight balance required of a small
front tyre. Therefore in some cases, it is better to get the best polar
moment of inertia and accept a little more roll. To do this, get the
centre of gravity proportionally between front and rear axles in such
a position that the heavy bits are acting fairly evenly on all wheels,
then adjust for the choice of front tyre.
The use of an anti roll bar is designed such that some of the forces
involved when cornering are transferred from the inside suspension to
the outside suspension, to limit the amount of roll. Roll bars are common
on most modern vehicles and should be employed on trikes and always
on taller trikes using motorcycle frames.
When seen from the front, if a rear wheel leans outwards at the top,
it has a positive camber angle. Leaning in at the top is negative camber.
One piece rear axles cannot be modified.
Independent rear suspension can be adjusted for camber, and usually
have a longer lower wishbone than the top wishbone to enable the camber
to change as the suspension compresses, or use McPherson struts or similar.
In normal use, the wheel should be vertical or have a slightly positive
camber, sitting square in the ground and ideally positioned for straight
driving. When cornering and the suspension compresses, then the outside
wheel should ideally become slightly negative in camber, to keep the
outside of the tyre fairly normal with the road and to help reduce tyre
wear and maximise grip.
Centre of gravity.
A lot of the above has mentioned the centre of gravity. To find the
centre of gravity of an item, simply hang it from a point and draw a
line vertically down from pivot. Then do so from another point. Where
they meet is the centre of gravity. For a piece of unusually shaped
card, use a pin through the item, and draw a vertical line down from
the pin, then a different point on the card, hang and draw another line.
Where they cross is the centre of gravity, where it should balance perfectly
well. Unfortunately for a trike, this is not so easy.
As the trike has not been built yet, is impossible at this stage, only
an approximation can be done. The further the engine and riders are
to the rear, the further the centre of gravity is to the rear. Likewise
for the height of the components off the road surface. This is then
modified during test riding.
Will it want to Roll or Skid ?
As a general rule, it is possible to find out approximately if a machine
is going to roll or skid first. This is important to those who are going
to thrash their machines along British country roads and Alpine passes.
As this is an early stage of the design, then general approximations
to overall weight balance of the trike can be made.
With all the parts arranged on the garage floor, weigh them and work
out the amount of each load on each axle. If the engine is half way
between front and rear wheels, then half will be on the front wheel
and half the weight split between the rear wheels. Mark it on a piece
of paper, to add up all the basic weights on the trike. Do likewise
for all the other bits including riders. Then work out roughly where
all this mass will be along the centreline of the trike. Mark this guess
of the centre of gravity on the floor as 'X'.
Next draw a line between front and a rear wheel, to go though the middle
of the tyre contact patch where they touch the ground.
Now make a reasonable guess of the height of the centre of gravity above
the ground. This can be guessed by averaging the centre of gravity of
the engine, riders etc, to get a rough idea of the whole machine with
riders etc. It may be a few feet above the ground for an average machine,
perhaps more, hopefully less.
The final step is to draw a circle on the floor, using point X as the
centre. Draw a circle with a radius the same as the height of the centre
of gravity. (in this example, two feet radius to give a circle four
feet in diameter.) If the circle goes outside a line drawn between the
wheels, it will tend to roll, but if inside, it is more likely to skid.
The further the circle is inside the line between the wheels, the safer
the machine will be, tending to skid rather than roll over.
See also how to check the centre of gravity of the basic rolling chassis,
Tyre adhesion will also effect the roll / slide situation. Modern tyres
often have the ability to retain friction with the road up to eighty
percent of their load. This will vary with roll, etc. and if problems
occur, then simply use less efficient tyres to allow the tyres to slide
before rolling the trike over. Tyre pressures will also affect this
In some conditions, the inner wheel may tend to loose adhesion before
the outer, due to the lighter load causing it to lift off the road,
and the diff will then transfer little or no power, causing the trike
to slow. Loosing power in this manner is dangerous. This usually causes
a line change, and can be considered a desperate warning just before
things get seriously out of control. If considering such problems because
you are a serious thrasher, then seriously consider limited slip differentials
as used in some Jag and Porsche rear systems and ideal for over powered
Refining the basic layout.
Once the centre of gravity requirements for a trike are well considered
and then refined, then the suspension can be used to improve the plot,
usually by optimising the engine position and keeping the load low.
The tyres are the main point of control with the road. The way tyres
are controlled is by the suspension. This means the load is carried
by the springs, the damping control by the dampers, and the way it moves
(the geometry) by the suspension arms and rods etc. The way the suspension
moves can be designed or modified such that the wheel moves in a positive
manner, to control and augment the natural steering of the trike.
When cornering, the outside wheel takes most of the weight and the spring
compresses, lowering part the trike. The design should be such that
the suspension can keep the wheel level when cornering. This is usually
done by using uneven suspension arms to control the wheel alignment
as the suspension moves. An anti roll bar can be used to reduce the
roll of the chassis.
When cornering, the suspension moves as the trike rolls, and when seen
from the front, the position from which the wheel seems to arc is called
the reaction point. If a line is drawn between the reaction point and
the road contact point on the tyre, then the place it crosses the centreline
of the machine is called the roll centre. The roll centre should be
as low as possible for trikes.
McPherson struts usually work in a similar manner, but as they are
from the front of the donor machine and therefore used for steering,
the centre line of the strut is also designed as the steering axis.
This axis may not be directly in line with the centre of the tyre contact
point, causing the steering under the strut to want to pull the wheel
off line. As this is normally on a two wheel set-up on both donor and
on a trike, the effect of both sides is evened out. When the machine
corners, the more heavily weighted side has greater effect, which should
be designed to act in a positive way. Placing the engine and suspensions
systems of a front wheel drive car to the rear, as in a trike, these
actions will remain in play. But what is good for the front of a car
is not always the best for the rear of a trike. Normally this is not
of much importance, but on powerful machines such minor imperfections
should be recognised, if handling becomes problematic.
In general, a lot of theory can be applied, but not always necessary,
but a basic understanding helps.
The standard components of most cars are usually quite acceptable for
most trikes, but can always be improved. The tyre sizes, aspect ratios
and pressures will also affect the steering. Within sensible limits,
many items can be adjusted to refine a machine.
Getting the balance right is not easy, and often best assessed by riding
as many trikes as possible.
Test ride while understanding what exactly what a test session is looking
for. Write the parameters on a piece of paper and choose road conditions
to test each one. In an ideal world it is preferable to have a few different
types of trikes available for back to back testing. With a single test
machine, simply set standards high and expect the best, whereupon the
problems will often be seen more easily.
Bear in mind the understeer or oversteer, suspension, roll, dive, braking
around corners, pulling away uphill, steering stability or twitchiness
and the general ability to be thrashed through twisty roads. If the
test session is short, it is best done in an unused, large carpark,
so the limits of roll or slide may also be assessed, with plenty of
room for a safety run off.
Take time to assess the various requirements, noting each in turn, then
understanding how they will all work in best possible harmony.
Have a general look at the machine before riding it. Start by pressing
down on the rear suspension to see how stiff or soft it is. Guess the
centre of gravity. Then make a guess as to how you think it will handle.
Then ride it. Afterwards, decide if your guess was correct and modify
your thinking to suit. You will probably want to look again at the machine
to see why it handles thus.
No machine will be perfect, but another refining stage is to get the
many conflicting aspects of the design sorted into the best compromise
as possible from the outset, then by gradual steps, improve the design
by various means.
Having the facilities to make complex engineering parts from scratch
is great, but few have such luxuries. Searching out parts and ideas
from other vehicles, already built, or closely manufactured to the intended
purpose will save a lot of work. This will also give greater reliability
and make parts replacement so much easier.
There are perfectly good solutions to most problems somewhere in other
vehicles, or perhaps in divers other machines, so keep eyes open and
use imagination. It should all fall in place with a little time and
When starting to use parts from many machines, use a permanent paint
marker pen to ensure the make, model and year of the donor vehicle is
permanently on the item. This way it is possible to replace or repair
with minimal hassle. It is easy to forget much about the components,
so make life easier from the start with a simple parts list.
Never modify a standard component such as engine mount or prop shaft
until the last moment, as the design will change many, many times.
Once the engine is positioned on the garage floor relative to all the
other items in the best possible compromise, then it is time to consider
where you will start building the frame.
(Engineering is always a compromise in a search of perfection.)
Car engines can, and do leap about in their mountings, so keep the original
rubber mounts for the engine as these will reduce the chances of frame
If making special engine mounts, they should be 'tuned' to the engine
vibrations, to minimise the worse effects and be able to resolve the
torque reaction from the engine into the frame. Always use any original
engine steady bars in the same way as used in the car, as they are not
always obvious in the way they should be mounted.
This Jag efi V12 engine is mounted on just two main rubber blocks
the size of a fist, with a simple spring at the rear of the gearbox.
Very simple and very effective, but then, V12's are delightfully smooooooth.
This may sound obvious, but make sure that parts can be reached easily
and that it is easy to remove the engine. Some poorly designed trikes
are atrocious to work on. If it is necessary to remove the engine to
set the valve clearances, try again. All maintenance should be simple.
In an ideal world, it should be possible to lift the standard engine,
complete with mountings and all ancillaries, out of a standard car,
straight into the trike with just a couple of friends, a plank and some
It is not unusual for car based trikes to get through many engines
a year, being thrashed regularly as their owners demand the same acceleration
as their motorcycle.
Wherever possible, make the engine easy to replace. For those who wish,
the frame can be designed to have removable sections for extremely easy
engine replacement. Far too many trikes either need the engine to be
stripped for removal, or to be hoisted out from above, or fitted from
underneath. Make life easy for yourself. If design problems get bad,
at least make it easy to drop the engine and simply lift or roll the
trike off. An adequate compromise is to be able to block the rear wheels
and lift the front wheel very high, to extract the engine from underneath.
Even a five litre V12 can be designed for easy engine removal and yet
such engines are easily designed to flex safely upon their standard
engine mounts, albeit with attitude to enhance the experience.
Ordinary engines should be an absolute doddle to maintain and replace.
If the popular transverse engine is mounted normally on its rubber blocks,
then most engines can be removed easily. The rear of trikes can be simply
removed or unbolted for total and easy access and removal. This is particularly
useful for changing the clutches of some transversely mounted engines.
If the engine has a turbo, complex fuel injection system and loads
of computers and electrical junk to make it work, then consider mounting
some complex assemblies in modular form so they are both waterproof
and easily removed as discrete units to allow a complex engine to be
more easily repaired or replaced.
Once the rear is reasonably well defined, the general layout of the
frame must know just where the tubes are to end at the front. The front
end tubing is important for trikes, as not only is structural integrity
important, but the style is also a critical component of the design.
For many engineering or style reasons, the steering head angle (known
as castor or rake), is up to the builder. Cars use about 2 to 3 degrees,
bikes about 20 to 25 degrees from vertical, especially if using telescopic
forks. The best is to find trikes which handle well, then find out why.
There are no real hard and fast rules. You may be surprised what you
can get away with.
Some of my road-legal hubcentre steering motorcycles have been ridden
quite happily with almost vertical steering angles, while some of my
friends severe customs seem to get away with extremely long forks.
If in doubt, don't go stupid, stick to what looks right. That is, the
same as bikes, especially if using standard bike forks. Steering head
angles are often chosen to reduce stiction in telescopic forks.
Extended forks are weak on bikes and even more so on trikes, especially
A rake bigger than normal as on extended forks may occasionally lead
to an enormous turning circle, so at least make sure reverse gear is
easy to find to get out of tight situations. As trikes do not lean,
they can get away with less radical front tyre profiles, allowing a
greater foot print to take a larger load while maintaining sensible
Good design will allow even a long raked set of forks to have a sensible
amount of trail. Alternative front ends are mentioned later.
With the above in mind and much of the rest of the text well considered,
plus with everything blocked up and in place, start to design the frame.
Take at least a week to design a couple of frames, preferably a month
or more with a difficult design. The average is about a couple of weeks
to a month, but for some, it takes so long that rust gets there first.
Do not give up easily, but definitely do not rush the design.
As the design develops, you may soon fall into the trap of following
a single, obvious frame design. Use your drawings and trace out at least
three different frames. At least one frame design should be radical,
- really off the wall, blue sky thinking.
The final frame will probably be a mix of the better aspects of each.
Always work in all three views, side, plan and front views, as what
seems good in side view can be awkward or dangerous in front view. It
is a process of continual refinement.
When satisfied, you will surely want to make it better a couple of days
later, in the light of inspiration when daydreaming at work. Talk it
through with friends when they call, make a cuppa and stand around in
the garage discussing, with all the bits arranged as intended. It happens
all around the world.
Always start frame design with imagination, with a feeling of the weight
and position of the components. Then imagine just what is happening
to the main components. Get a feel of the whole machine. Write down
good ideas immediately so they won't be forgotten later. (All too easily
done.) Even experts forget superb insights and possibilities for want
of a piece of paper. Backs of cigarette packets and napkins attest to
the ambiguous nature of the design process.
From the start, mark in the steering head, engine mounts and suspension
positions which are often demanded by the chosen engine and suspension.
Carefully rearrange or compromise anything which gets in the way of
a strong frame with good weight distribution.
Play around with the components until they look about right. To get
the forks positioned (if used), simply rest them against a chair, or
strung from the roof by the handlebars. Use modelling clay or tape to
keep the front wheel in position on the floor.
Tubes that are spread wide and well supported to make various triangles
will give some of the strongest frames.
Design the main tubing to connect the steering head, engine and suspension
first. Then subtlety add any secondary tubes to improve triangulation
to prevent these main tubes from flexing or buckling. For simplicity
and strength, main frame tubes should be one length from front to rear.
Wherever possible, make the frame design a mirror image each side, as
this makes for easier manufacture and alignment. More importantly, this
also keeps any frame flexing even, creating less distortion and better
handling under heavy loads. Try not to have all welds grouped close
together unless well gusseted.
The style of the frame is an open book, there are no all-encompassing
constraints other than common sense and safety.
Only 'mass produced' trikes have any similarity in design. The standard
trike is often far less than the art form it could be. The exceptional
trikes, - and there are quite a few select machines out there, - have
an overriding theme to their form, with form being drawn into the function
in a positive way.
An exceptional trike will naturally draw people to it. Occasionally
a trike does it so well, while making a bold statement. This is art,
possibly even aggressive art. A trike should be a statement, be it parked
outside a pub or cafe, conveying bridesmaids to the church, on show
in an exhibition, or being thrashed around a corner in a power drift
past open jawed pedestrians.
Trikes need not be simple front ends with tubing to hold bits together.
They can be gracefully swan necked in the Swedish style, perhaps styled
as an alien artefact, or a techno or engineering tour de force. As car
based trikes are not afraid of a few extra pounds of weight, consider
using stronger tubing if a 'swan neck' design is preferred.
Trikes should always be art forms and a little extra strength in the
right place will keep them looking great.
A few more weeks drawing radical designs can often change the whole
path of the project.
Then sweat blood to keep and enhance this style so it will also stand
out from the crowd when built.
Whatever is designed, do not be happy until your sketches stand out
from the page.
Occasionally, the concept shouts at you from the page that it must
be built. You will know when this happens.
Everyone has at least one exceptional idea hidden inside them. This
will surely need to be built for the real world, so engineering is the
With the sketch pad in one hand and a tape measure in the other, study
the components laid out in the garage and consider the following.
Looking down from top.
How much weight is on the front wheel with rider(s). Too much, too little?
Sketch in the radius arms and where they will mount to the frame. (to
prevent the rear wheels jumping ahead of the machine when opening the
throttle, or flying off behind when you apply the rear brakes.)
What part of the frame actually supports the weight of the trike at
the top of the shock springs.
What will keep the top of any McPherson struts from flexing fore or
aft when accelerating or braking, it may be a light force, but it exists.
Will the bracket support or foul the rear of the passenger seats, or
can it be angled back and down slightly with extension brackets.
Where will the gearchange linkage fit relative to the riders seat.
Will the rider be able to reach the handlebars or is a linkage needed.
Will there be enough room for passengers and a trunk. (boot).
Are the riders and passengers feet going to be in the right places.
Looking from the side.
How much weight is on the front wheel.
Will the rider be comfortable, and how low can the seats be positioned
without compromising strength, or will the rider be hanging onto the
handlebars like a flag in the wind when thrashing corners.
Will the steering head bend upon landing after the first wheelie or
over a hump back bridge. Steering head extra support tubing and fillets:
size and shape.
Are the tubes from the steering head to bottom of the frame securely
positioned at their low points and what type of fillets or gussets are
needed to maximise strength.
Is the ground clearance adequate.
Are wheelie bars needed because you decide to use an air-cooled Porsche
engine hanging out the rear.
Will emergency stops become dangerous.
Are the riders and passengers feet going to be in the right places.
How can an exposed engine be made to look better.
Looking from the rear.
What exactly is holding up all the weight. Decide what is actually holding
up the top of the rear shock absorbers and the springs. Also decide
what is preventing the shock mounts from being pushed up and inwards
when landing off a hump back bridge at fifty miles an hour.
Is the ground clearance adequate.
Is the engine easily accessible for replacement.
Where will the gearchange linkage fit. - Is there a suitable gap between
gearbox and sump on a transverse engine. Can it run safely under or
over the engine in a straight line towards the rider, or need to be
routed over the motor or gearbox.
How can an exposed rear engine be made to look better.
Looking from the front.
Can you see the side lights.
Will the passengers be safe when cornering.
How will cooling air flow be captured and directed to the radiators.
How can an exposed front engine be made to look better.
Also consider the general style from all angles.
Will the passengers look good for the camera, or are they stuck like
flags in the wind. Will the radiator ducts blend in and around the frame
When not using safety belts, the passengers should be considered as
dumb, unsecured loads, especially when braking or powering around corners.
Also give them decent foot rails to take the braking forces. Seat side
support or hand rails also offer a chance of survival.
With the above in mind, the main structural areas are now marked on
the drawings. These are then gradually refined, especially the steering
head, engine mounts, rider load points. This is the important part of
frame design, but the engine and frame component mountings will decide
and constrain much of this work.
Also mark in the forces of both the static loads and the full acceleration
and braking forces, and when landing off a jump. Mark them on the paper
as arrows if necessary, to maintain the most effective use of such drawings.
Marking the arrows on the sketch pad proportionally large to the forces
involved, helps direct the subjective design of the frames form and
structure. A yellow felt tip pen will allow the drawing to be modified
over these underlying guides to highlight what will be happening to
the overall structure.
Always try to break the design in your mind.
Where are the weakest places, where are the places of greatest load.
What happens to the frame when the bike is cornering hard with a full
load? What will break first?, What happens if.....? Get to fully understand
the designs and ask everyone what they think and how they would design
the frame. This gives more options and time to spot any hidden problems
in the design at an early stage.
Overall design and bracing will require careful design of the chassis.
Computer aided finite element analysis can help. Those without access
to such assistance can model the structure and test load until inappropriate
The main tubes are often four long tubes with engine and suspension
fittings often mounted directly.
On a recent V12 the front frame was essentially a massive Norton Featherbed
frame. On another, the frame was four almost parallel tubes with the
flat four engine slid in between them.
If you can make a real frame, you can make a wire model. It doesn't
have to be accurate, just use solder and straightened paperclips or
similar materials. With a soldering iron and some wire, build an approximate
model of your frame, then load it to see where it breaks. If you have
a small soldering iron, then straighten some paperclips. If you have
a big soldering iron, then scrape the flux off a few arc welding rods.
Don't just see which wires bend, but also the direction that they bend.
Model the engine and suspension at their mounting points to apply the
loads at as required. See what the engine and suspension mounts are
going to do. Modify and try various designs until feeling confident.
Do not confuse poor soldering with poor design. If you make three different
wire frames, comparative tests can be used using standard weights such
as bags of sugar balancing precariously on the structure for spot loadings.
Load and twist it in many ways so it distorts or breaks. An evening
spent like this tells you loads (pun intended) about your design.
Consider the frame as a means of holding all together and the forces
under acceleration, braking and cornering. The rider and passengers
are just loads, whereas the engine and brakes are much more interactive
parts of the structure and apply the larger loads and forces.
If you don't like soldering, then get some drinking straws and blue
tacky office putty and make a lightweight test rig. If you want to know
what type of loads are acting on each weld, then make a model from straws
and blue tack, then load gently to see how the structure pulls apart.
If a trike is to take a few months or more to build, just one evening
studying and testing the structure is always time well spent. The final
frame design will probably be a mixture of the initial frames envisioned.
More importantly, you will have much greater understanding as to what
is happening to each part of the frame. Design it many times, so you
need build it only once.
Which would you prefer - build a model and find out problems on the
kitchen table, or after you have welded up the real frame ?
Reading the way the designs finally fail will highlight the probable
way the forces are acting and where. Scale models do not always model
truthfully at full size, but anything which gives insight will always
help understand the forces and their problems. Final testing will be
at full size, although the loads are much higher, which can get awkward.
See testing later.
Passengers deserve consideration, so always make your machine comfortable
and safe. The best trikes are very comfortable for many hours, often
employing modified car seat components. The best trikes should have
the passengers luxuriating in comfort comparable with the best cars,
with plush armrests and well angled foot rests. Your grandmother is
usually the best tester for comfort.
Trikes do not lean, so thrashing around corners will have the rider
hanging off the handlebars like a flag in a tornado. This is acceptable
in cars with side supports on their seats and doors. But trikes with
unsupported riders can cause steering problems of rider leaning inwards
against the centripetal forces while trying to steer. Therefore ensure
the riders legs and butt are positioned to handle excessive twisty lane
thrashing. For the rider, the handlebars can be hung on to if the pivot
is fairly central between the grips, but if the handlebars are long
pull-backs, things can get annoying, so consider the design well.
Monster amplifiers and cup holders although not compulsory, may also
be considered, as some superb trikes are sometimes naturally used for
posing on boulevards. Not everyone has serious thrashing as the main
goal, for others a trike is used for daily transport. If polished walnut
trim, connoly hide and champagne is the style required, then go for
it. Trikes are designed and built to be enjoyed. See sculpting later.
All frames will differ. The problems with the Alfa 1500 flat four engine
meant the lower frame rails will have to run partially under the front
of the engine, but with the main support tubes over the engine to allow
engine removal. The frame will have four main tubes from the steering
head, triangulated with smaller tubes in between, like a space frame.
A Ducati trellis is similar. Two tubes run above and two tubes spreading
wider and lower to hold the engine mounts. The upper tubes will let
the rider sit astride them, then have hidden box section support tubing
widening out and up to the upper suspension points at the rear. The
suspension is mounted to the frame at the top. As the suspension is
pushed upwards, a cross member will prevent them folding. The radius
arms are mounted on the lower tubes near the engine in a rubber bush
at the front, near the clutch housing via welded brackets. This was
later changed to a combined radius arm and anti roll bar to improve
strength and reduce complexity. The rear swing arms pivot near the gearbox
in the original bushes. The upper arm is also the suspension unit, fitted
to the frame using the original rubber block. The biggest problem with
the Alfa was that the engine will tend to push out of its rubber mountings
when braking or accelerating hard. A rubber mounted rod was chosen to
transmit the braking and accelerating forces between the engine and
frame. This was later replaced with a small suspension A-frame as it
also prevents sideways motion. Engine vibration is not transmitted as
the rod is placed neutral to the way the engine vibrates. If needed,
a triangular engine brace will allow an engine to move without misalignment.
All the parts you need are available, they just have to be discovered
and decided how to be used to advantage in differing ways.
For all designs, there are many problems, but their solutions are not
always obvious. Spend time to check the various possibilities.
On most trikes, the front end is usually the steering head, although
hub centre steering and other options are also available. The distance
from the steering head to the nearest upper and lower engine or suspension
mounting points will usually decide the general shape of the front of
the frame. In plan view, the width should be reasonable, allowing the
rider to straddle the frame comfortably. In side view the front may
not look quite right with straight tubes, so tubing may need to be bent
for giving a better shape to the tubing. Trikes with rear engines often
look good with a gently reducing frame taper or swan neck, but this
must be strong. If the steering head support tubing makes a triangle
when seen from the side and from above, then this is unlikely to flex,
with only a few fillets or gussets needed to keep the head stock from
distorting under load.
Extreme swan necks may need extra support near the headstock to prevent
distortion. For those who want to keep the clean lines on their front
tubing, the usual side fillet plates can be replaced with a much stronger
central fillet plate between the frame tubes. This may need to be fully
welded to the steering head before fitting to the tubing, so that it
is welded securely in an area otherwise impossible to reach.
Trikes with engines at the front will often naturally have a well supported
head stock as they often employ tubes over and under the engine, which
naturally curve up to form a well supported head stock.
Hydraulic pipe benders can be hired. When bending main tubes which
are also cosmetic, make sure the hydraulic benders formers do not make
scratches or other imperfections. A light polishing of the formers with
emery cloth or wet and dry paper or a flap wheel does no harm, and if
pampering the tubes, consider a nylon cloth lining. Consider using sheets
cut from old plastic oil containers, as the HDPE (high density polyethylene)
is a superb material, as used on replacement hip joints and takes high
loads with minimal abrasion.
It is not necessary to make just one bend in the frame tube. A series
of gentle bends can enhance both the styling lines and riding position.
As the rear of the frame widens past the front rider, the tubes can
sweep up towards the top of any shock absorber mountings, but these
may often compromise passenger seating. Secondary or alternative upper
frame tubes, running each side of the engine can usually support separate
triangulated suspension tubing which clears the ideal passenger seating
In both plan view and from the side, the main tubes must not be able
to spread apart under load, so upper and lower central cross tubes are
often used. When designed badly, cross tubes can prevent engine removal
and cause other annoying problems. It is better to position two well
spaced tubes for an easier life than a single tube to save a little
weight. Alternatively one very large frame tube may make servicing easier.
The lower frame tubes will usually support the radius arm loads and
must not spread apart under load.
The Rob North Trident frames show what can be done with a tube bender.
Assuming a four tube frame with motorcycle forks : Take careful note
how the main tubes from the steering head will flow backwards and downwards
to the obvious engine mounting points. There may be a problem with decent
seating and so the upper tubes may need to curve low to allow the rider
to straddle them comfortably, and then up to the upper engine mounts
or rear upper suspension points. If the upper tubes are low, then the
lower tubes must be even lower to allow a decent distance between them
for structural strength. If the tubes were too close together, as seen
from the side, then the front end would want to bend upwards and collapse
the frame. If the tubes are close together, then consider a trellis
design of intermediate strengthening as seen on mass produced roof frames
in sports halls and cheap conference centres. This is a pair of tubes
with an intermediate zig zag to give intermediate triangulation to prevent
bending and collapse. This applies to both side and plan views.
Like many trike engines, the Alfa engine was front wheel drive, so
the original steering linkage is stripped to use just the inner cross
shaft which holds the inner steering ball joints. This shaft is welded
to a frame bracket to prevent moving left and right, and positioned
in the same way as the original, so that up and down suspension movement
will not affect wheel alignment.
It is often seen that the rack outer retained for easier mounting, with
the steering shaft stub welded to prevent movement. The best method
is to retain just the inner rack shaft and weld mounting brackets directly
onto it near the ends for greater security and lightness.
Retaining and fixing the steering linkage is very common on trikes and
if done properly will allow adjustment toe-in of the rear wheels. This
is important during testing so always build it so it can be adjusted,
usually at the outer ball ends. The angle of the steering link arm should
parallel the drive shaft or lower wishbone link, as seen from the rear.
Toe in, is when the wheels point inwards slightly, usually measured
in degrees, or in differences in millimetres between front and rear
of the rear wheel rims. Toe out is simply the same, but the wheels point
out towards the front of the vehicle. Camber is the amount of lean from
the vertical on the wheel, as seen from the front. This is often easily
noticed on some formula one front ends. A simple ball park position
is to set the wheels straight ahead and straight up when normally loaded.
From this the toe in can be adjusted during testing to get the best
handling. The camber is best left as vertical for best tyre wear in
a straight line. The upper mounting of the suspension could be given
adjustable positions to allow the camber to be adjusted, but is rarely
applicable for most machines unless building your own suspension.
There are many variables which decide the optimum toe in or out and
the camber, such as when cornering, where the outside wheel is the most
heavily loaded and can take advantage of a little toe in or toe out
to help steer the machine should it exhibit oversteer or understeer.
Under power, the driving wheel will want to gain traction in such as
way as to cause problems in poor suspension, where toe in or out can
counteract problems. Camber could be set-up so the outside wheel in
a turn, when it's suspension is more heavily loaded than the inside
wheel suspension, then the outside wheel will lie flat on the road for
maximum grip. There are many variables which are mentioned earlier and
can be studied in many standard books on the subject. If in doubt, set
at the standard for the original machine. If it's a front wheel drive
donor car components used in a trike, some tyre wear may occur, requiring
gradual adjustment for a few weeks until the optimum is attained. Use
the worst two wheels of the four until the steering is optimised.
Suspension must be stopped just before maximum travel by a strongly
mounted rubber block. These are usually stuck to a plate on the frame
and can be carved to size, using any of the many blocks available.
The McPherson strut design uses a rubber block in the upper damper and
spring unit to absorb the road shocks. This shock unit also maintains
the camber and supports the weight of the vehicle at maximum load. On
McPherson struts, alignment can be done by simple positioning of the
upper mounting point, which also supports the weight of the machine.
A little rearward movement is possible, allowing the top of the rear
shocks to be further back by an inch or so, especially if the passengers
can sit lower, but may require similar angluation of the lower wishbone
or arm and anti roll bar or radius arm, only possible with rubber bushes
or spherical pivots.
When accelerating, the power to the wheels will make the wheel hubs
want to move forward. For wheel hubs to push the weight of the trike
forward, this is done by using the radius arms or wishbones connected
from the wheel hubs to the frame or engine. Braking forces are the same,
but simply working in the opposite direction. Brake drums or callipers
must not turn and the radius arms or wishbones usually handle this problem.
When the suspension is at mid point, the suspension arms and propshafts
should be about horizontal. If you use a double wishbone design, keep
them the original length, unless you know your geometry. Always make
sure the drive shaft splines are correctly positioned.
If making your own double wishbone design, then design the upper and
lower wishbones so that the wheel will remain as close to vertical throughout
the suspension movement. (In a roll situation) This is usually done
by having the upper wishbone about 10 to 20 percent shorter than the
lower wishbone, depending upon the position of the pivots from the chassis
Always build as matched left and right hand side symmetrical pairs wherever
possible, using a jig. A simple welding jig will greatly assist the
alignment of such suspension components. The distance between the inner
and outer axes should normally be the same length as the distance between
the centres of the universal joints in the propshaft.
If you have a subframe such as used by mini's, then simply keep the
original set-up intact.
Although not recommended, there is nothing from an engineering point
that prevents three wheel steering, taking advantage of this ability
to steer the rear wheels. Not recommended for road use, but may make
very long show trikes easier to manoeuvre and more fun to ride and easier
to park. Some 1990's cars offered all wheel steering, but it seemed
merely a fad.
Once the basic frame has been decided, refining the frame will make
life simpler as you work around, or even remove problems that are discovered
while looking at the assembled parts.
Sketch out ideas on paper. With a little extra time, parts can be made
simpler while adding reliability, by simply keeping your eyes open and
pinching ideas from other designs.
The more you look and think, the better your ideas will be, so take
time at this stage to make for an easier life later on. Make loads of
drawings no matter how bad they are, they are worth more than gold at
this stage. It must be right and if you don't know why, then give up
now or decide that you want to learn more, and keep trying before building.
The more thought applied, the more possible it is to get the centre
of gravity lower, make the frame stronger, lighter and also easier to
Whatever the frame design, the steel tubes used will be either tubular,
square or rectangular, or a selection of all three. Where parts are
hidden, use square tubing, as its easier to fit, stronger and easily
shaped. Square section tubes which are open to public view are usually
considered a styling failure unless styled really well.
Composites are still difficult for cars and bikes, so don't bother.
Likewise for monocoque, as the panel work will give a little more rigidity
and lightness at the expense of far too many hours work and inability
to repair easily.
If you want to go the composite route, start with studying formula one
design and modify from there, choose your engine very carefully and
consider at least six cylinders to reduce vibration. Best of luck and
feel free to email the author.
There is nothing wrong with tubes, they have a long history of both
success and failure.
Always mount engines as the manufacturer intended. Building an engine
into a frame so it is part of a rigid structure is OK for bikes with
their high revs and low reciprocating masses, but a car engine is often
more agricultural. Only six cylinders and over should be contemplated
for rigid fixing, as their vibrations are less. If rigid mounting is
used, be very wary of fractures in the frame over long periods of time
and spread the load into the frame with smooth and well spaced engine
mounts. Rubber mounting helps resolve torsional effects around the flywheel
axis and for this reason, most engines are rubber mounted and also have
an engine head steady.
If you have an engine with dry sump, you may want to use the frame
for the oil tank. Use a good MIGor TIG welder which causes far less
slag in the tubing. Do not position any connecting pipes where they
can encourage fractures to occur. Drill adjoining holes for both oil
drain and air venting between the connecting tubes before welding and
always have an oil filter after the frame outlet and definitely before
the engine. Oil holes in the frame tubes must be large enough for maximum
oil flow at top revs, otherwise oil starvation will occur. An average
engine will pump well over a litre every ten seconds at LOW speeds,
so always ensure the holes in the frame can handle a lot more than this,
and never rely upon pump suction to prevent oil pressure loss.
A simple vented cap from a moped two stroke oil tank will suffice for
filling and venting, if hidden from sticky fingers. Never take the oil
feed from the bottom of the tank / frame, always allow an area for unwanted
sediment to settle, with the oil pipe a little higher, preferably with
a wire mesh screen. Make sure most of the oil will drain out.
The simplest oil level assessment is via a dip stick. This can be a
flexible piece of thin wire strip to access the curved frame tubes,
possibly even an old speedo cable. Make sure the oil level area of the
dipstick is protected by dimples or bumps, so the position of the oil
level is not wiped off when removing the dip stick.
Where oil level cannot be assessed by a dip stick, then the oil level
can be seen via small tubes above and below the level, connected by
a clear plastic tube. If welding small pipes is difficult, simply push
the pipe in a small hole in a safe part of the frame, below the intended
oil level. To save bends in the small pipe, place a steel rod in the
hole and lever the hole so the pipe is fairly vertical and weld from
the inside if possible. Then run a drill though the tube to allow oil
access. Then solder around the outside of the tube to seal it. For safety
reasons, the oil must not be allowed to drain from a broken pipe, so
this should not be too far below the oil level, but low enough to see
when filling up. To protect the pipe, the clear plastic tube can be
protected along its whole length with strong sleeving, and just the
oil level area exposed for inspection. Alternatively a second, larger
bore clear pipe can also be employed to protect the smaller oil level
pipe. This can then be run along the frame tube to be vented into the
Oil in the frame can show up any fractures at an early stage and should
be considered a safety feature rather than a problem.
There are various techniques for welding frames.
Arc welding is the most common form of welding and when done properly,
can accomplish all needs of construction. Thin sheet is the usually
the most difficult, so fuel tanks can be flanged to make welding easier,
or tack welded then handed over to a professional mig or bronze welder.
Bronze welding is better for strength and ideal for reducing fracture
points of small tubes and fittings.
Very lightly loaded fittings such as oil level pipe can be heavily soldered.
Mig or Tig welding will leave the frame with minimal internal slag which
could flake off and clog the oil lines. Always clean the insides of
the tubes before final assembly and welding. Where welds are to occur
in the frame tubes, clean back to bare metal prior to tig or mig welding
to minimise internal slag. Follow up with regular inspection of the
outlet pipe to check for any clogging.
The Lamborghini Countach has a tubular chassis which is made up of
a large number of small round tubes arranged to make many triangles,
called a 'space frame'. The triangle is the most rigid shape around.
If you don't want to bend tubes, then try designing a frame from many
big and small triangles. The later Lamborghini Diablo used square tubing
for it's space frame, was easier to build than the Countach, and was
stiffer and lighter.
Do not have long unsupported tubes. Always employ smaller tubes to stop
the long main tubes from flexing or bending. The whole frame can be
made from large and smaller triangles. A rectangle can distort, so guess
what you should do. Some motorcycle trellis frames use an appropriate
With all your ideas down on paper you will soon see where you can improve
Creating a merely adequate design is a weak excuse, while common sense
and inspiration are infinitely more applicable for trikes.
Trikes based on bikes can be comparatively easy. You often keep the
frame, modify the rear and add a differential and wheels.
The builder will of course be accepting that there will be a large roll
component, caused by the ride height of the rider and this will need
reasonably stiff rear suspension to prevent roll if for some reason,
an anti roll bar is not used. This tendency to fling the rider sideways
in a bend, can be overcome with some clever rear end design and is being
researched for reader wanting his trike to lean, but this is presently
beyond the scope of this monograph until I have refined my designs and
tested them. This is particularly useful for some disabled rider, who
cannot always support the torso easily around a fast corner. Email for
Bikes and their engines will need accurate chain-drive alignment and
a sprocket on the differential.
A modified swing arm is not adequate for the solid type of rear axle
unless for slow riding.
Radius arms are needed for decent independent rear suspension. The rest
is widely open to interpretation. Whatever you do, keep it light, or
at least keep weight down, unless you are using a 'busa or dual engined
nitrous big bore Harleys.
Some quad bikes now use independent rear suspension with a differential
of a size and weight commensurate with a lighter bike-based trike. Such
items can be lighter and more appropriate than heavier car items for
a more balanced lightweight machine which does not handle too much power.
It is very important to match the gearing of the shaft drive systems.
Work out the revs of the shaft at top speed and calculate if this will
match the revs required for the proposed differential unit and wheel
size. Most shaft drive bikes use a similar arrangement and the differences
may not be far from what is needed.
If you don't like arithmetic, then wheel size can adjust the final overall
gearing to allow a decent top speed plus reasonable hill climbing ability
without trashing the clutch. Gearing can be raised by fitting larger
wheels, which may or may not increase top speed and vice versa. Gearing
can reduce any bad design tendencies to wheelie, usually at the expense
of the clutch.
If the radius arms of a solid rear axle are positioned so they pivot
concentric with the front sprocket, then chain play will be minimal
and your chain will have a happy and long life. A motorcycle chain can
handle a little amount of sideways play as the axle lifts on one side,
but the panhard rod will ensure it keeps in line and does not wear badly.
There must always be allowance for chain adjustment, so the differential
must be able to be adjusted on its mountings, or the radius arms lengthened
to accommodate for chain wear. If this is not possible, then you may
wish to use a roller on the lower chain run and a strongly sprung loaded
jockey pulley, or preferably an adjustable pulley wheel which can be
secured so that there is minimal slack on the overrun for a well behaved
One-piece rear axle units, consisting of the differential, brakes
and wheels will need to be kept central while allowing for suspension
movement. Front to rear movement is prevented by a radius arm on each
side, as shown in the little animation shown earlier, pivoting at the
front in rubber bushes and usually fixed to the axle unit to prevent
its rotation. On some designs, the radius arms do not prevent rotation,
so the design must prevent the whole lot turning when accelerating and
braking, requiring either an upper brace, or other method to prevent
the axle from turning.
Component choices: Swing arm and radius arm bearings are either rubber
bushes, metal bushes or needle rollers. Balls are not recommended, nor
are large rollers, because swing arms only pivot over a few degrees,
so the point loading of the bearing is far too localised to ensure long
life. Although taper rollers are used on the swing arms of shaft drive
machines, it may be easier to use needle rollers, which spread the load
wide and roll over larger displacements for even wear. Needle rollers
cannot take end loads, so either bushes or some other form of end load
resolution should be accommodated as trikes suffer vastly worse from
this than standard motorcycles. If the swing arm bearings are well spaced
and the swing arm a rigid one piece design, then rubber bushes are acceptable
for many reasons including simplicity and reliability.
There is no need to use metal suspension bearings to mount shock absorbers,
as the shock absorber is a flexible medium. The use of rubber simply
refines the set-up and reduces shocks into the frame.
Forks are always the weak point of trikes from an engineering point
Forks are often the strong point of trikes from a styling point of view.
The forks must have twin discs to stop a trike which is probably twice
the weight such forks and brakes were designed for. Standard motorcycle
front ends are not up to the job of a big trike.
From a safety aspect, the forces applied by twin brakes will at least
be matched to the forks and allow the braking forces to be applied evenly
and fairly safely. The forces on standard brakes will be similar to
that which the forks can take, ensuring a fair degree of safety. In
many cases, standard brakes may not be able to offer the braking forces
required of a larger, heavier machine.
Never accept the fact that because someone has already built a two
litre trike with 125cc trail bike front end, that it is a good idea.
Yes, they do exist, but probably not for very long.
I know of a car engined trike with 1980's 125 trail bike front end.
The owner says he 'only gets the front brake working once a year for
the MOT'. It oozes rust from the brake drum plate and patently only
there for legal rather than safety reasons. Such machines are a statement
of design failure far beyond mere ignorance, and are most assuredly
an engineering death wish. Everyone has the right to be stupid, but
never abuse the privilege.
Standard forks should be used as intended, with their rake angles designed
to take the shock loads as sliding tubes. The amount of trail will depend
upon how they are mounted, but keep it close to original as this is
how they are designed to work.
Long telescopic forks for styling purposes will often act as simple
beam springs, absorbing the shock by bending rather than telescoping.
This makes it a spring, not a damper, so will resolve the force by flexing
back in an uncontrolled manner. Go carefully and make sure your forks
act as shock absorbers, not as undamped springs.
Girder forks at least offer the chance for their small bottom swing
arms to flex through an arc as intended and thus take some shock out
of the legs. Do not expect such designs to handle too well or give any
subtle feedback as to what the road is doing with the steering, but
properly designed, they can act effectively as steering and suspension
devices, and with an easily adjusted amount of trail to refine the steering.
Long forked, custom front ends with a large amount of rake, will allow
a motorcycle tyre to be used in preference to other options. This is
because the amount of lean of the wheel in the forks when cornering,
(not to be confused with roll) will allow the side of the tyre to be
applied to the road surface. This also reduces the amount of side force
on the tyre, trying to push it off the rim as found on heavier trike
front ends. Manoeuvring around tight car parks will demand a reverse
gearchange or friends to help push the machine backwards.
Standard telescopic forks may not be up to the heavy side loading as
found with trikes, so the front tyre may want to roll off the rim. Therefore
any design where this can be limited or designed around should be used.
Tyres are more prone to bad effects such as wear on larger machines
and will tend to distort when given the unusual side loads of a trike,
which does not lean in the same manner as motorcycles. (An engineering
advantage of long forks is that the front wheel lean relative to the
road is improved, reducing the tendency of the tyre to roll off the
rim, but as such forks usually cannot apply any reasonable force, this
aspect of trike design is purely academic.)
Use of inner tubes should be considered where extreme side loads are
applied to motorcycle tyres. Where inner tubes and tyres are used heavily
with side loads, they may distort or lift off the rims and may on rare
occasions get hotter, so check during early tests on twisty roads. The
tyres should cool down to more sensible levels during straight line
running and is rarely a problem, but inner tubes are well worth the
Strength is a main area of concern. It must be kept in mind at all
times when choosing front end components. Therefore, where style comes
before practicality or suitability for the purpose, make sure you do
not put yourself in a position of danger.
With large engined machines, the builder must look for alternatives
to motorcycle fork legs unless the machine is primarily for posing.
For fast road work in country roads, where braking into fast corners
and subsequent powered fast exit cornering, then motorcycle forks and
wheel design will compromise the limits to which the design can push.
Weight balance and centre of gravity will also be major deciding factors
as mentioned earlier. A very low trike with strong, balanced front end
working in concert with the rear will handle almost any situation.
The car wheel is designed for, and less prone to the side load problems
of trikes. Unfortunately car tyres and wheels are not designed for fork
legs, where the steeper rake angle of fork design prefers a more rounded
tyre profile. There is also the problem of the car wheel not being compatible
with forks, or style.
Car rims usually have an inner lip to reduce the chance of the tyre
from peeling off under extreme side loads. Using car rims with this
attribute will assist with some extreme problems of thrashing a trike
in twisty roads and fast corners. If the wheel size does not have inner
lips on both sides, then either build up a similar profile inside the
rim by careful welding, or mix split rims or lathe the rim on the trike
and weld two halves together. This also allows for custom wheel rim
widths, as found useful on some of the authors machines. See also wheels
A few pointers.
Most heavyweight trikes use serious front alloy wheels on special axles,
but the tyre is the main component, choose it well. The basic car tyre
can often be found in almost, or partially round profile, usually on
cheaper tyres with narrower cross sections. For ordinary wheels such
as the standard car 13" wheel with narrower section, the cheaper
tyres are often of a partially rounded profile. So off to the local
tyre dealer and look at the tyres, then choose the one with the most
rounded profile. It is also usually the cheapest tyre.
If worried about fitting bike tyres on car rims, then check the rim
dimensions and profiles with the SAE standard dimensions. SAE= Society
of Automotive Engineers. I've been doing this for years.
Look at the options available in tyre dealers, and choose your tyre
The tyre is the main component, choose it well. Then mount it on a
decent front end.
If making new front ends, then making the wheel rim and hub is the
best place to start. See making wheels later.
If not using a bike front end, get the steering head made professionally.
Invest in a decent item using larger taper roller bearings available
from any bearing shop.
As a good alternative, choose the often cheaper yet equally suitable
bearings as used in car wheel hubs. These often use excellent large
taper bearings at sensible prices and offer excellent spares availability.
Where wheel bearing kits are supplied with two sizes, usually a larger
outer taper roller and a smaller inner, then buy two sets, as the price
is still often much cheaper. Alternatively, use the smaller bearing
at the top, where the forces are much lighter and the larger one to
take the main load.
Whether with identical top and bottom bearings, or a more suitable,
cheaper and lighter form, - always ask around first, before building,
as many people will machine a steering head for a small fee during the
Keeping to standard components from other sources, means keeping it
cheap and keeping it reliable.
If making a steering head, get tubing much stronger than the original
and take time to get everything perfect. Where possible, reassemble
accurately using old bearings, so you can weld to it without damage.
Then be prepared to replace with new bearings after welding if they
become damaged through excess heat.
The simplest steering head is a large tube with a close fit for taper
roller bearing outer race which can be carefully ground or machined
away inside to accept the bearings firmly. Alternatively use a split
tube slightly smaller and clamp firmly over the bearings with Jubilee
clips or exhaust clamps, then weld the gap. Alternatively use a larger
tube and grind down the slot, and again clamp tightly then weld the
tube to fit the bearings. Tack weld the tube, then remove the bearings
and weld fully. Make sure the bearings are a firm fit, if they are not,
saw a slot and tighten the gap slightly before re-welding.
The final tube must fully support the taper roller at each end and
must be perfectly parallel, and axially concentric. If the bearings
are a slightly loose fit, simply hammer the outside of the tube to reduce
the diameter by a few thousandths of an inch. Do this evenly while rotating
the tube, to ensure the tube remains circular. Gently fitting the bearing
in position for checking during the process then removing before further
hammering will allow the swaging to be applied with some engineering
Then make an inner spacer tube to fit snugly inside the main tube to
keep the taper roller outer races apart. Carefully lathe the ends of
this spacer tube so they are perfectly set at right angle to the tube.
Alternatively use a set square, file and a practised eye. This is the
work of a genuinely qualified engine fitter. (No GNVQ's here!) The final
head stock tube should fully shoulder and support a taper rollers at
each end, and they must be perfectly parallel and axially concentric.
A variety of large holes and slots are then made in this inner tube
so that it can be securely welded inside the main tube. The welding
of the inner tube must be strong, as the bottom bearing presses against
this to take the whole weight of the front of the trike.
If the bottom fork yokes are close to the steering head, then weld failure
will not be catastrophic, as the bottom yoke should be designed to collapse
only a few millimetres until resting on the steering head. A very small
gap reduces the need for a dust seal, requiring just a lightly fitted
O ring or a foam washer to protect the lower bearing from corrosion.
Careful design of all main components should be fail-safe wherever possible.
The central spindle is usually a solid bar or large wall thickness
tube, machined to fit firmly into the bearing inner races. As the spindle
need only snugly fit the bearings where they are positioned on the spindle,
the rest of the spindle can be slightly reduced in diameter, to allow
the bearings to slide easily into position. Only where the bearings
will fit, will the spindle need to be a snug interference fit, needing
the bearings to be lightly pressed into position. If the machining is
a little too keen, simply build up with weld and file or machine until
Securing it all together will need a threaded adjuster to apply just
enough pressure to the taper rollers so they will turn freely, yet have
no play. This can be done by simply welding a strong, fine threaded
bolt, with spacers and lock nuts on the upper part of the inner spindle
or to weld a large barrel nut inside the spindle.
Many firms can build steering heads, as it is basic engineering. Take
the chosen bearings along, plus details of the length needed between
them. Get the spindle made at the same time. Likewise, many engineering
firms will make slab yokes. Always ask around first, as someone often
knows of someone else who can make a set at work during the night shift.
Always make a strong shoulder on the bottom of the spindle. It is preferable
to make the bottom yoke a very firm fit on the spindle, preferably with
a small taper section to ensure the spindle fits securely and aligns
perfectly in the yoke.
If alloy slab yokes are not suitable, too expensive, or just wanting
something for testing purposes, the yokes can be built up from round
and rectangular tubing and steel plate. It is possible to build steel
yokes, then smoothed and alloy sprayed for styling purposes. (Alloy
spraying is also useful for improving the external longevity of one-off
steel exhaust systems, when used in conjunction with petrol additive
to give a light oily internal film to the otherwise easily corroded
Most bike engine trikes use standard bike front ends. This can also
apply to average car engine designs, but forks are not suitable for
trikes with large engines.
Heavyweight trike steering is either by a variation of fork legs, or
hub centre steering. Usually highly modified and often employing some
car components. Custom made units will go though a series of refinements
with time, so begin with yokes which can take strong, easily available,
replaceable fork leg tubing. This will allow various improved versions
of fork legs to be slid in easily without other modifications.
By using easily replaced tubing which can slide in the fork yokes, a
variety of fork heights and design options can be mounted; leading link,
trailing link, Hosack, or a host of others are possible.
The usual set-up for heavy front ends, such as where a V8 is used, is
leading link and is often the first attempt, as it is reasonably fail
safe, adaptable, strong and comparatively easy to build and can be set
up to greatly reduce dive under braking. It also has the advantage that
it is much easier to play around with the amount of trail to refine
the handling prior to more advanced designs. The down side is lack of
style, so careful effort must be made to glean every ounce of style
from such designs.
The two main fork tubes should curve down and backwards from the yokes
and end in pivots. These pivots are usually either side of the rear
of the front tyre and a couple of inches above the front axle height.
This is best done once the steering head is on the trike chassis. Use
the yokes and a long bar as a guide for the position of the front wheel
Once the front wheel is positioned, a pair of arms will pivot forwards
from brackets mounted on the bottoms of the curved fork legs. Standard
motorcycle style shock absorbers will maintain the swing arms and axle
in position. When testing, the steering may be heavy or light, so be
prepared to shorten or lengthen the arms as required to adjust the amount
of trail. If in doubt, start with a couple of inches of trail, but prepare
to modify as all machines will require their own geometry. The easiest
way is to adjust trail is to remove the legs and slightly bend them
to suit until perfect. When in the hydraulic bender, pump up until just
the slightest movement is noticed, then count the number of pumps. If
in doubt, one pump, relax and check against the other leg until the
required difference is attained. Then use the first leg as the gauge
for the second. Always replace the fork stanchions in the yokes with
the spindle to ensure the pivot is perfectly aligned.
Use plastic sleeving in the U groove of hydraulic benders to prevent
scratching of the tubing. HDPE high density polyethylene from old plastic
oil containers is ideal.
Trail is the distance between the ground position directly under the
wheel axle and the position on the ground, as projected through the
steering head axis. The normal amount of trail for standard rake angles
is the same as that for most motorcycles
It can be difficult to measure the amount of trail, as getting an accurate
line through the steering head is difficult. A piece of extruded angle
metal bar can lie alongside a steering head if the head stock has parallel
sides. This will help project the steering head centre line to the floor,
from which the wheel axle can be positioned slightly behind, depending
upon the design. Although this way is good for checking, unfortunately,
this is not the best way steering heads are fitted to the frame. See
later. The rake and trail are best decided on the drawing first, and
built into the steering head, forks and yokes accurately prior to fitting.
It is common to temporarily weld the steering head in position to check
prior to final welding.
If trail needs adjusting, the fork tubes can be bent or straightened
slightly or the swing arms shortened or extended. They can also be slid
up and down the yokes to level the rear of the machine, so always make
the fork stanchions longer than needed, to allow for later adjustments.
The front swing arm pivot bearings on the bottom of leading link fork
legs must be strong and the whole arm assembly must be able to take
the high side loads. (Trikes don't lean). For good results, machine
the pivot tubes with internal shoulders to mount two deep groove ball
races or taper rollers each side. Internal spacers are often needed.
Needle rollers are even better, but side thrust washers are also needed.
For the strongest pivots, use small motorcycle steering head ball races,
or taper roller head races and use a very accurately fitting spindle.
The spindle must be able to lightly adjust the pressure on the taper
rollers and will therefore employ a lock nut or similar adjustment.
Bronze or brass metal bushes are possible, tend to last only a year
or so and will require regular greasing.
Rubber bush pivots are only acceptable if the whole swing arm assembly
is a single, well cross-braced item with the left and right rubber pivots
spaced well apart and this is usually a large bore U bend tube.
No matter what bearings are used, the two swing arms should ideally
be joined as one piece, similar to a conventional motorcycle swing arm.
This is to prevent twisting under side loads, especially when cornering.
This usually means bending a single tube to make wrap-around design.
The front wheel and brakes should be able to fit easily into the assembly.
When the fork legs, swing arm links and front wheel are assembled and
you are ready to mount the shock absorbers, lift the front end of the
machine so the swing arm is at the middle point of travel. Then raise
the front of the trike by a further half the vertical shock movement.
This is normal rest position of the shocks. The front wheel and it's
swing arm are then positioned for the shock absorber units to be in
their fully extended, 'at rest' position. Knowing this before building
the frame helps to create a little leeway in the frame manufacturing
If the engine is at the front and you want a little anti-dive to counteract
the heaviness under breaking, then lock the front wheel to the swing
arm prevent rolling, lift the rear of the front suspension swing arm
on a freely rolling trolley jack, to adjust the height until the front
end lifts a little when the trike is pushed forward to simulate braking
forces on the front wheel. Do not exaggerate the movement, just have
the slightest lift possible to counteract the braking forces. This may
need a few friends and a long bar to lever the trike against the wall.
This will get you into the ball park but real testing will be needed.
When braking for real, this will tend to lift the front end, thus compensating
for the dive effect, which causes forward pitching of the trike. In
an ideal world, a little dive is recommended, to enable feedback from
the braking to enable the rider to get a feel of what the front is doing
while braking hard, so back off a little from the ideal position.
Once on the completed frame, the temporary front shock positions can
then be further refined so they are compressed slightly under the static
load. The shock positions should also be adjusted so their movement
is tangential to the arc from the pivot, so they will compress in an
even manner. Only use tack welds at first and test lightly. This will
give a rough starting point for the suspension.
Do not confuse the difference between the position of the swing arm
angle to give anti dive, with the position of the shocks for supple
suspension. The swing arm angle is decided first, then the shocks are
mounted to allow a slight compression on standard load. So first get
the anti dive angle about right on the trolley jack, then make a guess
for the shocks, tack weld in position, remove the trolley jack, and
test. Then change the shock positions relative to the amount of sack
or stiffness in the initial test. do many times until its about right
and you should be in the ball park for your first road test.
It will be noticed in the drawing of a front end, above, that the upper
and lower shock mounts are plates either side of the main tubes. This
will allow for almost any sort of positioning, not only for choosing
the ride height of the swing arm, but also for the angle of the shock
units to give a suitable spring and damping rate.
Correctly set up, the shocks should compress about five to ten percent
when at rest under the load of the complete trike. On a trike with a
heavy front end, the suspension should also want to rise slightly when
forced against a wall.
When about correct, weld a little more fully and try loading by jumping
up and down on the font end. Be prepared to readjust if the full movement
is too soft or too hard. If the action is too soft, moving them further
from the pivot increases the spring rate at the expense of movement.
If the action is too hard, moving the shock units closer to the pivot
makes the suspension softer with more wheel movement.
On a recent V12 trike project, the single front shock compressed just
a little while at rest, but it took a person jumping on the 2 inch thick,
CNC machined alloy front end slab yokes to get a decent amount of compression
movement. In this case, the shock was ready to compress further under
the weight of the machine and respond well to the road surface in bumps
as well as hollows. The main trick is choosing a suitable shock unit
and optimising its position. Carefully considered rough guesses are
fairly reliable for initial testing. During testing, the machine will
show up if the springs and damping are not in the ball park. Most shocks
are easily adjustable or replaceable. (For the V12, the front end used
a monoshock with adjustable spring rate and damping from the rear of
a 1200 cc motorcycle.)
Always ensure that the main fork components, especially the main tubes
are not compromised by badly positioned welds which will weaken them.
Always make the welds up and down the length of the forks tubes and
most definitely never fully around the tubes. Warning: Welding around
the tubes will cause a weak area.
The swing arms should be linked for strongest alignment under all suspension
settings. A single large bore tube which wraps around the back of the
wheel is ideal, but not too bulky. Also consider a strong wrap-over
support to add further strength which can be disguised as part of the
Where a car hub is used, the leading link 'fork' could be single sided,
but must be very strong. An upright support tube from the axle, over
the top of the wheel, curving back down to the rear pivot will help
reduce distortion of a single sided axle mounting. This support tube
can be disguised by a mudguard. Ensure the wheel can be easily removed,
by using the standard car hub items as a starting point. For single
sided axles, always make them stronger.
Other forms of front end should be done in the light of experience.
The ultimate for some machines is hub centre steering, such as the variants
used on the ELF 24hr racers. Also consider three wheeled cars as starting
points for alternate front ends of heavier trikes, then gradually replacing
parts to keep strength while enhancing style.
You have chosen the best engine and transmission.
You have checked it runs, then carefully deconstructed the donor vehicle.
The basic components of forks, engine, wheels and suspension are laid
out on blocks in their intended position.
you have now spent at least a week just looking at he layout and considered
how it will handle.
Some modifications and final juggling have led to the best possible
The frame has now been designed to fit the layout and three designs
developed and the final frame is probably a mixture of the best aspects
You have checked the ergonomics and seating are as you desire.
You have checked the gearchange will be reasonable and reliable.
You have checked all components are accurately aligned and blocked to
prevent any inaccuracies.
Building the frame.
It may seem a long time to get to this stage.
But the frame holds all the rest together, and must do so with the many
demands as mentioned which are placed upon it. This is now the final
chance to refine the frame design, ready to commit the design to metal.
Understanding all these other requirements first, will always help make
a better frame.
New stock steel tubing is surprisingly cheap. So are simple hand-held
angle-grinders, so make life easy for yourself.
Goggles, a dust filter mask and ear protectors are even cheaper and
will pay the highest dividends in the long run, while also reducing
hospital visits now and in later life.
There is no point building a trike if you cannot ride it.
Get safety equipment the same time as the tubing and welding rods, plus
the grinding and cutting discs for the angle grinder. Make sure the
discs are for metal.
When building a frame, alignment is everything. Accept nothing less
When problems raise their ugly heads, use your head, not a hammer. There
are many subtle ways to ensure good alignment.
Important notice: Never be afraid to discard a poor first try of building
a frame, as the cost of tubing is minimal compared to the time and effort
involved. Getting it right from the start ensures a much better machine.
The first tubes to be built are the most important, so go for gold from
the outset. If the first attempt at a main frame tube is less than perfect,
then remove and refine, or simply make another and use it's remains
for smaller cross tubes and other secondary items.
Decide how the frame will handle the loads and forces, then choose
your tubing accordingly. Look at tubing used on bikes, trikes and cars
to get a feel of the sizes needed. Find out the wall thickness of the
tubing used, for this is just as important as the outside dimensions.
If in doubt, always use stronger tubing. You may be able to afford a
lighter seat lug to break, but not a structural part of the frame. A
few extra pounds or kilos on the main frame tubes are always good insurance.
If in doubt about tube diameter and style, always make a cardboard
tube to see what diameter tubing will look best when set beside the
parts laid out on the garage floor. - Use those old kitchen towel roll
centres as a starting point and reduce or enlarge as needed for good
looks with strength.
If you dislike metal work, use square tubing, it's easier to fit. Round
tubing needs a lot of profiling work to join properly.
Make sure you use ordinary steel and use seamless tubing if you can.
Iron is never used and stay clear of fancy steels unless fully competent.
Don't try saving money by buying cheap tubing for the main structural
parts of the fame, and stay clear of wrought iron.
An cheap 4.5 inch angle grinder with cutting and grinding discs is a
Types of steel. - For most frame purposes, just use mild steel.
TYPES OF STEELS.
DEAD MILD or low Carbon. 0.07 to 0.15 percent carbon.
Available as Black and bright bars. tubes, wire.
Pipes, chains, rivets, screws, nails, wire. boiler plates.
Easily worked when hot, but difficult to machine owing to tendency to
MILD. 0.15 to 0.25 percent carbon.
Available as Black bar sections and sheet Bright bar strip and tubing
Ship plates and forgings, gears, shafts, nuts, bolts, washers, rivets,
Easily machined and welded, and is cheapest steel.
Ideal for bike frames. Welds easily. Available in many sizes shapes
and wall thicknesses. Preferably non seam welded tubing, but seam welded
tubing is perfectly good too.
MEDIUM CARBON. 0.25 to 0.5percent carbon.
Available as Black bar, sheet, sections and plate Bright bar. rods,
flats and strip Forgings.
Machine parts and forgings. castings. springs, drop hammer dies.
Responds to heat treatment and can be machined satisfactorily.
HIGH CARBON. 0.5 to 0.7 percent carbon.
Available as Black bar and stripSilver steel rod.
Hammers, sledges. stamping and pressing dies. drop-forging dies, screwdrivers
HIGH CARBON. 0.7 to 0.8 percent carbon.
Punches, cold chisels, hammers, shear blades, drop-forging dies, lathe
centres. spanners, band saws, rivet sets (not rivets). vice jaws.
HIGH CARBON. 0.8 to 1.0 percent carbon.
Punches, rivets, sets, screwing dies, screwing laps, shear blades. drop-forging
dies, saws, hammers, cold chisels, springs, axes, rock drills, milling
cutlers, lathe centres, reamers. See also my knife monograph.
HIGH CARBON. 1 to 1.5 percent carbon.
Drills, milling cutters, lathe tools, files, wire drawing dies, hacksaw
blades, ball bearings, screwing dies and taps.
CHROMIUM Up to 1.5 percent. Used with nickel and / or molybdenum increases
hardness and allows high UTS with considerable ductility
COBALT. 5 to 10 percent. Retention of hardness at elevated temperatures.
COBALT. 12 to 18 percent. Increased corrosion resistance in stainless
COBALT. up to 40 percent. Improves coercive force in magnet steels.
NICKEL. 1.5 to percent. Increases tensile strength and toughness.
NICKEL. Over 20 percent. Used in corrosion- and heat-resisting steels.
TUNGSTEN varies. Strengthens steels at normal and high temperatures.
MOLYBDENUM varies. Used in stainless steels to provide resistance to
sulphuric and other acids.
VANADIUM varies. Increases hardensbility.
NIOMUM. TANTALUM. TITANIUM. All three prevent weld decay in chromium
steels and in nickel stainless steels.
BORON 0.003 percent. Great increase in hardenability.
COPPER 0.2 to 1.0 percent. Increases corrosion resistance.
When built, you will be loading the frame to see where it flexes, so
expect to add some more tubing, fillet plates and/or gussets as required
Make a rough guess of the sizes of tubing you will need, but prepare
to change them slightly when confronted with the metal stockist's options.
A good looking trike is a subjective analysis of a machine which needs
not only strength, but also style and proportion of the frame tubes
in relation to the other components. To get a good idea of what looks
good next to the engine and wheels, make that cardboard tube as long
as possible, so it can lie along the arranged components to help gauge
the general look of the frame tubes. Then find the nearest match in
the steel tube available.
Always measure the length of the main tubes, so they can be cut a little
overlength as a single length for strength and reliability.
Grab your drawings, metal tape measure, a pencil, then find the local
metal merchant and see what they have to offer, and ask their advice.
There are many metal stockists around the world, and you can buy anything
from single tube and a pack of welding rods, to enough to build a battleship.
The best way of deciding is often simply looking and deciding what seems
best. - 'I'll have two lengths of that heavy tubing, four of that smaller
square tubing and a sheet of that'.
This is not at all scientific, there are no calculations and no structural
analysis. If in doubt, use the scaffold tube as a reference point. Do
not put yourself down, even a poor mechanic has a working knowledge
of what has been used in similar circumstances. Your main assessments
are comparative to similar structures plus a safety margin. The ability
to use the eyes in conjunction with common sense is a very powerful
The good engineer and designer would consult engineers tubing data,
to check the actual working loads, then choose from suitable tubing
and give a safety margin. Later versions of the design would then be
refined according to bending tests and real world loading feedback data,
as mentioned later.
As trike builders do not like arithmetic, then use common sense and
a sense of proportion and comparison with other machines. I have seen
lightweight trikes safely using three scaffold tubes, and car engined
trikes with four scaffold tubes.
If in doubt, look for similar successful engineering equivalents. If
in doubt, ask friends. If in doubt, build stronger than expected. If
in doubt, be cautious and try it anyway, you will often be pleasantly
surprised during early testing. Doubt is a positive attribute, it can
also be a safe one.
If in the worst case, the frame fails during initial testing, then you
will need to strengthen, or even rebuild parts with stronger tubing,
simply returning to the start in the light of experience before too
much expensive work is done. Initial testing is always done on the basic
rolling chassis, so that in the worst case, the whole basic frame can
be affordably discarded and a better frame made, before all the fiddly,
time consuming work is done to turn it into a work of art.
You may be surprised by the vast selection of tubing available and
it is always in a variety of wall thicknesses. Always measure the tubing
on equivalent machines for comparison.
Circular, square and rectangular tubing, strip and rod. Make yourself
a shopping list and be prepared to have it cut for a small fee, as it
usually comes in twenty foot lengths which the supplier can cut to what
ever length you need. Measure three times, cut once, or do they deliver?
I take along a hacksaw and a few spare blades in a friends van, to keep
There will also be alloy sheet, wire mesh and a host of other stuff.
Don't forget to buy the welding rods and grinding and cutting discs
at the same time.
And to repeat; goggles, ear defenders and breathing mask too.
A decent set of leather welding gloves is useful when handling hot metal.
If in doubt, ask for a photocopy of their materials list, and retire
to a local cafe to think, or return next week.
When carrying long tubes in a car, always take newspaper or rags to
cover the seats as the tubes are covered in preserving oil which stains
easily. Take plenty of cloth to wipe off excess preservative. Most trike
frame tubes can be cut overlength and still fit in a car if stuck into
the passenger foot well, and the tail gate open with a warning red flag
attached. The passenger seat may need to be removed, so take a few spanners.
Take bungees to keep the tail gate from bouncing around.
When the tubing meets the trike bits, it may be decided that it is
not the right size. At this stage, a rethink will be a lot better and
the original tubing will become stock for other work, such as to align
the wheels to the floor lines, or gateposts and drains, or perhaps an
Therefore just get the main tubing first, and if in doubt or on a tight
budget, simply get one length, then return for more as needed. Practice
bending and welding on the first choice of tubes, and when competent,
get the perfect tubing later.
To repeat, if worried about wall thickness, go safe. A few extra pounds
in the main frame is weight well spent. You can be less cautious for
non structural parts such as seat bases, battery box mounting brackets
Check out the local hire firm for tube benders if needed. Get the hydraulic
type and check the tubing diameters that the bender can handle the tubing
you have chosen.
Before making the main frame tubes, it is better to make the suspension
and engine mounting items first and position them correctly. Then the
frame can then be made to fit the set of perfectly aligned suspension
Understand the hierarchy of the structure you are building.
The engine powers the tyres. The tyres transfer forces to the machine
and the steering controls the direction. Therefore the wheels are the
prime concern, with the suspension used to keep them in an ideal state
under all conditions. The frame is there to keep the suspension in the
right place, so it can do it's work properly. The engine and riders,
although not structurally important, also sit on the frame, as this
is a very convenient way to accommodate them. Therefore if suspension
is to be custom made, it should be made first, to fit the perfectly
aligned wheels, but with the frame mounts left until later. The frame
then made to fit the perfectly aligned suspension. In reality, the chassis
is always made first, so the engine is well supported, and then the
suspension is built and probably lightly adapted to ensure good wheel
alignment to a possibly unsymetrical chassis. The mounting of the steering
head is left for much later.
If you have to modify or make new suspension components, always build
them as mirror pairs before making the frame. A simple wooden dimensional
welding jig will help enormously. This applies not only to front fork
parts, but to all symmetrical pairs of components, right through to
the symmetrical rear radius arms. Fit them to the components such as
hubs etc and ensure they work as required.
When making the suspension arms, fit the spindles and bearings in their
housings, supported level and straight on Vee blocks, then carefully
make the A frames or whatever to fit. Then tack weld in position, with
three tacks per join, remove bearings and fully weld. When cooled in
air, return to the jig and tweak if distortion has occurred during welding.
Where shock units are to be mounted, leave these only tack welded, as
they may need to be repositioned once the rolling chassis is refined
for overall balance and suspension rates.
Never cool metal components by plunging in water, as it can cause uneven
hardening and fractures. Allowing the metal to cool in air is much safer.
Tweak, adjust and modify the frame tubes before assembling to fit these
pre- aligned components. If the suspension units are symmetrical and
built in a simple jig, the frame mounting lugs are fitted easy to be
tack welded to the frame, and the wheels lined up accurately, then the
frame will naturally be positioned accurately.
Working from accurately positioned wheels to the frame will allow the
whole machine to be accurate and handle well.
The frame can now be built.
Building the frame should be surprisingly straightforward as by now
you will know what it is that you are intending to create, and should
have thought it though many times. The main clues to the overall frame
design are the components which have been sitting in place ready to
be joined with a competent structure to take the forces which have to
Clean all parts and tubing, then practice with, and set up the welder.
Have safety equipment at hand and ensure plenty of room. Check the fire
extinguisher, preferably carbon dioxide, or at least a bucket of water.
Always make welding a positive experience. When everything is prepared,
frame building can, and should be fun - serious, but enjoyable. Very
Warning: If you have never welded before, expect to spend a month of
an hour a day or more getting to learn to weld to an acceptably high
standard. Some people are born welders, but most people are not. It
takes skill and it takes time to make a neat, fully penetrated, and
clean weld with no distortion. So if you have never welded before, get
the welder six months before you intend to start building the frame
and practice, practice, practice. If you are really bad at welding,
go to a night school on the subject, or learn to tack weld and hand
over the assembled frame to a professional welder.
A section on welding is in the appendix to this monograph.
Clean a flat and level floor.
If you don't have a level floor, then three concrete paving slabs in
the garden will suffice, but they must be level. You may be able to
get away with building on a less than perfect floor, but it is imperative
to keep the spirit level correctly aligned. Therefore mark one end of
the spirit level so it will always be aligned pointing to the right
and the front of the machine. If this is not done, a less than accurate
bubble will soon be followed by a less than accurate machine.
If you have not done so yet, mark a thin and perfectly straight centreline
on the most even part of the floor, and another centre line at ninety
degrees to it for the alignment of the rear wheels.
Straight lines can be made using a chalk string, pulled tight and flicked
vertically to leave a straight chalk line. Standard building site practice.
Then use tape either side to allow a painted line to be made. This line
is a guide, the final accuracy will be done with a metal rule directly
on the machine. To get the perfect line at ninety degrees for the rear
axle, divide the main line in half, draw an arc from each end, and where
these intersect at each side, can be joined to give a line at exactly
ninety degrees to the centre line. Alternatively use the sides of a
good, big square machine-made cardboard box, or fridge door or similar
as a large set square. Double check this alignment.
The original engine mounts should be ground out of the donor machine
if required, reprofiled to fit the new frame tubes and lightly bolted
on the engine to hold them in place. The transmission is double checked,
aligned and centred. All the suspension will be blocked in place and
accurately aligned, with frame mounting lugs in position ready to accept
the frame tubes. Double check that all mounting bushes, brackets, spindles
and relevant components are in place.
Where the engine mount and suspension cannot both easy fit onto the
line of a frame tube, the suspension takes priority if they cannot be
easily modified or shifted slightly to clear the engine mounts. The
engine mounts can be extended or modified later to fit the frame in
a slightly better way. This may also be a good opportunity to tease
the centre of gravity a little lower without upsetting the layout.
The gearchange should by now be well considered for future reference,
and decide where it can and more importantly, cannot fit. If in doubt
about the gearchange path, use temporary dummy set-up using broom handles
or whatever is suitable so it is not obstructed by frame tubes. See
Use blocks to accurately position the engine, transmission and rear
wheels in position above the centreline with the right ground clearance.
Use a spirit level, straight edge, plumbline and your eyes to make sure
everything is aligned and level. If there is a propshaft between engine
and differential, do not cut it yet, but make sure there is adequate
room so the splines will be positioned to take all movements into account.
On independent suspension rear ends, it is important to have all drive
splines from the differential to the rear wheels in the correct position
for the movement they permit.
It is assumed the tyres are pumped up and the rear tyres are of identical
size and type. If you have four wheels to choose from, always use identical
wheels and tyres, with similar amounts of wear, pumped to the same pressure.
Set up and check the rear wheel camber and toe in, ground clearance
and any other aspects of the design. If the steering rack is retained,
make sure it is set in it's mid position and prevented from moving.
Leave the toe-in as per original machine until after the first few test
rides. Refer to car manual.
Make sure any drum brakes are on the correct sides of the machine.
Block securely and mark it all so you know when it's disturbed; do
not line up perfectly to wrong positions.
Measure diagonally from points on the wheel mountings to front and
rear of the centreline using a metal tape measure. Do not use string
or a cloth tape measure which can stretch too much.
Accuracy should be less than 5mm across the widest parts, preferably
zero and don't take just one measurement, double check, and triple check
for all the main parts.
Position the front end with steering head just ahead of its intended
position, to allow a little room for excess front frame tubing. Align
with spirit level and plumbline, then block in position. If this is
difficult, fit the handlebars upside down then rest them between two
chairs. It's not ideal, but as long as it's approximately in the right
place when you start welding the main tubes in position, this will do
for now. Front end will be accurately aligned later. Block or tape the
front wheel on the centreline.
The trike has the advantage of being a triangle in plan view, so overall
accuracy is easier than most other vehicles.
If simply building a trike rear end to fit a bike frame, then it is
often easier to build the rear frame to align the differential to the
chain run, then build the suspension afterwards.
There are two ways to build a frame from scratch for a car engine design:
Front to back, or back to front.
Front to back means building the front end complete with steering head
and mounting it to the engine mounts first, then aligning and then building
the rest. This can lead to gradual misalignment. Used only for bike
based trikes, which use a ready built standard bike frame.
Back to front is safer, because all the heavy work of building the
engine and suspension is done first. This then allows a solid assembly
for mounting the steering head and front end. This allows the builder
to tweak the bare front tubing after the major rear alignment and welding
When mounting the main tubes to fit the temporarily positioned steering
head, leave a little excess length at the front which can be finally
aligned and trimmed to size.
With the rear assembly tack welded in position, the front tubes can
then be teased and coerced into line for a perfectly accurate steering
head relative to the rear wheels. When perfectly aligned, the steering
head mounting tubes can be ground back and fitted until a perfect rake
angle is achieved, then aligned and tack welded.
Preparation is the key to good welding. Clean the tubing first and also
weld some test pieces and break them until you get it absolutely right.
For deep welds, cut through the welds to see that the penetration is
of good quality, with minimal slag inclusion or holes. Unfortunately
the first few welds are the main frame welds. If in doubt, tack weld
and hand over to an expert.
If you know of a professional welder, then they will often do extra
work in their spare time and may come to the trike, so all remains accurate.
They can also offer advice prior to final welding. Do not be surprised
if the welder asks for many areas to be dressed or chamfered and other
requirements, as they know their job, and are always worth the cost
of a second visit. See also welding later.
Always try to employ full length tubes from the rear suspension mountings
through to the steering head for the strongest frames.
The bottom frame tubes should be able to have the radius arm mountings
or pivots welded to them. Likewise the bottom wishbones and similar
items. Where structural components are welded, try to position the fittings
to be fail safe. Check the direction of the forces and position appropriately,
so that if a weld or tube fails, it will fail as safely as possible.
Remember the wire and solder model frame.
A strong frame will hold everything together.
A rigid frame will ensure the bits hold together without flexing.
For best results, go for both.
Start making the frame by aligning one main tube, bending if and where
needed. Never exert any force while offering it up to the machine for
checking the fit. Always remove the tube and modify until perfect. Then
gently mount in position and check, or remove and tweak further if needed.
This reduces chance of upsetting the alignment of the whole machine.
It is much quicker in the long run than causing unseen distortion in
the aligned components.
The more common designs use dual upper and lower main tubes. Such a
main frame tube will be running from the rear suspension, past the engine
and curve up to the steering head.
Where possible, always try to make frame tube as mirror images. When
the first tube is made, it is easier to make a mirror of it when it's
off the machine, allowing ease of comparison. (It also helps the frame
to flex evenly under extreme handling conditions :)
Chalk or a felt tip permanent marker pen is also priceless at this
stage. It allows accurate marking of the centres of the curves for the
bender, where to clean the metal for fitting the brackets and where
to modify the engine mounts etc. A felt tip pen can also stir the tea,
as this is a slow, steady process with plenty of looking and refining
as the main components gradually take shape. It is not a rush.
Align the main tubing on the engine and suspension mounts with excess
metal sticking forward for the steering head. Then mark their position
on the tube and carefully remove the original engine mounts to allow
final trimming to fit the frame tubes. Replace and tack weld the tubes
just enough to hold in position. See welding appendix.
You may be very keen to get the main tubes in place and fitted, but
this is the time when a very slow approach is needed. You can afford
to rush the seats and battery box, but not the main frame tubes.
Take your time and always take some time out to just sit and look at
the main frame tubes which are lightly tack welded in position. your
initial sketches will surely be modified at this stage as you work through
in 3D reality and this is what makes a much better machine.
Now recheck the alignment of the wheels, engine, forks and adjust as
By making the tubes as mirror pairs, inaccuracies in alignment will
show up more easily, such as misalignments of suspension or tubing etc.
Tweak and adjust as needed. When accurately aligned, add some more evenly
spaced tack welds on each join to prevent it all moving about.
Then the other main frame tubes can also be added, again as mirror pairs
Build the whole structure to make the smooth, clean lines so exemplified
of better trikes. Making the tubes to fit the assembled components helps
the builder refine the whole machine as it grows. There will be unseen
problems, so take time to work out at least two different ways to solve
any problems, as this is a crucial time in the machines creation and
extra time spent now is well repaid.
Now check that the engine can be removed and replaced fairly easily.
There may be other main tubes, which may suspend the top of McPherson
struts or similar items and these secondary frame tubes can now be positioned
to support the main tubes.
To keep the main tubes aligned during side loads of cornering and jumping
hump back bridges, secondary tubes are required. Unlike main tubes which
should maximise the most natural and strongest forces, secondary tubes
can be fitted in a variety of positions to help minimise distortion
in the main frame tubes. Triangulation between the tubes is will always
make for stronger and more rigid frame.
Once the basic frame is built without the steering head, the tack welds
can be built up to be structurally competent enough to allow removal
of the blocks. Some of my machines are road tested with fifty percent
welds, but at this stage, just enough weld to hold all together will
At this stage the basic frame tubes are in position, with the suspension
and engine lightly tacked in place.
Tack weld a piece of tubing to roughly replace the forks for basic testing
purposes. This should keep the front of the trike in the correct position
off the floor as the frame is allowed to relax when you remove all the
If you have tightened any mountings, then lightly loosen all engine
and suspension mountings, as this will allow the whole structure to
Lift one rear wheel and slide a piece of plywood underneath and a few
ball bearings or marbles under the plywood. Now you can gently load
the structure, to see how the suspension units behave and the rest of
the structure distorts when gently loaded with a rider.
Make another check of the alignment and look for any signs of untoward
distortion in the frame structure. If a rider can sit gently on the
structure, the differences when being on and off can be viewed from
various angles to see how the structure behaves, especially the suspension
units and also general frame flexing.
Gently push on the upper suspension mounts to check the suspension
settings are reasonable and to see how the frame flexes. If you have
a digital camera or cam corder, you can make a little animation of the
frame flexing from front and side and the rear, then run the animation
sequence to check where the main frame tubes flex.
Check if anything has bowed badly, curved inwards or other unexpected
problems. Likely areas are between the lower suspension wishbones, where
the frame wants to pull apart and the upper shock mountings, when may
not yet be finished, so use this opportunity to assess the best possible
way to keep these highly loaded structural areas well designed and built.
- Well deigned and built does not mean lots of heavy metal.
Where the upper suspension mounting points can be adjusted to fit the
frame tubing, it can be advantageous to lightly test the rear suspension
mountings, adjusting them so the frame sinks just perceptibly on the
springs indicating a reasonable amount of suspension in the rest state
for a finally loaded frame. If a light machine is intended, then the
springs should compress about ten percent with a single rider. If a
heavy shell or three or more riders, then just a slight amount of spring
compression with one rider may suffice at this stage. Reposition the
suspension units until a balanced rear end is attained. This does not
apply to McPherson struts, which may need the strut to be modified.
NOTE: It is very important to test the frame with one rear wheel which
can be allowed to slide sideways. This will show up any sideways spreading
of the frame. Place one rear wheel on a piece of plywood so that it
can slide on small balls or marbles and then watch the way the rear
of the chassis spreads apart under careful loading. This will show if
the rear frame is spreading. This cannot be tested with both wheels
on the ground, as they prevent such spreading, but must be able to spread.
Where any spreading occurs, cure at this stage with suitably strong
tubing, as this is the main structure of the machine. Do not fully compress
the suspension, but a moderate load will show if any unwanted distortion
is happening at an early stage and that the shocks are reasonably well
positioned for their purpose.
Also carefully check the top shock mountings, the bottom frame cross
pieces and radius arms or wishbone suspension components.
With the shocks removed to allow the suspension to move fully, check
the wheel alignment as it compresses and that the wheels do not change
inappropriately from their vertical alignment. The rear wheels should
lean in slightly at full compression, so they will stay fairly flat
on the road, with just the outside of the tyre being slightly more compressed.
If the trike can be removed from the blocks, then by using a plank to
lever the sump, the frame can be raised and lowered as if cornering,
to see how the wheels align to the road. The plywood on marbles now
shows its worth.
If all is well, add a few more tack welds to strengthen the frame and
If all is not well, it is easy to replace the blocks and wedges, grind
out the tack welds and replace or modify any components as needed and
this may even include the main frame tubes.
Perhaps you may wish to shorten the upper wishbones and make new mounting
points on the frame.
Perhaps you may wish to make a deep sump brace, so the engine can be
removed, but still have a strong lower frame. Perhaps the upper shock
mountings need a re-think.
This first test is a good time for reflection on the overall design,
so use it to good advantage. It's called sitting in the garage with
a cuppa tea or a can of beer.
If all tack welds are fairly equal, and wishing to know what part of
the frame will break first, then this is an unique opportunity to do
so in the simplest way possible. Loosely replace the blocks so that
any component drop is less than an inch.
Once satisfied, a few welds to strengthen the frame are added, you
may now tweak, kick and/or adjust the whole assembly as needed. This
is a good time to begin to understand the way the frame performs / distorts.
Remember the wire frame model. If a weld breaks, then little is lost
at this stage and knowledge is improved. Then re weld and try again
until the frame is behaving well.
If necessary, the whole chassis can be disassembled and re-shaped by
grinding off the tack welds with only a loss of time and effort.
If all holds together well with minimal distortion, then confidence
Re-tighten components and check for distortion when tightening them
to resolve such problems early. It is often possible for a 'relaxed'
frame to distort slightly, causing engine or suspension bolts to become
misaligned. Check for this by partially removing each bolt to check
they slide easily in a well aligned frame and it's mountings.
Further distortion will occur with full welding, so getting it close
beforehand will minimise any further misalignment and make heavy maintenance
For mid or rear engined trikes, the non structural, minor seat tubing
at the rear of the frame can be removable, leaving just the basic frame,
engine and suspension in position. It can be a good alternative for
particularly awkward engine removal or for maintenance on a fuel injected
transverse Vee six with turbo etc. This is similar to some motorcycles,
where the rear is bolted in place. It also allows for a rear shell to
be fully opened for showing the engine at custom shows.
Do not mount passengers on removable sub frames unless the design is
Fitting the steering head last will allow all the main parts of the
frame to be sorted first. The wheels accurately aligned, the engine
correctly aligned to the differential, and engine mountings correctly
positioned and tested under load.
Once the rear end is sorted, the main part, the steering head can now
be done at leisure.
Double check the rear end and add more tack welds to keep it all in
position. If deciding to fully weld the rear at this stage, it should
only be done after the gearchange linkage is made and fitted and any
prop shaft modified, as many problems may yet be unseen, especially
on transverse engines. See gearchange later. There is no need to fully
weld at this stage, but all frame joins must have at least four evenly
spaced, strong welds (three plus a safety) to prevent any movement or
breakage of the temporary joins.
Check list for the engine:
Ability to flex on the original rubber mountings.
Alignment of the differential to the rear wheels.
Restraining of engineering using original engine struts.
Ability to remove engine easily and to change the clutch plate.
Clearance for the carbs and exhausts.
Gearchange routing clearance.
Check list for solid axles:
Radius arms which pivot at the front either side of the engine output
shaft or sprocket.
Upper suspension mounts.
Check list for independent rear suspension:
Shorter upper and longer lower wishbone sets, the lower ones including
radius arms, or have other support for fore and aft force resolution
into the frame under acceleration and braking.
Differential mounting and any chain adjustment.
Fitting the front end demands good accuracy.
The two rear wheels do not worry if the engine is slightly off centre,
or a host of other minor inaccuracies. The front end alignment requires
Assemble the steering head, forks and yokes and front wheel.
Pump al three tyres to correct pressure, ensuring all is secure and
perfectly aligned on the floor once again. Use a plumb line to get the
wheels centres aligned on the floor.
Measure the position of the steering head from the two main alignment
points, these are usually the centres of the rear wheels or their bearing
housings. With the wheels perfectly aligned and set, (double check)
tyres pumped up, and blocked underneath to prevent any movement, mark
in the centre line of the wheels.
Check the rear wheels are horizontal with a plank on them and a spirit
Assuming the wheels and tyres are identical, then the most accurate
point is the outside edge, directly above the axle centre line. Each
rear wheel should be on the accurately positioned floor line, securely
blocked and identically aligned with the other rear wheel and their
axles at ninety degrees to the centre line. Mark the top of the tyre
above the central spindle, using a plumb line to check. Block securely
and do not disturb anything. Marking a tyre is difficult, so use masking
tape on the rubber and the alignment mark should be easily made to within
It is not possible to make a mark exactly at the edge of the tyre, so
an accurate point must be made on the masking tape, close to the outside
of the tyre, which is evenly positioned from the centreline of the machine.
For real accuracy, usually the wheel mounting flange faces are used
for this purpose, by measuring in the distance from the outer rim to
the flange face and marking this on the masking tape. Formula one rigs
have dummy solid wheels for alignment checks.
NOTE: It is imperative not to disturb these points, so block the wheels
securely by making four wooden wedges. If in doubt, then use the upper
pivot points of the outer rear suspension, which cannot be disturbed.
If in doubt, such as the kids playing around without you knowing, always
use a symmetrical part of the wheel bearing housings.
To position the steering head central with the whole machine, measure
the identical distances from the alignment points on each wheel.
If the front wheel is perfectly on the centreline, the rear wheels are
perfectly spaced on the cross line, and all else is well, then the front
end tubes can be tweaked into position to match the steering head. Use
a plumb line (string and weight) to get these tubes accurately over
the centreline while the rear wheels are at perfect right angles to
the centreline on the floor.
The front tubes may need a little persuasion, by hammering with a length
of similar tubing, (most hammers are too feeble) with a block of wood
to protect the tubes. If larger adjustments are needed, then bracing
a length of tubing through the frame using blocks of wood and ropes,
such that the tubes can be bent with minimal stress on the welds.
Once the front tubes are perfectly central, AND the frame alignment
checked yet again, the ends of the front tubes can be ground to take
the steering head. The front wheel is fixed on the ground and the steering
head and forks rotated on the fixed front wheel until it kisses the
frame tubes perfectly. If the frame tubes are a little low or high,
then just jack up the front of the trike frame. The steering head should
now rest on the frame tubes, equidistant from both rear wheels. The
frame tubes can now be ground and dressed to fit the steering head perfectly
and at the correct rake angle.
As the steering head begins to sit snugly in the tubing, gradually
roll the front wheel along the floor centre line until the desired rake
angle is achieved. Careful grinding with the angle grinder will then
help to create a perfect fit.
If the frame tubes are a little low or high to fit the steering head,
then simply raise or lower the front of the frame with wedges or a jack,
as this does not appreciably change the overall alignment of the machine.
When welding the steering head in position, the heat will damage the
steering head bearings. Just tack weld the steering head in place, then
check carefully. New bearings can be fitted after initial testing. If
special pullers are available, which will NOT upset the steering head
alignment, then this is acceptable to remove the races after the steering
head has been tack welded. Do not hammer them out, as a misaligned steering
head is infinitely more expensive in the long run than a new set of
head races. It is better to leave them in place to reduce chances of
misalignment. Yet another advantage of using affordable, easily available
Getting the steering head tubes equally positioned relative to the
rear wheels is simple, just two equal measurements. Making the forks
vertically takes a little more work prior to tack welding the steering
head in position.
To get the front end accurate when seen from the front, use a straight
plank across the top of the identical rear wheels and check with a plumb
line and a spirit level. If the tyres are not identical, probably with
a slight more wear on one side, then measure the difference in overall
diameters then place a shim of card on the smaller wheel to make the
plank level with the axles. Now mount the spirit level in a similar
manner beside the front wheel and note the bubble position. Then a set
square can be positioned on the spirit level to give the accurate alignment
needed. A plumb line will confirm.
Measure many times, then tack weld the steering head in three places
for each frame tube, plus a couple of strong welds on the bottom of
the lower tubes.
The rear wheels will be perfectly horizontal with the spirit level,
so the front forks can be aligned with the spirit level, as seen from
the front. On well raked machines, this is often done by suspending
the plumb line from the centre of the top yoke, over the centre of the
bottom yoke and dangling close to the ground, to be perfectly in line
with the centre line on the floor. It is called being accurate.
When the steering head is fitted, gently allow the whole machine to
relax, free of any supports.
Unblock the wheels and always roll the machine backwards and forwards
to allow the chassis to fully relax.
Now check ALL alignments again.
Check the front end accuracy from two independent methods, to help
confirm accurate frame alignment. Also checking the distances between
front axle and left and right rear axle bottom pivots. Checking the
alignment of the top of the steering head from the top of the wheels,
and also checking the alignment of the bottom of the front wheel from
two lower wheel hub mounting components will give a confirmed check
of the accuracy. If a third check is needed, mark the centreline on
the rear of the machine and view from this point, to confirm the front
wheel is accurately aligned relative to a plumbline hanging off the
centre of the steering head.
If anything seems wrong, take your time to find out why. Also use your
eyes and common sense for anything obvious or dubious.
A classic trick for most of us humans with mismatched eyes, is to look
down the length of the machine using a pocket mirror as well as normally,
as any non symmetrical aspects will show up more easily.
You now have a basic rolling chassis, which is tack welded so that
it can be easily modified or even replaced.
Place each of the three wheels in turn on a bathroom scale and note
the load. Do the same with the rider and make a note, so that you can
adjust the load on each wheel according to its size and profile, by
moving the rider and later, the fuel and battery etc.
If you have a mid - mounted car engine, then your three wheel loadings
should be close to a very nicely balanced machine.
If you have a VW with a moped front end, then you may wish to consider
your wheel loadings very, very carefully.
Take your time at this point and give yourself a good long breather.
Allow a day or two, to remove doubts or reconsider any suspect or marginal
You can still break the tack welds if needed. Be prepared to do so,
as you will find it increasingly more difficult to overcome inaccuracy
as the work progresses.
Checking costs nothing but is extremely important. Keep in mind what
happened to the Hubble space telescope.
Now carefully assess the forces ruing though the frame, and decide
where the bracing is to go. For long lengths of unsupported tubes, then
triangulation is needed, unless you are using very strong tubes. Flex
the frame and see where any secondary strengthening us needed.
Where fillet plates are to be used, such as either side of the steering
head, these should be done after the main welds are finished.
When the basic frame is complete, carefully remove the engine and all
Fully welding a chassis while it is off the machine will allow easier
and thus better welding.
It also encourages the builder to add any little fillets and refinements,
and also to add any late changes, flourishes and to dress the welds
for a smoother shape and reduces chance of fracturing from any sharp
stress points. A clean profiled chassis makes checking for fractures
much easier during initial testing. A bare frame can also be measured
for assessing general accuracy from it's basic alignment points.
Where any last minute changes are to be made, usually in awkward areas,
such as a better fitting tube, always brace the area with tack welded
tubes before removing the item, then fit new and finally remove the
NEVER weld on one side of the chassis and then the other side, as this
will cause distortion. Weld both sides of the chassis as pairs in the
same manner. For example, weld the left, then the right upper suspension
mounts, then the left then the right rear engine mounts etc.
A fully welded chassis will allow the chassis to be fully loaded at
rest position, and the steering head to be checked accurately for distortion
prior to final welding of any head stock fillets. You still have the
chance to twist the steering head into perfect alignment if the welding
Replace the fully welded chassis, note the problems and then tweak,
or grind out and reweld parts if distortion occurs.
Use the tape measure and spirit level with a vengeance.
When fully satisfied, check and double check the steering head and
then add any steering head and other fillets when confident.
A bare, fully welded chassis will often show up imperfections when
the components are replaced. This may require minor grinding or tweaking
for an easy fit of the engine, suspension etc. Occasionally the steering
head may need a little tweaking back into line with a scaffold pole,
which is best done before the side fillets are welded in place, and
old bearings are still in place.
No chassis is perfect.
Having made all the effort, the chassis may well be a great deal more
accurate than most. Accuracy does not ensure good handling, but it does
eliminate many handling incongruities.
When fitting the engine again, there will probably be a few holes to
file to get a clean engine fitting, but if the holes need a lot of filing,
then just make another check that all is well, as this is sometimes
a way to tell if something is amiss.
Removing big engines.
Where a big engine is fitted, perhaps a V8 in front, then it may be
necessary to extract the engine by having a lower frame rail removable.
If particularly heavy, such as Detroit lump or a V12, both bottom frame
rails could be removed as part of the engine, and supported on a rolling
dolly, allowing a more rigid upper frame which can be lifted off the
When building a removable tube, first get the main frame strongly tack
welded in position to keep it all together. Do not use full welds at
this stage, as distortion may be incurred, causing springing when the
tubes are cut, thus helping to misalign the frame.
Support the engine just enough to take the load off the frame, but still
keeping it in place on the trike. Then cut the tubes where needed to
remove the engine. A hacksaw is ideal as the resultant gap is small.
Undo any engine mounts and remove the section of tube.
The removable tube can be secured in place in many ways. The simplest
is a slightly larger diameter tube which is split lengthwise, to act
a split sleeves, so the inner part of the split tube is welded to the
bottom of the fixed frame rail, and the other half welded to the removable
tube, so that both halves will support the engine and ensures that failure
of any bolts will still keep the engine from dropping.
Slash cutting the main frame tube will allow the engine to rest on the
lower cut of the frame, and if done with a little sophistication, will
be self aligning and allow easier removal and replacement. It can also
be a little more fail safe.
Only tack weld the split tube components, to check the tube can actually
be removed and will not distort under load. When satisfied, fully weld,
fit bolts and release the engine weight to check for frame distortion.
Adjust as needed. This is an advantage of building rear first without
the main frame fully welded, as any deformations are accounted for before
final front end alignment and final welding of the steering head.
If through bolts are used, the inside of the frame tubes will need spacers
to prevent the frame tubes from squashing when the bolts are tightened.
Solid split bar ends are also possible, but heavier, requiring an engineering
firm to make matched pairs to fit the tubing. Also study motorcycle
split frame tubes for alternative mountings for lighter engines. Reassemble
and fully weld the removable parts and refit to the engine, suspension,
forks and wheels. Allow the frame to relax fully and check before further
welding. Always build up and fully weld split frame tubes before fully
welding the chassis.
A build sequence.
As all the differing parts need conflicting requirements, there is always
room for confusion or pitfalls. To sum up the many sequences, the following
is a generalised build sequence for a trike based on a generically common
transverse donor car engine and transmission.
Find the most level part of the floor, make a paint line with a second
line at right angles to align the rear wheels. If in the garden, place
three concrete paving slabs so they are level when checked with a spirit
level and a straight plank. A central line is scratched accurately on
Block up and align the engine and wheels, the anti roll bars, radius
arms and prop shaft splines.
Make any special suspension items such as wishbones and radius arms,
preferably on simple wooden welding jigs to improve accuracy, and fit
them in position on the hubs etc.
(For front engined trike with a shortened prop shaft and a one-piece,
solid rear axle, reposition the front mounting of the radius arms to
be either side of the front end of the prop shaft.)
Align McPherson strut suspension units, which may need tying a plank
over the engine to keep them in position.
Position the front wheel, forks and steering head, to give a guide position
of where the front of the frame tubes should reach.
Start the frame by bending and fitting the two bottom tubes of the frame
using two long, symmetrically shaped tubes. Such tubes are often similar
to scaffold pipes in diameter and wall thickness. These often run from
engine mounts and suspension mountings, to a little beyond the steering
head area. Check alignment and tack weld in position to align engine
and suspension. Front of tubes may need a simple offcut of sheet steel
support to keep them in position while tack welding.
Fit a dummy gearchange linkage using an old broom to check the clearances
of subsequent tubing.
Add upper main frame tubes as needed. Check accuracy.
Add cross braces and any suspension mounting lugs for the rear springs
which take the main load of the trike.
Add all other main tubes, such as for cross bracing and to reduce flexing.
Strongly tack weld all parts with four tack welds per joint. Three to
maintain alignment, and one for luck.
Loosen all engine and suspension bolts to allow frame to relax. Remove
all blocks. Allow one wheel to slide sideways on a plank and rollers,
then lightly load the structure to check for any obvious deformations
and suspension movement. Decide on any strengthening requirements.
Check alignment and tweak as needed. Tighten components and check. Expect
a few welds to break. If all welds are equal, then any breaking will
highlight the areas of most concern, as this may be the weakest part
of the design.
Replace the machine accurately on the centre lines.
Fully align front end and steering head, yokes and forks etc. Check
trail at proposed steering head rake angle. Adjust position of the front
of the frame tubes as needed.
Grind out shape on front of frame tubes to accept the steering head.
Align the whole machine on a perfect centre line and roll the front
wheel on this line to align to the front fame tubes. Adjust height of
front of frame for perfect fit. Align rear wheels to be level to ensure
a plumb line will give accurate front fork alignment.
Use metal tape measure, spirit level and plumb line to check front end
alignment relative to the rear wheels. Tack weld the steering head in
position and check. Tweak as needed. Add more substantial tack welds.
Add support or localised strengthening where needed. Gently test until
Place each wheel in turn on bathroom scales and note the load. Do the
same with the rider and make a note, so that you can adjust the load
on each wheel according to its size and profile, by moving the rider
and later, the fuel and battery etc. If you have a VW with a moped front
end, then you may wish to consider your wheel loading very, very carefully.
If you have a mid -mounted car engine, then your three wheel loadings
should be close to very nicely balanced.
When it is as good as possible, remove all items and weld the frame
fully and evenly.
Reassemble, check alignment and tweak if needed, then add any steering
head side plates. At this stage a structurally complete, if very basic
trike is created.
Now check you can easily remove the engine, and also gain access to
service the engine completely.
Ensure easy access to replace the clutch plate may be particularly useful
for thrashers, or those with unusual gearing or excessively large rear
Check the exhaust and gearchange routing and any other potential problem
area is acceptable.
Once the basic frame is built and fully welded, now try to break it
Trying to break the design is necessary to ensure the basics are right.
There is no point doing anything else until the basics are right. It
is better to find out at this stage if there are any dangerous aspects
as yet unknown.
NOTE: If anything may break, it should be allowed to break at this stage,
as it is much easier to remedy.
Remove the blocks to allow one wheel to slide sideways again, as mentioned
above using a plank and dowels or marbles. Now, with at least three
people on it, jump up and down on the basic trike frame, complete with
engine, forks and wheels. Give it a really hard time.
Simulate hard front braking by rolling it gently into a wall, so the
front telescopic forks will just bottom out, many times.
The steering head bearings may need to be adjusted as they settle. Jump
up and down on the inner rear suspension mounts to get the suspension
to move fully, right up to the rubber bump stops and preferably beyond.
As a group, kick the wheels really hard from the front, back and sides
to simulate rocks and kerbs. If this is your first trike, you may well
misjudge the kerbs, so do this testing with real dedication.
Do not omit this initial testing, you know why, so don't delude yourself.
Continue until confident.
After this disgusting act of gross abuse, inspect everything carefully,
especially where the wire model frame broke. If the frame fractures
or breaks, you have everything on hand to repair and modify the design.
Check to see if the frame has twisted or become distorted, then straighten
it and design a cure for the problem, possibly a little more triangulation
or a fillet plate, cross bracing etc. It is better to do this now, rather
than after the paint and expensive work has been added. Load to max,
see how it flexes, then think, then modify as needed.
If not at all happy with the design, then simply design and build a
new frame in the light of experience. You may simply wish to grind out
the upper or lower main tubes and replace with a different design, or
reduce the wheelbase, or make a better riding position, or any of many
aspects of the design.
Now is the time to get the basics as good as possible. Small changes
may make minor differences to handling, but may make a stronger, or
less flexing chassis.
You now have just the three wheels, suspension and engine
in what is hoped is perfect harmony.
The most important part is now completed, give yourself a pat on the
back, you deserve it. Now a real breather is possible and to take time
to truly appreciate your work.
Will it handle well ?
If a first rolling chassis, the builder simply cannot know if it will
handle or not. This is very common, as although a lot of work has gone
into the machine by this stage, it is purely hypothetical and not really
very scientific. (I've tried to steer clear of the arithmetic.)
It is rare for a reasonably well thought out machine to handle badly
enough not to be of little use, but for some, it is worth while at this
stage to get a closer check of your machine.
Now that the basic design is available for assessment, (as much of the
work from now on will be fiddly and cosmetic), but the fundamental must
always be as good as possible.
Even if not up to expectations, it often needs just a little modification
to the basics to make a good machine. The toe in, tyre pressures, even
the rake and trail can be modified.
From now on, it is the rider, battery and fuel weight distribution which
will help refine the last few percent of its potential.
If in doubt about handling, then make a temporary lash up to see how
the machine handles.
A simple moped fuel tank, a bungeed plywood seat and a lots of nylon
tie-wraps or luggage straps around a small battery or use jumper leads,
and minimal wiring will often get most machines up and running.
A quick thrash around a few quiet bends or carpark, once the brakes
are working, will usually instil confidence in a reasonable machine.
It is possible to bump start the machine in second gear with a little
help from friends, and pull the wire off the battery to stop the engine.
This is also a good opportunity to refine the riding position and suspension.
If a bracket is made, so the front wheel is replaced with a towing
hitch, then the trike can be towed behind a car like a trailer, using
it's own rear wheels, so it can be towed to a testing area. A simpler
design would have a special spindle or special bracket to replace the
front wheel, so the trike can be attached to the towing hook. A simple
Y frame bolted to the frame, possibly with a couple of bars to make
a rigid structure and to take the towing hitch. Or you can make a ball
cup to replace the front wheel axle. (Make sure the trike cannot jump
into gear while being towed, or remove the chain.) Don't forget to fit
trailer lights and a copy of the towing vehicles number plate.
Centre of gravity: Part II.
With a complete rolling chassis, but not a finished trike, it is a good
time to check the basic weight balance, especially if you cannot test
ride the machine at this stage. This will give a good view as to where
the weight is acting and allow you to modify the seats and secondary
components to refine the weight balance. As mentioned earlier under
the section on the centre of gravity, it is also possible to predict
if the trike has a predisposition to roll or slide. This requires knowing
the centre of gravity of the basic machine, so it can be further refined.
On a trike, the weight probably precludes the option of hanging a complete
trike from different positions from the roof and probably not a good
idea unless you have a chain block or other tackle. Luckily, the centre
of gravity is usually along the centre line of the trike. The centre
of gravity when seen in plan view will depend mainly upon the position
of the heavy bits.
If you decide to hang the trike from the ceiling, make sure it is as
complete as possible, or at least with all the heavy bits and wheels
etc. Then take a photo, with the chain or rope in view, plus a plumb
bob, so you can draw a drop line. It will probably be best to put a
strop or the hook through the rear suspension or around the diff or
gearbox area, or somewhere near the middle of the trike, so that it
hangs at an angle which will highlight the centreline below the pivot,
usually the top of the chain or rope. Where the vertical crosses the
trikes centreline will be the centre of gravity, although for most accuracy,
check from two different points.
A safer way:
If your roof is weak, but you still want to know where your centre of
gravity is, then pump up the tyres, grab a few strong friends and balance
the trike on the ground on one wheel. You will have to block the wheel
or apply the hand brake. Now lift the trike up so it balances with no
effort on a single point on the ground. Use a plumb line to see where
the centre of gravity is directly above this point on the ground. In
this example, it goes through the gearbox and assumed to be on the centreline
of the trike.
As shown in the second piccie, when hanging or balancing the trike,
also look for the vertical line from the side of the trike, with all
three wheels level in your sight, so you can see how far above the ground
the centre of gravity is. The riders weight will raise this, but it
is not recommended to have a rider sitting on the trike in the search
to get perfect data.
Now that you have a couple of chalk lines on the trike, one to show
where the centre of gravity is along the centre line, and another to
show the height of the centre of gravity as seen from the side, then
you will truly know where the centre of gravity is for the basic trike.
The centre of gravity will be somewhere near the mid point of all three
wheels, and should not depend too much upon where the engine is.
If you have a flimsy front end, then you may wish to move the weight
back a bit. If you have a special front and want serious stonking ability,
then you will be looking for almost even balance on all three wheels,
dependant mainly upon the relative sizes of front tyre and rear tyre
The centre of gravity when looking down from above the trike in plan
view, will give you a good approximation of the overall balance on the
Although you will have known the weight on each wheel from the bathroom
scales, until now, you did not know just exactly where this weight acts.
This can now be improved with sensible rider placement fore or aft of
this point to get the axle loading just the way you want.
Now you can re-read the section on heave, yaw, and slide or skid etc
- to assess what you have in front of you.
Heave up and down. The amount of stiffness in the springs and the damping
rates. These are best sorted out with test rides, but the shocks should
be such that you can push them down to make them move with a reasonable
force. If they are really stiff, then you have to modify.
Pitch fore and aft. You can asses the chassis under braking by using
the bike front brakes to see how the trike pitches.
Yaw side to side. This cannot be easily assessed, but if the engine
hangs out the back like a VW then expect a dumb bell effect. The best
machines have their mass centrally, like a fighter aircraft.
Roll. This can be assessed by pushing the trike sideways, to see if
it is too supple or too harsh. The real test is on the road, but a rough
approximation can be made at this stage, and a hard push sideways from
the tallest part of the trike will show up any tendencies which may
need to be restrained later, perhaps with an anti roll bar.
Camber angle. At this stage, the wheels should ideally be pointing
straight ahead, and any adjustments should be made for this, although
a slight toe in may help with cornering. If the engine is from a front
drive car engine, then you will probably be using the steering linkage
to make easier adjustments to the wheel alignment.
The Camber will also be set up to allow the tyre profile to remain as
ideal as possible with the suspension at 1/3 rd compressed, where most
cornering forces will be applied. So remove one rear shock and see how
the tyre lies relative to the ground as one side of the trike is lowered
across its full movement, to simulate a side roll or over a big bump
in the road. Also check the toe in while under this extreme movement.
See also camber, above.
Will it want to Roll or Skid ? See above, especially now that you have
the actual centre of gravity measurements. Don't expect big fat tyres
to give more grip, as they will be applying lighter pressures, so the
overall effect will not depend solely upon size. (excuse the pun).
When seen from the side, this check will indicate the height of the
centre of gravity above the road surface and will depend upon the height
of the heavy bits. The lower the centre of gravity, the less roll. See
earlier concerning whether the trike will roll or slide. Height will
often be limited by sump clearance and how the riders are seated. Have
a look at a Porsche V8 and consider why it's sump is wide and flat,
allowing the whole engine to be so low.
You now have a general idea of the overall balance of the machine and
can further refine it by carefully placing all the other bits and pieces,
including the riders.
Poor integration of the rider and styling can now spoil all this good
work, so don't let standards slip.
Even an excellent rolling chassis and engine can be turned into a pile
of poo if not finished decently.
Do not worry too much, as a good frame can have many and various generations
of superstructure and brackets ground off and replaced until a perfect
trike is achieved.
The above offers much towards spending a lot of time and effort for
a decent frame. Unfortunately it can also cause the reader to decide
against bothering with the effort entailed.
It is better to make an adequate frame than to be frightened off by
too many expectations of having to make a perfect frame.
If deciding to try a rough frame rather than take the effort of a more
involved approach to design, manufacture and testing, then do so. You
may possibly be on a tight budget and using scaffold bar, off-cuts and
recycled bits to keep costs down, then do so. I do.
It is preferable to make a second rate machine than to make none at
(One of my finest ever handling chassis was just thrown together to
check a design concept. The whole bike cost 35 quid to build and handles
far better than my Ducati.)
Now that the main frame is in place, the next stage is to fit the parts
which take priority over all minor items. Start with the just the riders
seat and gearchange as first priority.
The steering, brake, clutch and passengers should then be positioned
ergonomically. You may have to juggle these with the overall style,
gearchange, fuel tank, the airflow for the radiators and all their associated
Before building the rest of the trike, an appraisal of the various
parts which must be considered more closely now that the rolling chassis
is ready for the seat, the controls and the many other aspects. Building
these onto the rolling chassis are discussed, so they can integrate
better, once they are more fully understood.
This should be simple as there is often only one ideal position for
the rider, which was decided when all the parts were laid out on the
garage floor, but the actual rolling chassis is no more easily considered
in a pragmatic way.
As there is often a wide range of positions, then use the opportunity
to help get the axle loadings as well balanced as possible.
I always build my machines without the seat, then place the machine
on bathroom scales, to position my weight for an ideal front to rear
axle loading. Do the same for the trike, but taking into allowance the
type of front wheel and whether it is a lightweight custom front end,
a standard bike forks, or a special heavy sort of front end. If the
front end is too heavy loaded, then always try to get the rider and
passengers as far back as possible.
Use a foam base from an old car seat and check all possible positions
for comfort. Check that controls including handlebars and foot controls
can be positioned effectively and safely. Remember what it is like when
thrashing around tight corners, so ensure the riders control is as perfect
Use this opportunity to give the trike the best axle loading.
A trike need not be an example of discomfort over style. It should
always be an enjoyable experience and this is the time to get it right.
Trike riding positions range from a racing bike forward lean, to fully
recumbent as in a reclining chair. Whatever is decided, do it well.
If wanting a comfy seat, but not the style of a car, but needing spinal
support, then get a car seat and cut the frame down to be narrower at
the top. This is simple cut and weld, so that you can retain the adjustment
of the squab (backrest), which may make a trike usable for many hundreds
of high speed miles, especially if disabled.
If very disabled, then you can retain the electric adjustments of a
second hand car seat, allowing you to power yourself into position and
perhaps even allow the seat to power sideways to slide into a wheelchair.
- The technology is there for pennies, so don't be afraid to use it.
See disabled options in the appendices.
In some cases with front engines, exhaust routing will be a problem
for the legs, so either work around the standard exhaust for convenience
of replacement, or be prepared to modify or build new items. Seriously
consider the heat flow from the engine mounted between or around the
legs, and how it will be shielded, or have fresh air flowing around.
Exhausts are incredibly light, so they can be fitted anywhere without
upsetting the balance.
This is the time when remote or direct steering must also be finalised.
Foot controls should be positioned for best control in conjunction with
the seating. See later.
Only when the ideal position is decided should any extra support tubing
be added for the seats. On some seats, a removable base will allow access
to the electrics, plumbing or an air filter under the rider.
This is often a can of worms.
Gearchanges can also be a superb piece of engineering, if done well.
Like all development constructs, all gearchange parts should be built
with tack welds until everything works fine.
Fit the riders seat in place to decide the most natural position of
the gear stick. You will surely have problems with some areas of design,
so start with what seems worst to sort out. This is usually deciding
on the best path for the gearchange linkage, as nothing should get in
the way of smooth gearchanges.
Left or right hand gearchange will depend on personal preference, often
by the country in which you normally drive.
There is nothing stopping the designer from having the gear lever sticking
up from below, or pointing forward out of the engine bay, or whatever
works best. Car-based trike gearchanges are a riot of up-down, left-right,
fore-aft, and pivoting from all points of the compass. Whatever suits
your fancy, it's usually possible, and probably been done before. If
using a hand clutch, you may have problems.
The mid engined transverse engine is often the worst gearchange offender.
If lucky, the gear linkage may be above the gearbox. Always bear in
mind such annoying problems when choosing a donor vehicle.
The biggest problem is when transverse engines have the gearchange entering
the sump. On many engine / gearbox combinations, the gear linkage is
often a stub-shaft mounted low down and to the rear of the engine, the
worst possible position. The paths of such linkages are particularly
It is this offender which will be used as an example of how to solve
The linkage must obviously pass over or under the engine. On low gearboxes
the higher route may be preferable, especially if the gearchange is
modern, very slick and easy to use. This allows a small, slick gearstick,
and occasionally a gate similar to Ferrari's. It may be necessary to
allow room for an intermediate linkage. Where the sides of the sump
have a gap, usually between sump and clutch housing, study this as a
possible path for the linkage.
It is not recommended to pass any linkages under the sump where ground
clearance will be a problem. A gearchange over the gearbox may conflict
with the passengers seating area. Also consider the fact that engines
move about on their rubber mounts, where a low linkage, positioned close
to the area of minimal engine movement will tend to be easier to control.
Think it through very carefully.
Automatic gearboxes also need a change mechanism, which usually employs
a cable. Always use the standard components wherever possible. This
must be set up carefully, so begin by mounting on the gearbox to see
where the standard controls can fit for the riders benefit. If required,
use a longer cable from a similar design. If no suitable cables available,
then consider small aircraft throttle cables, or carefully modify a
thick car clutch cable, such as from a Ford Escort Mk4. A rigid link
or rod, if used, must allow the gearbox to move without upsetting the
As modern gearchanges are appearing with increasing regularity, then
for those with the luxury of paddle or button shifts, similar to formula
one gearchanges, then these can be integrated into motorcycle handlebars,
but will need to be on adjustable mountings until the ideal ergonomics
are sorted. This is especially important while hanging onto the handlebars
when cornering. Paddles allow a strong grip on the handlebars and interferes
less with the brakes. If using a handlebar mounted front brake lever,
then consider changing down from third to second etc, with the free
left hand. (80's BMW bike indicator switches are rather good for this.)
The design mentioned below is not the only way to make a manual gearchange
linkage, but it is one of the narrowest and more reliable. The other
main methods include using two separate link rods which in many situations
may be preferable and can utilise parts from a similar dual bar linkage
such as from a box van.
If the gear connection is a small stub shaft exiting the rear of the
sump or gearbox, it is usually rotated and also moved in and out. There
are usually three positions for rotation, plus two for the in and out
Always insist on being able to use reverse gear.
On most well designed engines using an awkward stub shaft gearchange,
there will also be a fixed mounting point on the gearbox casting. This
mounting is for the original gearchange linkage which must be securely
connected at the gearbox end. This is an important part of any design,
by ensuring the linkage will not misalign as the engine leaps about
in it's mountings. Use this mounting appropriately for mounting the
gear linkage on the engine, and expect the riders end of the gearchange
linkage to move relative with the engine.
The gearchange 'in and out' is normally indented. This is so that each
gear is mechanically aligned inside the casing.
In some cases, the rotation of the sub shaft may not be indented, as
the external part of the original gear lever may be sprung loaded externally
so that the driver of the standard machine will know the levers default
position when in the middle. (Sit in a car and note that the gear lever
is normally sprung to sit in the middle of the left - right movement.)
Often the low gear means having to push the lever to the left, and higher
gears pushed to the right, with a couple of fun gears self aligning
in the sprung loaded middle position. This means that this (slight rotational)
alignment may be controlled with an external spring or pair of springs.
In such cases, the rotation of the shaft will need to be centrally sprung
loaded by the new mechanism. This is not difficult and can be left until
later, with a spring each side of any new linkage, or a single centring
spring and simple arm often doing the job perfectly well.
Two control rods are needed. One rod is to rotate the gear shaft, and
the other to move the shaft in and out. A narrow tube with internal
push rod is often ideal for both the rotating and sliding linkage between
rider and the rear of engine.
The rotation tube is considered first.
The rotation of the gearbox stub-shaft is often about thirty degrees.
This is easily managed by fitting a simple lever on it.
The rotation control tube that will lead forward to the rider, can lie
over or under the engine, and the engine end of this tube can employ
a similar lever to match the lever on the gearbox stub shaft. The engine
end of the rotation tube should rotate on a bracket mounted securely
on the engine or gearbox.
A simple link arm connects both these arms, so that rotating one, rotates
the other in a similar manner. If the gearchange action is back to front,
then simply rearrange the levers to give the action in the other direction.
The front of the rotation tube will contain the gear lever so it can
rotate about the angle required. Because of the rotation forces and
the distance involved, the rotation tube should be of a reasonable diameter
or wall thickness to prevent buckling. This rotation rod need only be
fixed on a simple pivot mounted on the engine, but the front of the
tube must be mounted flexibly to allow it to move as the engine moves.
Push pull shaft.
The push-pull part of the gear linkage will need to slide the engine
stub shaft in and out.
This can be accomplished by moving the stub shaft in and out by using
a forked end on a lever which fits either side of the rotating lever
already connected on the sub shaft. A simple forked end around the stub
shaft which rubs against the rotating lever, to pull it out. A single
finger pressing on the end of the stub shaft can push the stub shaft
By ensuring the forked end of the arm acts directly on the stub shaft
lever, good alignment and feedback is improved.
This forked lever is part of a longer arm which is pivoted half way
between the stub shaft and the rotation tube. The pivot for this arm
may not be easy to mount on the gearbox, and may require a large plate
or bracket to position the ideal pivot mounting which must be attached
to the engine or gearbox. See drawings.
A simple bracket welded onto the tube so the gear lever pivots above
central axis of the tube will move the inner rod and also rotate the
outer. If the fore aft movement is the wrong way around, then simply
mount the front gear lever pivot below the rotation shaft, rather than
Pulling and pushing the top of the arm should be able to easily move
the sub shaft in and out.
Rotating the tube should easily rotate the stub shaft.
If an external centring spring is required to centre the rotation arms,
one or a pair of springs can be fitted in one of many places along the
It is very sensible to run the push-pull rod through the centre of the
This layout makes it easy to swap gearchange movement at the riders
end for standard gearchanging positions. If the in out movement is the
wrong way around, then simply change the arm pivot at the front of the
Large scale engine movement.
As engines flex on their rubber mounts, especially under acceleration,
then they can cause the gears to be missed or even jump out of gear
when the engine rocks about. Therefore the rear of both gearchange parts
of the linkage must be mounted on the engine, not on the chassis. Because
the rear of the linkage is mounted directly on the engine, the riders
end of the linkage must therefore be rubber mounted to take into account
the engine movement.
If you have a lively engine and a long or heavy gear lever, then always
add a mass balance on the other side of the gear lever pivot, so the
lever does not jump out of gear - or far worse, jump into gear when
revving the engine in neutral !!
Because of engine movement, some pivot links should be slack, so they
can flex with the engine.
Therefore some of the pivots are allowed some play, in the Kalashnikov
tradition, and some foam or rubber padding added to stop them rattling
around noisily. Expensive spherical rod ends will also do very nicely,
but can be added to exhibition trikes, once the initial design has proven
Because the front of the tube is rubber mounted, and the engine often
rocks fore and aft in the chassis, the rear mounting of the control
linkage will tend to fracture. Therefore it is very important that the
engine mountings at the rear of the linkage must be secure, but also
rubber mounted to account for any bending forces caused by the engine
movement. A basic engine steady is very important to prevent the engine
rocking too much.
As the rotation shaft is ideally a straight tube, the push pull rod
can run inside it. The outer tube works the rotation, while the inner
works the fore and aft movement.
A few simple plastic bushes slid inside the tube will prevent the inner
push-pull bar from bending and a little extra rubber foam will reduce
rattling. The advantage of a single tube is that it will pass through
a fairly narrow gap in the engine or frame and just as importantly,
will not catch or snag any other components.
There is a large amount of design freedom to allow such linkages to
clear obstacles. The only real concern is to ensure both ends of each
rod will slide and rotate freely under full control of the riders gearshift
lever, and to take into account the effects of a flexible engine mounting.
The front of the rotation tube must mount the gear lever such that it
can move the push-pull rod along the tube and also rotate the tube.
The riders end of this gear linkage must be flexibly mounted to allow
engine movement. For simple rubber mounting bushes, use old motorcycle
swing arm bushes or rubber blocks compressed between bolts and washers.
For simple alignment bushes and pivots, such as for the rear push pull
arm pivot, also for the front upright gear pivot arm bush, simply use
Honda C90 stepthru front fork bush kit and push fit the plastic sleeves
into old handlebar tubing.
It will be seen from the little animation, that if the rear end of the
tube is not connected to the engine, but allowed to float and slide
freely on a sufficiently strong inner bar, then the upper linkage can
be loose. This allows the rear linkage to have adequate movement as
the engine moves on its rubber mounts, yet the linkage will still work
effectively. Therefore only the middle point of the in/out lever need
be mounted on the engine casing.
Do not use rubber bushes in the actual linkage, only for their mountings.
Rubber bushes in the links will want to return to a mid point, causing
the gears to jump back to the neutral position.
A slick gearchange linkage requires a smooth, slop free linkage. This
will take time to refine, but well worth the effort.
As some modern gear changes are extremely slick and very smooth, there
may be no need to use a traditional large gear linkage. The use of modern,
small stub gear levers makes for a neat layout, especially if ergonomically
positioned. This also helps the trike riding experience to be faster
and more responsive.
The front ends of gearchange should be positioned for the best ergonomics
and will depend upon rider preferences. Because the described linkage
is nicely concentric, the orientation of the riders gear lever can be
at almost any angle. If the tube ends level with the rider, the gear
lever can be straight up in the traditional manner. If the tube ends
a little way behind the rider, the gear lever could be bent upwards
and forward, to give an angled action. If the gear linkage can be made
to end in front of the rider, the gear lever can be angled back to face
the rider. A simple, solid bar front gear lever arm can be easily bent
to clear obstacles such as frames and knees.
To repeat: If you have a lively engine and a long or heavy gear lever,
then always add a mass balance on the other side of the gear lever pivot,
so the lever does not jump out of gear - or far worse, jump into gear
when revving the engine in neutral !!
This is the system I prefer for most trikes, but the Alfa gearchange
finally used two bars, adapted using the gearchange from a small Japanese
box van, extended with a little extra tubing. After a few attempts,
the front gearchange eventually exited close to the handlebars for minimal
hand movement and for fast gearchanges. A small lever allowed reverse
to be locked out or engaged.
A reversing light plunger switch was fitted on the rear gearbox mounting
via a bendable bracket and adjusted to work when in reverse by shorting
the live reverse light to earth. As this was a live connection near
the fuel tank, this was soon changed to a sealed switch for safety reasons.
If in doubt, check out the arrangement and how to design the linkage
before buying the donor vehicle. The scrapyard can often supply the
automatic variant, but this may only be considered as a final option,
or as a temporary measure until gear linkage design skills improve.
Use whatever is available from other machines, as there is often very
little need to reinvent the remote gearchange.
Gear changes can pass over the top of the engine or underneath, but
the underneath is occasionally difficult if there is lack of room between
sump and clutch housing. No one would want to pass the gearchange under
the sump if trying to keep the centre of gravity as low as possible
for better handling.
Yes, I have seen trikes where the gearchange passes under the sump and
often smashes up a gear when rubbing over a speed bump in the road.
- Just don't go there !
Where there is a gap, then underneath is common as it allows the front
lever to be long, allowing easier control, especially on older, clunkier
gearboxes while it also clears the passenger area. As the engine mounts
are usually on the bottom of the engine, a lower gear linkage will not
Make sure that all gears - including reverse - can be EASILY distinguished
from each other and do so smoothly. This may take some fettling and
tweaking of the assembly, often a little redesign work too. Then remove
any sloppiness at this stage by removing and refining the linkage until
slick rather than slack.
When building a linkage, some play is quite acceptable. In the Kalashnikov
tradition, a little play prevents the links from getting locked or stuck,
which can be ameliorated by light springs or foam rubber to prevent
the assembly from rattling.
Work the linkage hundreds of times until it beds down well. Take time
to get the gear change right, as it is often the biggest disgrace on
trikes and can destroy the enjoyment of the driving experience.
Gearchanges are difficult, but after about three attempts, it should
be working as required. If the gearbox is well designed, it may only
need a small amount of effort to transmit the movement, allowing a light,
slick gear linkage with a small control arm.
To see a really classy piece of engineering design, check out the original
Porsche Boxter front gear change linkage as shown at it's Geneva launch,
it's a work of art. (Unfortunately the production Boxter gear levers
are a very lame design and nowhere near as good.)
Make all other trike owners jealous by making the gearshift a work
of art, not just a suspect metal bar with a brass skull screwed on top.
A couple of weeks of intriguing work is not unknown to get awkward gearchanges
working well. The effort is always well repaid over the following years
Actuating the reverse gear usually requires a simple lock out mechanism,
often by pulling the standard car gear knob up, or pushing down to release
before being allowed to move into the reverse position. This is usually
done in the linkage. Reverse can be a problem for trike riders, especially
if forgotten while riding.
When building a simple mechanical reverse interlock, place the gearlinkage
in reverse and then decide a basic mechanical lock-out. This is often
fiddly and annoying rather than difficult, so keep trying. On a particularly
sloppy gearchange, this should ideally be close to the gearbox stub
shaft or arm.
A simple movable block, lug or arm and corresponding obstruction plate
often works well. Fit a small spring loaded lever under the gear stick
operating via a pedal cycle brake cable so the block can be lifted away
to allow reverse to be engaged.
If the riders gear stick is tubular, then a plunger or pull action could
be used by making the top lever slide on the shaft, with a stiff spring
to move the block.
If like some brave or foolish trike builders, it is decided that a reverse
lock out is a little too complex, then leave it out, but remember the
consequences that can ensue.
Such gearchanges are the sorts of problem I've developed carefully
for my production trike designs so the customer always gets a well behaved,
reliable machine. I've spent a lot of time over trike gear changes,
and so should you.
In many cases simple motorcycle handlebars will do. On long, front engined
trikes, long pull back handlebars which act more like a tiller may suffice.
As most riding above ten miles an hour does not need much steering movement,
most designs will do the job adequately well. But with long pull back
bars, high speed cornering can be a problem, and inner city manoeuvring
will cause unusual arm actions which may impede handlebar controls such
as throttle with some awkward wrist angles.
On particularly big trikes with a front engine, such as V8's, the remote
steering will need a second fork yoke to mount the handlebars nearer
to the rider. Steering engineering takes precedence over steering style,
so get the steering sorted before fitting instruments and such like
which may mount in the steering area. Remote handlebars allow almost
perfect handlebar position, so use the opportunity to advantage. This
occasion should also be used to maximise the available space for easy
interaction with the steering and engine. With such a big engine requiring
remote handlebars the cornering forces may well be large, requiring
larger effort and control.
Always try to make the pivot point centrally between the grips, so the
rider can hang onto, even wrestle with the bars around fast, bumpy,
off camber corners, without upsetting the steering.
Wherever possible on distant front ends, use parallel push-pull rods
for a remote fork yoke. Two link rods offers higher reliability in this
area which must not fail. Keep the linkage parallel and equispaced on
both front and rear yokes. If the front pivots are X mm apart, and Y
mm forward of the steering axis, then make the rear pivot points X mm
apart, and Y mm forward of the steering axis. Geometrically similar.
Keep the rods widely spaced apart for best control. This eliminates
any compound geometry misalignment which could lock up the steering
at high angles. Use spherical 'Rose' joints and their rubber covers
for reliability. The threads on rose joints will enable slack to be
removed. Keep a minuscule amount of tension in the rods, to reduce buckling.
Low speed cornering.
If the machine is large and long, then a front end with a large angle
of steering lock may cause damage. Most front ends are ideal when pointing
straight ahead, but at full lock, the angles of the forks can get desperate.
Find out which is the maximum safe steering lock, then weld stops to
prevent the front end turning too far.
Trying to get around tight car parks in one go, may cause a poorly designed
front-end to tuck in, or even collapse in on itself. This is particularly
important where the front brake is suddenly applied at full lock such
as in car parks, where other drivers have sudden, dangerous or simply
During testing in a clear car park, always check the steering close
to full lock with a blip of throttle power, because the steering may
pull out of your hands. Steering dampers will not cure low speed problems.
Fettle the rake and trail if needed, then finally weld strong steering
stops to prevent extreme steering angles from causing problems. Always
fit the steering stops between bottom yoke and frame. If needing maximum
steering lock left to right, but worried about the forks tucking under,
then use heavy bolts as the steering stops. Weld them to the frame using
barrel nuts, which are long nuts. Then bolts can be fitted and adjusted
to give the largest amount of safe steering lock. Always use locking
nuts or machinery adhesive, or a strip of nylon in the threads to prevent
the bolts loosening.
If the machine is a monster, you may wish to retain the power assisted
steering and use a car set-up using the original steering wheel at first,
purely for testing purposes, then modify this to assist normal handlebars
later. The control valve on the donor vehicle steering will need to
be carefully modified. For both style and lifestyle reasons, use of
a steering wheel is often frowned upon. For disabled bikers, variations
on this theme can be a godsend.
Even granny should be able to safely ride a V12 trike.
Wherever possible, use either motorcycle OR car control layouts, so
your reactions will be natural and instinctive in an emergency.
Do not mix your drinks, and do not mix your controls.
When properly designed, even an extreme invalid can ride a V12 trike.
Controls are personal, but don't expect to design a foot gearchange
for a car gearbox with reverse overnight, unless you cheat with an automatic.
Car clutches working off the handlebars are no fun, try if you must,
but practice by squeezing tennis balls first.
A realistic approach for car engines is to use a hand gearchange with
foot clutch and foot rear brake. Using automatic transmission is a perfectly
legitimate cop out.
Throttle can be a handlebar device similar to a bike, or foot similar
to a car. The foot design will also need a foot rear brake close by,
being ideal for posing / cruising hands off, such as looking cool while
rolling a cigarette in a traffic jam, on a hot bank holiday. This may
also be preferred for custom shows, where waving to crowds is expected
while under power. Choosing car style foot controls will help clean
up the handlebar clutter to just a couple of switches for horn and dip,
or even less.
The classic bike throttle is often considered as part of the biker image
and should be decided according to lifestyle. See also cables later.
Warning: Contrary to popular belief, designer shades are not the most
important part of a trike, especially if the rider ends up stuffed into
the side of a bus.
Stop looking in the mirror, put the sunglasses down and prepare for
a little truth.
There is no point in making a trike if it's going to be dangerous. Brakes
are very important, they save lives - but only if they work properly.
There used to be an awful trike in my neighbourhood, VW engine with
small trail bike forks and rust coming from the front drum brake. He
said he "only got the front brake working for MOT's".
I have not seen him recently.
There is little to worry about when balancing the pressures in a dual
system, as both outlets of the master cylinder are pressurised identically.
Where you have to worry, is where this pressure is applied.
The main reason for dividing the outlets is to allow the design to fail
with at least one front and one rear brake. (When two independent front
callipers are used.) It is the relative diameters of the pistons and
the disc rotor diameters which will decide the overall braking balance.
On some cars, there is a pressure limiter in the rear of the system,
so that a lightly loaded rear axle does have too much pressure applied
relative to the front to help prevent skidding in cars. This is often
operated via a lever sensing the load on the rear wheels but can be
adapted to a manual control.
If great differences in luggage and passengers are expected, arrange
a pressure limiter as on the original vehicle. It may also be used with
a manual adjuster to allow the builder to simply modify the front to
rear brake balance during testing and should be considered a useful
option if excessive rear braking problems occur.
If keeping any of the original car plumbing, then blank off any redundant
splitters with blanking bolts and copper washers, or steel ball bearings
under the old threaded pipe fittings to seal the internal holes. Do
not use small ball bearings, as these may get trapped, so always use
large balls so they can be easily removed.
If using a jet engine, then seriously consider using two sets of 320mm
diameter bike disks on each rear axle, separated by the width of the
callipers and well ventilated. If you can fit inboard and outboard disks
then do so.
Like any vehicle, the front brakes should be the strongest.
As some trike front ends leave much to be desired, it may be preferable
to have the rear brakes with a slightly heavy feel, to prevent the rear
brakes doing all the work. Some people prefer rear braking, but is not
conducive to ultimate twisty road thrashing.
Rear brake effort can be increased by removing the servo from the brake
master cylinder which was designed for a four brake system on cars.
This will also make mounting the basic master cylinder easier. The pressure
needed can be easily accomplished and the pressure modified to suit
rider preferences by using a longer lever or suitable ratios in the
A servo will be needed if using a fully linked car system to operate
both font and rear brakes from one foot lever, or if disabled. There
is no need to fit the servo where it may be seen.
Both the brake and clutch levers should be adjustable for leverage
to sort out any problems when testing on the road. Use temporary adjustable
actuating arms, with various connecting rod mounting holes to allow
adjustment of the lever pressures applied to the master cylinders.
The brake and clutch master cylinders can be positioned under the seat
to prevent little fingers from messing about with filler caps and because
these cylinders are often ugly items. Motorcycle items are less ugly,
but may not always manage the volumes of fluid displacement required,
unless used in the standard manner with bike components. Check first
and try to match with the original components.
On a recent project, the trike had forward controls using stainless
steel link rods to the brake and clutch master cylinders hidden beside
the hidden rear car engine.
Always prefer a tension rod to actuate brakes. If going for a push rod,
make it a reasonable diameter tube so it will not buckle. Also make
sure it cannot be stepped on by the passengers to prevent it being used,
or buckled. If they are running near the passengers foot well, then
decide if you need to run them inside safety tubes.
Make sure the brake and clutch systems work exactly as required, modifying
the pedals until they work smoothly and efficiently. Make sure it is
easy to check and fill the brake and clutch fluid levels. Wherever possible,
use the original donor machine clutch master and slave cylinders in
conjunction with the original donor brakes and clutch actuator.
The designer may want to use a right foot brake lever to couple both
the front and rear brakes off the master cylinder. When using a single
master cylinder for all the brakes, the vacuum servo assembly should
be retained, but hidden under the rear. It can be activated using a
remote linkage and a longer length of special vacuum hose, available
from many car shops. Vacuum hose is specially designed, thick wall tubing
that will not collapse under the effects of high vacuum, especially
when on the overrun.
Do not attempt to fit fiddle brakes as per trials cars and Formula
one, as setting them up is a nightmare.
The brake master cylinders of most cars operate two diagonal circuits
If connecting to just the rear brakes, then use both pipe outlets, one
to each rear brake. This arrangement gives an even and balanced pressure
across both, due to the nature of most single barrel master cylinder
designs. The two separate pipes also give a degree of redundancy for
extra safety. For rear brakes only, a servo may not be needed.
If connecting the car brake master cylinder to dual front discs and
car rear brakes, then connect one master cylinder outlet to one rear
and one front brake and the other outlet to the other front and rear
brakes. This ensures that should a brake line fail, the other will still
allow reasonable braking.
If you only have one front disc, then fit one master cylinder outlet
pipe to the front brake and the other to split to the rear brakes. This
way, if one fails, you will either have the front brake or both rear
brakes for even stopping. If you had it linked to the one front brake
and a rear, and the other outlet to just one rear brake and one failed,
it may well leave you with just one rear brake - not a nice thought.
The single foot brake car set-up is open to interpretation, even though
this is how a car works and would leave the handlebars free of clutter.
Linked braking is often less than well appreciated, being either a
fixed design by the manufacturer, or a cobbled together design without
adjustment. It is not difficult to see why such brakes are often ridiculed,
even when expertly made by large manufacturers.
Simple braking application from a single lever is an ideal, but only
if it can be set up for personal preference and the road conditions.
Ideally a braking system should be able to sense and adapt to the axle
loading, such as passenger or not and if the weather is wet or not.
Anti lock braking is for the oft common real world scenarios where inaccurate
braking skills, unknown road variables or poor feedback are to be expected.
The following is a simple yet effective design to see if the builder
wishes to reconsider linked braking for a particular design.
Never try to link braking with other components such as electronic gearchanges
until all other parts of the primary design have been fettled and proven
reliable and safe.
For the simplest, yet effective linked braking with cables, a linked
cable dual braking from one lever is possible using a swingle tree.
A swingle tree is a cross piece for an equal pull on two horses when
ploughing a field. (See appropriate text books. - Any farming text from
the Middle Ages onwards should suffice.)
The basic principle is equally valid for linked braking on modern vehicles
and systems. More so, as it can be adjusted for a proportional load
on front and rear brakes. Yet even more so, as by using cables, one
of the brakes can be also independently incorporated into this design
without an extra brake being needed. This is applicable for any cable
brake or a hydraulic system with the master cylinder force applied by
For cable and hydraulic brakes, the swingle tree is best employed by
a direct action on front and rear master cylinders when positioned close
together. This allows easy adjustment of front to rear braking bias,
even while riding, so that even this simple system can be adaptive.
The basic set-up uses a linked bar between the front and rear master
cylinders, acting on the pistons. The pull on this lever is offset,
with a bias for the front brake and should be adjustable. The rear brake
should also have a secondary, independent action on the rear master
cylinder end of the lever. Do not use linked hydraulic braking unless
a second, separate brake system is also employed.
As shown opposite, Formula One now use a similar system which is adjustable
from the cockpit. The system has the brake pedal pushing against the
front and rear master cylinders, with a central link which can be offset.
The F1 design is poor, and uses a primitive adjustable pivot, rather
than a proportionally adjustable movements which would be far more subtle.
Another fault of the F1 design is that it is not fail safe should one
system fail, whereas fitting a back stop to allow one side to work if
the other fails, will be far more relibale.
There are many variations on this theme which can be used to assess
If separate front and rear brakes, then the leverage of each is easily
modified to give good braking.
Warning; Because the pressure in the car and bike lines are probably
not designed to be the same, the braking effort of the rear and front
brakes on a linked system may be out of balance.
There are ways around this.
To get more braking effect on the front brakes, use larger diameter
piston cross section at the front than at the rear, or use larger discs
and callipers on the front than those used on the rear brakes. A mixture
of both usually helps balance out the braking to match the handling
If using a linked system acting off a single car master cylinder, where
all the brakes receive the same pressure, then the brakes themselves
will have to be modified. -
You cannot add extra force into the system unless using a servo. Therefore,
if the main brakes are good and just wanting to decrease the offending
brakes, then these can be ameliorated to behave properly.
Light Laden Valve. If you suffer serious problems with fore to aft
imbalance, then the offending braking circuit could employ a light laden
valve. This usually operates via a lever which can be adjusted to balance
out the rear brakes relative to the front brakes. These are often found
near the rear underside of cars and vans, where the rear load makes
a great difference to the braking and enables the rear to be less effective
if the van is unloaded. To decrease the firmness of rear braking, a
car load limiter as fitted on vans (e.g. Ford Escort, connected to the
underside via a lever to the rear axle) is a way to be able to adjust
the system to the rear braking forces. By adjusting the lever, you have
the ability to modify the pressure applied to the front and rear brakes,
as used on dual braking line systems.
Alternatively, the brake pads could be cut down to offer less braking
material to the disc or drum.
Another option is to change the callipers for smaller units. Reducing
the disc diameters is not recommended, as they are usually proportional
to the wheel diameter and will ensure the forced needed to be applied
will be of the correct magnitude and within safe limits.
Where the front brakes need to be stronger, then the trike with a bike
front end can have the latest large diameter discs and multi piston
callipers. DO NOT apply servo assisted braking to motorcycle discs,
as they may possibly warp under the excessive pressures. Only apply
hand pressure, to stay within working limits of these flimsier types
Where the front end uses a car disk brake, then TWO callipers can be
fitted onto a single chunky car disc, preferably working off separate
mater cylinder outlets for balanced braking under partial failure. This
doubles the braking force with no other modifications. Where possible
use the ventilated disc from the sports version of the donor car, especially
if using dual callipers on it. But do not put excessive pressure on
the disk, as the tyre will be limited in its ability to transmit the
force to the road.
Dual callipers should be used as part of a dual linked system, such
as used from just one foot brake in a car style, linked system.
When fitting dual callipers to a front car disc, the symmetrical donor
callipers will be handed pairs, so the bleed nipples of both can be
mounted to allow easy bleeding.
On a trike, the braking will be compromised by the amount of weight
on each axle and the tyre profile. A lightweight front end with a skinny
tyre is not going to be able to handle too much of the braking. Therefore
a truly reliable rear braking system, well balanced and effective will
be necessary, even though it is not ideal for best control or handling.
Conversely, a trike with a heavy front end should not have too heavy
a rear brake set-up, neither should it apply all the braking to the
front, even if of a soundly built design.
In small trike set-up, the front brake is usually a motorcycle handlebar
set-up, simple and easy, with a car rear brake without the servo, just
acting on the car master cylinder, without the vacuum pipe attached.
If the rear is then too soft, the servo can be connected, and the vacuum
pipe partially strangled and the foot brake linkage modified to get
a good balance with the front brake.
On a recent V12 trike project, the whole machine kept the Jag braking
system, acting off a foot brake lever, but the front axle was replaced
with a much stronger axle machined from EN steel allowing heavier single
axle loads and braking. The original Jag front disc and wheel was retained
but a second calliper was added, so the whole system was balanced fore
and aft, although the front tyre had to do more work. Because it's a
trike, and the prop shaft was shortened to get the engine rearwards,
there was a little less front axle loading, to help ameliorate the overall
braking balance on the wheels.
When using a front wheel drive set-up as from a transverse engined car,
with the front brakes now on the rear, and the original handbrake no
longer used, then another form of parking brake will be needed.
The options are fairly wide if occasionally awkward. The early 2CV's
used to be supplied with wooden wheel blocks but don't try this in modern
The parking brake is often a problem for trikes. The transverse engine
front wheel drive being the worst offender, as most parking brakes are
on the rear wheels. Mounting a second calliper on the rear discs can
work well, or alternative callipers from a car with discs all round.
Using the car's REAR wheel callipers on the trike (front, now) rear
discs often works well, if the disc rotor diameters are not too dissimilar.
Because most cars have the same wheel studs front and rear, and the
cast iron brakes are often mounted on these, then it is often very easy
to fit standard rear disks to the front wheel assembly of car wheel
hubs for the use at the rear of trikes.
Mount the callipers on the disc, then look for the easiest way to retain
them. Sometimes just cutting off the original mounting lugs, fixing
them on the calliper, then rewelding into their new positions. Sometimes
a simple extension plate will suffice, but make sure it tends to straighten
when braking in the forward direction, as this is how the heaviest braking
forces will act.
When mounting callipers, use new pads and always slip a strip of thick
cardboard on the edge rim of the disc, to give suitable clearance and
maintain even radial alignment while fitting.
Where no room for extra calliper or suchlike is possible, then a special
parking brake cylinder which works in-line with the standard hydraulics
and acts on the original callipers is available from some racing suppliers.
This often fits between the master cylinder and the rear brake callipers,
allowing the brake line to be locked hydraulically, usually by a hand
lever. It closes off the rear hydraulic line and then applies pressure
on a standard handbrake ratchet.
Some front engined modern cars with rear discs have the parking brake
integrated into the design, needing little or no modification. Occasionally
a modified calliper mount or cable mount is needed to employ this particular
set-up on the discs.
For many of the lighter show trikes which need a much better disc than
the lump of iron normally supplied with cars, then motorcycle discs
and callipers can be used, especially if seen through three spoke wheels.
These lighter trikes will also require motorcycle callipers and if rear
engined, will probably also need the intermediate hydraulic hand brake
Some Honda callipers use dual systems on single callipers, allowing
the main braking to be on the outer two of the pistons, with the builder
adapting the parking brake to act on the centre cylinder. Similar alternatives
are also found with car systems.
For front engined trikes with central prop shaft, use the following
to eliminate complexities and to have completely independent parking
brake for emergencies. This also allows for a cleaner inner wheel look
with a single calliper of choice.
On many cars with a prop shaft leading from the gearbox to the rear
differential, then a single motorcycle or car brake disc can be fitted
on the prop shaft flange on the differential. A brake calliper can then
be fitted to lock the whole drive assembly. This is excellent yet common
practice on 4WD's such as Land Rover, allowing them to lock all wheels
with just one brake. This is simply done by welding on a mounting flange,
or inserting a thin flange between the prop shaft and the differential,
then running the engine and prop shaft while truing the disc mounting
flange in situ.
If machining without a lathe, mount the blank metal disc carrier on
the end of the gearbox , as the diff and gearbox flanges should normally
be the same dimensions. Then fire up the engine as a lathe. Carefully
apply the angle grinder or file until a perfect fit is made to mount
the brake disc. Ensure a shoulder is included to align the disc before
drilling its mounting holes.
If there is no room in the differential area, then the parking brake
disc may possibly be mounted on the gearbox output flange of many car
As the differential has a large gearing ratio, the effort required on
such a disc is low compared to a wheel mounted brake. Because of this
gearing, small discs are possible. A second calliper on this disc can
act as the rear brake if wanting to have a clean rear axle for show
If a cable is preferred but a cable operated calliper is not found,
then simply use a standard car drum brake on the prop shaft, which can
also fit on the rear wheels or around the propshaft, although the brake
shoe backing plate will need modifying to fit the appropriate mounting.
There are a few cable operated car disc brake callipers and these should
be considered, although they are rare and will need hunting down in
Please note that drum brakes with a leading and trailing shoe are usually
better in one direction, so choose the donors vehicles left or right
drum brake appropriately so that pulling away uphill will be easier,
requiring less force on the handbrake lever.
If the gearbox is integral with the engine with no prop shaft, there
may be room for a small disc in the inboard coupling of the drive shaft.
The inboard discs of the Alfa and later 2CV's and 4CV's make parking
brakes an absolute doddle. They also allow a totally open and clean
inner rear wheel area, ideal for wire spokes and skinny three spoke
When mounting disc or drum brakes, always mount and true the disc or
drum first, then fit new pads or brake shoes, and apply pressure to
the calliper or shoes, to align the supporting assembly in position.
Then the backing plate can be welded in position with perfect accuracy.
When mounting parking brake callipers, remember that they must work
in both directions, - when parking both uphill and when pointing downhill.
Ensure the calliper mounting is secure in both directions. If using
a car control layout, always ensure the parking brake will work easily
and safely, especially when pulling away uphill.
Some trikes have problems with a basic parking brake which works on
single piston callipers. In some cases, a simple valve in the rear hydraulic
brake line can suffice, as shown in the picture. Push the brake pedal
down, then lock the hydraulic line. I personally don't like it, but
evidently this has passed the MOT. In such a system, I would prefer
cheap rubber pipes, which allow a degree of flexible 'pressure reservoir'
for any minor leakage, as the high spec. hydraulic lines would not give
this slight margin of safety.
I have ridden a trike where the clutch was a hair trigger with no chance
to reference the foot to enable some subtlety. Do not go there, get
the controllability of all systems correct from the outset.
On the clutch, (and rear brake) the foot should have complete control,
so design the foot rest and it's lever to pivot as one, usually near
the heel or instep. Often known as an 'organ stop' pedal. This will
allow the rotation of the foot to work the action for accurate control.
This is particularly important for a sensitive foot clutch.
If the movement is large, then use running boards with a heel support
to act as a reference point for the foot on the lever. This way you
will have much better control over the clutch 'bite' point.
Car clutches working off the handlebars are no fun, try if you must,
but practice squeezing tennis balls first. See also cables later.
Only if the trike is a light weight design, and not intended to carry
extra loads, then a car clutch can be operated by a hand lever, especially
if the fingers of a clutch diaphragm spring are reduced. This can be
modified by removing opposite fingers of the clutch spring until acceptable.
Always note that if too many fingers are removed, the clutch will no
longer be able to transfer the same amount of power, so clutch slip
may occur at top speed. (where aerodynamic drag is high).
For an easy life in town use with a 2CV engine, always consider fitting
the superb automatic clutch option, which releases at low revs, not
dissimilar to a Honda C90.
Trikes don't have to use conventional bike tanks, possibly employing
one, two, or even more fuel tanks to make use of otherwise unused areas
on the trike, especially if using a massive and thirsty engine such
as a V8, V12 or Wankel rotary.
Always consider two large sheet steel fuel tanks hidden under the shell,
with a stylised motorcycle tank containing just emergency fuel and used
to fill up the fuel system.
Side loads when cornering will cause sloshing in long across-frame tanks,
so ensure they have baffles, or use a standard tank such as some cars
mounted in their normal alignment.
The fuel capacity is normally similar to that of the donor car, so that
the range is sensible. If touring abroad, a second long range or emergency
tank can also be of use.
All tanks should be rubber mounted to prevent fracturing. All tanks
should be away from damage by other vehicles to minimise fire hazard
It is very popular to have a small motorcycle tank for styling purposes.
This need not be a limitation, but an advantage if a secondary, hidden
main tank is also employed.
If filling a main tank from a primary tank, always make the interconnecting
pipe large enough to allow petrol to flow reasonably fast when filling.
This will mean modifying with a large bore stepped pipe in the bottom
of the 'bike' fuel tank.
Please note that there is a very good reason to have the large filler
interconnecting pipe high on the primary, filling tank. When filling,
the primary tank will fill and then overflow into the secondary or main
If one tank is the reserve, make it the smaller of the two and always
fill it first. Don't let the emergency tap leak so that both tanks empty
without knowing, leaving the trike stranded without a reserve.
If the primary tank is a small capacity, traditional bike tank with
the main filler cap, and it is used as the reserve, then the filling
connecting pipe should be positioned high inside the tank. In this way
the first tank will always be filled first, ensuring the tank is always
full of fresh emergency fuel. The bottom of the upper tank can be tapped
for reserve only.
Ensure a breather pipe is fitted on each tank. If the tanks are at
different heights, use long breathers to a high point above the highest
tank, or into the highest tank for a neater look. A small plastic fuel
filter makes an excellent vent filter on the end of such a pipe.
Where a large bore intermediate pipe is used, then it is very easy to
fit the lower vent pipe inside the larger pipe, up to the upper tank,
so the plumbing is neater, with less chance of fuel leaks and only the
upper tank needs a vent hole. Make sure that each end of the vent pipe
is in the top of both tanks.
If no emergency tank is used and dual tanks are fitted, then only one
fuel gauge sender is needed if the tanks empty evenly. If they do not
empty evenly, put the gauge in the last tank to empty, to get a genuine
reading of when fuel is low.
Most fuel gauges work in the same manner, allowing the float arm to
be reshaped to give sensible readings. Always keep the same matched
fuel sender and fuel gauge. Always test and check by moving the arm
when wired up, but before fitting into the tank, then adjusting it's
arm as needed.
If using bike or car fuel senders, simply cut out the sender and its
mounting for welding into the new tank. A C90 sender and gauge will
do just as well as any other fuel sender. Simply modify the arm to sweep
through the full displacement of height of the fuel tank.
On some trikes with high fuel tanks and low mounted carbs, a fuel pump
may not be needed. But high, heavily loaded fuel tanks will make cornering
a little more difficult by accentuating roll. Wherever possible, keep
all heavy items as low as possible, this includes fuel and passengers.
For better handling, the fuel tanks should be mounted low, so their
mass does not cause the trike to roll sideways excessively when cornering.
Low fuel tanks require a fuel pump.
There are two types of electric fuel pumps for ordinary car engines.
One about three psi, the other about six psi. The low pressure type
is for a pump mounted near the carb. The high pressure pump is used
when mounted near the rear fuel tank of a front engined car. Use the
low pressure type as the first choice unless the trike is long and the
fuel pump is far from the carbs.
Connect the fuel pump on the ignition circuit so it won't pump when
parked. Use a separate fuse, because pump contacts occasionally weld
themselves together. Spare contacts are normally available for decent
electric fuel pumps.
In rare, exceptional circumstances it may not be possible to connect
the fuel pump directly to the carburettor, whereupon a header tank is
required. Possibly a set of carbs fed from a motorcycle tank, with a
secondary, main tank elsewhere. This should maintain a reasonable height
(head) above the carburettors and maintain the level with an overflow
back to the fuel tank. With such header tanks, the fuel pump will want
to over-pump constantly, so a restrictor can be used, capable of being
adjusted to supply fuel at just a little more than constant full throttle
requirements. This can be easily calculated at max miles per gallon,
then the time for this distance, then time and measure the fuel flow
from the pump into a measuring jug, then restricting the flow as required.
For simple, adjustable restrictors, the use of the very old technique
of fitting a larger restrictor, then adding more or fewer fine wires
though the restrictor to attain the required flow. It also has the advantage
of being partially self cleaning, as the loosely held wires will help
to unblock any small particles. Wire brush strands are ideal. This is
also fail safe, as an escaped wire will increase the flow, but be trapped
by the fuel filter. This is an old technique from the steam age, but
still applied on modified or development engines to vary their oil flows.
An alternative is to fit a simple level gauge in the tank to operate
a relay to the pump. On a small plastic tank, a simple float with a
magnet on its base can operate a reed switch on the base of the tank
and thus a relay for the pump. For micro header tanks, there is a vast
choice of discarded two stroke oil tanks with level sensors, which are
ideal for operating fuel pump relays of engines with moderate fuel needs.
Never fit a fuel tank where it can be damaged in a crash. This is especially
important at the bottom rear of the trike, where a shunt will spill
the contents and lead to serious burns. On a trike you are less likely
to be trapped in the flames, but never take chances.
Most fuel tanks are mounted in rubber and held in place with steel
straps. Use donor vehicle components if they are appropriate.
For those who build their own fuel tanks, then either make the shell
mould first, so the fuel tank(s) can be built to fit within the shell
without upsetting the overall shape of the trike. Or make a special
fuel tank, making sure the shell can be well styled. This may also require
juggling the shell mounting points to clear the fuel tank. Hidden fuel
tanks can be built in any shape and should be considered as adaptable
items which can utilise wasted space.
When making sheet steel fuel tanks, arc welding can be tricky, so
the edges should be flanged outwards and clamped, tack welded and then
finally fully welded. Tack welded outer flanges allow a neat seam with
a little extra flange strength to prevent fracturing. There is nothing
worse than poor welding on a fuel tank. Unlike a frame weld, a fuel
tank weld can rarely be ground out and neatly repaired.
Always fit baffles if in doubt, which can be soldered into place using
plumbers solder before the tank is sealed.
It is often easier to weld the filler pipes and fuel level sensor mounting
flange prior to assembly of the fuel tank outer surfaces.
If not at all happy about making small pipe outlets at the base of
a fuel tank which can leak, simply because welding such thin metal is
too difficult, then use a punch to pierce the top of the tank with a
hole. Into this hole can pushed a long tube which will touch the bottom
of the tank. Always make sure the bottom of the tube is a little way
off the base of the tank to prevent clogging and to allow good fuel
flow. The top of the metal fuel pipe can be soldered in place using
plumbers solder, which is stronger than electricians solder. The shape
of the punch hole will give a little extra strength as it helps create
a longer pool of solder. Always clean back to bare metal before soldering.
The shorter filler and vent pipes can also be done in a similar manner.
Where the bottom of the fuel pipe is located, make a small sump in the
fuel tank base to allow all the fuel to be used. If you can get hold
of brass wire mesh, then this makes a neat sediment filter around the
base of the fuel pipe, and the larger it is the better. As the fuel
sloshes around, it may even be self cleaning if designed well.
Always fit a cleaning hole, probably the fuel sensor plate, and if this
is not used, then make a small bolt which will allow the fuel to be
drained out, especially if the fuel tank is not easily removable for
If worried about sludge or sediment, then leave a small sump in the
fuel tank and also a small magnet to catch any rust. The fuel filter
should preferably be transparent and with a paper element. A good engineer
will always align the filter so the sediment can be easily seen.
The connection between the fuel tank and the filler cap is done with
a simple length of fuel resistant rubber pipe and if needed, an intermediary
length of standard car steel pipe, all secured with hose clamps.
On cars, the carbs are hidden under the bonnet (hood) and rarely suffer
from rain. Some are even heated with ducted air. If open to the elements
as on some trikes, the carbs may be prone to water ingress and severe
winter cooling. Also little, and sticky fingers. Therefore some form
of protection may be required after testing and setting up.
Heating ducts are possible from the exhaust headers, use them if the
trike is needed to be ridden in cold climes. Alternatively isolate the
carbs from excess cold with shielding and some insulation.
Little, or sticky fingers may also find carburettors irresistible, so
some stylised form of shielding or security may be suitable.
Alloy sheet can be easily shaped by using a ball pein hammer and a bag
of sand. Panel beating is an art, but even minor attempts can make a
sheet look like it naturally belongs there, rather than just another
nondescript bracket. When shaping aluminium, it will work harden, so
regular softening is needed. Rub some ordinary soap on the alloy and
heat until the soap begins to turn brown, then quench the alloy in water
to anneal it to make it malleable.
There are alternative ways to secure expensive carbs to engines, including
special nuts, or simply making the removal components very difficult
If out in the open, the carbs may get cool in winter so the covers should
try to duct some warm air over them in the winter, to keep from icing
at high speeds and in bad weather. Shielding should also prevent any
linkages from sticking from road salt and general road dirt. If this
is not possible, liberal amount of rubber boots and thicker silicone
maintenance spray may suffice.
To make custom plastic boots, cover the linkages with plaster of paris,
then covering in silicone rubber. This will allow the plaster moulding
to be picked out, leaving a perfect silicone rubber boot. Using white
foam is much easier, as petrol will dissolve it after the silicone has
set. Carving with a concertina shape and some styling will offer a degree
of style to the proceedings. Using silicon bathroom sealant which is
colour matched to the trike, creates a little more perfection. If not
for show, but used in harder climes, preferably look for harder rubbers,
such as shoe base material which can be applied from a tube.
Fibreglass suppliers also supply a plastic dipping moulding material
similar to that used on the handles of pliers and similar tools.
The authors simplest and shortest throttle cable was on a fuel injected
V12 trike. (14 inches).
Unfortunately, few cables are this easy.
As many engines are rear mounted, the cables will be often need to be
modified and lengthened. It is increasingly difficult to find anyone
who will make a custom cable, causing the builder to improvise or make
Improvise: Using a standard bike twist grip and cable, position the
cable in the best route towards the carb. Then fit the standard engine
throttle cable and route it towards the front cable. They will either
reach or not reach. Then make up an intermediate connection to fit the
standard cable ends of both. This intermediate linkage can often be
a third standard cable or a light rod mounted along a frame tube. Make
suitable clamps to securely position each outer cable in a suitable
position along the frame.
By employing standard cables and components, many hassles will be negated
and spares will be much easier to buy and fit.
Make your own: Some motorcycle aftermarket suppliers still sell reels
of Bowden cable and a selection of cable ends. Find a cable supplier
and buy plenty of inner and outer cable. With many trike friends, cable
skills will soon be in demand. Choose the more flexible inner type of
cable, as all throttles should be a light action. Outer cable should
ideally be nylon lined. Also buy a good selection of nipples and ferrules
at the same time.
In Britain finding cable may be a pain, but it does exist. Go to a
friendly dealer, the sort who is a small motorcycle shop and ask when
the parts supplier representative turns up, they invariably arrive within
the same hour every week.
"Hi, when does the pattern spares rep turn up? Tuesday afternoons?
- great. Is it OK to be here to see if he can supply some rolls of control
cable and bits, as it's a bugger to hunt down. - Cheers, - I'll pop
in early on Tuesday afternoon."
The problem behind making a direct approach is that most big dealers
want to sell full price cable, and smaller shops simply don't want to
have the hassle of ordering bits you may or may not want. If you turn
up in person, then you can ask the rep yourself and the shop owner will
have no hassle over what is available and what you think you may need,
nor end up with unwanted stock.
Be polite and ask it its possible to be there when they arrive, Then
ask the rep what cable they have and then order it though the shop,
leaving full price as it's not really expensive. It should arrive within
a couple of days. My friends shop's rep can supply four sizes of wire
and outers, plus a host of cable ends, nipples and ferrules. But I can
only get the stuff if I am there to quiz the rep.
Use light cable for throttle, and strong cable for clutch. If a cable
operated car clutch, preferably keep to the original components. Again,
if too short, use two standard car clutch cables and make a simple cable
Scavenge the ends off old cables to make a good fit for the twistgrip,
then clean up to fit the outer cable.
Where the cable outer will not fit the standard mountings and will tend
to misalign, it is often possible to slide a short length of rubber
fuel pipe over the outer cable join to prevent misalignment of the cable
When cut to length, fit the outer and check the run. If suitable nipples
are not available, then make them from steel or brass bar. Brass is
better as it solders easier and wears better. Old brass screws can supply
the twist grip nipple, by drilling a small hole first, then countersinking
the hole slightly and then cutting to length evenly either side of the
hole. Larger nipples may need to be made from old steel bolts. Always
countersink the nipple holes.
The inner cable should be soldered around the new ends before cutting,
so the strands will not distort. When the strands are in the nipple,
file a small nail to a tapered point and gently hammer into the centre
of the strands to swage the strands open and spread in the countersink.
This is particularly important for clutches with their heavy loads.
Then solder fully and file flush when solid. Make sure the nipple will
rotate freely in the twistgrip to prevent undue wear. Always lubricate
fully before use with a light grease around the nipple and light oil
in the cable, allowing the oil to drain all the way through the cable.
Always use a light oil in the throttle, not a thick engine oil, as this
causes drag. Always make the cable route as smooth as possible with
The carburettor end may require an unusual fitting, possibly the use
a push bike brake type of clamp to secure to the carburettor linkage.
If the car carburettor return spring is too heavy, try modifying, or
use a different spring. Double check it will not stick open and always
use an ignition kill switch if in doubt. (See my 'Builders Guide to
Motorcycle and Trike Wiring'.)
Choke. Where a choke lever is needed, it can be mounted almost anywhere,
possibly even with a simple high tech variant of a piece of string and
a return spring. (Please don't use string.)
Some automatic chokes work on engine or water temperature acting on
a bimetalic strip or similar device. As a trike carb is mounted in the
open, some adjustment may be possible, such as adjusting the setting
for winter use. See the appropriate car manual.
Some vehicles can use aftermarket manual choke conversions for carburettors
for those who prefer this option. As the engine may be front mounted,
the choke lever on the carburettor may even be operated directly or
by using a simple extended lever.
Always fit and use as the manufacturer intended. Use standard chips
in any engine management computer until everything else is fettled.
A fuel filter must always be used and must be the recommended type for
a pressurised system.
As fuel injection is expensive, use a new fuel filter and strip the
old filter to assess the state of the fuel supply. If doubtful, consider
adding fuel injector cleaner for a little while to reduce nozzle pintles
from sticking. With multi point injectors and engines with many injectors
such as V12's and with the engine running, a cheap kiddies stethoscope
or sounding tube will help diagnose sticking pintles, as will separate
exhaust headers dabbed with a wet paint brush. Engineers stethoscopes
are also available for about a fiver from the big red shops which sell
lots of welders and tools. Have a good listen and compare each injector.
As the fuel lines forward of the fuel pump are at high pressure, make
sure all pipes are protected and rubber mounted to prevent rubbing or
wearing on the frame. Always keep fuel lines away from exhausts.
Electronic fuel injection invariably imposes a control box or similar,
so keep this dry and mounted in soft foam which will not absorb water
or oil. Usually placed under the rear shell, or make a safe box for
it with the other electrics. If a finned case, or the case gets warm,
allow cooling air flow. Ensure all wiring is protected well and further
protected with rust preventing maintenance spray on the connectors.
Some of the controls or commands can be overridden, but rarely worth
On trikes, where bonnets (hoods) are not used, the fuel injectors are
open to the weather, so protect the injectors with the genuine rubber
boots with a little extra clear silicone sealant, and prior to this,
fully spray with maintenance spray which dispels moisture, to prevent
corrosion of the wiring and connections.
As most fuel injection systems employ pressure and volume sensors in
the air inlet plumbing, air and engine temp sensors, plus a host of
other sensors, always start by using the wiring and plumbing exactly
as the manufacturer intended. Nothing removed, nothing replaced and
nothing added. Keep the airflow sensor and the whole air filter system
etc. These parts may be able to be repositioned later after initial
testing, but must retain their original purpose and general orientations.
If problems occur, then have the engine set-up and fettled by the certified
specialist. They usually know what they are doing and have the tools
to do it. They may often offer priceless advice to improve the system.
(Ask the mechanics quietly if the motor will take the 'sports programmes'.
This is because some computers can have their programmes wiped and the
faster upgrades written into the EPROM's for an extra 10 percent horsepower
over the standard model. Usually a 'test drive' to somewhere quiet with
a laptop and a few minutes reprogramming with the updated software and
a few quid changing hands for an easy extra 50 horse power.)
Do not expect people to get excited over radiators. For many, there
is nothing worse to destroy the looks of a trike than a huge, ugly car
radiator stuck in font of the engine. Hopefully the car engine is all
alloy, with dual rocker covers and some degree of style. So don't spoil
In most cases, only oil coolers look good at the front of an engine,
more so if using racing stainless steel braided plumbing.
If the engine has an engine driven cooling fan, simply remove it and
place the radiator anywhere suitable by employing electric cooling fans
The pulley part of the fan mounting may need to be retained, as it is
often part of the V belt drive for the alternator and water pump, or
a mass damper to prevent unwanted vibrations building up in the longer
crankshafts such as straight sixes.
When choosing different radiators, keep the radiator cooling area at
least the same as the original or a little larger. See what the scrapyards
have to offer. Radiators are a design opportunity, so don't be afraid
to experiment with them.
Radiators are essentially simple technology with only a few booby traps.
They are fairly cheap and are easily made to measure from most local
radiator suppliers at prices less then original components. You can
specify the positions of the inlet and exit pipes, choose from a variety
of widths and have the matrix any height you want. You can also specify
single or double thickness matrix. So get the tape measure out and study
the possibilities. Make a cardboard cut-out as a pattern to check fitment
and for the local radiator maker to copy if you can't find anything
suitable in the scrap yards.
Radiators are prone to stones, road kill and general clogging, so keep
the airflow away from wheel tracks or similar impact problem areas.
Wheels can also cause air turbulence and upset an otherwise superb air
flow. A wire shield or F1 style 'barge board' deflector may be needed
in some cases.
Keep the engine areas looking sleek, so consider placing the radiator(s)
out of sight. Hide radiators unless they are stylish such as the styles
so enamoured of formula one and some supercars. Even then, some stylised
ducting to control airflow should be considered. See also shell later.
Study the Lamborghini Countach and formula one cars, they seem to have
more than just a little style in the radiator area. Always consider
if two smaller radiators will be preferable for aerodynamic and aesthetic
reasons. Or maybe different shapes and mountings can be used to enhance
Styling of the rear shell will open up many possibilities with air ducts
and such like. The Ferrari Testarossa, (Red head) for all it's faults,
had world famous side mounted air scoops.
Modern cooling systems use a header tank to allow for expansion of
the coolant when hot, which must be placed at a virtual 'high' point
in the system. Make sure all air in the system can bubble its merry
way up towards this tank or can be bled from the system at a high point.
Many modern cars use little plastic air vent taps for this purpose.
Recycling the cheaper screw-in schrader cycle and motorcycle inner tube
valves can also be employed for awkward plumbing, but good design is
Rubber mount the radiators as they can be fragile. Make all connections
with rubber tubing. The plumbing can be a mix of radiator hose and steel
pipes that can be easily shaped to fit awkward bends. Ask the radiator
builders what types of inlet and exit pipe positions are available to
make plumbing much easier.
The thermostat, temp sensor and the cooling fan control will do their
jobs whether in a car or trike, it doesn't matter which. As the temp
sensor and thermostat are built into the engine, they all work at the
temperature that the engine designer requires. If a remote thermostat,
it must be kept very close to the engine.
If the radiator is large and mounted horizontally or at an angle, then
the matrix should be supported at various points to prevent collapse
when jumping hump back bridges. Use light steel bars and heavy duty
foam which will not collapse, with a hard rubber pressure spreader sheet
between matrix and foam, to prevent the matrix cutting through the supporting
On front engined trikes where the water pump is positioned at the front
of the engine, use large bore coolant pipes hidden under the frame rails.
If they cannot be hidden, use stylish tubes and routing, possibly stainless.
As the radiators may be much further away, the use of larger bore coolant
pipes will reduce problems of restriction from the longer coolant flow.
Never use smaller pipes as the water pump may not be up to the effort
of a restricted flow. If things get really desperate, such as for big
motors, an electric water pump or even two can be used, one for each
Connect the engine with steel or stainless cooling pipes to match the
shape and style of the engine, so they won't look out of place. Alloy
or copper pipes can fracture with time, so only use if building for
show or custom. Steel pipe will rust unless using antifreeze, so always
use antifreeze except when on racing circuits. If in doubt, clean the
steel pipe fully, then coat the inside with epoxy resin. Paint may flake
off and impede the water pump or radiator matrix.
For many trikes, the coolant can flow through the frame tubes. As coolant
rarely exceeds boiling point, most paints will be unaffected. Another
reason for having long, uninterrupted frame tubes.
It may be advisable to place the small coolant header tank under the
steering head, so it can be seen when it overheats, especially during
testing or if wiring up a temperature sensor and gauge is too much hassle.
Ensure the header tank can accommodate the difference in volume between
cold and hot as the system reaches operating temperature. The cap will
normally maintain pressure in the system and allow excess coolant to
be vented if overfilled.
On the Alfa, two smaller radiators are used, partly to keep the height
down and partly for posing in style. They are wide and short, rubber
mounted an angle either side and just in front of the suspension, angled
to catch the updraft of the hidden air dams under the passengers feet.
The coolant split to flow into both radiators to prevent causing too
much drag on the water pump. If the water pump had to pump through one
radiator then the other, the increased pressure drag may cause the flow
rate to drop, and overheating could occur. By using two radiators in
parallel, if one radiator becomes damaged, it can be clamped off and
allow the other to be used to get home. If one radiator becomes clogged,
the other will still work.
Two vent pipes allow trapped air from the top of the radiators to go
to the header tank via a Y piece from a windscreen washer system. Wire
mesh protects the radiators from damage.
With passengers either side of the rider, make sure the footrest position
is chosen with heavy braking in mind, or you will be scraping friends
off the wheels. On the Alfa, two seats are fitted between the wheels
and driver, slightly higher, to clear the radiators, the back of the
seats resting against the suspension cross member. The front of the
passenger floor panels could then be angled up to channel the air into
the radiators, acting horizontal air scoops with side dams while maintaining
styling. It also helps to keep road spray from the front wheel off the
On most car cooling systems, cooling fans are used and controlled by
the standard car temperature sensor via a relay. The water temperature
sensor often shorts a fan wire to earth when the max temp is reached.
This can be used to control one radiator fan, or control a pair of fans
via a simple relay. Some temp switches work directly on the fan without
need for a relay, but check the manual first.
The radiators may not get enough air at low speeds, so make sure the
thermostat, cooling fans and temperature gauge work properly. The temperature
gauge should be the standard donor vehicle item, as the engine designer
prefers it this way, although just about any thermostat will do. The
temperature and fuel gauges may need a voltage stabiliser from the dashboard
to keep them reading properly, as most gauges are voltage sensitive.
Check the wiring diagram, or check by noting the cold and then the hot
position on the gauge at running temperature.
Make sure the cooling air can flow easily between the engine and passenger
seats so no-one gets too warm. For trikes used in more Arctic climes,
switchable positive heat ducting louvres should also be considered.
Radiators and aerodynamics.
The biggest problem with cooling is not the radiator size, nor bad design
causing the coolant flow to be restricted, but the inability to get
sufficient cooling air though the radiator to begin with.
If the cooling fans are often on, or if the engine keeps overheating,
check the thermostat, carburetion and ignition timing first. Then check
the water pump and at the same time flush out the engine block and all
waterways with a hose pipe.
If the engine still overheats and all else fails, then check airflow.
Cut some three inch long strips of bright wool, grab a friend, a bamboo
stick, some blue tack and find a quiet road. If you can see the radiators
while riding, stick some wool strands in and near the radiator matrix
to highlight the airflow. Blue tack some tufts of wool around the air
flow areas, wool strips around the radiator areas, with the passenger
using a piece of wool on a stick to check other areas.
Ride the trike through different speeds and wind directions to find
out just where the air actually flows. Problems may involve the action
of the wheels, a 'dead spot' of air flow, or turbulence which can break
up or destroy a clean airflow through the radiators. Not only must the
air reach the radiators in a clean flow, the heated air from the radiator
must then exit cleanly away to ensure a totally balanced and effective
The passenger may also be able to use a flat piece of card while driving
to deflect the air to effect possible solutions, followed up with Duct
(gaffer) tape and cardboard ducting modifications. See also aerodynamics.
Too many trikes suffer poor cooling, especially when thrashed. Poor
cooling will destroy an engine especially on a long run. It should be
sorted at an early stage.
If you have a laptop with a remote USB web cam, then this may also suffice
while riding, if its secured to the seat with bungees and the camera
to the radiator area with lots of blue tacky office putty. (More fun
with laptops later.)
If suspension fails, a rider will slide to a halt, but if a wheel fails,
the consequences can be far worse. Where possible, buy commercially
On rear wheels, ridiculous oversized rear wheel spacers will soon trash
axle bearings, so are only applicable for show use. Rear wheel spacers
are not a good idea.
On light trikes, a motorcycle front end will often suffice.
On heavier machines, some work is involved to get the best from the
The tyre is the most important item, so choose it well. The front wheel
profile is mentioned earlier and will help get the best from a trike
Buy a steel wheel to fit the tyre. Sensibly compromise rim width, to
retain the little rounded profile on the front tyre, but not that it
looses its lateral stability. Check by moving the mounted tyre in the
manner expected by the trikes front end, taking into account the rake
angle, to see how the profile matches the road surface. As the trike
does not lean like a motorcycle, a partially curved profile tyre is
By using a steel rim, a special wheel and hub can be more easily modified
to fit a set of forks.
A steel motorcycle hub with dual discs can be built up to take a car
rim, but make sure it is as strong as possible and with strong bearings.
As such hubs are rare, simply make new items using similar techniques
to the steering head to give a strong, twin taper roller or ball race
hub and axle. Motorcycle wheels rarely take side loads, except for sidecars,
whereas a trike will be pushing standard motorcycle wheel bearings to
their limits, so always build a better, stronger hub. Harleys and some
BM bikes use taper roller wheel bearings and are recommended for medium
There are two basic front hub designs. Either to build a simple axle
unit similar to a steering head or to modify or re-engineer a bike or
car hub. Re-engineering a car hub or a bike hub such as a Harley rear
hub with taper roller bearings is often easiest, but it must be steel
to allow easy welding. Those who can afford to commission special billet
wheels should have few problems.
For those who need to, or prefer to engineer and build their own wheels,
then there are many ways, and careful consideration always repays the
The standard car dished wheel centre will only easily accommodate a
single disc. If a standard car wheel is used, choose one piece car disc.
Shy clear of a lightweight motorcycle floating bike disc except for
show use. Trikes need all the help they can for front end braking, so
get strong tyres, a good footprint and strong brakes. With a very strong
solo disc such as used for a car, it is possible to use dual callipers,
usually spaced 180 degrees apart on the disc, to double the stopping
power. The tyre will often handle this, although severe braking on cheaper
tyres may lead to more regular disc and tyre replacements for purposes
of safety. Don't go stupid, so never put more braking than the tyre
can handle. If desperate, consider using rim bolts as used on motocrossers
and trials bikes which can prevent the tyre from slipping on the rim,
but these are only available for bike rim profiles.
Car disc and pads are very cheap, even the ventilated types, costing
less than a set of bike brake pads and they last much longer.
The only limits to building a decent front end are the strength of
the hub, brake components, a decent tyre and a strong fork design.
For wheels which look more like bike wheels, it is easy to demount
the steel car rim by grinding away the inner spider. Drill or grind
out the six or more heavy spot welds keeping the rim on the spider.
If you don't want to remove the centre, a lighter, 'motorcycle style'
inner design can then be built up by carving the original centre to
maintain some motorcycle styling. Alternatively, use tubing to build
three or five spokes or whatever wheel design is appropriate. Most custom
catalogues offer some ideas on the wide variety possible.
I often rebuild car rims to make narrower or wider rims on standard
spiders for rear wheels, or my own specialist centres for front wheels
for my hub centre steering bikes.
When suitably strong, the shape can then be built up with filler or
fibreglass to match the style of the rear wheels. Sometimes it is possible
to wax the rear wheel and take a cosmetic moulding using cloth and plaster,
then apply this to the front wheel and lay up the identical shape for
If required, a car rim can be drilled and recessed for heavy wire spokes,
but must be mounted on a strong hub. Always spend plenty of time getting
the spokes accurately positioned. Indent the nipple recesses using a
simple jig and nipple profile socket BEFORE drilling the holes at the
correct angles. Some earlier sports cars had spoked wheels - seek and
Alloy car wheel rims can be deconstructed and rebuilt onto motorcycle
alloy wheels. Both will need careful machining and welding. If using
alloy sheet, the new wheel may also need heat treatment prior to final
machining. It may be preferable to use a rear motorcycle alloy wheel
at the front if needing a wider rim and tyre profile. Many car tyres
will fit bike rims and vice versa. Check S.A.E. rim specifications.
Building stronger front ends does not mean that style flies out the
window, even though many trike alternative front ends leave much to
be desired. Most front wheels for car tyres can be built up from a wide
variety of parts. When forks are not acceptable, especially where the
engine is large and intended for serious thrashing, then strength and
suspension control are major design concerns.
For alloy wheels, choose the tyre first, then find a suitable wheel,
probably styled to match the rear wheels. Many custom wheels can be
matched in a variety of rim sizes.
Buying two very fat versions of an alloy wheel and one skinny version
may cause the retailer to give you a weird look, but you are the customer,
so get what you want. If they get worried, say the small wheel is for
an emergency backup wheel to fit in a small boot (trunk) storage space.
Some top of the range car alloy wheels are built from split rims, where
the rim is in two or even three parts. If lucky, the manufacturer may
be able to mix these parts to give wide rims at the rear and a narrow
version for the front wheel.
Where designer alloy wheels are used at the rear, possibly low profile
racing tyres, then the front should consider machining back a similar
wheel rim area and adding an alloy rim machined from a much narrower,
larger diameter car rim. This rim can be machined to a narrower version
by careful deconstruction followed by welding. Cross breeding the two
will maintain compatible styling. This is often the case where an excellent
rear tyre is not available in a suitable front rim size.
For those on a budget or who prefer to try this themselves, then off
to the scrap yard and buy a set of four wheels. Two for the rear, one
to deconstruct for the front wheel centre and one for a rear spare.
Then either cut the sides to fit a narrower tyre or cut to fit a different
Alloy can be machined comparatively easily. Mount the wheel with the
new front rim in the trike and run the engine. With a differential,
it is necessary to lock or brake the other wheel, which puts a strain
on the diff, so do not go stupid. A high tick over is usually sufficient.
Using a strongly mounted lathe tool, carefully trim back the inner part(s)
of the alloy spokes until the rim is left with a sensible amount of
metal so it can be welded the reprofiled inner rim.
If brave or stupid, you may be able to get away with a coarse hacksaw
or old woodsaw mounted incredibly strongly to a broom handle to cut
away the wheel rim as the wheel turns. Always wear strong gloves, jacket
and goggles and be ready to jump out of harms way.
You must ensure the rim sides of the wide car wheel can be remounted
to the new, narrower inner section, therefore make the cut stepped to
allow easy alignment for welding.
Once the side of the rim is off, leaving a bare wheel centre, then a
chamfer cut, so it parts off cleanly. Do likewise to machine back the
inner wheel section of the wheel with the worst rim, so it matches the
chamfer of the new outer rim for perfect alignment. As the new front
wheel is often of a larger diameter, just the sides of the rim may need
to be removed. If there remains a gap between the rim and the wheel,
then a spacer strip of alloy can be shaped to fit the gap.
A slight interference fit keeps it all together prior to welding.
Do not use magnesium alloy wheels.
Always take great care when using power tools and similar set-ups. If
a cutting tool is not available, it is possible to use an angle grinder
with the wheel spinning to ensure concentricity of the cutting process.
The wheel must then be tested. If possible, use as much water in the
tyre when pressure testing, as this reduces the explosive effect should
it fail. Place the wheel and tyre on the trike, then load it fully and
then a bit more, to about 30 percent more than normal load, to simulate
heavy braking forces. With the tyre pressure gauge at the top to prevent
water damaging the pressure gauge, check the tyre pressure as the reference.
Then remove the wheel and pressure test fully. Always pump up the tyre
behind a brick wall, so nothing flies your way. An alternative is to
have a tyre pump with a pressure gauge, with the connecting pipe running
under the garage door to the test tyre on the ether side for enclosed
The tyre is then pumped up to 25 percent more than the maximum reference
load pressure and left for at least an hour. If all is well, the water
can be drained out and the wheel inspected.
If a wanting a different rim, perhaps from a motorcycle to fit a car
centre, then trim the inner item to fit the new rim, then get it welded
by an expert. For best results, leave a full circle of the original
rim area around the outside of the machined down centre section, so
the rim can be welded fully around the rim.
If the two parts are machined such that they are a concentric, firm
press fit, then this is ideal for checking and adjusting the centre
line alignment to the rest of the trike prior to welding. Alternatively
a corresponding alignment ridge, step or flange could be accurately
measured and machined on each item to ensure perfect alignment prior
to welding. Three self tapping screws will prevent misalignment before
welding, but always remove them and fill their holes after. If thrashing,
this is a good time to get the rim welded on both sides with an inner
ridge, similar to a car rim, to reduce the chances of the bead parting
from the rim during side loads. The welds can then be dressed to shape
on the axle used as a lathe. If you take the axle along, it can be mounted
in a vice so the welder can more easily make a truly concentric, neater
internal bead lip.
Once the wheel and discs are mounted, it is possible to weld on brackets
to fit better brake callipers to position them where they will not foul
the steering. Clamp the callipers in position on the disc prior to welding
by connecting the plumbing and pressurising the system, as normally
used. With new brake pads and a clearance spacing strip of thick cardboard
on the edge of the disc, adjust the callipers as required. Then the
mounting brackets can be accurately made and welded onto the hub carrier,
torque plate or other brake calliper mounting device.
The use of dual callipers may be considered for both front and rear.
Dual front for extra braking or linked or biased braking. Dual rear
for separate main braking, with the other calliper for the parking brake.
See also brakes.
When fitting dual callipers to a front car disc, the symmetrical donor
callipers will be handed pairs, so the bleed nipples of both can be
mounted to allow easy bleeding.
For rear custom steel wheels using donor components, the standard axle
mountings may not fit the larger wheels required, either for gearing
or style. Begin with larger wheels using the same studs, or redrill
the hub to take a new stud pattern or have adapter plates made. Adapter
plates are similar to wheel spacers, but without excessive overhang
which destroys the wheel bearings.
If redrilling the flange, always make sure the central aligning shoulder
is accurately machined first, so the new wheel will align concentrically.
This can be done by simple welding of three alignment lugs followed
by machining in place, using the engine to power the wheel flange. When
concentric, the wheel is then mounted accurately on the flange to align
the new stud holes. This must be done extremely accurately.
For greatest accuracy, drilling the stud holes is best done on CNC or
a milling machine with an indexing head. Alternatively spin the hub
in the axle and carefully cut a fine groove to the 'pitch circle diameter'
of the new wheel studs. Then weld up spot welds then spin the hub and
dress the alignment welds to accurately become a minimal mounting flange
so the inner hole of the new wheel will align. Then the four or more
stud holes can be positioned accurately around the PCD. Not all hub
flanges will be able to take slightly larger wheel stud patterns, but
some can. If the stud holes are close to the edge of the flange, add
a safety band and weld it fully.
Rear wheels can use similar techniques as for the front wheel.
There are many basic front and rear wheel hub to rim support designs,
including carved from a single sheet, modified or re-engineered car
parts and a set of new identical spokes built onto a hub with central
The simplest is using a standard bike or car steel rim and modifying
a standard car centre. A car rim can be removed by drilling out the
large spot welds then cutting and reprofiling the centre to run true
to the new rim position. By slitting the outer bell of the standard
car centre, it can be opened up and reprofiled to accept larger diameter
rims for lighter use.
Alignment of rim to hub. If jigs are not available, the hub can be
built up and assembled in position. Jigs are second best to building
on the actual bearings and spindle which allows absolutely perfect alignment
For first attempts, consider re engineering car or other steel wheel
centres, trimming them down to suit any lighter loads and new profile.
Rear wheel and single sided front new wheels centres which bolt onto
the hub can be built from steel and fitted accurately to the hub flange
and studs. Fixing is usually via conical faced nuts on studs. Always
dish the areas where the nuts will fit onto the new wheel centre. Then
spin to mark in the various alignment and other features, which can
then be perfectly concentric. Double check by repositioning on the other
studs to check concentricity. Then add the spokes and spin to run true,
spinning the wheel and gently grind down the rim mounting points for
a accurate fit to the rim.
If the studs do not allow perfect alignment on all holes, make a detent
and corresponding hole in the wheel, so only that particular wheel can
be used, and it can only be fitted the correct way.
Push fit the rim firmly on the spokes until running true, then tack
weld and double check.
Spokes can be built up in many designs, from simple square bar mounted
in a triangle pattern, to the many complex designs seen in catalogues.
Heavy gauge sheet can be shaped and flanged for a variety of styles
to make three or more identical spokes which should align perfectly.
Round bar can be gently squashed to create basic aero style spokes.
When building spokes from new, balance is especially important. Always
mark out the degrees of equal spacing to ensure accurate centre lines,
to which a cardboard profile can be applied and drawn around to ensure
even weight and thus better balance. Clamp the bare spokes together
and trim them as a matched set before fitting.
If the rim is slightly heavier on one side when the valve fitted, then
the rim should be rotated on the spokes until the whole balances as
well as possible. Then the spokes dressed to balance perfectly.
If large alloy or steel spokes need some depth in cross section for
more rigidity, such as for extreme offset for hubcentre steering, then
they will need flanges. These can be made by panel beating grooves along
the edges and centres of flat plate spokes. Use a leather covered sand
bag, or profiles in the end grain of a wood block and use a ball pein
hammer. Edges can also be flanged inwards to create ribs, similar to
early Honda Comstar wheels. Cutting lightening holes in wide spokes
will allow the edges of any holes to also be flanged for more rigidity.
If making from separate sheets, usually as a set of spokes, always grind
them to shape as a set, clamped together. On heavy machines, consider
using a butted, stepped or overlapping design of spoke to improve both
strength and alignment. Align the steps to improve braking load resolution
and the central angles to assist accurate radial alignment.
It is possible to use a single sheet of metal for a one piece inner
wheel. Start with the mounting either a set of studs on the hub flange
or the hub itself. Then a series of concentric lines marked into the
sheet for alignment by spinning on the hub and the spokes cut then bent
to shape. Rest is as above.
If heating very thick aluminium to assist bending, a rough temperature
guide is to rub some soap on the surface and heat the sheet until the
soap turns brown, to give a safety margin. Then use a modified pipe
bender to give a series of gentle bends so that all the forces are not
directed at one place.
Do not plunge hot alloy into water to cool, as this makes it softer.
For wheels, always allow to air cool evenly. Then test the design by
subjecting the wheels to twice the maximum forces expected under the
worst circumstances. See also testing later.
If a hub centre design is employed, always build the hub unit and steering
pivot first. This allows the steering axis to be used to align the rim
perfectly onto the steering centreline. The swing arm(s) and whole front
assembly can then be aligned to the frame.
Most motorcycle engines have the exhaust sorted from the outset, as
their exhaust systems are polished and stylish.
Unfortunately car exhausts are notorious for being rusty tubes.
Fortunately car engines are more tolerant of inexact exhaust systems.
Try to get the airflow matched by cylinder capacity, a 500cc car cylinder
pumps almost as much as a 500cc motorcycle cylinder. (The difference
is the revs involved, numbers of valves and inlet tract design and carb
When making car exhausts, routing will be the biggest problem. This
splits into two main problem areas, the visible engine mounting area,
and the hidden exhaust routing.
The engine vibrates, and so must the exhaust. The exhaust is therefore
held in flexible mountings form the original donor machine design, and
will thus prevent the more common fracture problems.
If securing the exhaust to the chassis, then a flexible section will
be needed. This can be a special flexible exhaust tubing, or a spring
loaded ball and socket join, made by panel beating the exhaust pipe
ends to a cup and socket which is retained as a sealed flexible joint
by strong springs.
Keep to standard donor car exhaust components at first, until the design
has proven reliable, then consider any fancy exhausts at a later date,
as this is simple customising work.
If making the rear of the trike to look like a formula one car, please
note that the vertical exhaust system may need to be a dummy in some
countries or may need to be quiet. The public may never know that the
2005 style F1 exhaust has a pair of silencers, or even catalytic converters
hidden just under the rear shell.
In lands of excessive bureaucracy, some specified exhaust markings
may be needed, requiring specific aftermarket exhausts to be employed,
so start here and work backwards from this soulless burEUocracy.
For trikes with open car engines, it is most unlikely that the trike
will look exciting with a cast iron exhaust header. If possible, use
the exhaust header but cut it down to give the best exhaust mounting
flange or brackets. This ensures the standard gaskets can be used. Fit
stub pipes into this header flange and bell out the ends to a tight
internal fit, weld them to fit internally, then file flush to fit the
gasket face. Alternatively, spring mounted exhaust pipes can be used,
similar to racing exhausts. This is particularly useful for rubber mounted
engines which will need a degree of flexibility between chassis, exhaust
Where a standard exhaust is used, study how the fixing between engine
and chassis is achieved, copying the original manufacturers set-up to
prevent fracturing of the exhaust. The standard exhaust may be rigid
on the engine but flexibly mounted to the chassis along its whole length
to prevent fracturing. Always try to keep to the original exhaust rubber
mountings as they are designed to ensure minimal fracturing.
Anything up to twelve separate exhaust pipes may need to join into a
silencer. The easiest way is to make each pipe enter a box separately,
which can be easily welded from the inside for greater neatness. This
can then be joined more easily to an approved aftermarket silencer.
Alternatively, separate exhausts for each cylinder can be employed,
using aftermarket, pattern VW Beetle exhaust flutes inside the end pipes
to keep the noise reasonable.
Unfortunately some rear exhaust systems may need to be bolted in place
to route through some tight or awkward area. This may require a flexible
joint. Flexible exhaust joints can be built from special flexible exhaust
tubing, available from some retailers. Another method is use of spherically
swaged ends to pipes with the other pipe 'belled' or rounded to fit,
and the two parts held together with flanges and springs. There are
many variations of this on cars, such as the font lower join on Ford
Escorts Mk 5, which can be salvaged according to use and adapted to
spring loaded use. Keep your eyes open - you don't have to reinvent
Trying to make a heavily convoluted formula one exhaust requires many
skills and such exhausts may preferably be bought. For those with real-world
budgets, get as much new tightly bent exhaust tubing as possible and
prefer using oxyacetylene when making tricky snake-nest exhausts. If
keeping the trike, use stainless steel and tack weld, then hand over
to an expert. If testing, use second hand pipe from scrapyards or exhaust
fitters, where a great deal of good piping is thrown away.
By law, exhausts should normally exit to the rear of the vehicle, although
some side exiting exhausts are possible. Local regulations may even
allow the incredible vertical exhausting slashed systems as per formula
one machines - no one need know there is a bog-standard silencer just
under the fibreglass shell.
All exhausts get hot and must therefore have good airflow between themselves
and other parts. On lumpy engines, heat shields are prone to rattling
and falling off, so mount securely. Where exhausts are close to other
components, use heat insulating sheets available from most car parts
retailers or some caravan / camping shops.
NEVER allow any fuel related tap, pipe, connection or other fitting
to be near or above an exhaust.
When mounting turbochargers always keep to the manufactured set-up
and waste gate settings until the machine is sorted and fettled. Use
standard chips in any engine management computer until fettled. Where
the engine is open to public view, cover the turbo with a metal guard
and always try to shape the guard to ensure good airflow around the
turbo. Panel beating softened aluminium is excellent. Always use an
oil cooler with turbo engines.
Catalytic converters are now often mandatory and should be hidden wherever
possible. They work best when they get hot quickly, so keep them close
to the engine and nice and cosy under their own little heat shield.
Likewise any lambda sensors which check for unburnt oxygen.
A V8 or V12 exhaust should be a work of art, not only for looks, but
in the music available.
An American V8 throaty burble is never forgotten.
A V12 'on song' is a wondrous song.
Try not to stifle them too much.
Rotary Wankel engines should use the original exhaust, as they have
many unusual needs. They get much hotter than others and may have unusual
over-run requirements. Done properly, they should howl nicely.
Racing or power enhancements are best left to the individual experts
for each particular machine. This is often simple, if expensive catalogue
I hate catalogue 'customs'.
If building on a budget, the best engine modification for more power
is more cubes.
Fit the 1600cc car engine in place of the 1300cc. Fit the turbo version
instead of the 1600cc.
Simple, reliable, effective.
If building on a reasonable budget, consider buying a complete, running
old Porsche 5litre V8 for a grand or so (2002 prices). It instantly
makes engine customising a total waste of time and money - in one simple
stroke. It ensures real reliability when thrashed and imbues an instant
and serious street presence that few other trikes could ever hope to
achieve, but check the insurance first.
If using low, expensive engines such as the Porsche, always consider
a sump guard. A steel cage under the engine will take the force without
deforming enough to damage the engine. For very low engines, where room
is at a premium, this is usually a thick sheet of aluminium restrained
firmly at the front, to resolve any drag, and loosely held at the rear,
to allow for deformation. There should be a stout piece of rubber between
the sump guard and sump.
Do not change too much until primary testing has proven the trike handles
and brakes to a high standard. When the design is deemed acceptable,
then a programme of engine and chassis refinement can take place over
the lifetime of the machine.
When a front engined trike is designed, a lot of junk can be removed
from the engine to clean up its looks.
When removing the front radiator for styling purposes, the plumbing
and some fan pulleys can be removed or dressed down. Some engines also
use the front pulley as a vibration damper, so check first and if so,
always leave it in place.
Only the alternator drive may not be negotiable, but if it is a V6,
8 or 12, the alternator can nestle between the rocker banks, out of
sight under the steering head gussets. If a belt adjusting bracket is
difficult, a spring loaded jockey pulley may suffice to keep tension
on the V belt on its slack side. V belts come in many sizes and can
turn various corners if needed. Always make sure the drive to the water
pump is correct.
A mechanical fuel pump sticking out the side of an engine may look
awful, so blank off the hole with a plate and use an electric fuel pump.
Alternatively for show use, the hole may be opened up and windowed with
polycarbonate, using an internal light to show up the polished crank
and con rods for petrolheads. The starter motor must be left on the
engine, but it can be colour co-ordinated, plated, covered or disguised
with a beer label, such as Old Speckled Hen.
An alloy engine crankcase may often be first target for polishing.
The mounting points for alternator, air-conditioning and power steering
may look ideal subjects for grinding down for better looks. Do not succumb
unless the trike has been fully tested, or if spare crankcases are easy
to find. It is better to keep any mountings, simply making them look
like they should be there - by employing them as brackets for holding
any coolant pipes, cable brackets and such like. Where unused, simply
fit short dummy bolts in any threaded holes or use flush fitting plugs
or button head Allen screws.
If the engine is long, such as a straight six, the standard head steady
may want to fit part-way along the top frame rail. This may not be good
practice, as it may cause fracturing of any long unsupported top frame
tubes. Therefore consider the use of two lighter head steadies, one
at each end of the engine. Use softer rubbers to allow the engine to
move as intended. If two head steadies are not desired, then use the
standard head steady, but repositioned closer to a strong frame point
where it will mount with less flexing of the frame and spread the load
into both top frame tubes with a secondary cross brace. A wide Y-shaped
head steady may suffice. Then check by blipping the engine, to see if
it twists too far out of line, then tune or adjust the bushes as required.
The positioning of 'other bits' is often arbitrary.
I position my battery only after the machine has been checked out on
Battery box out of the way of rain and dirt, fuses where they can be
reached easily. Likewise the air filter, fuel pump, hi-fi amp, beer
cooler etc. Easy access for all maintenance work is a must. A tool box
with wheel wrench, jack and foot pump should be carried. If the front
wheel is a car wheel, carry a spare front wheel if it will also fit
the rear axle in emergency (if you did your homework).
If a bike front tyre is used, carry a spare rear wheel and a spare front
inner tube and levers.
If the trike is poorly balanced, then consider positioning the battery
such that it helps balance the trike. In most cases, the battery is
positioned after the fuel tanks, then the axles checked on scales and
the battery positioned to even up the axle loads. If you have a VW engine,
then the battery is probably best positioned near or under the steering
head or any frontal small or dummy fuel tank, to reduce the tendency
to lift the front end.
Tool kit. Always carry a tool kit when testing. Carrying it on the person
is dangerous. Always carry the tool kit in a secure container on the
frame. During testing, the tool kit is always larger than for normal
use, so make container accordingly, or use an extra strap on tool bag.
Always include a first aid kit and carry a cellphone when testing.
If the donor vehicle is a common machine and spares are cheap, and
you intend to tour many countries, then consider adding a backup fuel
pump, electronic ignition unit, coil and other parts. They could be
mounted beside the original and protected in sealed plastic bags ready
for use, ISDE style. Likewise cables.
This and lots of other stuff is available on my website, including 'A
Builders Guide to Motorcycle and Trike Wiring'. A couple of generic
trike wiring diagrams are included. There is a lot of other useful stuff
here as well.
My home website resides quietly at www.btinternet.com/~jhpart/index.htm
The first and best check is to check it all works properly before the
donor machine is stripped. Removal of the loom from the car can be difficult,
so be very careful. An extra half an hour teasing a loom out of a car
is still faster in the long run than having to fault-find, then repair
or rebuild a damaged wiring loom.
As mentioned earlier, the modern car alternator is a self contained
item, supplying perfect 13.8 volts and even a warning light connection.
It can be positioned almost anywhere a V belt will fit. Make sure it
rotates the same way as originally fitted, remount, or use a different
alternator. Alternators are very easy to mount and adjust for V belt
To get started, simply use the standard wiring loom and carefully blank
off what is not needed. If preferred, lay the donor wiring loom in position,
then connect up all relevant parts, even if they are not in the right
places. Then cut away the loom binding and rearrange. Do not remove,
but tidy up any redundant wiring, as it may be needed later. Connect
the battery and check all works as intended. Modify as required.
Main beam, indicators and horn switches can be made to fit by reading
the manual or opening up the car stalks, then deciding which wires are
which and paring them back to connect to bike switches. It is preferable
not to use car switches, which are only designed for a dry environment.
They can be waterproofed, but rarely integrate with trike styles.
Check that the battery charges at about 13.8 volts with the engine running
and all works well. Then make a special loom later if needed, or simply,
but carefully reduce unwanted wiring from the original car loom.
The way the loom is routed on the trike will depend upon the complexity
of the design. If a fuel injected design, then the electrics will often
encourage the units to be fitted in just one place, which may require
a special housing. If making a front engined trike for show, then consider
making a modified custom copy of the wiring loom to position all components
out of sight. This includes the loom itself, which can often be well
As trikes are wide, 5 Watt side lights will be needed which must show
a white light to the front and a red light to the rear. As most trikes
use dual car rear light units, the rearward pointing red side lights
are often unnecessary. Side repeater indicators are also recommended,
especially on very long trikes.
If a fuel pump is used, it should be wired in the ignition circuit,
preferably with a separate fuse and if a big engine, with a relay. See
fuel system above. As the fuel pump is important during testing, make
sure you are able to wire it directly in an emergency to get home. Also
include an emergency direct connection to the ignition coil for the
Where complex electronics such as computers and engine management systems
are used, keep them on their own cosseted little circuit, well protected
with the correct fuse rating and bagged in foam. If they are finned
or may get warm, then always allow cool air to circulate.
As many custom builders have a reputation for poor design and manufacture
of wiring looms, consider self resetting thermal fuses, which will reduce
the number of blown fuses from poor wiring until the fault is found.
On a good day, they may even allow you to travel ten miles before the
If in doubt, get wiring done by an expert, or keep it very simple and
use separate ignition circuits for sparks and for the fuel pump.
Email the author for a re-wire quote. Prices from a hundred quid, even
if there is nothing there to start with.
Also consider a separate circuit for lights, with a separate circuit
for the rest such as horn, brake lights etc. Protect each circuit with
its own fuse.
Always put the fuel injection and such like on a separate circuit.
A basic wiring guide.
The output from the alternator goes to the battery, then to the main
The main fuse then supplies the ignition switch and any relays.
The ignition switch will also supply power to three other fuses.
These three fuses normally supply 12 (13.8V) volts to:
1. The ignition circuit / electronic ignition.
2. The head and tail lights circuit.
3.The auxiliary circuit which contains the indicators, horn and brake
Three or more separate, fused circuits from the ignition switch output
are easier to design, build and repair than one big circuit.
On sophisticated (expensive) engines, the ignition (sparks) circuit
should also split into fused circuits for any fuel injection and the
fuel pump. Each should be protected by its own fuse. When you switch
off the ignition or kill switch, all must switch off.
See also fuel injection.
If required, separate switches can be used to supply power from the
main ignition switch (or independently) to each circuit, aircraft style.
E.g. sparks on/off, fuel injection on/off, fuel pump on/off. (Mainly
for show use or if building with aircraft engines.)
For styling purposes, starter switches can also use an identical looking
switch but with a momentary action.
A small light above each switch can be used to check if its on line,
or to tell if the fuse has blown and the circuit is out. Safety flip
covers or preferably protection bars between each switch are also useful.
Do not put a safety flip cover on the spark / ignition switch if there
is no dedicated kill switch or if the ignition key is hard to reach.
Preferably have a safety cover over the starter button unless an electrical
lock-out circuit is employed.
If using this style, always have the switches in a sequenced row, so
you can easily switch each in turn, - fuel pump first, to build up pressure,
then fuel injection computer to begin reading the temp sensors etc and
settle down, then the sparks (ignition circuit) and finally the starter
button. - Flick, flick, flick, press.
The passengers are also a load. When not using safety belts, they should
be considered as dumb, unsecured loads, especially when braking and
powering around corners.
Give passengers decent foot rails to take the braking forces. Mounting
the passengers in a luxurious reclining manner will also help during
cornering and especially braking, with a rise to the front of the seat,
as shown opposite.
Side loads when cornering will have passengers complaining after fifty
miles of country roads, so consider seats with side padding or armrests
as shown opposite.
If not offering any form of security for the passengers, at least include
hand rails or strong straps to hang on to.
Position the standard car seat belts with consideration for left and
right. This way, the passengers get maximum safety and will not slide
out from under a right handed seat belt when a left handed belt would
save them getting squashed under a bus.
Even if not making an art form, preferably get an expert to make the
seats in water resistant leather or vinyl. Also consider a cloth based
waterproof lining between seat foam and covering. Fit closed cell foam
on most components, but open cell foam or similar between seat base
and backrest, so that rain will not accumulate in the seat.
Where required, there is no excuse for not having a trunk (boot) on
a machine. My friends first trike shown opposite has a boot (trunk),
is incredibly comfortable and can take four people. It also handles
Good details not need to be sophisticated. A flush fitting cover in
a fibreglass shell, carefully cut from the moulding can be cleanly secured
with internal bungees and opened with a simple finger recess. Hinges
may also help. The luggage compartment can be built onto the frame to
take the loads without actually touching the shell or boot lid.
See shells later.
The bare rolling chassis can now be built up to become a fully functioning
If in doubt about handling, then a simple lash up can be made before
fitting the seats and controls in a finalised form, as mentioned earlier.
If the testing shows the trike is reasonable, then start with the riders
seat. This should be positioned with reference to frontal axle loading.
If a lightweight front end or a VW, then weight the trike, then place
the bathroom scales under the font wheel and sit well forward without
upsetting the styling and ergonomics.
If the engine is mounted forward and heavy, then sit to the rear as
much as possible to ameliorate the poor effects of a heavily loaded
The passengers can also be positioned to maximise the best handling.
Passenger side seat supports are always recommended on trikes.
The fuel tanks should ideally be positioned close to the centre of
gravity, so that changes in mass do not upset the overall balance, but
in reality, the fuel tanks are mounted low and in a convenient place.
See fuel tanks, above.
The battery can now be positioned to help refine the balance.
Once the heavy parts are positioned, the superstructure can be made
to support them. This should be such that the riders and passengers
are kept low, where the gearchange and suspension permitting.
Most superstructure can be built from three-quarter or inch section
square tubing for ease of manufacture and lightness.
Where the engine needs to be replaced often, then the superstructure
can be pivoted or lifted off, with a few bolts to hold it in position.
Always use nylon locking nuts or other safety retainment to prevent
Where a boot (trunk) or rear engine cover is used, then make a suitable
superstructure to support the hinges, and support the lower load carrying
floor, either from steel or heat resistant or coated plywood on a steel
If using countach style radiators, then make up suitably shaped superstructure
to support the radiators in rubber supports, and without airflow obstructions.
If supporting exhaust systems, then the superstructure tubing should
have strongly supported exhaust brackets which can take the rubber or
flexible mounting lugs.
Onto the superstructure may be mounted any electric fuel pump, electronics,
fuse box, etc. It is often preferable not to mount too much directly
onto the chassis, as there is often a major rebuild just a few months
or a year away. This ensures the main chassis is kept clean for inspection
for faults and reduces the need to respray the trike, other than to
build an new, or rebuild the old superstructure. I prefer to mount ancillaries
to the superstructure, as this is often changed as the seating and styling
are changed, without upsetting or damaging the main chassis components.
Unfortunately, the radiators) and exhausts often need secure chassis
mounting points so some additional modifications to the chassis will
The battery is ideally kept low in the frame unless you encounter a
lot of river crossings.
Seats with folding bases make excellent access points for the battery
/ fuse box and for small luggage areas. Keeping the access areas secure
should be done well, with standard locks as used for motorcycle top
boxes, or using hidden, spring loaded cable pulls, often hidden under
the seat, engine or mudguard area, where only the builder knows how
to easily reach the toggles or opening levers.
If very heavy loads are to be carried, consider pulling a trailer.
Trailers are straight forward attachment and often considered boring.
But for trikes. . . .
If a four wheel drive engine is used, then a powered trailer is possible.
Army Land Rovers do it, then so can trikes. A classic example is the
Subaru engined trike, using the excellent flat four engine with four
Build a trailer using the standard Subaru rear axle. The trailer prop
shaft should be able to slide onto the spline drive on the rear of the
engine and be restrained by the standard towing ball joint or a more
Make sure the ball is just above or below the universal coupling on
the prop shaft, as this greatly reduces wear and reduces handling problems.
For this reason, the ball joint may be recessed under the back of the
trike to get it all properly aligned. Using such a set up makes a good
starting point for the ultimate field churner when exiting muddy fields
in winter or to roost gravel.
It may be better to be able to disconnect the drive for general purpose
use, or even have a differential lock on each axle for happy triking
See also the German Kettenrad, a 'half track trike' - thing.
Keeping it tidy.
Either you want to, or you don't. No coercing in print will help.
The rear end of the last trikes I worked on was often mistaken for a
Lotus or 'something Italian'.
This should be a basic goal.
Lamborghini Countachs and Diablos look nice too, as do many other vehicles.
For those who want to try, a few words of advice: Take your time and
use sketches. 3D computing will greatly help, as will a simple lump
of modelling clay or plaster.
If the donor vehicle is a Porsche, an XJS or something of note with
a well recognised rear end, and the tail lights are available, then
consider making a mould of the original.
Trying for a Ferrari or Lamborginini style is always worth the effort,
but the downfall will often be in the details. See later.
Always invite others to offer advice, as the designers ideas are not
always what the rest of the world will see.
But despite all best intentions from others to the contrary, always
follow your dream.
The first test should be before the trike is begun, when the donor vehicle
is still intact. Run the engine, check the clutch, all the gears, tacho,
electrics etc. Settle it down with a decent service, then drain the
fuel and cooling system and preserve the rest carefully. If the build
is to take many years, squirt some two stroke or engine oil down each
spark plug hole and turn the engine a few times, add more oil and lightly
replace the spark plugs. Gently rotate the crank every three months
or so. Spin the gearbox output shaft regularly to get the oil covering
the internals. Cover the clutch holes with polythene or duct tape to
prevent moisture from corroding the internals.
Secondary testing has been mentioned above, where it is important to
test the flexing of the frame with tack welds, allowing modifications
to resolve any deformation and fundamental structural problems at an
early stage. Then tests after fully welded and the basic rolling chassis
loaded with a few friends aggressively testing the structure, plus any
front end distortion to be sorted prior to steering head side plates.
The next stage is to get the whole machine ready for basic road use.
This may be riding to the testing station to become legal, or preferably
on a trailer to a local disused airfield or other site for gradually
increased thrashing and fettling. Fitting the trike front wheel to a
car's towing hitch can make it a trailer. If so, use the appropriate
number or licence plate. Will need a special bracket to clamp the front
At this stage the machine will need fettling.
The first few hours of running will be in the garage to adjust the carburetion,
wiring, fuel gauge settings, radiator cooling assessment in still air
and to get the gearchange and brakes working reasonably well.
Testing is done with the following problems in mind.
If the engine has lain idle for a year or more, test the clutch carefully.
The front end may jump up if the clutch is fierce, so use second gear
when testing for the first time. - Choose the wall you want to crash
into. Use second gear with the front wheel of the trike against a wall
and a brave friend standing on the front wheel. Second gear is more
likely to stall the engine rather than lift the front end too far. Be
ready to jump off if the clutch is too fierce or stuck, causing the
front end to lift or plummet you down the road. An anti-wheelie block
jammed under the rear of the frame is a must, so place blocks tight
under the rear to lift the wheels off the ground if a wheelie should
happen. Do not rev the engine as the gear is engaged, but allow the
engine to stall, as this may be enough to release the clutch after a
few attempts. In some cases, it may be possible to start the engine
and pull away in first gear along the road, frantically working the
clutch while pumping the brakes and blipping the engine until the clutch
releases. It is preferable to strip the clutch if in doubt, if only
to save blood or embarrassment.
The engine will need anything from a tune up to a total rebuild. Leave
full rebuilds for later. Just get the engine reasonably reliable.
New steering head bearings are probably needed if they were welded with
them in place, but old ones can be used for initial testing and if you
suspect you may want to rearrange the rake angle.
The radiators may not get enough air at low speeds, so make sure the
thermostat, cooling fans and temperature gauge work properly.
The carburetion and exhaust may need fettling.
If a fuel gauge is not fitted, carry a spare can of fuel until the range
of the fuel tank is known.
The gearchange may take some getting used to and adjusted.
The brakes will probably be exciting too, so make sure there is some
Ensure the brakes are bled properly and all brake items are in good
condition and not binding. No serious rust on the drums or discs, with
drum brakes on the correct sides and no squeals or rattles. If necessary,
lift one wheel at a time in the garage and run the engine gently, to
check each brake works as intended and to bed in the pads or shoes.
To check REAR brake balance, allow the FRONT wheel to roll sideways
on a plank on dowels, then very lightly apply the rear brakes and ease
out the clutch a tad, to see if the rear brakes are balanced, or if
the front of the trike tends to swerve sideways while stationary.
Be prepared to find that the rear brakes may be too severe or too weak.
During the first few hours of use, the rear wheel alignment and the
tyre pressures may affect the way it handles. Be prepared to experiment
with both. Signs include poor wear of the tyres, such as scuffing or
uneven wear patterns. Carry tools to adjust the toe in or toe out as
they are compared and refined over a good test road.
Stamp your own frame number or that of the donor vehicle on the steering
head or as required by local laws. Use proper stamps and take your time
to get it tidy. Your own frame number could be your initials, date of
birth and other numbers to show its your fifth frame, or whatever.
When stamping, temporarily glue a cardboard guide plate to help make
a neat line as the frame number is stamped.
The SAE, (Society of Automotive Engineers) have a special frame number
coding, showing the country of origin, manufacturer etc. If it is necessary
to have the new machine tested by the authorities, they may stamp their
own frame number on it too, according to SAE rules.
There is nothing to say it cannot have your own frame number too, but
just one frame number makes for an easier life.
Always keep the receipts for the parts and try to get any documentation
such as log book etc. It may even have a 'valid' MOT or tax disc. The
ministry will often demand proof of ownership of each and every important
part such as engine, frame, differential, etc. In the UK, it may well
need to be put through the SVA 'single vehicle approval' for one off
designs. This is less than 200 pounds and checks it complies with legal
requirements such as mirrors, assembly standards etc. A Retake is twenty
pounds. The SVA manual /guide is about twenty five pounds, or visit
your library. 1998 prices.
Never assume that because you can ride it, that it is safe. Others
trikers may test your machine and offer an endless list of improvements.
Therefore it is always advisable get many second opinions before finally
deciding the final settings for brakes, handling and a host of other
Spare a thought for the official tester, who may have to test three
cars, a campervan, a restored 1920 tractor - and your machine. This
poor soul does not always like to have to test a machine which is so
far out from the norm that he has to frighten himself before deciding
if it's safe or not. At least attach a note as to where the gears are,
plus any 'interesting' points of note, definitely including the kill
switch. Tape this information where it can be seen. The tester has probably
seen it all, so use his knowledge to make a better trike.
Destructive testing should not be necessary if a sensible and cautious
approach is taken. If the very rough, early attempts to trash the basic
frame were unsuccessful then the reader should be feeling cautiously
If a cautious approach is not taken, the test rider may unwittingly
be undergoing a destructive test regime, with one of two possible outcomes.
- One involves a long wooden box.
If deciding to test on the road, always wear protective clothing until
confident. Always test first on quiet roads until confident and the
machine is fettled as much as possible. Suspect all possible frame,
steering, suspension and brake problems until confident. Never be too
There are two main types of testing. Basic testing using the whole
machine. The second form is a more involved structural tests using just
the bare chassis so that its flexing can be measured and predicted on
a graph. The latter is for techno heads who wish to develop ultra light
weight chassis, or simply to understand the structure more fully.
The usual method is to load and test the while machine to about twice
what the worst case is likely to be. As leaping off a hump back bridge
at seventy miles an hour is difficult to replicate in the workshop,
some assumptions must be made. Most other tests are a little easier
to do. A variety of tests are mentioned so the reader can get a reasonable
feel for the limits of the chassis.
Non destructive testing.
Before loading further, the basic, unpainted trike should be settled
down and bedded in during intial tests.
The frame must be checked regularly for fractures caused by engine vibration
and road conditions. Check every 20 miles for the first few hundred
miles, never easing off the observations completely as the miles build
Use easily cracked lacquer over any suspect welds or tubes etc. This
will help highlight any problems before they get too serious. Thin,
white hard varnish is useful to highlight cracks, or use clear varnish
and good eyes.
In some cases, cover large areas which my distort with lightly lacquered
fine tissue stretched over suspect areas. This will highlight potential
fracture areas and general distortion on long term tests and also during
If in a country where corrosion is a problem, use a light coating of
clear lacquer to stop the frame from rusting for the first few months,
allowing regular checks for problems such as fractures.
Plastic coating the frame from the outset is never recommended for obvious
Before applying the finishing touches of paint and trim, grab a few
friends, take the machine somewhere quiet and literally thrash the nuts
off it. Jump over ramps, slide into walls, and generally commit positive
vandalism. You know it makes sense. You will also get to understand
the handling much more intimately.
If you have fuel or oil in the frame, pressurise it for a couple of
hours after testing. Use the valve of an old inner tube clamped or tied
over the filler hole and a cycle pump to pressurise. If any leaks, lightly
grind back and reweld. Preferable not to fill with fuel or oil prior
to initial pressure testing, as further welding can cause explosions.
Initially pressurise with air and then 'paint' the empty frame with
soapy water to check for leaks.
Once the machine is deemed physically safe and seems to work well,
then full testing can begin.
The first test ride must concern safety; mainly structural strength
and brakes. All cables, bearings and brakes settle during extended testing
and will require adjustment.
ALWAYS try pulling away up a steep hill, a short bank, or wheel ramps
in a garage to balance the clutch and brakes.
There is nothing more annoying than taking a machine out to test, only
to find some simple, annoying problem has halted the test.
Once the machine holds together and the brakes work, the handling can
be studied. If using differing or unusual tyre dimensions and profiles,
pressures may be even more important. This can only be fully assessed
by riding, but start by noticing tyre deformation on standard load.
Then experiment with pressures to get suitable deformation patterns.
Try to steer clear of maximum rated tyre pressures and be prepared to
aim for a sensible and balanced set of pressures. Larger rear tyres
may need less pressure for a sensible footprint.
Load the trike to normal conditions. Then roll the tyre over a flat
piece of road or a wood sheet. While carefully noticing the contact
patch, lower the tyre pressures until the tyre contact profile begins
to sag. Note the pressure. Now pump up the tyre until it starts to get
too rounded. Note the pressure. Now set your starting test pressure
midway between the two.
If you can do this on a wet sheet of glass, then you can easily see
the actual contact patch as seen from below. If you have a similar tyre,
perhaps on a well set-up Porsche or Jag, then use this too, to check
the contact patch as a reference. If no glass floor, then jack up the
wheel, rub on a little dark grease, then lower carefully onto a sheet
of paper. Then carefully jack up to remove, without rotating the wheel.
Use this as a standard starting reference profile for the tyre in question.
The tyre pressure will probably change after various testing sessions,
but gives a good starting point which should be in the 'ball park'.
Basic tests includes riding in a straight line, applying the rear brake
and checking for veering to one side while very lightly holding the
Test the fastest constant speed into a sharp turn such as a right angle
street junction. The use of real or imaginary road cones, chalk to mark
the ground and a big, quiet car park is ideal.
Although this should have been done a long time ago, when setting up
the suspension on the bare frame, once again push the wing of a car
down, to see how the shocks behave, then do the same on the trike to
see if it is in the same ball park.
Important tests include the minimum turning circle, both slow and under
power. Both in first and second gear, plus reverse. Check the steering
does not want to dive under on full lock.
With smaller front wheels with light loads, the limits of the front
wheel may need to be pushed, especially if worried about safety, such
as sudden breaking away without notice.
In a safe area, try to get it to break free in faster tight corners,
with and without braking. Find out how the front or rear breaks away
first and under what conditions. This puts a reasonable load on the
suspension and helps show up problems such as sloppiness as the suspension
and other components bed down. A little tightening of parts between
tests goes a long way.
Always aim to refine the overall handling from the outset, which is
always more important than finding the top speed.
Don't loose vital information: The first test gives you a major opportunity
which will soon disappear. The first ride will have no reference points
and you will be assessing the way the trike behaves in a raw, untainted
As more tests are done, you will naturally adapt to the trikes peculiarities
and thus loose totally subjective assessment.
You will get used to the machine and its foibles, so from the very outset,
set high standards and always be critical, so that your assessment does
not become devalued with familiarity.
A minimum cornering radius at a natural speed will soon be found and
could be recorded for comparison with other rakes and trails. As the
subtleties of handling are gradually refined, there may often be a trade
off between tighter cornering vs straight line stability. The final
decision will depend upon use. A comfortable touring machine often turns
less well, but with better stability, whereas an animal machine will
usually be set up for urban motocross. A comparison is where transport
planes are usually stable, whereas modern fighter aircraft are intentionally
designed to be partially unstable.
If the machine wants to pull to one side when trying to brake or when
driving hands-off in a straight line, then the brake imbalance, steering,
frame or rear wheel mis-alignment may be the cause of problems. All
machines must brake in a straight line with hands off. Start by checking
chassis and wheel alignment, tyre pressures and then the brake components,
ensuring they are properly bedded in. Therefore the brake imbalance
tests should be done near the end of the test, when the brakes are probably
better bedded in.
The front and rear suspension may need to be stiffened or softened.
The normal amount of adjustment on standard shocks may suffice, but
proper positioning may need a little refinement.
If antidive is integrated into the forks, test to see how well it performs.
Tony Foales excellent website contains all the theory. A section for
trikes can be added here if requested.
Learning the handling and braking characteristics in a quiet area will
be advantageous for knowing the limits. This will help the adjustment
of the braking system by modifying and refining brake lever ratios and
pressures for best use. It is very easy to build a machine with misbalanced
front and rear brakes, yet fairly easy to cure. Choice of pads, reduction
of braking material, lever ratios and many other methods can lead to
matched brakes which can be a pleasure to use and brakes save lives.
Play around with the toe in to see how this changes the handling, straight
ahead and especially in the bends. Adjust the camber and toe in, just
to see what happens, If it gets worse, then try adjusting the other
way to see what happens. If al beings the overall package closer to
the best possible.
Unfortunately, adjusting for tight turns in urban terrain may make the
machine handle worse at high speeds. Always make sure the machine handles
best at high speeds, then adjust to get the reasonable handling at low
speeds too, if possible. While riding in normal use, you may be able
to correct an unexpected handling problem at 20 mph, but not at 80 mph.
When it is as good as possible, measure everything, shock settings,
tyre pressures, toe in, camber, (rake and trail, if adjustable,) and
anything else you have changed.
Mark it all down on paper for the first minor rebuild.
There is no excuse for inadequate or poor braking.
With reasonable brakes, the handling envelope can be pushed.
First practice riding close to walls on each side of the machine, so
you learn that bikes are narrow and trikes are not.
Pushing the limits:
Use of a water patch and a gravel patch will help understand the machine,
so carry some water for any depressions in the car park, and a small
bag of sand to make some impromptu testing areas. An area of sand about
four times as long as the trike is excellent for getting a feel of the
way the machine breaks away in loose conditions. If it handles well,
it may be preferable to choose less efficient tyres if a little power
drifting is required.
If no kerbs, a rounded edged wooden strip or preferably an old door,
held to the ground with blue tack (after brushing clean) will make adequate
bump strip for straight and side angle kerb testing. Kerb tests are
not suitable for delicate wheels, unless replacements are available
for general road use. (The scrap yards have plenty of cheap wheels.)
Kerbs will be an annoying part of learning to ride a trike, especially
when used to motorcycles. Be prepared to build up a set of reactions
for the times when judgements into corners are not always accurate.
During testing, the more specialist suspensions with custom suspension
arms, shock units and front end must be carefully assessed in accordance
with what the designer and test rider require. This may require gradually
bringing the machine up to roll or slide, and will require a good, accurate
speedo and plenty of run off area. Getting the turning circle tighter
may require many hours playing around with rake and trail, tyre pressures
and profiles. Do not be put off by science or expertise, as most moderately
well designed trikes will usually handle quite well first time out.
If it handles quite well from the outset, just think how good it can
be with a little tweaking and fettling.
Testing must be built up to put a reasonable load on the suspension
and help show up problems such as sloppiness as the suspension and other
components bed down. A little tightening of parts between tests goes
a long way. Always remember what gets loose, so that simple tightening
can be done, while also looking for problems such as fracturing, misalignment
There are many other tests, such as engine reliability, cooling airflow,
comfort, but these are comparatively all fairly straight forward.
After as many problems as can be found are written up, and the builder
has decided whether the machine handles poorly and is unacceptable,
then it may be preferred to modify or even to rebuild the frame until
it handles well, from which a final design can be created.
In less extreme cases where just the steering is not ideal, the builder
may wish to modify the front end trail or rake angle until ideal. Do
not assume the rake angle is the main culprit of a poor handling machine,
as a surprising amount of rakes can be applied on otherwise similar
Always test with all other variables where possible, such as adjusting
the fork leg offset angle to adjust the trail, by variations on the
upper fork yoke or front suspension pivots if using leading link forks.
It is highly recommended to have extra pivot points either side of the
intended fork pivots, to allow back to back testing of various amounts
Suspension settings will need careful assessment, especially the front.
In easy cases, simply adding fork spring spacers and a little heavier
damping oil may suffice for standard bike forks. On special front ends,
the spring rates can be too soft or too stiff, which can often be solved
by repositioning the shocks slightly.
Never test with a steering damper, as this merely hides bad handling,
and you will never get a truly better machine. If you must use a steering
damper after final testing, then do so, but it is hoped the machine
should never need this level of compromise.
Mark it all down on paper for the first minor rebuild.
Rear suspension should be fairly acceptable, possibly a little soft
for three up riding of a transverse rear engined design. If too soft,
simply use components from the sports version of the donor machine or
fit spring spacers to add a little extra spring preload, or use slightly
heavier shock oil for increased damping firmness.
In some cases, you may prefer to angle the rear shock to make a better
ride, but this is often about right from the outset when doing initial
Although not officially a good idea, most of the cheaper standard shocks
can be drilled near the top of the body and the fluid drained out. Beware
of pressurised systems. Then a nut soldered over the hole, ensuring
the heat does not damage the seals. Then new, heavier or lighter oil
can be pumped in and the shock compressed fully a few times to allow
excess oil to drain to prevent any hydraulic lock. Seal with a screw
in the soldered nut, preferably sealed with PTFE thread tape.
Mark it all down on paper for the first minor rebuild.
Once a good handling machine is achieved, very accurately measure the
rake, trail, toe in or out, axle offset and axle loadings, rider position,
steering ratios and whatever else can be measured. Mark them permanently
on the main drawing. This is priceless information and will form the
basis of the next machine. During any refining process always measure
and record all other rakes and trails used for future reference, with
descriptions of the effects at slow, medium and high speeds. Also mark
this information permanently on the main drawing for future reference.
Yes the next, even better trike is not far away.
If the machine is terrible and a new frame is to be built, consider
use of the machine for test riding to destruction.
Grab your kids skateboard knee and elbow pads, thickest leather jacket,
a helmet and a friend with a cell phone.
Begin by riding over bumps, jumps and anything else it may encounter.
Test, Test, Test. This is positive vandalism. If the machine remains
complete, even after many modifications or bodges to improve the problems,
then confidence is the first survivor and a lighter machine may be it's
progeny. All testing will depend upon the purpose of the machine and
its unacceptable problem areas.
If deemed unsuitable, it can be heavily modified to improve it's handling.
- Refitting the steering head, rear shock mounts or whatever is needed
can be done in light of feedback.
It is such situations that allow the best research to be done. You
will soon understand if your ideas make the trike better or worse, and
from that you can try modifications in the other direction, or to find
that your original idea was pretty close to the ball park.
Do not be afraid to experiment.
The hacksaw, grinder and welder are your best friends.
Saw part way though the frame tubes near the headstock, reposition
the steering head angle and weld up fully. Play around with various
rear shock mountings. Reposition the anti roll bar or radius arms. Adjust
the toe in or out, and finally lower a tall machine, just to see how
this makes handling better.
Remember - a lot more can be learnt from a poor machine than from a
There may still be a complete machine to test. Where breaks occur,
reweld and prepare to test further. So use the opportunity to keep modifying
until it is as good as it is likely to get.
The last test, if the machine is not acceptable for general use, is
by loading to destruction. Chassis deflections against load could be
taken for future reference.
Like JPseries crash testing, if one can't get help from the experts,
then study their work and do it anyway. (Always be painstakingly careful
when crash testing with real riders.) It is hoped that computer crash
analysis will be made available to all vehicle builders as soon as possible.
Please contact the author, as the safety of many testers, including
the author are directly affected.
Structural testing can be studied from books then applied, but for
most purposes, it is just a case of seeing how far a design and it's
quality of manufacturing can be pushed.
The headstock, handlebars and linkages are unlikely to be damaged, so
can be salvaged later. Remove all expensive non structural components
such as lights, carbs, disc brakes etc. Leave the structural parts in
position to prevent the machine from distorting unnecessarily, including
the engine and suspension.
Unless extremely expensive, the forks should be considered sacrificial
and part of the dynamic testing procedure, although fork legs can be
replaced with simple tubes for static tests.
Choosing somewhere quiet and safe with good lighting, will allow the
builder to see and hear cracks as they form. Always wear eye protection
goggles. This is important, as this will help to discover the weakest
points earlier than in less refined environments.
Final testing is accomplished by copying the basic loads as found in
use, but more so.
First clamp the rear wheels to the floor or a solid wall, or use a plank
over the wheels and block with heavy weights or concrete blocks etc.
If this is not possible, then weld up a vertical brace and jam it in
a door frame.
Lift the front of the machine lightly off the ground with a jack, or
simply place the wheel on a plank which is allowed to roll sideways
on dowels. Apply a bar across the front fork yokes and measure deflections,
by gradually loading to twist the frame. If clamps are difficult, place
a bar over the front wheel spindle nut and suspend using a rope from
the handlebars to give a crane jib effect. Although unlikely, do not
distort the frame too close to permanent failure of the structure.
If you have a digital camera which captures video sequences, then these
can be run in a loop to see which part of the frame flexes the most.
Try to get visual deflections in plan and looking from the front and
rear and from the side, so a tripod is particularly useful. If you cannot
run video sequences, then mount the camera on pre-set points, so that
it can take individual photos of the deflections which can be built
up into sequences using programmes such as Gifcon.
It is important to assess torsion on the front end, as traditional
motorcycle forks are not set up for heavy side loads, although symmetrical
tubular types are capable of the same forces from braking and gravity.
All front ends will suffer from the side loads found when cornering,
but also the frame, so checking the way the steering head support tubes
behave will highlight any areas of concern. Problems can often be ameliorated
with plates or cross brace tubes.
To help recognise fractures early on ultra light machines, do the tests
somewhere quiet, so cracks can be heard easily. Also cover the frame
in fine strips of tissue paper, tightly glued across suspect surfaces
or similar sections, possibly using little strips or larger sheets which
will easily tear or distort, or larger sheets which will buckle or ripple.
If the machine does not fail where expected, this helps refine the design
process by real experience. Listen for creaks and worse noises.
Not all distortion may be in the frame. As the rear suspension is the
first part which deflects, block this with wood blocks or temporary
welded struts, so that it is the frame which flexes.
Record the torsion deformation at various forces and at various positions
along the frame, to see where the torsion is most pronounced. Record
for comparison with other machines. Using a video camera looking along
the frame to record the deflection will allow the sequence to be rerun
back and forth faster on a computer to closely study the chassis deformation.
Where possible, viewing from above also helps.
Single sided front suspension systems may need mounting bars to fit.
Always test from the front and rear axles, otherwise the exercise is
not highlighting all possible weak points along the structure.
This involves adding increasing load onto the trike until a load which
is higher than the worst case load is applied. This may be the forces
applied to each part of the trike which are needed to survive leaping
a humpback bridge at seventy miles an hour, or whatever your approved
riding style may be.
To know what sort and ratios of loads are to be applied over the chassis,
check the final wheel loading using bathroom scales or something bigger
if needed. On a heavy axle load, use two bathroom scales and a plank
to spread the load, then add these loads together. As weight balance
should have been decided at an early stage, be prepared to adjust the
position of the passengers, fuel tank and battery if needed to improve
the overall weight balance.
Once about right, measure the wheel loads with a full complement of
heavy passengers and luggage. Mark the load for each wheel in pounds
or kilograms on the chassis in felt tip pen. This gives the static load
on each axle of the structure which can then be used to calculate the
maximum 'safe' load. This is NOT a guaranteed safe load, merely an approximation.
As maths is not everyone's favourite subject, consider the front wheel
resting on the ground, which is not suffering a heavy load while static.
In reality, it is supporting the mass of the trike under the effects
At top speed over a bumpy road, this force into the trike can be four
times the static force, into the tyre and suspension, and will do so
many times a minute, creating lots of stress as well as the general
This force and load must not distort the trike suspension or chassis
in a dangerous manner. All structures will distort, but they should
not impair handling to a dangerous manner. Knowing how much the structure
will distort and in what way, is the aim of testing and checking. Some
tests must be done while riding, some can be done while stationary.
If you ride gently, then the front end may only need to take three
times the static load. If a thrasher, then this can rise to six times
or more. Luckily, if suspension is fitted, then the actual force into
the structure is gentler, due to shock absorbers which spread the force
from an instant shock, to a gentler force over a short time, possibly
as long as a second, or as short as a tenth of a second. The tyres usually
absorb minor road irregularities. This reduces the shock load onto the
frame, but the forces must still be absorbed. As the analysis of the
way a structure is loaded dynamically and everyone rides differently,
then making the trike to handle three or four times the fully loaded
static load will usually suffice for normal safety. If during testing,
this load is easily accommodated, then perhaps the trike is overbuilt,
or you can thrash the beast a lot more.
Mount one rear wheel on rolling blocks so the frame can spread sideways.
The wheels will normally allow the frame to stretch lengthways. If the
wheels are not fitted, perhaps just testing the bare frame, then use
planks and rollers. This is to ensure no constraint as the machine spreads
under the load. To check gradual deformation under the machine, use
an extended matchbox mounted on blocks under the frame mid point, so
the inner of the matchbox touches the bottom of the frame when extended,
and can be marked or measured at each stage. During flexing, the inner
will be slid inside the matchbox, and can be read off at each stage,
to help generate a graph. Use a matchbox with a stiff sliding action,
improved with extra paper in the slit. Anything taller than a matchbox
will allow a failed machine to drop too far. Mark with pencil line and
the load applied. For basic tests, measure with one rider, then one
jumping, then with two riders, and finally measure with two or more
jumping up and down. Be ready to support yourself if the frame suddenly
The crumpled matchbox can be straightened and assessed later.
To see how the machine behaves, a graph can be plotted of load against
deflection. Start by gradually applying twice the expected maximum load,
as most general purpose machines should be capable of this with minimal
flexing. If many plots are made, then the graph may even be able to
predict the failure point.
When preferring a subtle approach when loading, it is possible to use
two or three dustbins or garden water butts placed on the machine, mounted
more securely on a sand bag or a welded support and gradually filled
as deflection is measured. If mass measurement is needed, measure the
water by pouring in one gallon at a time.
It is important to mount the water butt so that its load will be applied
in a similar manner to the ratio of the static load of the trike. If
a heavy front end, then place the waterbutt nearer the front. If a light
front end, then place the water but closer to the rear. The ideal position
would be over the centre of gravity when fully loaded. A reasonable
position will often have to be the best guess.
As most vehicles rarely go beyond 2G, in any plane, other than the suspension,
then twice its weight is fairly safe, but three times its weight is
getting close to a reasonably safe structure.
When filling a water butt, a reasonable load can be applied. Water
has a density of 1000 kg/m3. A cubic metre is quite large, but equates
to the weight of more than ten average riders.
One litre of water weights one kilo.
If wanting to find out how much load is being applied,
One cubic metre of water weighs one metric tonne. ( 0.98 real UK tons.)
One gallon of water weighs 10 lbs. 2240 lbs per ton. 1 ton = 224 gallons.
Static testing could take all afternoon and best done in the garden.
As big buckets are not too stable, consider using a long plank or small
ladder balanced on the seat, its other end on a suitably level item,
but free to move. This will keep the water butt level should the frame
Always have the water pipe under the water, so that creaks can be heard
as the load increases. As the load gets towards the limits, it is worthwhile
checking the distortion once the suspension has reached its limits and
can move no more, where it is the frame (and tyres) which must absorb
further extreme loads. Now the real frame distortion tests can begin,
but should not be taken too far, just enough to ensure the frame can
take twice the expected load after the suspension has reached its maximum
If forks are removed and not replaced with steel bars, then the genuine
bending force on the steering head will also be lost.
At first, the suspension and tyres will compress, then the rubber blocks,
and finally the frame will begin to deform. Suspension curve will be
a gentle curve, followed by a steeper curve, then as the frame begins
to distort, the load will increase for little deformation.
For simplicity, it may be better to remove the wheels and block at
the upper suspension points, (upper shock mounts) so that just a frame
curve is measured, but this does not allow the tester to see how the
suspension load deflection curve builds up to the fully compressed suspension
point, then extended into the purely frame distortion curve.
The frame distortion should be fairly straight for a while, then begin
to curve. Note the load as the curve starts. This is the maximum load.
Relax the load at this point, or if wishing to test to destruction,
the curve will get worse, until failure occurs. Failure may be a broken
weld, a bent tube or one or more of many other failures.
When the suspension units bottom out, take the process very slowly,
and always be aware of any creaks or other untoward noises. Always wear
eye protection. At a very basic level, deflection should be proportional
to load, to give a straight line. This will gradually deflect more as
the maximum safe load is exceeded, so the graph is no longer a straight
line. When the graph starts to deviate from the initial line, you know
something's getting desperately unfit. Hopefully it's just a weld ripping
out, or a tube bending, so take note and stop when you can see the fault.
Do not get too close, unless the load is removed, or considerably lightened,
otherwise you may get a face full of steel.
A maximum working load (which is not the maximum load, when it can
break), but the maximum working load can be calculated from the maximum
load to compress the suspension to the rubber blocks, then reduce this
figure to take into account high speed heave and roll. About half to
two thirds is often acceptable. If the load is too light, the suspension
will feel stiff.
For a reasonable safety factor, it is assumed the maximum overall load
when testing with the water butt will be at least twice that used to
compress both the suspension also the rubber bump stops. These are only
rough approximations, so always study your own machines and play safe.
If getting keen, and with at least six points on the graph of load
against deflection, (two of the suspension compression and four closer
ones for frame distortion), a graph can be plotted of load against deflection.
If many plots are made on the graph, then it may even be able to predict
the failure point as the curve begins to deviate from the early profile.
At a very basic level, deflection should be proportional to load, to
give a straight line. This will gradually deflect more per unit load,
as the suspension bottoms out and the frame begins to bend seriously.
After this point, when the graph is no longer a straight line, then
you must go slower, making more accurate plots.
As the maximum safe load is reached the graph will have begun to change
from a straight line and stop, and check as the frame may be close to
collapse. Therefore draw the graph as it is measured, so any danger
signs can be recognised. You may be very happy with a high load and
decide not to push the frame any further. It may well take a lot more
than you expected, and is not unusual with home made frames, where a
cautious approach to choosing frame tubing leads to overly strong metal
for the main frame.
Making three different measurements along the bottom of the structure,
evenly spaced between rear axle and head stock, will highlight localised
deformation and possibly predict the point of highest flexing, which
may or may not be the failure point, depending upon the design.
If you feel confident with the graph, you may wish to push further.
If the structure fails, and you are happy with the max load, it may
be better to rebuild the frame, as it should not have been allowed to
fail more than an inch, onto the safety blocks. It may well be returned
to its original state. If this is difficult, then turn the trike frame
upside down and do the same again, but to return the frame to its original
shape prior to stronger welding at the failure point.
After testing, look carefully for everything from general distortions
across the whole machine, to small fractures.
The frame breakage may not be the only failure point.
Soaking the suspect chassis areas in thin fluid such as dyed alcohol,
or ink, then lightly wiping dry, so the ink remains in any cracks. Then
spray or covering in an absorbent film which will absorb the fluid and
highlight cracks and imperfections. Dusting with chalk, or talcum powder
from your bathroom, or a thin spray water based undercoat paint often
works adequately. This is a cheap variation of the 'zyglo' method used
for checking gas turbines etc. Repair if suspect, carve back any damage
and repair as necessary. Do not be tempted to simply fill a crack by
welding over it until after perfect grooving and cleanliness is done
to check the extent of the problem.
If the frame does not break, then seriously consider making the next
machine a lighter design, with thinner metal and / or other design considerations.
Wherever possible, try until an unwanted frame breaks, as this will
highlight the weakest points and offer excellent feedback of the design,
its manufacturing and welding abilities and a host of other clues which
can only be read directly from the 'failure.'
If needed, return to making a better machine in the light of experience.
Many components can be salvaged, such as the steering head if they survive
acceptably. Re-use only after extreme checking for cracks.
The components which did not break should all be carefully studied.
The remaining components will probably include the bearing housings,
seats and steering linkages which all take time and effort, to leave
the next step with 'just' the main frame to build.
Do not get despondent in having spent so many hours building a machine
to the highest skills, as this is never lost. Yes, heartbreak may follow
such preparation, but the next machine will be even better. A good apprenticeship
is never easy. The builder invariably learns a great deal more by mistakes
than making a perfect machine first time.
Most trikes are poor, but a few are superb. The poor ones are usually
plenty good enough for most purposes, but a few of us aim for perfection
in style and handling.
If the second machine is also poor, then consider making a more adaptable
design, until the handling is correct. Use the second poor machine as
a continuing test rig until a satisfactory design is created. Then use
the vital info you have gleaned to build a refined machine from this.
Salvaging whole sections from the old machine is often possible by reintegrating
engine mount sections, and such like, even if using a very different
design, or possibly most of the original.
When just a few problems of flexibility occur, a few gussets or fillets,
or cross bracing may cure minor handling problems.
On the occasionally complex or precision machine, testing may take
on another level of intensity.
If making a lightweight, or very refined trike, then it would be nice
to just use the trike on the road to see what the day to day forces
are. Then it is possible to see just how much the trike can take in
the workshop, and from this work out the safety factor.
If you have a frame you suspect as being less then strong as you intended,
then this will also help you to decide the working safety factor of
There are many tests to assess the normal forces exerted, so you can
statically test the trike later, as you already know the normal working
At a basic level, a digital thermometer can be augmented with temperature
sensitive memory strips, - such as where exhaust cooling airflow or
cooling from the radiators may be a problem.
It is the frame strength which may worry most people. While testing
on the road, the normal levels of stress (load over area) or strain
(elongation over original length), can be measured by simple devices.
See also Young's modulus in any engineering text book.
Strain gauges need not be electrical, as mechanical deflection devices
such as amplified arms can be welded at an appropriate point on the
frame, to accentuate movement and to rub on a matt white painted surface
somewhere else on the frame to give feedback of the distortion in both
directions. A light, flat bar which will not flex in the plane of measurement,
by using a wide strip of metal, will often suffice. Similar to the basic,
'bendy bar' torque wrenches, but where it is the frame which bends,
not the arm. Make sure it is the frame deflection which is measured,
not that of the measuring device. Weld the long, wide plate across the
length of the frame, and house the end in soft foam to prevent vibration,
and allow a point to rub in a small marker area. This can then be carefully
recorded by marking the extents of the flexing during use, by very carefully
scratching a fine upper and lower line with a sharp knife. Then the
frame can be loaded well beyond this working load to see just how much
safety margin is available.
Static load testing, probably with a water butt to the maximum road
use, will show how much the machine flexes under road conditions, allowing
you to se just how much the suspension has moved and how the wheels
align to the road. This can then be loaded further to compare during
this non destructive testing to research the true safety margins.
The non-bendy bar in use, when compared to the deflection during static
testing is probably your best bet to know just how strong the overall
trike actually is. The initial deflection from thrash testing, then
compared to static testing until failure will give the best insight
to the true safety margin.
For those wanting to know the shock forces on the frame are, then a
simple spring loaded pendulum pivoting on a ceramic potentiometer can
be calibrated for acceleration and deceleration of the bike or swing
arms and other components.
For one G, (acceleration due to Earth's gravity) calibrate with the
spring against the effect of gravity. (Turn it ninety degrees).
By using a rubbing mark, then the builder can later read off the maximum
acceleration that was acting on the device.
A potentiometer as the pivot of the spring loaded weight, will make
a simple electronic G meter. Connecting it to a good battery (not the
trike battery which will fluctuate between 12 and 14 volts) and across
a volt meter will give a G meter. I would prefer to use mechanical devices
as they rarely give false readings if designed well.
Another means of testing is to use electronics such as strain gauges,
(although the bendy bar is also a form of strain gauge) but lots of
electronics is not only expensive, it does not offer much extra insight,
unless running an experimental machine. For most people, a bendy bar
will be enough to measure the general parameters.
Real engineering is a craftsman doing for pennies what any commercial
company usually does for a fortune. Never be put off by the 'sophisticated'
talk and equipment of 'experts'. You can spend a fortune on expensive
equipment, but it is rarely necessary. Know the data to gather it and
how to assess it. It's not black magic.
If keen, an old laptop or hand-held has analogue, usually joystick
game inputs and these are reasonably capable of differentiating between
minor changes, then an interface can be built to read resistance's for
strain gauges, pressure, temperature and other sensors. Even if the
hard drive and batteries have failed, a basic computer can run on 12
volts for simple check routines stored into memory from floppy and stored
and down loaded to floppy, powered from the trikes battery.
The BBC micro was a particularly excellent machine in it's day for the
purpose of static testing and I soldered up small interfaces and wrote
programmes for testing a wide range of things. In 2005, any of the old
laptop PCs are usable data gatherers despite their age and can become
a part of a test rig. Always mount in foam rubber. Always mount away
from moisture or in a poly bag when testing in the rain.
If an old laptop with no hard drive or screen, then make a boot floppy
on a desktop PC, so that when the laptop boots, it starts measuring.
Then remove the floppy an fit a new floppy ready for the next boot run.
Easy-peasy and for pennies. I have three old 'useless' 386 laptops for
this purpose; all modified to run from 12 volts supplies because their
batteries are defunct. Minimal DOS 5 with a few simple utilities, or
with Q Basic will usually suffice. (See my monograph on aerodynamics
and wind tunnels for more info.)
If new to this game and just needing a simple counter, use a pocket
calculator and connect a wire to operate a switch connected between
the + plus sign contacts, then input 1+1= and the switch will count
on the calculator for ever. Using the rolling circumference will give
an odometer. For rotating or non-contact parts, a magnet and a reed
switch are ideal and held in place with glue.
Most PCs can accommodate a variety of simple or complex home made input
boards, often using analysis software and virtual oscilloscopes. Basic
second - hand laptops with simple home made interfaces are ideal for
road testing. Hand help digital oscilloscopes are also useful, especially
those with large memories. Cheap temperature sensors are available using
a variety of car and other devices.
See my website for windtunnel computer interfacing for pennies to get
some idea of the possibilities.
The basics of a good machine still come from optimising the rake or
trail of the designs, the wheelbase, centre of gravity etc.
Handling or specific ergonomics must come from experience, so begin
by measuring angles and dimensions on the next club run or catalogues
and deciding if they have the right answer, or at least the ball park
Once the frame is good, the rest can now be assessed.
Not all machines will be ideal.
Even the worlds best manufacturers make the occasional blooper. The
vehicle industry is littered with vehicles best forgotten, not only
by reputation, but also by serious basic design flaws. After an atrocious
machine is built, a vastly better machine often appears next time around,
in the light of the excellent understanding from the many design hurdles
and pitfalls encountered, which focus the mind very effectively.
View a bad machine as an opportunity, not a problem.
Occasionally, an impeccable machine is created. In the JP programme
a couple of machines have been created which are sheer bliss to ride.
Such machines occasionally exhibit excellent handling, ergonomics or
control harmony and occasionally all three.
Never destroy an impeccable machine, but allow others to test it to
understand why it's so good. Just knowing it's good is not enough, you
must always take this opportunity to understand the fundamentals and
subtleties. Always get other riders points of view, ensuring as little
as possible is missed from such opportunities.
Some machines 'thrown together' to quickly test an aspect of a design
have turned out to be outstandingly good machines.
If not completely happy with the first attempt, possibly because manufacture
is not superb, or the ergonomics are unsuitable, it simply does not
handle well enough, or a host of other reasons, do not despair. Test
ride it anyway to fully understand where the problems are, as bad machines
can often highlight what to steer clear of second time around. Only
then should destructive testing be considered, possibly with the intention
of a partial or total rebuild afterwards.
Much more can be learnt from an imperfect machine than from a perfect
Once a good trike is built:
Very accurately measure the rake, trail, toe in or out, suspension settings
and tyre pressures.
Only then can you fully strip, check for fractures and for misalignment
between engine and frame etc. Some springing of the frame will occur
from normal welding, and possibly after the first few road tests, but
not too much if reasonably well designed.
Check the overall alignment of the frame, wheels and engine fitting.
If subsequent misalignment is large, then this may be because the engine
may intentionally or unintentionally be part of the structure. Modify
if needed, possibly a few more fillet plates or an extra cross tube
Sort out the annoying problem that has occurred from the beginning,
and add the little flourishing touches that should have been there from
Sort out the nasty little rattle and redesign the constantly fracturing
exhaust system. Fit the splash guards under the wheel arches and tidy
up the wiring loom. Tweak the gearchange to perfection.
If wiring is not a strong point, learn more and in the meantime buy
plenty of fuse wire. (Note for traditional bikers who hate wiring: never
waste money buying lots of fuses, simply straddle the fuse holder with
correct rated fuse wire and hold in place using a blown fuse. If desperate,
use ordinary copper wire from ordinary wiring, and guess a similar cross
section of the wire because copper is the same everywhere.)
Decent paint and leather may now be considered.
Perfection is in the detail, - don't spoil it at this stage. Public
image may not be the same as the builders image, so consider a variety
of form, styles and paint for maximum public effect for all.
Paint and finishing has been covered by many specialist books and magazines
and need not be covered here. See also shell later.
Always check for disastrous ideas with friends first, such as colours
or floral pattern seats.
The advantage of building the machine oneself is that money, time and
skills are the only limitations. Never be put off by all the hype about
the expense of racing or development teams. The costs need not be high.
Being able to spend money like water is a luxury, whereas being poor
is not a limitation, merely a chance to truly understand just what exactly
Building your own machines and test gear makes the whole process much
better understood and develops a natural curiosity with a genuinely
innovative approach to design. Having a brain is the best gift of all,
Practical design and manufacturing skills are not that difficult, although
often takes time to become refined. Test riding is often a safety based
extension of daily riding skills. The refining of designing, building
and testing skills as they are developed should not be limitations,
but seen as distinct advantages. Designing is often a state of mind
with occasionally wonderful insights.
There is no point in building trikes if the builder does not enjoy
riding them. Always take every opportunity to enjoy the ride, as this
is the ultimate goal of such processes. Always carry a notebook, because
further improvement is often just another ride away.
If the machine is so radical that it gets strange looks from others,
always smile when parking up, and engage in polite conversation, for
the perception of others is always welcome.
A radical machine is often a conversation starter, so use the occasion
to advantage. The stranger may well be an old biker to whom you can
enlighten to the advantages of new ideas. They will probably want to
have their photo taken sitting in it. You may well be invited to the
next local bash.
The JP5 when ridden to a show had a massive crowd around it before I
could alight. Sometimes I prefer to walk away with helmet on and then
quietly rejoin the crowd as another spectator, passively asking questions
of others for a true reaction.
You may be followed by police vehicles for a few miles, so get the
paperwork sorted, but usually they just want to look and chat, so ride
politely and don't bullshit when they enquire.
On one occasion, a radical JP machine was chased for miles across Bordeaux
roads to end up in an impromptu photo session by many excited French
Life is for living.
Nailing an alloy beer barrel on the back for a fuel tank may be saying
something, but what do others read into it?
Even ugly sheet steel fuel tanks can be hidden.
The rear of a well engineered trike does not need a bodyshell, but many
builders prefer it. Shells are wipe-clean and visually acceptable to
the public and keep little fingers out of places they should not be.
An open trike is difficult to get looking perfect, as the many small
items must be co-ordinated into a single style, which can be horrendous
engineering exercise to get just right.
Shells cover the whole and make the many uglier unseen parts much easier
to live with. Shells are ideal for hiding home made tanks, square tubing
and to direct radiator airflow.
Shells widen the possibilities for luggage, passenger comfort and aerodynamics.
When styling, the shell moulding must take into account the servicing,
shape of the fittings such as lighting, cooling and passengers.
The styling ideas are totally personal, so just one tip. Make it look
good from all angles and do not be afraid to beat the Italians and British
at their own game.
A cheap method of developing a basic sculpted shape.
Decent shells can be made later if required. What you are building is
a first attempt, to ensure the aerodynamics are in the ball park, that
the radiators get enough airflow and don't overheat the engine, that
the passengers do not fall out at every corner, and that the boot (trunk)
opens as intended etc.
If in doubt about any aspect such as cooling airflow, then begin with
gaffer tape and large cardboard sheets grabbed from behind shops or
from recent large purchases.
Use the cardboard to build up an initial airflow test shell for the
first few test rides, until the basic shape is decided. All too often
the shape is built first, and then modified the hard way when the airflow
The best start is cardboard and gaffer tape lots of it, plus wool strands
held by blue tacky office putty in the radiators and run a quiet, open
test area. See also testing.
It is not always possible to find a test area for a cardboard test shell
to be built up to check airflow. Therefore a first guess is often used,
so always ensure the first attempt is as minimal as possible, allowing
for hidden air ducts to be rearranged or modified until satisfactory.
This usually means a minimal covering for styling purposes, with temporary
plastic sheets for under shell adaptations.
If you don't live next to a disused airfield, or even a municipal football
car park, then make up big cardboard sheets to fan the air over the
rig in the back lane to see how the cotton tufts behave when making
the biggest draught possible.
Once the basic chassis, airflow, passenger seating and other problems
are sorted, the shell can be built. There are many ways, but a simple
and effective way is as follows.
First get the passengers seats, fuel tanks and other parts built and
tested. Cover the basic trike with thin polythene sheet to keep it all
clean. Food cling film is ideal.
Then build up the trike with large white wall insulating foam blocks.
They are available from most building merchants. Restraining the blocks
is a problem, but some non solvent glues or double sided tape will suffice.
The blocks can be taped or glued together with cheap silicone roof sealer
and possibly sewn firmly with string. Anything which will prevent the
blocks from moving.
The blocks can now be carved with hot wire cutter, or the very messy
sanding disc on an angle grinder technique. (If brave or stupid enough
to power sand, do so either in a garage, on a day without wind and have
plenty of vacuum cleaner bags and a face mask, or do so in a hurricane.)
White foam is cheap and easily cut.
The cheapest method is to scrunch up lots of newspaper and then lay
over sheets of paper with cheap wall paper paste, and gradually build
up to the shape you want. The make it stronger with more paper or old
wallpaper and then with plaster of Paris and unwanted cotton cloth to
acheive the final shape. Do one side first.
On smaller trikes, consider using aerosol rigid foam as used by building
trade for sealing holes. It sets rigid and can be carved. Another alternative
is a two part rigid setting foam as supplied by fibreglass suppliers
for filling buoyancy chambers in boats. These are very sticky and the
trike must be completely protected with heavier gauge plastic sheeting
and this can be held in position with string or tape. Lay the bike on
one side, then apply the foam, expecting to smooth the foam around the
bike as it sets using cardboard spatulas. This is very messy.
With faom, now perform the art of the sculptor.
The sander, serrated bread knife, wood saw or hot wire cutter will allow
the general shape to be developed.
A hot wire cutter.
If using some foams, especially white or blue foam, a hot wire cutter
can enable long slices. These slices need not be in a single plane as
demanded by a conventional saw.
To build a hot wire cutter, carefully unwind the element of a 1kW domestic
electric fire, or heater from an old washing machine or similar item.
Stretch this firmly between the ends of a one metre bow, weak bamboo
pole or similar, so it is tensioned enough not to distort under the
pressure of cutting. A broom handle with end arms tensioned by a Spanish
windlass or a spring will also suffice. There is no need to straighten
the wire fully, as it will straighten itself wonderfully when heated.
It need not get red hot. (Mine stays the same dark metal colour when
Connect each end of the wire to a 12v transformer output such as a domestic
car battery charger and test. If it does not heat up enough to cut cleanly,
use a larger amperage transformer, or tap off prior to rectification,
or position one of the connectors to heat a shorter length of the wire.
Although accuracy at this stage is not important, a length of hot wire
longer than is needed is not a good idea, as excessive bowing of the
cut can ensue. Likewise, if the wire is too short, the ends will cool
too fast and will not give an even cut.
Speed of hot wire cutting is important and must be decided by the pressure
felt by the builder, as bowing of the wire will cause a variation of
cut. Greater wire tension is a solution, but hot wires can only be tensioned
so far, whereupon a shorter bow, hotter wire or variation thereof must
be contemplated. As this is only to crop the outer layers of foam, there
is no need to get too sophisticated.
The use of pinning profiled thick card or wooden side plates on the
foam will allow the wire to be cut along an intended path. Reversed,
they will allow perfect symmetry on the other side. This has been the
stock in trade of most model aircraft builders for many decades. Before
doing so, mark out the centreline, using a piece of string from steering
head to rear mid point.
When the basic shape is carved and is slightly undersize, apply plaster
then smooth to get the shape perfect. Where the foam blocks leave gaps
next to the seats and other areas, simply use a mixture of plaster,
cloth and foam bits to fill the gaps.
At first, get one side sculpted as needed, then mark in the centre
line and use cardboard or wire templates to copy this profile to the
Thick wire templates allow you to modify the template on an ad hoc basis.
If one side of the foam is cut and shaped, these wire template can be
bent to fit. When heated they can mark the identical profile of the
other side in the foam for easier sanding or cutting to shape, or simply
to melt the rough profile.
If the shape is not what you want, simply add more plaster, or sand
away and continue until one side is perfect. If not too sure about how
it will look, splash on some cheap poster paint or some pigmented plaster
to see how it will approximately look. If you have shaped only one half,
use a long, dress mirror on the centreline to get a double sided view.
When the shape is finalised, smooth the whole and make a symmetrical
profile on the other side. Take time to get it perfect.
Where needed, carve out the gaps to fit the tail and side lights.
Go berserk, pop down to the scrap yard and get those tail lights and
fog lights you always wanted to use. Mask up the lights with tape or
thin polythene film then fit in position using a little plaster to hold
in place. Then smooth to blend into the profile. The light mounting
brackets can be moulded internally after the shell is built. Likewise
fit other items which need a carefully profiled interface with the shell.
When the lights are removed and the fibreglass laid up, the lights can
be covered in polythene, then pushed into the fibreglass just before
it begins to set, to make a perfect fit.
If air scoops are to be used, (always recommended, even if only for
dummy styling purposes), then carve the smooth radiuses just enough
to allow internal ducts to be added inside the recesses later, to make
sure that the moulding can be removed.
The seats should fit neatly and be covered in bin bags for protection.
Do not forget the moulding around the side lights. Always allow the
lights and other items to stand off the shape by a few millimetres,
as this is to account for the layers of glass fibre and resin which
will be laid on the profile. Ensure the various items will lie flush
when the shell thickness is built up. This is not too important, as
the various items such as tail lights can be adjusted to lie flush later,
before final brackets are moulded in place.
The above use of plaster allows the shape to be refined, easily shaped
and built up over and over again with more plaster until perfect. Take
full advantage of this opportunity to search out the best shape of side
and other light units from the many cars available, to integrate into
the plaster shape to best effect.
Extreme customs can take just as long to create the styling as it is
to make the rest of the machine.
The act of integrating the tail lights and number (licence) plate can
become a work of art in it's own right. Sculpting the recessed hi-fi
mounting should keep it clear of most rain while remaining stylish.
Even the access hatches to the electrics can be sculpted to stylised
panels to blend in with the overall form of the machine - simple square
openings are rarely necessary. For some, the styling just will not appear
easily, taking weeks until the subtlety becomes refined enough for public
For many, this is the best part of trike building, where the imagination
If you find yourself just standing and looking for an hour or so, with
a cuppa or beer, do not worry, this is quite normal.
Use a pencil to highlight and develop the styling lines in the plaster
work as it develops.
When all parts are fitted into the foam and plaster shell, the lay-up
is almost ready to begin. Do not forget items such as the radio slot,
any top, bottom and side vents and air scoops, also the badge and fuel
filler recesses. Keep all access hatch screws flush and never fit any
accessory or item which will impale or damage the rider or passengers.
The simplest theft proof panels are flush fitting and bungeed from behind,
requiring blue tack or a sucker from a kiddies arrow or bathroom sucker
hook to remove them enough to unhook the bungee from behind. Dummy screw
heads will also help. Dummy screw heads can be mounded by using a genuine
item as a mould. Prefer the unusual, torx or safety screw head, so vandals
are deterred further.
One of my favourite openings is to cut the hole neatly in the shell,
then put a small shoulder step on the rear, so the cover lies flush.
Then simply put a bungee on the rear of the pannel to keep it in place.
To open the panel, simply leave one corner of the support shoulders
on the rear missing, so that pushing that particular corner allows the
panel to lever open enough to get the fingers behind it. Ideal for engine
and battery access, hiding hi-fi, or glove compartment etc. Fitting
dummy screws further reduces the chance of theft.
You can always cut the shell later but if you have the mould in place,
then take advantage of it for greater styling and accuracy.
Where major openings or slits (cut lines) in the shell are to be made,
then it may be useful to make a shallow accurately aligned groove then
inset a piece of thick vinyl covered wire or waxed string. This should
stand proud of the underlying shell mould, to create a thin recess on
the inside of the main moulding, allowing an easier cut very accurately
after the shell moulding has set to accurately segment the one piece
To accurately mark any grooves or cut lines, use a chalked piece of
string pulled taught over the shell profile. Then draw the string back
and forth for a neater line in the plaster.
Where the cut lines are made with string cut into the foam and plaster,
a thick plastic strip can be slotted into the groove, to make a plastic
wall, allowing the shell to be built in separate sections.
Where the shell is to be later sliced into separate sheets and is of
a structural nature, then also carve two strengthening ridges into the
mould an inch or so either side of the proposed cut. Do not make the
strengthening ridge on the cut line unless they are to be bolted together
at the cut line, as the slicing may not align perfectly. It may be better
to align and make mounting brackets later.
If the shell is to be separate pieces, then the string can cut a deeper
cut, a thin sheet of waxed metal, firm cardboard or plastic inserted
and the groove deepened to create flanges.
If the shell is to be a single piece, then take this opportunity to
carve strengthening ribs into the foam and plaster profile, to ensure
it will retain it's shape as intended. It is very common to fully remove
a one piece shell, especially ultra light shells. Therefore it is important
to ensure it can support it's own weight when off the machine. Such
shells may be hinged for easy access, so will need suitable internal
bracing, applied now and refined later.
When all is ready, wax the shape using anything suitable which will
allow fibreglass to be removed. Simple candle wax will often do, but
do not crack the plaster, so warm the wax and apply with a gentle touch
and a hot air gun or old iron or similar. Margarine, grease or the kids
old crayons will also do, but may get messy. A couple layers of cling
film separated by a thin layer of water may suffice.
Begin by building up the various strengthening ridges in fibreglass
and sand them smooth until flush with the profile. Then cover with layers
of fibreglass so it is sufficiently strong. Always try to mould it smoothly,
followed by sand papering to remove surface imperfections. Pulling on
the fibreglass cloth before it sets can give a smoother shape. Build
up until sufficiently strong, then smooth again.
While laying up the shell, cover the tail lights in masking tape and
offer them up into place to make sure the tail light sockets are perfectly
accurate. This is best done just before the green stage, just before
the resin is beginning to set.
Remove the lights and seats, then carefully peel off the shell.
Clean and trim to thoroughly to remove any imperfections. The shell
may still be a light, flexible structure, so handle very carefully.
If very light and flexible, place it upside down on a partially inflated
beach air bed.
Thoroughly scrub clean the inside to remove any wax, then build up the
inside of the fibreglass shell with more ribs and gussets to create
any strengthening and mounting points needed. Simple ribs can be built
up over rolled paper, folded card etc.
Cover the lights in polythene. Tape the lights in position making sure
they are neatly positioned, then use them to accurately mould their
inner mounting brackets in fibreglass.
Loosely mount the metal shell mounting brackets onto the frame, so
they will align and support without distorting the shell. Adjust the
shell in position on the frame. When aligned, tack weld the final positions
of the brackets to the frame. This will allow the shell to fit perfectly,
without any undue stresses or distortions. Now the shell mounting lugs
can be fibreglassed into the shell. When set, they can be unbolted and
the shell removed for more strengthening in these areas. Always make
sure all the items can be easily removed.
Remove the shell, then use the internal grooves or ridges to cut any
slots or into sections, or hatches to service the engine, access the
trunk (boot), fuel cap, or replace air filter, fuses and such like.
The waxed string lines will now make themselves very useful.
When cutting the shell into separate sheets after it has been made,
such as a centre section and two side sheets, then fit the basic shell
on the frame before any gel coat or finishing, Then mark the proposed
cut line with a stretched string, so the line will lie as neat as possible,
then carefully use a ruler to make the initial cut using a sharp knife.
Hopefully, the internal cut grooves from the plaster profile will have
been made beforehand to ease the process. This can then be cut deeper
until it can be used to guide a hacksaw blade. Use the blade at a shallow
angle to keep the cut line straight or gently curved. When refitted
on the machine, use waxed cardboard or thin plastic sheet between the
gaps to ensure the gaps remain neat and even when building up further
layers and ridges. These gaps can then be sanded smooth with sand paper
wrapped over a piece of thin metal to ensure a straight, or gently curving,
neat, even gap. Always integrate cut lines into the styling profile.
It is extremely bad practice to have a cut line down the centre of
a shape. Bugattis excepted.
When applying a pigmented resin or gel coat for many components, mix
just the resin and pigment fully, but do not add the catalyst. Then
decant to smaller containers, for use with greater convenience when
required and to later allow a perfect match should accidents occur at
a later date. Then use the pigment coat with catalyst only when needed.
Once the shell is removed, leave the foam or scrunched newspaper in
place on the trike, then carve the luggage spaces, hi-fi boxes and air
ducting from any airscoops towards the radiators. It is now possible
to lay up these in fibreglass for very integrated components which could
also fit and perhaps support the shell perfectly. This is the time to
include ducting for heated components such as exhausts, where heat shielding
can be formed in metal or in fibreglass with alloy foil coating.
A difficult case may be a transverse V6 with turbo, where some fresh
air ducting may be needed, possibly from underneath, or an upper airscoop
in the shell, plus a heat shielded area and rear hot air flow vent.
As making smaller ducts is difficult to carve, simply use a small powered
sander or a powered wire brush, or perhaps a heated piece of metal which
will allow the foam to be sculpted into perfect ducting. None of these
will damage the chassis components if cutting a little too keenly into
the foam. In some cases, such as luggage containers, then the base should
be carved until flush with the chassis or superstructure for support
of heavy luggage.
If preferring to make the ducts to shape first, then simply carve and
sandpaper the required duct in white foam, cover in cling film and fibreglass
to shape. The white foam can then be picked out or dissolved in petrol.
When making ducts for external components, it is best to position
them for aesthetic and aerodynamic reasons on the shell, then cut out
the holes in the shell using the ducts as perfect guides. External scoops
should be made in cardboard until final testing on the road.
For those with low mounted radiators, it may be necessary to copy the
foam sculpting process after turning the machine on its side, to allow
the lower half to be an efficient airflow design. Aim for a low pressure
zone at the rear to help extract the air at the rear of the machine,
in the same way as formula one cars.
After the shell is built, it may be necessary to fit extra strengthening
ribs underneath, often where the shell is sliced.
Where the panels are to bolt together, a thin, stiff, waxed plastic
sheet can be slid in the gap and two internal flanges can be built up
either side from the inside. The flanges can be built up form sheet
fibreglass or plywood. When set, these flanges will align accurately
and can be drilled for bolting together. A thin rubber sheet between
panels and rubber washers will prevent water ingress and reduce rattling
Now is a good time to mould in the tubing to carry the wires to the
side and tail lights if the lights are moulded into the shell. It is
often preferable to be able to lift the shell section off as one, needing
to only disconnect a single multipin electrical connector for convenience.
Where the shell section is also part of the radiator ducting, do not
route the cooling fan wiring into the shell, but keep them routed on
the frame with the radiators. If the shell gets trashed, you can still
Where people are going to be sitting, it is preferable to build the
seat base and possibly the backrest as part of the frame. If the seats
are to be part of the shell, then reinforce locally to ensure this area
will be supported on the chassis by moulding directly over the frame
support tubing. Position the tubing for the seat support, cover the
frame tubes in polythene to allow for easy removal and build up the
seat base along with the rest of the shell.
Under the shell will be problems requiring further panels or ducts.
Check whether there is a need to build up the undersides of the shell
to deflect rain coming off the wheels, to stop it going on the passengers,
engine or electrics. Such items may be best mounted onto the frame,
separate of the shell.
For those who have an engine with expensive components, a full bottom
pan can be moulded using similar methods as the shell. Preferably in
such a way as to improve airflow using techniques similar to formula
one to improve airflow or for cooling the exhaust and engine parts.
It is unlikely that a general purpose trike will be able to have the
bottom pan low enough for low pressure ground effects, but it looks
good for shows and can improve radiator and exhaust cooling.
Some parts of the shell will want to vibrate, either in harmony with
the engine, poorly balanced wheels or quite often from wind effects.
These can be reduced by extra internal ribbing or brackets, or selective
use of tarred felt to act as a mass damper, as used in cars. A little
extra strengthening fibreglass moulded over a piece of folded cardboard
or rolled paper is much lighter and stronger than tarred felt.
For both safety and for styling, it may be necessary to fit mesh or
slats in the air intakes. Wire mesh comes in many sizes, so choose to
match the styling. Never use variations on chicken wire unless it cannot
be seen. For light weight machines, some suitable nylon coated netting
is available from camping and caravaning shops.
For slats, an old venetian blind makes a good set of formers upon which
to build up a set of identical slats. These may be temporarily mounted
in the shell with blue tack, waxed and built up with fibreglass. Removal
will reveal perfect shapes, preferably on the upper surfaces, where
the public can view. Or simply leave them in place and just build up
the undersides. Slats also make excellent and stylistic rear air vents,
where the rear of trike styling often leaves much to be desired. (Ferraris
Remove all fittings and apply a final layer of pigmented gel coat or
various layers of paint over the smoothed fibreglass body, then cut
back and polish out imperfections. If painting, spend many hours to
cut back and smooth any imperfections prior to spraying.
If making seats is daunting or are building on the cheap, then use car
seats as a starting point. Make sure the seat padding can allow rain
to drain away in the gap between squab (backrest) and base. Use porous,
non absorbent foam or many small drinking straw sized pieces of nylon
tubing glued in position between base and squab to allow water to drain
away. This is another advantage of having the passengers reclining backwards
at a gentle angle.
Ask at any motorcycle or car workshop, they often know someone who will
cover custom seats. Always retain the original seat covering, as the
seat maker may need them as patterns for covering standard seat foam
For leather seats in the rain, seriously consider using waterproofing
leather preparation. Always add discrete drain pipes in the join between
the base and the backrest. A gap tends to lose loose items, such as
Keep all access hatch screws flush and never fit any accessory or item
which will impale or damage the rider or passengers.
For those aiming for the posh end of triking when using carpets, then
use removable, washable polypropylene, nylon or similar. Snap studs
make removal easy for cleaning. For those who may prefer a traditional
form of styling, there is no reason why a trike cannot use connoly hide
and have polished walnut trim. Again, keep the original seat covering
for the leather worker to use as patterns to match any standard seat
foam. For walnut trim, it is best to recess the wood area and use chrome
trim from coachbuild suppliers. You will be surprised what is available.
If a hydraulic jack is used to raise the shell for custom use, simply
tap off the engine oil pressure side, though a small hole into a small
bore pipe as used for oil pressure gauges, and pumped into a modified
car rear hatch stay, as this reduces the need for a separate hydraulic
pump and any expensive componentry. Alternatively, the guts of an electric
/ hydraulic car convertible roof mechanism or electric car seat mechanism
can be used.
Aerodynamics is not directly part of trike construction, but for those
who spend the effort, it can make the design better in many possible
If your trike behaves badly at high speeds, then some aerodynamics may
The following is far beyond that normally used on trikes, but occasionally,
someone will make a machine which may need some of the following, possibly
for studying high speed stability. If Merc can get it wrong at LeMans
24hrs, then all builders should treat high speeds seriously and with
If making a shell, then aerodynamics is always a good way to maximise
the top speed from the power available. Good aerodynamics also improves
comfort for the rider and especially for the passengers. It can also
help solve some handling problems and improve radiator airflow for engine
cooling at maximum power and even the cooling in heavy city traffic
in high summer.
Lighter machines are more prone to aerodynamic variations than the
mass of a heavier machine. If a very light machine is built with a rear
shell, and uncommon problems occur, especially at high speeds, then
always consider the airflow along with the many other common causes.
Front spoilers, airfoil or variations on such themes, such as an angled
screen may be needed if the front gets too light and skittery with speed.
As speed increases, the centre of pressure should be close to the centre
of gravity. This is unlikely for trikes, but gives a general direction
of what to aim for.
A great deal can be written, but until fully developed, here are a
few pointers to help get some ideas up and running. -
The conventional trike is an aerodynamic disaster area. Enclosing the
trike has been done on rare occasions, but rarely for aerodynamic reasons,
usually for show use only. Aerodynamics may not be generally acceptable
or always applicable.
Never confuse aerodynamics as simply the use of a wind tunnel. Aerodynamics
is the general approach to airflow over a body. Even simple improvements
can be considered aerodynamics, although some simple aftermarket 'improvements'
may not always turn out to have such positive attributes as expected.
The wind tunnel and it's associated testing systems are often applicable
and many of these practices are available without expense.
The subject of aerodynamics can be read in a vast number of books on
the subject. This area takes much development time, and unlike most
aerodynamic work, this should be done mostly in full scale, in real
environments. Cars with four wheels do not suffer the handling demands
of the trikes with it's single front wheel which needs greater rider
feedback for control in difficult areas.
Testing a trike at full scale in real conditions may seem less than
ideal in an age dominated by high tech wind tunnels, but such luxuries
are rare and trikes do not live in an ideal world as assumed by wind
tunnels. Wind tunnels are great for formula one, but they do not have
to live in, or even simulate the real world of traffic. Formula one
often dislike the high side winds at bleak circuits such as Silverstone,
upsetting their highly refined settings for the ideal world of sheltered
circuits. Wind tunnels are good for some things, but simply cannot afford
other machines with the serious and varying situations they encounter
in the real world.
The main aerodynamic areas of concern are not overall speed effects
from the traditional analysis of frontal airflow, but general cleaning
up what is there, to ensure the cooling is safe and the passengers a
get minimal buffeting. Trikes are aerodynamically messy and fairly difficult
to get close to an ideal, where aerodynamics can only be of limited
help. A trike with it's open front wheel and sculpted rear half has
only one, narrow front wheel, so can be good for airflow with a mudguard
and other ways to clean up and attempt to control the airflow. The bow
wave is a major concern for cooling.
Side winds can only be tested in the real world, as a wind tunnel is
usually incapable of simulating bow waves such as when passing lorries,
buffeting or intermittent and side winds near high interrupted buildings.
The type of forces which may be encouraged are such as downwards at
higher speeds, perhaps because of the need for a lighter front end to
assist low speed handling and manoeuvrability, or because of poor engine
choice, causing a light front end. Some designs could induce a possible
lightness at higher speeds but can be counteracted at speed by a belly
fairing, airdam or windscreen. These could act downwards against oncoming
air and some downforce panels can be disguised as headlight screen covers.
Also consider sensible airflows around the lower sections and through
a wide belly pan to control any pressure build-up in various areas.
At high speeds, there is a lot of power being applied at the back wheels,
so ensure the front is also capable of maintaining it's control on the
Never let a trike front end get light at high speeds, as there are many
influences which may try to upset the steering, from imbalanced brakes
to unusual airflow and dangerous road surfaces. It is for this reason
that powerful trikes should get the weight balance sorted at an early
stage of design.
Side ridges and other top, frontal and rear end refinements may be applied
later to offset some effects, as seen in back window edging of the MK2
The trike is not an aircraft generating positive lift, more like a
formula one car generating increasingly negative lift with speed. -
A clean block moving forward, generating the minimal resistive forces.
Because some trikes and rider are quite tall and therefore susceptible
to front wind, then whatever can be done to reduce rider drag is useful.
Whatever the drag forces that must inevitably be generated, they should
be as neutral as possible.
Tail vortices can cause snaking on some aircraft, and as the whole
machine could be compared with other dubious machines, especially with
a light front end. To use an old phrase, 'the tail wagging the dog'.
Much attention may need to be applied to ensure the tail airflow is
as clean as possible. Large, dirty airflow over a large tail section
may upset the stability of the trike, from frontal airlfow and also
from side winds.
Tail airflow should also help to extract air from the rear of the belly
pan to assist engine cooling. The tail of many exotic and custom machines
can have interesting aspects.
Without a wind tunnel, airflow studies need not be compromised.
If the real world cannot work in the wind tunnel, then turn the problem
upon its head. Use the world as the wind tunnel. Like JP crash testing,
if one can't get help from the experts, then study their work and do
it anyway. (Always be careful when crash testing with real riders, although
this can also lead to radical new ideas in crash design and more intensive,
first hand appreciation by the designers. First hand crash testing always
gives deeper insight to the design needs and possibilities.)
Wind tunnel testing equipment can be taken to the real world. Real
assessments can be done in real time on real machines on real roads.
Pressure gauges, airflow sensors, smoke probes, pattern assessors and
a few of the authors new methods awaiting patents, can be backed up
with various data collection and video. These allow most appropriate
wind tunnel practices to be applied and more importantly, can do so
in real time and at full size.
Most machines are steel framed mechanical devices, with airflow control
devices added later. Therefore the adaptation according to feedback
can be done easily without upsetting the underlying structure. (Unlike
most modern cars.)
Some trikes can be designed from the outset to be aerodynamic as possible,
from the minimal frontal area to the overall initial chassis and rider
layout. Such high specification trikes are often designed for long distance
touring or for top speed with minimum drag.
Choice of landscapes must be chosen to maximise the worst conditions
available by airflow over the countryside and in cities.
Using local test sessions and scenarios gives regular, fast and interactive
changes to refine the aerodynamics, and of course, there is no need
to book expensive wind tunnel time. The testing schedule should be based
on the highest, bleakest moorlands during winter and in the windiest
towns. This can also give a fine selection of both fast roads with the
highest winds normally encountered, with a choice of both clean air
and maximum turbulence plus a wide variety of buffeting scenarios. It
also has fewer vehicles in the way to allow much better testing.
You may occasionally find the author on Dartmoor in winter with a radical
machine, adhesive tape, cotton wool, home made smoke probe and pipes
and a video camera.
In such environments, get out the cardboard scissors and gaffer tape,
the wool strands and smoke probe. If nothing else, you will get much
better radiator airflow.
Once fettled and road legal, the trike can begin to explore bleak sections
of motorways in winter with high sided lorries to assess intermittent
buffeting, bow waves and whatever else could be thrown at the design.
Wind tunnels may give 'tight' data, but the excellent scenarios of poor,
twisty roads in high, buffeting winds probably give better feedback
than any wind tunnel could ever hope to achieve. This also allows the
rider to feel the true effects needed for improving the handling of
trikes. Trikes are unlikely to improve their aerodynamics greatly, but
untoward effects such as airflow causing the rear to behave badly (tail
wagging the dog) can often be recognised and corrected or ameliorated.
The ability to apply many techniques to real life scenarios does not
limit the study, as videoing of airborne particles gives the direction,
speed and orientation of the whole airflow which can be measured in
single and sequential stop frames. Park the machine on a windy ridge
and throw evenly chopped straw into the airflow. Do not use polystyrene
chips as these damage the countryside. Straw is available from pet shops,
so buy some sharp scissors and start cutting.
Always transfer the video to digital for storage on a computer, as there
will be much time spent analysing a selection of single or sequential
frames, which would otherwise damage a tape. The length of each strand
of straw will be streaked, allowing the distance to be measured and
thus the speed, as calculated by the exposure time of each frame. Usually,
just comparative speeds will suffice, as it is easy to plot the different
speeds across the machine, to see what is happening. Only when maths
is involved will the actual speed become relevant.
Conducting the tests in various windy areas at various speeds with video,
allows the various changes of airflow with speed to be studied at leisure
and videoed from all angles with airflow not only from the front, but
also from various side angles.
Use cotton tufts stuck on the machine then ride at various speeds to
video external and internal flows just above the surface layer. This
can be done in any weather. For radiator exit airflow, use longer lengths
of wool knotted and pulled though the radiator fins. On conventional
machines for road use, the cotton tufts will highlight a great deal
of airflow as well as highlighting positive and negative pressure zones
and are easily attached and removed using adhesive tape or blue tack.
For those who wish to use the classic smoke boom, this can be done
statically in high winds, or on the trike at high speeds. (Should be
done on old airfields or quiet roads.) When testing on the road, smoke
generators should be fitted on the machine and vented in various positions
to assess overall, general airflow. Most plumbing suppliers stock smoke
generators for testing gas flues, or consider fireworks or using a small
hand held, static, pyrotechnic flare as used for emergencies at sea.
Do not use the rocket/parachute type of flare. Use in a safe, lightly
pressurised metal container and duct via a selection of pipes. If of
a pyrotechnic nature, use a large metal container and position a downwind
vent pipe to prevent excess pressure generation and never use on normal
If too much smoke is supplied, carefully deconstruct pyrotechnics outdoors
using safety clothing and a bucket of water nearby. As emergency flares
are available in various colours, choose a colour to contrast with the
machine to highlight the airflow.
To ignite a soft firework at the appropriate time, simply wire a thin
piece of steel in the touch paper and short it via two thicker wires
and a switch via a battery. Simply choose a piece of wire so it glows
when shorted across a large enough battery, most torches (flashlights)
will suffice for ignition supply. Also consider using wire wool and
the ignitors from model rocket motors and also a few match heads. Done
properly, a smoke generator can be triggered from a simple handlebar
switch. Allow a little time for generation, so trigger well before the
test run area. If triggering is problematic, the fuse section of bangers
and the heads off waterproof matches will help.
Smoke generators using a heating element and special oil are also possible,
as used in discos and adaptable for the hot exhaust system as a generator.
This will require an exhaust box clamped over a hot area, plus a fast
oil drip feed and such like, plus an upwind pressurising system to ensure
reasonable smoke flow, but is preferable for stationary testing. It
is now possible to buy party smoke in an aerosol.
Although predominantly for dynamic airflows, smoke can be used in a
quiet garage while testing for overheating in a simulated summer traffic
jam. This is particularly useful for air cooled machines. Place smoke
candles under the motorcycle while it is running hot, to simulate traffic
jams on hot days in still air. Remember where the most overheated vehicles
are seen, usually part way up a long hill on a bank holiday on the way
to the seaside. Always check your machine for all forms of aerodynamic
It will take a little time to get a good smoke probe, as it must be
designed to minimise any disturbance upstream. Old brake pipe or similar
tubing may often suffice for the boom and nozzle. Make sure the tip
is a smooth aerodynamic transition to the airstream. Use the bow wave
to pressurise your smoke system.
A passenger on an accompanying motorcycle or car can do the videoing
from sides and rear, or the video camera on a broom pole.
If wishing to understand the airflow over the rider or shell, use of
a surface layer 'slime' across the shell should be water based, so the
machine can be hosed clean afterwards with a pressure washer in a trials
bike manner. When an emulsion is painted on the machine, study of surface
flow is possible, but is very messy, so use after the chopped straw
and cotton tufts. Different coloured streaks can be painted into the
slime tangentially to expected airflow, to highlight airflow direction
and strength. Almost anything will do, from emulsified olive oil, or
water based lubricants and many adaptable foams, gels and such like
at the discount beauty counter of most chemists. Streaks are easily
made with simple poster paints. Then test on the motorway. Some slimes
will be affected by the cooling effects of high airflow on cooler days,
so choose the materials according to the weather. If expecting rain,
oil bases are better. Rain should not be seen as a problem, as it will
help the process with its greater mass of the drops to deform the heavier
oil based slimes, but only for a short time. Always take videos or photos
immediately after a slimy test run. Then look for dead spots, especially
where cooling airflow is important. Look for dead spots or where the
airflow is reversed to that needed.
In rare cases, it may be necessary to see where pressure build ups
or low pressure zones occur. Where a handful of pressure probes are
needed, to see where pressures build up or extraction is effective,
cheap and simple water manometers can be mounted on the side panels
with blue tack and makes life very easy by using simple tubes and coloured
water against a contrasting background.
Use car windscreen washer tubing which is clear and flexible. Lightly
cover the atmospheric ends with cotton and tape to prevent spurious
readings, or route the pipes to a known 'dead' area of pressure. The
position of the static water line is not important, just the relative
differences between atmospheric and the point of study. If a specific
area of concern, simply have the sensor end of the pipe on a stick and
have the passenger move it to see where the pressures vary. Carburettor
vacuum gauges are rarely sensitive enough. An old barometer can be modified
to read various changes in pressure, with an extension tube for remote
readings. A digital barometer is often a good option.
There are other methods mentioned in companion monographs, but are
rarely applicable to trikes unless a wind tunnel is employed. It is
not easy to make a full size wind tunnel to take a trike, although details
for cycles are described.
More stuff on aerodynamics from 'A builders guide to wind Tunnel Design'
on my website.
Aerodynamics also includes engine cooling which used to be a problem
before water-cooling and radiators, but today there should be no excuse
for the many strange airflows causing cooling problems. Modern radiators
can usually be positioned in cleaner airflows, often with minimal drag.
If belly pan or ground effect airflow is problematic or suspect, simply
position a set of smoke risers on the road in still air and drive the
machine through the smoke risers while videoing the effects.
Do not be afraid to simply let the machine get hot in still air in
the garage and place a smoke candle under it to see if airflow is adequate,
when imitating a traffic jam on a hot day. Remember where one sees the
most numbers of overheated vehicles parked by the side of the road,
so always design the machine to be reliable.
When videoing any of the methods, always hold the video in each position
for a few seconds to get a decent sequence.
A vast amount of aerodynamics can be studied without recourse to wind
tunnels or electronics. Airflow is a fundamentally basic physical phenomena,
which can be measured by equipment developed a couple of centuries ago.
No formula one machine leaves the computer labs and wind tunnel ready
to run perfectly. It will leave in a 'ball park' condition, with most
of the refining work done by road testing. This applies to all machines
used 'near the limits'. Even for trikes, the final adjustments are done
over years of pragmatic, hands on testing.
Full scale road testing not only gives objective data, but also the
very important subjective assessments only assessable by road testers.
A variety of testers will always give better assessment of handling.
Welding is the ability to fuse two pieces of steel together by applying
sufficient heat to melt them in a localised spot and if necessary, to
add some extra filler metal.
The main welding is electric arc, with either a stick welder, (Manual
Metal Arc) or a Mig (Metal Inert Gas) or oxy acetylene. (Gas.)
The picture shows the authors stick arc welder at the top, with the
electrode partially worn down. This is useful mainly for steel fabrication
and little else, although specialist cast-iron grooving and welding
sticks are also available. This uses a simple stand-alone transformer
which can work off domestic mains electricity.
In the middle a Mig welder handle with trigger, and the thin welding
wire exiting the nozzle which also creates the gas shield. Suitable
for most welding of steels, including stainless and aluminium with the
appropriate gas and wire. This again uses a stand-alone transformer,
but also needs a gas cylinder to create the shield and a motor to feed
the wire, which are usually included.
Below this, a standard oxyacetylene mixing handle with a copper nozzle
tip. Useful for most metals and also for tempering and hardening processes
and many other heat related processes. You will need to rent oxygen
and acetylene bottles from a commercial supplier, usually for ten years,
then purchase the gas and return the bottles for replenishing. There
are small cylinders available which are no bigger then camping gas cylinders
for those who do jewellery and small work, right up tot he large industrial
cylinders. Always take complete safety procedures with handling of the
cylinders, storage and preparation. (See supplier for full safety information
- then follow it.) It is possible to flame weld aluminium and the author
has done so, but it is very difficult, a bit like trying to solder cheese.
Safety. Welding causes sparks to fly, so no combustible material must
be near the welding area. The welding arc is very bright and everyone
must be shielded. Welding eye is very dangerous and may last for months,
in bad cases it can lead to loss of sight. Always use an approved welding
glass. Always throw away a cracked lens. The electrics will need a carbon
dioxide fire extinguisher.
Do not cool welded metal in water, as this will cause hardening and
cracks. Always ensure a good earth for the welding metal, as a poor
earth is accompanied with a poor weld. Always set up the weld to give
a comfortable handhold. Always make a couple of practice runs to check
and adjust the settings.
Head protection is done with a face mask with a heavily tinted lens.
Over the lens is a piece of clear glass, to be easily removable as weld
spatter will eventually build up. The face masks may be either hand-held
or on a head strap. The head strap must have hinges, to allow the welder
to see where the work is, then get into position before a nod of the
head allows the mask to fall into position. Rubber washers in the adjustable
hinges make life easier. The easiest mask has a light sensitive LCD
screen which is transparent when no welding arc, but turns dark upon
seeing the weld arc and these are expensive.
Always wear a full length leather apron or similar clothing when welding,
as the spatter will burn many holes in clothes. An old (thick) leather
coat can be recycled for this purpose. Not-too-thin pure leather gloves
are also useful, especially when handling hot metal parts. More spatter
is likely to fall on the welders feet than the hands, so never have
the boot openings such that they will allow weld to enter the boot,
it is not fun.
The two metals can be joined in various ways, such as end to end,
or a T or other join. The weld must penetrate sufficiently to be secure,
and this means full depth. On thin plates, this may only need a single
run of weld to sufficiently penetrate to the other side, ensuring full
penetration. On thick plates, then the weld may be done from both sides.
The simplest and still the most effective welder is the manual arc
welder. This consists of a transformer to step-up the mains current
sufficiently to be capable of welding steel and is quite adequate for
bike and small vehicle frames. The currents are usually from 30 to 1000
amps at about 20 to 40 volts.
The heat is generated by the arc. This is the jumping of electricity
between electrode and the metal to be welded, creating a localised hot
spot which creates a pool of molten metal.
If the metal had no gap, then little or no filler rod would be necessary.
But due to the nature of the manual arc welder, the filler rod will
still deposit some extra metal so a small bead will form above the join.
It is for this reason that a small gap is sometimes left, which also
helps the arc to penetrate fully. Full penetration is best seen by a
small bead of excess metal on the other side of the weld.
The gaps and welding current will depend upon the materials and conditions
and this is where the welders skill becomes apparent. This involves
the choice of welding current, the rod size, gap and speed of weld.
To this can be added subtle skills and the teasing of the welding rod
over the welding area, and being able to read the way the weld progresses,
to give superb welds which can be an art form when done properly.
Beginners will not always make superb welds and getting to know the
art and preparation will take time. For this reason, it is recommended
to get professional help and to practice, as much as an hour a day or
a week may be needed to become basically proficient, but years of welding
are needed to match the professionals who make it look easy and who
create excellent welds.
Practice, practice practice, there is no other way. If you know a professional
or good welder, get them to help you to practice. Welding is an art,
but do yourself a favour, read the basics and practice adjustments for
different scenarios until you are fully conversant with most conditions.
The hardest part when learning is the striking the arc. This is not
unlike striking a match, where the rod and metal are struck against
anther just enough to create the initial arc, and this is then kept
just above the metal to ensure the arc is maintained at an optimum for
the weld pool of molten metal. A steady hand is needed. Eventually the
strike is not needed, just a dab on the parent metal and away you go.
Practice striking the arc with the power off, by striking the tip for
a few millimetres along the metal and then keeping the tip about five
millimetres off the metal. For your first time with a stick welder,
practice twenty times before switching on as this will save damaging
the tip when power is on. If problems still occur, try practising with
a short welding rod and a heavy gauge rod and parent metal test piece.
Beginners will find using a short welding rod will make handling and
striking the arc a lot easier, but this should only be a temporary aid
If a hole is burnt in the metal, reduce the current. If the weld sticks
on the surface with little penetration, increase the current or change
the speed and height above the workpiece.
Use a long pencil and try writing a comma on a piece of paper, then
lift the pencil off the paper by five to ten millimetres, to write a
line of V's or O's in the air towards the angle of lean of the pencil.
Keep the pencil at about 75 degrees towards the vertical. Now do this
while not being able to see the strike point due to the welding lens
and with a 450mm long metal pencil. You get the idea.
When starting, it is easier to cut the welding rods in half and to bend
the welding rod in the handle for an easier position. (See blue handle
above, with welding electrode bent downwards slightly.
Setting up the welder on a test piece before attempting important welds
is a must and well worth a few runs and the cost of a welding rod to
get the perfect weld.
Once the arc is struck, the metal will melt and if exposed to the atmosphere
the pool of molten metal will absorb oxygen and other gasses, making
the weld porous and therefore weaker. For this reason a welder has a
shield of flux or neutral gas around the welding area. On manual arc
welders, this is generated by the outer flux coating of the rod. The
weld makes the molten pool and the flux forms a protective layer over
Once the arc is struck and the pool is correct, the welder moves the
rod along the route of the weld, ensuring the pool is maintained and
the flow of the molten metal is such that it makes a good weld. It is
the pool of weld that is important, and maintaining it just the way
you want is the whole object of the excersize. If the pool is good,
the rest of the weld will follow naturally and the only thing to worry
about is loosing the direction in the dark, so make sure the run of
your hand is easy to make.
Get in a comfortable position before welding, so your arm won't shake.
Again, a dummy run with the power off, as preparation is everything.
Speed will depend upon the parent metal, the rods and current used.
Usually the set-up is such that a slow gentle pace will ensure good
heating around the weld area, and time to melt the area fully for good
penetration. Emphasis on slow, as penetration of the pool of weld into
both sides of the metals will dictate the speed, not the welder. Too
slow and it will burn a hole in the metal. But too fast and the weld
will be shallow and a pretty, but dangerous weld. Always try to go a
little on the slow side as is safe for the best pool of weld, as this
ensures best penetration without excessive heat.
You are NOT sticking two parts together, but creating a melt between
The weld is begun and a pool of molten metal created first. This pool
is created to the correct depth before movement. Then move towards where
you want to weld. It is usually necessary to tease the rod between the
two metals to be joined. This pool is then encouraged to flow at it's
own rate, so the rod melts and travels along the gap. Never rush a weld,
it must proceed at its natural pace, dictated by the size and shape
of the molten pool of metal, which must be allowed to flow in the manner
necessary to fully join the two metals. Get to know this pool well.
The rod is moved slightly between the two plates to allow pool to flow
fully and a good weld to be created.
A good weld will leave a smooth crust of slag which is removed easily.
In good welds, this will reveal a smooth weld with a slight raised bulge
just above the level of the metal. The penetration should be fully through
to the other side. On heavier metals, the penetration may only be half
way, then the rear surface can then also be cleaned and similarly welded.
The ideal angle for the rod relative to the weld for stick welding
is 70 to 75 degrees vertical, leaning towards the moving direction of
weld. (75 to 80 for mig.)
The height above the parent metal will define the nature of the arc
and the form of the weld. too high and porosity and a wide weld will
ensue. Too close and poor penetration is possible, but a more closely
controlled weld especially for thinner metal.
This picture shows a typical heavy penetration weld on structural steel,
in this case the front swing arm of a JP8 hub centre single sided swing
arm, where poor welds are not acceptable.
If you see a professional welder in action using a stick welder, grab
a welding mask and look carefully at the movement of the tip. The rod
will not be held to run smoothly in a line, but the arc is played in
a minutely circular or side to side action to ensure the heat is directed
evenly for the best penetration, but without overheating.
On heavy metal, getting the area hot before the weld arrives is beneficial.
For most purposes, starting the weld as a bead just before the start
of the actual area to be welded can help get the weld started and settled
by the time it reaches the required area.
As the welding rod melts down, the weld rod will need to be changed
regularly on long welds, so the slag should be removed and the weld
continued such that it makes a seamless fillet.
When welding vertically or part of the join is vertical, then the weld
will naturally want to pool under the effect of gravity. Therefore is
sometimes better to make a smaller central run, then return to make
a large fillet over the original, which will support the overall weld
more evenly. Start from the bottom and work up.
On thicker metal, penetration is made easier by chamfering the edges,
to give a Vee groove for the rod to access and fill. About 60 to seventy
degrees will suffice and reaching down to about three quarters depth.
If the welder cannot fill this in one run, then three runs are possible
to full the gap, plus another on the rear, or perhaps three on both
On most welds of thick metal as uses on frames, the arc is played gently
between the edges of the two parent metals in a V or small circular
motion so the weld flows evenly and deposits with full penetration into
both the parent metals.
Tack welds with small welds along long gaps, especially on sheet metalwork
such as fuel tanks, otherwise distortion will occur and the run may
buckle and distort.
The fuel tank in the picture had over twenty tack welds before final
teasing into shape before committing to the final long weld runs.
Preparation is paramount for a good weld.
Welding areas on the metal must be clean, with no paint or rust.
Wherever possible, a weld should be a single, neat run.
If a hole is burnt in the metal, reduce the current. If the weld sticks
on the surface with little penetration, increase the current, or make
a number of passes along a deeply grooved join. A good weld will leave
a smooth crust of slag which is removed easily. In good welds, this
will reveal a smooth weld with a slight raised bulge just above the
level of the metal. Leave it as is if the machine is to be inspected,
as this tells the inspector that the build quality is good. The penetration
should be fully through to the other side. On heavier metals, the penetration
may only be half way, then the rear surface can then also be cleaned
and similarly welded. Quite often the weld area is not ideal, so a number
of welds may be needed, possibly from one side or end, then the other,
In each case always make the weld from the best end, then remove the
slag and leave room for the weld to be made from the other end also.
This allows the welds to join in a safe area which can be cosmetically
dressed more easily.
An angle grinder, leather apron and gloves and face mask are integral
parts of a welders kit.
Distortion occurs during welding and is quite normal. This can be evened
out by equalised welding of the frame to minimise the effects of distortion.
When checking frames is common to saw through some tubes to see how
much internal stress is created and the amount of distortion that can
occur. Specialist frames can he heat treated to remove internal stresses,
but this is rare.
To help make a gap in main frame tubes, use a sliver of steel to lift
the component off, or simply make an 'adequate fit' by grinding the
ends of the tubes with suitable gaps or pips to allow better penetration.
Test by breaking, hacksawing or grinding through test welds to see
just how good they are. Carefully examine the depth of penetration and
for any air holes or slag inclusion which can weaken the weld. Keep
practising until certain the welding is good enough, or find an expert.
The problem may simply be a welder that is not powerful enough. A basic
140 amp arc welder is adequate for a simple bike or trike, but for tubing
larger than bike frames, use it for tack welding. For heavy welding,
hire a better welder for the final welding and check that your domestic
wiring is in good condition. On a recent V12 trike project, the steering
head was glowing red before the welding had finished.
Flame welding, such as oxy - acetylene is ideal for building fuel tanks
and to braze delicate fuel tank fittings and more delicate items. The
heat spread will cause distortion of large thin plates such as used
in fuel tanks, so tack weld all round before fully welding.
When bronze welding, keep all gaps small and check if any preheating
is required. Always demand absolute cleanliness of the materials.
Common mild steel tubing and plate should supply all your needs, as
it needs no special welding techniques. Welding rods must be chosen
to match the metal and the diameter of the rod relative to the thickness
of the metal to be welded. Store welding rods in a dry place. I use
the airing cupboard.
A basic, affordable arc welder is quite capable of building most bikes,
if the builder takes time to become proficient and follows sensible
Gasless mig welders are not recommended. Gas migs (metal inert gas)
are often better than rod welders, especially for thinner metals such
as fuel tanks. Expensive welders are not necessary, but always practice
There are often evening classes on welding for beginners at many technical
colleges and are priceless. After all the theory is read and understood,
there is only one way to learn how to weld, practice, practice, practice.
The picture shows a couple of welders, a second hand 130 amp MIG on
the left, with the swan neck and nozzle which takes the gas and feeds
the welding wire under control of the trigger. I got this one cheap
and simply repaired the wire feed drive.
On the right is the basic 140 amp arc welder with its welding rod covered
in flux stick into the holder.
Welding costs are not expensive, as a box of a hundred welding rods
is affordable and a length of steel tube for practice is well worth
the low cost involved.
When buying a second hand welder, check the condition of the bits and
see it in action if possible. When purchased, repair the earth lead
and check all the connections to ensure a good weld. Some welders seem
to be useless because of simple faults, so a full check and a clean,
internally as well as externally.
Most MIG welders have a bracket or strap at the back for the CO2/argon
cylinder. If using the small cylinders, then these can be awkward to
have standing up loosely at the back. As shown in the picture above,
there is usually plenty of room inside the welder, under the wire spool
reel. Even with the large spools, these is enough room. A couple of
slots in the base will allow the cylinder to be neatly strapped in position.
To access the cylinder valve, the front panel can have a hole made in
it, so all can be accessed from the front. (Bottom left of the picture.)
Likewise, the rear mains cable can also be moved to the front, so the
welder can be slotted neatly away beside, or under the bench, without
having to lug such a heavy weight about each time it is needed. The
author prefers to have the welders on the top of a head-high shelf,
so the welding cables and swan neck lie vertically downwards, tucked
to one side, neatly and away from damage or kinking. Being positioned
high or out of the way, they are more out of the way of grinding dust
and thus tend to run a little cooler. Once again, preparation can make
the workshop easier to use.
Unless you are a natural born welder, expect to get frustrated for
a few weeks until the skills are gradually acquired and you eventually
get the feel of welding.
Basic tool kit.
To create a trike is not expensive. You need:
A dream and plenty of time to get it right.
Somewhere to build. Anything from a nice, big, warm garage, to just
three level concrete slabs in a garden.
A3 notepad, pencil and eraser for envisioning the dream.
Lining paper for full size drawing and to work out the shape and size
of the frame and main components.
Chalk to mark it on the floor.
Basic angle grinder with grinding and cutting discs for metal. Also
linishing discs for cleaning and smoothing the metal and to carve the
Face mask for dust, eye protection goggles and ear defenders. These
are not negotiable and must be used, especially if you want to be triking
in later life.
An arc welder, mask, chipping hammer and various sizes of welding rods.
Electric hand drill, set of drill bits, grinding and other items as
Files, hacksaw, chisels and hammer.
Set of spanners (wrenches) and socket set.
Screw drivers and pliers etc.
Steel tape measure.
Permanent felt tip marker, chalk, spirit level, set square, plumb line,
wood blocks and wedges, blue tack, masking tape, small pot of paint
and a flat floor space.
First aid kit and fire extinguisher.
Hydraulic pipe bender for frame tubes. (From hire shop.)
Multimeter for electrics.
Decent vice mounted on a strong work bench.
A decent engineers vice may be expensive, but will last a lifetime,
so look around for a good second hand example. Then secure a few good,
strong decent planks, such as scaffolding planks onto cemented concrete
blocks for a bench. The bench should be big enough to hold a standard
car engine. When mounting an engineers vice, make sure the inner jaw
is just forward of the front of the bench, so it will hold a long bar
vertically without obstructing the bench.
Details of workshop design and practice are in the companion text 'A
Beginners Guide to Motorcycle Mechanics' in basic, intermediate and
advanced flavours. Available on my website.
You do not need loads of money, just time, unfailing motivation and
Basic materials check list.
Donor vehicle including documentation, receipts, engine, transmission,
wheels, brakes, wiring and electrics, ignition, cooling system, fuel
system / pump, speedo, air filter.
Front end steering and suspension - either decent forks, or parts to
make own front end.
Good selection of tubing for building the frame, from local supplier.
Steel sheeting for gussets and fillets.
Steering head, spindle and yokes, made to measure where applicable.
Alternate fuel tanks or steel sheet for fuel tanks.
Old fuel tanks for their fittings, either from bikes or cars.
Fuel tank mounting rubbers.
Selection of tubes and rubber hoses from scrapyards for radiator plumbing.
Tail, side and headlights.
Exhaust system and a selection of extra exhaust parts to modify.
Special radiators. Cooling fans. Fuel pump.
Shell building materials.
There is nothing exotic needed to build a good trike. The only really
important thing is knowledge. Knowledge is best learnt by doing it yourself.
If the first trike is not good enough, then the next will be a lot better.
Unless the engine is a poor choice, then the only thing lost is a few
lengths of inexpensive tubing plus the time and effort. You will have
gained, however, something far beyond price, - the knowledge and feedback
from the old machine, so the next machine will be much better.
A good artist always says his best work of art is the next one.
Cheap working donor cars are commonly available and can be easily replaced
by a better donor vehicle at a later stage. Trike building is not that
difficult and many people build for fun.
To make the trike legal, don't forget to check out Tony Alsops excellent
website. See details at end.
Trikes are often used by disabled bikers.
Typical disabilities are damaged legs or spines, caused through awful
bike accidents. This of course does not discourage a true biker, merely
changes the rules a little.
The main design problems arise from access and control. The main solution
of control is solved by three wheels. This just leaves the minor problems
of having no foot controls.
Access will depend upon the level of mobility and arm strength of the
rider. Access to a central position of a reasonably wide machine is
problematic, but possible with a few interesting ideas.
Getting the rider into position from a wheelchair is the worst case,
and involves making the transition as easy as possible.
For front engined trikes, then the wheel chair may be able to roll into
the back of the trike, but this will need a strong, well designed rear
end. The rider can then secure the wheelchair and slide forward to the
riding position, as a wheelchair, unless specifically designed, is not
ideal for riding a trike.
For rear mounted engines, start by making the trike seat the same height
as the wheelchair seat, then with the removable wheelchair sides, the
trike must be designed to allow the wheelchair to be sidled up and allow
the rider to slide easily across with minimum hassle and effort. The
problem with this of course, is getting one leg on the other side of
As the rider will slide onto the side of the trike, it may be possible
to lean back into the wide seat, probably capable of three people side
by side, and thus give plenty of room for access if the leg can be lifted.
If the leg cannot be lifted, then the frame will have to be compromised
and this will demand a rear engined trike, with a lower set of main
frame rails or large box section tubing.
Transferring from a wheel chair has a major problem. The wheel chair
is left behind or preferably need to be carried. While the rider is
beside the wheelchair, it should be reasonably easy to fold up and fit
into a cradle. Such a cradle will not be stylish, but making it close
to the seat, will allow relatively easy entry and exit from the trike
without help. Where the traditional passenger foot well is positioned,
a cradle for the wheelchair is easily mounted. A simple clamp or bungee
retainer should also be employed.
If you have limited use of the legs, then it is possible to make the
seat such that it is mounted on a parallel linkage, similar to a luxor
lamp, allowing the seat to be raised from the riding position, then
swung sideways and hydraulically lowered down to the wheelchair position.
This is fairly easy engineering using simple hydraulics from a running
engine or a remote, electrically powered hydraulic pump.
If you can build a trike you can easily build a wheelchair whose seat
is also the trike seat, to minimise the hassle of using a trike. email
me at firstname.lastname@example.org for details.
Once the rider is in position, remaining there may be a problem, especially
if thigh strength is minimal, so sliding sideways during cornering will
require a seat not dissimilar to a car bucket seat, with its side supports.
For easier access purposes, these can be lifted or folded up from below
or slotted in by hand, to ensure easy access.
If wanting a comfy seat, but not the style of a car, but needing spinal
support, then get a car seat and cut the frame down to be narrower at
the top. This is simple cut and weld, so that you can retain the adjustment
of the squab (backrest), which may make a trike usable for many hundreds
of high speed miles, especially if disabled.
If very disabled, then the seat can be placed on a locking pivot, so
that access is far easier, and you can retain and also adapt the electric
adjustments of a second hand car seat, allowing you to power yourself
into position and perhaps even allow the seat to power sideways to slide
close to a wheelchair.- The technology is there for pennies, so don't
be afraid to use it.
A well designed trike with one of a vast number of car engines, can
have a very low frontal frame and this is ideal for riding a wheelchair
very close to the riders seat for solo use, and still have room for
retaining the folded wheelchair and a couple of passengers.
Once in position, the controls will need to be adaptable.
An automatic transmission is worth its weight in gold. Manual transmission
using a foot clutch will not be so easy for a car, and if a manual transmission
is preferred, then consider a bike engine, as a car clutch is extremely
heavy. If using a car engine, but the clutch is too heavy, then strip
the clutch and remove a few evenly spaced spring fingers. As the trike
may not be pulling so much weight, this is a reasonable, if not guaranteed
bodge to lighten the clutch pressure.
Both brake and the clutch can be adapted to the vacuum servo of petrol
engines, so only the gearchange and throttle need be made smooth and
Motorcycle gears can be controlled in the same way as some Italian scooters,
using the twist grip control, but this is not very nice, nor recommended.
The latest fingertip gearchange controls of semi automatic cars is a
Car gearchanges involve a selection of moves, so the clutch if used
will need to be mounted as part of the gear lever, allowing one hand
to pull in the clutch and also change gears. A simple design for push
and pull of sequential gears as used for motorcycle engines which also
applies the clutch, is available from the author.
When pulling in the clutch on a hill, the handbrake may need to be used
and therefore this should be on the other hand, but the throttle cannot
then be used, to pull away. Therefore the handbrake cannot be used,
but the front brake is a good alternative and must be designed to be
easily used with the throttle. The handbrake can still be used on the
level or downhill.
The brakes will also need to be controlled by hand. Unfortunately a
hand cannot always apply enough pressure to stop a trike. Worse still,
a handbrake will need to apply the force to both front discs and also
the rear brakes. Therefore a servo system will be needed.
A servo assisted brake takes the vacuum from the inlet manifold then
uses it to amplify the force of the brake pedal. For hand operation,
the front brake lever can be used to apply the same braking system as
a car uses. Because the brake is operated from a single control, then
the front brake should be operated from a cable to push in the servo
the same as a car brake. Because the servo can be fitted anywhere, it
is best fitted for a reliable brake cable. In a big bike, then the servo
and brake can be mounted near the steering head, possibly under the
steering head. In a smaller trike then it will have to fit wherever
possible. The servo can then supply brake pressure to dual circuits.
As one hydraulic circuit may fail, then one rear brake and one front
disc is common on one circuit and the same for the other, so that redundancy
is available for safer braking. The handbrake is the emergency backup.
Using a disc brake on the prop shaft between engine and differential,
can offer a very sensitive hand brake, as it applies three times the
effort of a similar item on a road wheel axle.
If a handbrake is to be used on the prop shaft, locking this in place
can be done using a cam and lever on the hand lever, as on many quad
bikes, or with a releasable ratchet or many other devices. Ergonomics
for disabled people are important to allow the best control and force.
The handbrake is often a lever which allows lots of force though a large
arc. Alternatively, the handbrake can be similar to older cars, with
a hand control pulling out of the dashboard area to operate via a cable.
Power steering may also be possible, but as a rear engined trike is
rather easy on steering forces, then power assisted steering is often
not needed and just a light steering damper may be needed for higher
speeds. If power steering is needed, then the donor car engine should
also have the power steering pump and this is used to control the steering
via a carefully modified control valve attached to the fork yoke.
Disabled people may have serious problems looking after legs which
may not be under direct muscle and nerve control. Therefore some means
of securing the legs in position but not to the extent that the rider
is dangerously retained in an accident. Simple shallow foot wells just
deep enough to retain the boots from sliding around is often all that's
needed unless expecting to travel over bumpy ground. Should the foot
come out of the intended position, it must never be allowed to rub against
an exhaust or other dangerous feature of the trike, but have subtle
guides to ensure the leg return to the desired position.
The legs must not be allowed to become cold, so some form of heating
or shielding from wind is often needed. Such considerations will always
make each trike design specific to the owner.
In an ideal world, the rider should be able to reach the trike in the
wheelchair, slide into position with little hassle, lift the wheelchair
into a stowage slot, to remain secure in the trike. Then the trike controls
should be easy and natural to use.
If an electric wheelchair is used, then perhaps the steering forces
on the trike will be too difficult for the user. With automatic transmission,
Citroen type braking system and power steering, then very little effort
will be needed to control a trike, but manufacture will be complex.
Feel free to email me at email@example.com for details.
By now you will have thought of many ways to improve the trike, but
by now it's too late. Don't worry, as all great designers, craftsmen
and artists have this problem.
The secret is to continue thinking until ready for a better machine.
If the basic frame is good, a simple winter rebuild may ensue. If not
at all happy, sell the beast to finance the next, better machine.
If the legal paperwork was not fun, (Excessive Brit and Euro crap!)
and you decide to stick with this machine, then go back to start, and
enjoy the amazing power of hindsight and experience, then be prepared
to change everything except the frame number. Normally most of the machine
will be retained, with just the front end, the subframe and shell modified
You may eventually enjoy building so much that a new frame is already
in the pipeline, and possibly a better engine.
'Yes, I've had this broom for twenty years,
and it has only had three handles and five heads.'
Do not build your first trike with a Porsche or a V12. Always start
with a decent, honest donor machine, which will create a good, reliable
trike. Everyone needs an apprenticeship. If this works well, then you
can move up to the big boys toys, or loony machines, depending upon
one's point of view, and sell the first trike to pay for the ultimate
Keeping weight down needs using special tubing, a good grasp of structures
such as bending moments and shear loads plus special welding or brazing
techniques. These are all in standard text books for those who wish.
Some people think that life is too short for total engineering perfection,
as understood by white coated engineers. Always choose a suitable balance
between mechanical perfection and a life.
Designer shades will not prevent flies getting stuck in the teeth from
a big grin. Expect local kids to keep asking for rides. A strong waterproof
cover will help keep sticky little fingers at bay when parked outside.
Start sewing up a ground sheet or tarpaulin to make a neat fit.
Do not build anything which would bring trikes into disrepute.
Whatever design is created, make trikes something Mr average would
like, but would not dare to try and justify. - power with intimidating
yet refined aggression, overwhelming style and an outrageous art form.
Blend well for best results.
Copying others is no way to radically improve trike design.
By making full size drawings from scratch, the design of the machine
should evolve naturally with guidance and feedback from testing. The
few drawings in this monograph will hopefully not confine the overall
shape or form, as innovation should be the motivation.
It is the designers own drawings which can only mark out the path to
follow. This monograph is merely a guide. By now the reader has probably
generated many ideas and drawings, with more yet ideas to follow to
create a path into the future.
"The only place you never know is the future,
so that's the place you need to go if you want to make a statement."
John Partridge. B.Ed. B.Sc. Gizzajob.
Copyright (c) J.Partridge. 2000. 2005. 2006.
I'm an indentured engine fitter, licensed engineer and designer by trade
and enjoy designing and building trikes, have a teaching degree in technology
and a science degree in design, innovation and physics. I have worked
as a motorcycle mechanic, engineer and draughtsman. I build radical
customs for myself, help build more prosaic machines and help out in
some motorcycle shops for free.
I prefer to help local people in thier own garages, as I have little
room left in mine.
To assist those who want a trike, but not very good at engineering,
I've designed a series of clean, neat and lightweight, optimised design
of independent rear suspension trike rear ends compete with differential
and easily adjustable chain, ready for bolting straight into a standard
motorcycle frame using the swing arm pivot and the upper shock mounts.
The easy fit design does not damage any of the standard motorcycle parts
and can be fitted in four hours with the tools included. I presently
price them at 2,000 pounds, made to measure.
If you want to lower the back of your bike frame, then I build a trike
conversion with bare tubing for welding to your standard machine, complete
with easy follow, comprehensive instructions, although you will need
a welder, or tack weld it and hand it over to a competent welder.
All designs include a manual for maintenance and repair, are fitted
with linked dual rear brakes with hydraulics and a small choice of standard
car alloy wheels. Includes brackets for fitting various seat options
should you wish to modify or add items later.
For chain drive machines, the transmission components use lightly modified
Ford Escort Mk 4 differential, with a standard motorcycle sprocket to
match the gearing of your bike. Spares available within 48 hrs. Available
in standard or narrow versions for most bikes from 125cc to 1200cc.
Email your bike and rider needs. - Whether you want sport or a touring
version, each can be optimised for rider weight so the suspension can
be to your needs. firstname.lastname@example.org If you want the bike lowered
at the rear, have dual rear seats, luggage units, extra fuel or other
design considerations, then just ask, as this does not cost much extra.
Custom trike frames for car and bike engines can be designed and built
on request. I charge 300 pounds a week for my design and manufacturing
skills. A customised trike rear end takes about three days to research
and design and about two weeks to manufacture and fit. Material costs
are about 300 pounds for the diff, tubing, standard brakes and two alloy
wheels. Prices start from about 2,000 pounds per conversion. Shaft drive
machines are slightly cheaper.
Full trikes with engines can be designed and built from scratch from
Email me at email@example.com with details of your machine and needs,
for a free quote.
Please supply the following details.
Preferred bike / car and engine size or your donor machine.
If you don't specify a bike or engine, I can recommend a selection of
donor vehicles, so please state your working budget for a complete machine
and if any engine preferences, eg, Suzuki, Harley, Dnepier, Honda, Ford,
Skoda, 2CV, Ferrari or others. - ALL is possible.
Type of riding, general use, shopping, touring, thrashing, custom shows
Seating needs, tandem, R+2, R+3, or three side by side etc,
Special needs, such as lack of legs or weak arms.
Overall dimensions e.g. your garage or parking area.
If you want to start building trikes commercially, you don't have to
be a good engineer, but if willing to learn and prepared to work part
time to develop a mutually beneficial business.
If there is anyone in the Plymouth England area (or anywhere in the
world) who wants to build trikes for profit and has simple garage space
with electricity and light, then please, please email. I
've developed four generic trike designs including Suzuki Bandit, Gold
Wing, Escort Mk4, and Subaru donor vehicle designs should there be someone
who wants to start sensible custom trike manufacture. These can lead
to a very profitable business with zero start up funding, to custom
build the very highest quality design and built trikes and trike kits
for sale to a world desperate for some decent trikes of all styles and
with all sorts of engines.
Example, a generic 1400/1600 cc car-engine, three seat trike with independent
rear suspension and alloy wheels, and a standard bike front end with
dual disks can be built in Plymouth, SVA approved, ready for the customer
to drive away for about 800 pounds ! (excluding labour) This can be
sold at a sensible market price for a really well designed and nicely
built trike from about 3,000 pounds, with 24hr back up support and a
decent owners manual, a workshop manual and parts list. This gives a
profit of over 2,000 pounds to cover skills and labour costs and can
be done every month, as a decent custom trike can be built in just over
three weeks. If many similar trikes are needed, then the times are almost
halved. Complete DIY trike kits needing just a standard donor vehicle,
can be built in six days, with cables, seats, fuel tank, step by step
builders manual and wiring loom can be built from 300 pounds and sold
from 1200 pounds to cover labour. To this can be added extra profits
for turbo versions, fancy paint and special ergonomics, although I never
charge for any wheelchair mods.
The world needs superior handling trikes at reasonable cost for discerning
trikers. I'm happy to help develop such a trike shop, with just three
trike designs at first. Then build up to the worlds premier trike shop,
but need someone with the space and funding. Eventually I would like
to be able to sell really good range of trikes from 600cc to 2 litres,
at sensible prices and also a few Porsche V8 and Jag V12 trikes to keep
the profits healthier.
If you need help in building your one-off trike, or considering production,
please email. I'm sure there's a market for good trikes. If you have
some garage space with electricity and a little elbow room, then I can
make a trike within three weeks for a few hundred pounds.
If in India, then I can design the components and jigs to build the
shells and frames in India. The fully working trikes and home build
trike kits are assembled in the USA and UK to get around vehicle import
bureaucracy. Start off with a generic Ford transverse engine, common
to the USA and Europe, to allow a range of engines from 1,000cc up to
2,000cc, in various specifications.
John Partridge. B.Ed. B.Sc.
When developing machines, few will have the funds to develop finely
finished machines, nor should it be needed to build superb machines.
Brains is always more important than money. Discovering acceptable methods
of building should be considered part of the innovation process.
The poor have most to gain, needing to understand problems first hand.
Compare the history of innovation of 'professionals' with those of 'amateurs',
to understand the social implications. Throughout history, the best
experts are often amateurs, as well documented in many excellent articles
on the subject.
In the modern world, most high tech items are discarded despite being
perfectly serviceable, due to the decreasing ability to educate hands
on engineers, where ability to pass exams erodes the ability to do real
work. The official engineer is evolving into a creature who plugs in
the diagnostics box and replacing the component. This often seems efficient
on paper, but has one advantage, as it gives the resourceful innovator
an excellent source of componentry if the discard point is targeted.
Always aim to be a much better engineer than this.
The world is awash with excellent surplus equipment. Always become friendly
with the suitable sources and local recycling centres and carry suitable
cash or negotiable goods. When strolling though industrial units, a
lightly worn disposable boiler suit makes the scavenger invisible. (See
Father Brown book, Postman.) Always carry a large foldable bag, big
enough for a small welder. Carry a rechargeable screwdriver with the
usual tools to reduce loitering.
Scavenging makes a vastly better engineer and improves confidence, realising
just how easy many expensive components are to repair. The most expensive
tool of all, a wind tunnel and its test gear, can also be surprisingly
affordable. See companion monographs.
Real engineering is a craftsman doing for pennies, what any commercial
company usually does for a fortune. Never be put off by the 'sophisticated'
talk and equipment of 'experts'. Know the data to gather, and how to
assess it. It's not black magic.
A classic example was an expensive piece of modern hardware in the trash
of the engineering department of an esteemed university. It needed less
than five minutes work to get working perfectly and has been used by
the author for many years. Thank you taxpayer. (The author did not get
an interview for the universities vacancy for a part time lab technician,
so a sense of humour helps in modern Britain.)
Never be too proud to stick your nose in the back of factories, offices
and other likely places. Be polite and always ready to lend a hand.
With time, you will build up a surprising array of useful resources.
Lateral thinking is a powerful tool. By not having many drawings in
this monograph, the mind will hopefully have improved, in a natural,
unforced manner. It is the ability to build a mental library of seemingly
unconnected knowledge which will eventually express itself with flourish
onto paper from the start, and throughout the subsequent evolution of
The ideas touched on in the text are deemed suitable for beginners,
but are just the tip of the programme. The basis of the publications
was written as research notes between 1990 and 2000 to ensure the final
study of the twenty year single track vehicle programme will be comprehensive.
The intermediate availability of this information was condensed and
offered to help fund research. Trikes are not part of the core programme,
as the main work hopes to develop the various future, truly radical
machines and advanced systems needed to integrate man and machine.
As mentioned earlier, learning does not mean following others like
a sheep. This monograph is not the answer to all, as no text can offer
a personal path to perfection, so always glean what is useful, then
move forward. For safety reasons, always improve skills as seen fit
though careful, well paced steps. The rest of the process usually follows
naturally. There will be upsets along the way, but careful thought should
ameliorate most and make the process a rewarding one. Enthusiasm will
wane occasionally, but is quite normal. It is the open minded approach
to making a dream machine that is important.
Keeping eyes and mind open will allow the designer to glean all possible
advantages towards the ideal machine, and occasionally a totally radical
design may be created for a great leap, hopefully forwards.
Present projects (2001) include JP8a single seat KTM powered recumbent,
aimed to be an ultra-light slalom development machine to refine the
most important area of research, first developed and ridden on the JP4
and JP5. This requires much higher funding, hence these monographs.
JP9 will be a more advanced JP7. JP10a/b will hopefully be the two definitive
forms of the JP-FCM which the programme is working towards.
The bigger picture.
Look around you, it was innovators like Babbage and Ada Lovelace, Tomy
Flowers and Alan Turin for the computer. Edison with sound and light.
From the cup holding your coffee, to the glass window, seat covers,
paper, pen, they all needed ordinary people with a dream of inspiration,
who created just about everything you now use.
Too few people innovate and build customs, their effects on the environment
is minimal, while their effects on human nature is liberating.
Things won't get better unless those who can advance research and design
have the chance to do so.
If we all blindly follow the 'experts', then, heaven forbid, we may
even end up in a world where all cars begin to look alike, and the only
options will be the exciting variations of cup holders or other such
facile crap. If (when) this happens we will know we are dumbed down
ready to become consumer sheep, fit only to graze in malls. No one has
a monopoly on true, radical innovation. History is littered with all
types of innovators in philosophy, sociology, religion, economics, science,
and of course, applied technology.
There is no point writing monographs like this if they cannot be used.
Always use your vote, even if only to keep politicians and bureaucrats
from making our lives constrained and boring against our will. Always
vote for home built machines, not the Euro crap 'type approval'. Human
nature must always ensure its creativity from a world dominated by (m)asses
of corporate 'logo based life forms' and parasitic lawyers. Never vote
for anyone who wants 'type approval', excessive paperwork or restrictions
of custom machines for road use.
SAY NO TO A POLICE STATE
SAY NO TO ID CARDS.
The price of freedom is eternal vigilance.
Cherish your aspirations and abilities, and always protect them.
Begging is the bottom line of this work.
Vast numbers of excellent designers and engineers are laid off from
the declining British manufacturing industry who then study at university
level and beyond, leaving with a piece of paper and a massive debt.
The author has managed two full degrees without debt, no mean feat,
and presently trying for a post grad, but no capable universities in
Britain. In the authors case, the Open University (God bless it) was
the nearest equivalent.
Most of the vast numbers of 'begging bowl innovators' have ideas, so
please help. British venture capital is unfortunately an oxymoron, a
joke comparable with our railways and education system.
Working on a begging level is an eye opener, requiring innovation to
make things happen. Each JP research machine needs funding just to build.
The two JP7 chassis cost almost too much. Each carefully considered
machine has to develop many innovative ideas.
Funding is fundamental to a research programme, hence this monograph.
So please order a copy, or offer a donation. Send what you think it's
worth, as this also gives feedback. All profits directly support research
and honest donations welcome.
If you are embarrassingly rich, please be so kind as to sponsor the
research. Just three thousand pounds a year will eliminate delay, allowing
the final forms to be developed quicker, and thus be more refined and
subtle. Ten thousand pounds a year donations or simply materials supply
underwriting will allow headlong path to a truly innovative form of
two wheel transport. For those wishing the author to design and build
a dream machine, a technology demonstrator or even a two wheeled exhibition
piece, or something from the above text, any design can be considered.
Full sponsorship will receive an exclusive JP10/FCM.
If nothing happens and the Longbow or JP7 have no public support, they
will be allowed to die by simple Darwinian processes.
Being just one of the many long term unemployed English science graduates
with a strong engineering background in nuclear, marine and other spheres,
the author would like a job. A job teaching motorcycle engineering or
creating composite machines would be most tempting.
Please consider this monograph a rather blatant CV.
Thanks and best wishes,
John. Partridge. B.Ed..B.Sc. etc.
The excellent guide to trike law in the UK by Tony Alsop at www.zyworld.com/tonyalsop/trikepage4.htm
Motorcycle Engineering. By Phil Irving. ISBN. 0-85113-075-5
Build your own sports car. By Ron Champion. ISBN1-85960-636-9. Nice
one Ron !
Tony Faoles website. at http://www.ctv.es/USERS/softtech/motos/
Converter prog. via http://www.joshmadison.com/software.
These are the suppliers the author uses.
McArthur Group Limited. Plymouth. All the metal you could possibly need,
at excellent prices.
Examples: Rectangular tubing, 20mm x 20mm x 1.6mm, to 150mm x 100mm
x 10mm. Solid strip. 12 x3 to 400 x 25. Sheet. 2m x 1m x 3mm, to 4m
x 2m x25mm.
Woolies. Whitley Way, Northfields Industrial Estate. Market Deeping.
Peterborough. England. PE6 8LD. All the fittings for the traditional
design. Rubber window strip, carpets, headlining, fittings for vintage
and classic motor trim and a host more.
Vehicle Wiring Products. Buxton court, Manners Industrial Estate, Ilkeston
Derbyshire DE7 8EF. Excellent catalogue available. Tools wiring, accessories
If interested further: Companion monographs by the author.
A Builders Guide to Motorcycle Design.
A Builders Guide to Composite HPV Cycle Design.
A Builders Guide to Trike Design.
A Builders Guide to Composite Motorcycle Design.
A Builders Guide to Motorcycle and Trike Wiring.
A Builders Guide to Campervan Design.
A Builders Guide to Basic Wind Tunnel Design.
A Beginners Guide to Motorcycle Mechanics Basics.
A Beginners Guide to Motorcycle Mechanics Intermediate.
A Beginners Guide to Motorcycle Mechanics Advanced.
Stonehenge and spanners.
Simple alternative electronic ignition. No spark in your MX, trials
or moped ?
Make your own glasses. (spectacles.) 150 quid glasses rip-off? You deserve
A Beginners Guide to Building a Computer. Build your own computer, system
Domestic repair and maintenance.
Save money on plumbing, electrics, cars.
How to walk. A beginners guide to the outdoors, from strolling to evasion.
A Builders Guide to Survival Knife Design.
A Builders Guide to Survival Kit Design.
For those interested, other books which could be published include:
A lateral look at innovation. From Polynesian monkey traps to BV141.
An approach to preventing design stagnation in small businesses. Early
Ergonomics and control possibilities for single track vehicles. Early
Building the Future: Development possibilities for single track vehicles.
Stagnation of innovation and the development of the car cup holder.
If you found this monograph useful and build a machine, please feel
free to Email. Any requests for a dedicated trike web page or site?,
complete with drawings and assembly details. Perhaps the public may
be interested in a set of trike chassis kits, with fitted gearchange,
fuel tank, steering head and such like. Ready for a variety of donor
vehicles and standard bike forks and yokes.
Any other donor vehicles out there that are popular? I'm thinking of
three sensible choices.
1. A cheap and cheerful rolling chassis kit for about 2000 quid, using
any choice of up to 1600c transverse engine, with unpainted chassis,
a set of good second hand Japanese front forks and front wheel with
dual discs, full electrics, seats covered in vinyl, but needs paint
1a. SVA approved, styled shell and/or ready to run optional for about
2. The other option is a ready to run, serious but sensible trike, a
Subaru engine (with PTO) or Alfa Sud engine, low stonking chassis made
to measure, special front end using a car rim and antidive suspension
and low, comfy seats for three across behind the driver, plus a boot
(trunk) plus paint and finishes to customer spec, plus whatever else
is needed. Rear end styled in choice of fibreglass Lamborghini or formula
one styles (upward dummy stub exhausts optional). Probable cost about
six thousand quid on the road, ready to run, or four thousand quid for
the rolling chassis with engine seats and wiring. Wheelchair aids and
other options included.
3. A simple daily trike, using a 600cc 2CV engine, lightweight chassis,
with rider plus two or three comfy passengers and a boot (trunk) for
All would use generic, easily replaced components for longevity, with
minimal specialist items other than chassis, suspension and gearchange,
wiring and shell.
You don't have to be called racist to love your country.
Website at: www.btinternet.com/~jhpart/index.htm
Always try to improve society rather than just take from it. Until
then, lawyer stuff. Copying or duplication of this material is prohibited
without written permission of the author. The content is for information
only. No responsibility is accepted for any damage or any injury caused
by the above information. Errors and omissions excepted. No-one should
try building machines without reasonable abilities and know that injuries
can ensue from the materials, tools and from test riding of machines.
Have a nice (lawyer free) day.
Copyright (C) J.Partridge. 1999. 2003. 2005.