TRIKES.

Under New Labour, everyone should just pay taxes and do nothing politically incorrect, so do not act upon this information. I have no wish to be closed down like other useful websites from threats by parasitic lawyers. The dogs of law lie around every corner. As lawyers get richer, society gets poorer.

Men are from Mars, Women from Venus and Politicians from Uranus.

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. I'm here to help.
Lots of other 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 consider this monograph a bit of a C.V.

Feel free to email me at jhpart@btinternet.com

This monograph is a bit long. Don't try reading it all in one go, (I wouldn't.)
I'd recommend a skim through, then properly read each section when you need it.

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, I'm a licensed engineer and have a science degree, just ask !

This monograph does not get to building a trike until about half way through, which is far different to the design processes of most trikes I have seen, and it shows.

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 ask for free advice.

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 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.

I have many emails from those who have built trikes and can't get them to handle, often from simple failures of design. Not everyone gets to find this website before venturing into trike building, and although I commend their wish to trike, the pitfalls are still there. Therefore there is an appendix called Redesign, so for those who suffer this part of trike building. One poor chap spent eight thousand pounds on his trike and could not get it to handle, and is now doing a compete rebuild. This is mainly for those like him, I hope it may help many others too.

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 bad designs.
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 hope this helps make a mechanic into an engineer, and then a designer.

A mechanic is a person who repairs by replacement. but never bothers to find out why it fails. (Usually a GNVQ monkey).
A fitter is a skilled mechanic who can repair by repairing the worn or damaged items, and thus find out why it fails and if possible, eliminate the original fault. (Usually a time served apprentice under the tutelage of a skilled old bloke who has seen it all before.)
An engineer knows the underlying design of a piece of engineering, and the theory behind it, but may not have the skills to make or repair the item, so has to get a skilled person to do the job. (Often a college trained manager or freemason.)
A designer not only understands the underlying theory, but has the skill to design structures and machines from scratch, then understand why they fail and redesign further. A bad designer will need a PR manager or MP to cover up the crap. A good designer will be venerated - Brunel, Mitchell, Issigonis, Dyson. (Ships and rail, Spitfire, Mini, Dyson.)

I realise that most who build trikes are not engineers nor perfectionists, but usually know that a better trike is possible, hence this monograph. So I've written the following 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 that is usually the main reason why so many potentially good trike concepts remain less than perfect.

Designing a trike is not just a case of building the nearest idea that will work. Anyone can design a simple machine, and many trikes look like they are thrown together rather then designed. Take your time to think first, only then can you build the best.
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.

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 could, and should be far more exciting.

To make life more interesting and highlight what this can involve, the following is based on a a good 'ole car engined trike approach with the whole frame designed from scratch, with bike framed trikes also considered where appropriate.
The following describes a path through the design stage, the building jungle and traps, to properly testing and fettling 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.

I hate spending money because I don't have any. Only the foolish or rich can waste money. Great art is not expensive to create.
A budget trike can also be a work of art without compromise. It can be easily based on a fairly sensible (and surprisingly cheap or free) 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 (20 quid) and a good second hand engineers vice (40 quid) mounted on a strong workbench make for a much easier life and are always worth the cost. (Some concrete blocks and two halves of a scaffold pank make a perfect workbench.)
The only real costs are having the steering head, spindle and slab yokes made professionally, although even these can be circumvented as described later.
Both the donor vehicle and stock metal tubing are surprisingly cheap.
I can build almost ANY trike for about three hundred quid using a scrapped donor car. So can you.
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.

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 design progresses.
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 knife blade.

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.

Typical problems. An Example.

I receive many requests from emaily interwebby-land. Here is a typical example.

A Yamaha 1100 V twin modified into a trike and a perfectly acceptable choice. The owner had many problems with it and emailed me as the mechanic he hired seemed less than happy to solve them. I suspect this builder had no pipe bender, and although not vital, it does help produce a nicer machine.
There are superb welds, but also some classic trike design 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 mechanic knows the need for accuracy, but has not taken time to design the trike on paper, and thence refine the design for greater strength, less weight and less hassle.
The Yamaha 1100 front end was standard right back to the swing arm. This shows a lack of courage to modify parts, especially the prop shaft and the wheel drive shafts.
Because it was a shaft drive, a ford rear end was used and there is nothing wrong with this, although I'd use something a little less heavy. Both engine and trans are very reasonable starting choices. What was wrong was the serious lack of forethought. 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.
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. 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 made with a stepped machined face, so are fairly easy to fit. Because the modified prop shaft is much shorter, balancing it is also easier.
The angle of the prop shaft to the differential will need it to be offset, and this not a problem, as the motorcycle pros shaft is designed to work at angles causes by a moving swing arm.
Like many, the rear end is far too wide and so shortening the left drive shaft will have two advantages: It allow a less wide trike, and also allow the differential to line up with the bike shaft would be much neater, and the overall width would be decided by the right hand drive shaft length, the other being shortened, Both left and right side wish bones wold be matched to the shortened left hand side.
I believe the prop shaft length and inability to solve it from the outset, has led to most of the heavy front end problems. This in turn causes poor handling.
(Perhaps the mechanic was not a designer or fitter. A designer would see the need for a shorter prop shaft. A fitter can cut and shorten the prop shaft, then balance and thereby redesign a better trike. Anyone can see that the engine on the far front would need a short rear end to improve overall balance. Anyone can learn to use a hacksaw, file, set square and welder to shorten the prop shaft.)
With a short prop shaft between engine and differential, (and another shortened prop shaft on the left drive side,) 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 and would be far closer to a good trike.

But there is much more to be done before I could live with this trike chassis. The radius arms are appalling, the shock mounts are poor, it's far too heavy and has no style or shape. None of this costs money to resolve.

Secondary solutions.
Staying with this example, the width at the rear was atrocious. I believe that lithe trikes are better.
Therefore I would also 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. This would also align the diff to line up with the bike shaft output. I would also check if there were any mass dampers on the original wheel drive shafts. 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 could be triangular, . more akin to Formula One, etc, a little narrower and designed to match the left side, 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 impeccably balanced.
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 as shown in my sketch.
The trike example will need to change them from a rectangle in top view, to an upper and lower pair of triangles. I would have made the lower triangular wishbone extended forward, with the extended front tube pivoted in simple rubber block to take the acceleration and braking loads, thus making the upper wishbone lighter and leaner for easier passenger room. The bottom wishbone does most of the work as it has the suspension unit mounted on it, so it takes most of the load. Therefore the upper wishbone can be smaller and used mainly to maintain geometric accuracy when the wheel moves up and down.
In the example, 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 shocks in this example are poorly placed and offset. The vertical shocks, just under the arrow are not the happiest of items.
As an extra to the design, and to reduce unsprung mass and improve style, 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 spoke or three spoke alloy wheels with a very light, clean and open look.

My sketch is for a car engine, whereas the trike example with the Yam 1100 bike engine will need a shorter rear sub frame, unless the forks are greatly extended to ensure the front wheel does not take too much of the load. Never put more then half the trike load on the front wheel, preferably less.

If needing a low profile for perhaps a top rack or seats, then two lighter shocks on each side (4 in total if carrying many burly bikers) is preferable to maintain balance, although it would look much nicer to take the opportunity to use Formula one technology and fit compression struts from the bottom wishbones to shocks mounted horizontally above the differential. This would also allow the shocks to be adjusted in leverage to match the final 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.)

Simple rebuild option:
First, shorten the left drive prop shaft to bring the differential more in line with the bike shaft, then move the differential forwards to take the load off the front wheel. Then cut the frame tubes beside adjacent the bike frame and move the whole forward to an optimum front prop shaft length and alignment. The width of the bike frame will allow a slightly offset differential.
Mount the differential offset as needed, then build the long side wishbone first, then make a symmetrical copy for the other side using a cut down drive shaft for a narrower trike. The shaft is cut shorter near the inside splines, then welded, sleeved and welded futhur.
Then position the bottom of the shocks close to the prop shafts to minimise distortion, then decide the shock loading, and mount the tops of the shocks accordingly, while allowing reasonably 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 bending force would be reduced with a shorter frame, but must be checked nevertheless. This should be checked under a load of sandbags or a bathtub of water, and see if the rear engine bolts are too tight to remove, indicating a distorted frame which could crack the engine casings. 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.

Nice ankles:
Here is a nice example of a trike rear end I just happened to find parked at my local shop.
The axles originally had 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 nice 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.

Apart from the whole assembly being closer to the engine as mentioned, the bottom wishbones could be better if pivoted from more forwards of the frame to assist acceleration and braking forces more safely into the frame, with rubber ftont wishbone bushes from a small car or from a 250cc bike swing arm.
The rear shocks are very neat, strongly supported and may be close to the original Yamaha shock angles. Frame triangulation could 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 to flexing. Adding an anti roll bar would be simple, with just a couple of U brackets under the frame 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.
The other photos shows how the lower car shock mount has been neatly employed for the wishbone pivot mount.

I would implore all trike builders to contemplate a few similarly neat arrangements.
Consider the simple 3D graphic, which shows what is possible with sketching before turning to metal.
This is not complex and is just plain old standard arrangement found in many trikes and kit cars. - Just look and learn.
The bits are out there for pennies, beautifully made - so use them.

Other notes.
Like all trikes, the example 1100 Yam car rear end uses discs, so parking brake may also 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, then mounting a simple mechanical or hydraulic brake calliper onto this, restrained by a bracket on the frame such that any excessive braking forces 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 drum brakes have twin leading shoes and only work well in one direction.

In such cases, the owner often say 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. This is why I leave the front end until last on complete frame builds, so my machines are supremely accurate.
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, a classic complaint. 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, trying a little toe-in to see how it feels, (rear wheels pointing just slightly inwards at the front, so the outside wheel takes most of the load and helps turn the machine in the desired direction). 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, to make it as good as any trike.
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.

Some trikers minds are seriously warped - trust me on this. But luckily, most trikers minds are about right, close to, but not too far from the real world. This is the best place to be.

From the outset it is necessary to get the handling right.

Handling 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 of course, the overall set-up.

Basic chassis design will always be dependant upon the engine, causing the design to require certain engine mounts and the way the transmission and wheels are 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 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 any wheel break-away 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 about imbalanced wheel sizes and loads and footprints, then just consider how much weight is on each wheel 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 balance or brakes modified to ensure the braking is done sensibly and safely.

If is for such reasons that some car engines cab benefit trikes, so they can give more optimised weight balance over the rear wheels.
(Car engines are also free and very cheap to maintain. the cost saved on a bike engine can pay for the whole build of a decent trike. Yes, I highly recommend you build your perfect trike for mere pennies - I do.)

As the fundemantal 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 your overall design 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.

You do NOT have to thrash someone else's trike to discover how well it handles.
I simply park up and have a few minutes looking at the trike firstand guess where any faults may lie. The ride and build up the braking speeds and cornering to discover where any faults are, then again decide where the problems(s) lie, and re-test using body lean to see if this improves feedback. Gradually build up the speeds around your favourite twisty roads. I then park up and have a few minutes looking at the trike again.
Get to know the break away signs and refine the riding reactions necessary to control them. See testing later. Unless the trike balance is good, then take care and consider the weight distribution carefully.

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 and can ride the pants off sports cars. (Thanks Spike !)

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 always possible on some trikes, but a mid mounted engine greatly helps.

So : 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 the following chassis design also applies.

The bottom line is that using car engines is the best way for maximum stonk for minimum pennies.
Car engines are 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 in detail 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.
Modern electronically controlled metal tapered belt auto transmissions are excellent ways of beating most vehicles off the starting grid.
Only use fiery engines if they have an automatic transmission or have electronic 'paddle' gear changes. (Yes, you can fit paddles to handlebars.)

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 engine.

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 for choice.
Or perhaps one or two bike engines.
Perhaps a snowmobile or small aircraft engine.
Jets are mentioned later.

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 weight balance.

We now live in the age of political correctness gone mad. But I highly recommend you hunt out a few scrap yards.
Scrapyardin' used to be a traditional British hunting sport and I have the old oily, scarred dockers leather boots to prove it.
I was taught by an expert: Thanks Andy.
The only thing missing from scrapyarding as a British working man's sport was copper top boots, hunting pink jacket and a horn.
The usual rig was an old pair of boots, big pockets a pair of pliers, 'Stilsons' and a multi point screwdriver.
Oh - such happy days.
(Stilsons shown bottom in the 'how to fix a tap web page').

Today, due to the assholes of the burEUocracy, there are very 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 truly 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. I'm 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 every time.

If you find a suitable engine, then you will be either buying the manual, or taking lots of photos. As digital photography is pennies, then snap away. Don't forget the specs page and fitting sizes, and ignition diagrams. If you can take the book out for a week, then do so and photo or scan every page, so it does NOT get dirty when returned. If the pages are dirty in some places, then always take note of this and additionally scrutinise the donor vehicles in this specific area.
I don't dislike dirty or badly thumbed books, as they can tell much more than any pristine tome.

(Tip for college students. - Always go to the library as soon as possible before anyone else. Then check the racks for your subject. Then look for the most popular book, usually many copies, and check all of them. Hopefully one or more will be annotated in pencil in the margins and this is the area which you need to study well. Such an annotated book saves a lot of time and helps get higher marks. Always annotate books with light pencil marks in the margins. Never use highlighter pens. Learning from boringly written computer screens certainly makes the process sterile. )

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.

Free monkey.
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.
"Hi mate, need any help? - I can sort out that pile of plastic and alloy or whatever needs doing, in exchange for a half decent ending engine for a project I'm doing. No cash, just mutual benefit."
They may ask you to do a small test sort or clean, and then, if you are not completely incompetent, may ask you back in the morning for a couple of days work.
Make sure you turn up in tough clothes and boots, be honest with them. If no immediate work, leave your phone number and mark it 'free monkey in exchange for car engine', 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 apprenticeship.

Car engines offer a wide expanse of options.
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 well enough.

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 fun 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.

Engines: An example.
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). These 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 - and probably the T shirt if you suffer from excess of vanity or are a poser.
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 Ducatisthat'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, yet nicely overpowered trike design.

I am not advocating the fancy German crap as the only choice, far from it. But with car engines, for bang per buck, you can not only get excellent power, handling, but also get that feature missing all too often - charisma.
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 prefer to start with a bike engine and end up with an overpriced Harley motor and cute frame, but they all look the same from a distance. I now tend to yawn at (yet another) Harley custom.

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. Yes, you read correctly.
This is at the economy end of the engine world, but is a superb example of having an almost ideal trike engine if you don't have an overdeveloped ego or a fat belly.
The weight is forward of the rear axle and very low, with inboard brakes and the gear linkage on the top.
Such an ideal layout 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. They are simply indestructible and I consider them far more reliable than Porshes or Harleys.

For a large capacity compact and low engine, with fuel injection or carbs, then this is a water-cooled VW motor I recently played with and makes a very low profile option to most standard car engines.

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.

Whatever you choose, 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. See later.

These are just three of many very different yet good possibilities.

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 rather excellent if rather rusty Subarus in farms that I have lined up for future customs. - They just need me and a customer needing a trike, to make them very happy again.

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, complete with receipt and paperwork.

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 every 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 hunting.
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 your design.
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. Wait and ask the mechanics at lunch time, when they are not busy and never annoy. 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 break.

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 preferably privately buy a rough but legal donor vehicle for its identity.
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 radiator layouts.

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 again !

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 and truly wonderful classic car, but a totally irresponsible choice for any 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 specification when based on a typical donor car.

In these days of political correctness and recycling, many car dealers will buy an older make so as to sell a new car to the same owner. The y may well have old Volvo (other makes available), siting in the back of a dealership which were bought to sell the new car. They may even sell it to you for one pound ! It may even be road legal and you may even be able to drive it home. Try - they can only say no if you ask politely.

I've got my dream engine!

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.

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.

Tip from an old scrapyarder: 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, (he Viking heritage of real bikers) or the newer method of angle grinder and saw.
The petrol 8 inch angle grinder is now affordable for those who are not afraid to loose their arms and legs. I hate the things.
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 centre.

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. So start with open eyes.

Engines:

The transverse engine is 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 the rear.
The top of the 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.
Where 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.

Jet engines. 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 where the exhaust turbine and power take off turbine are near passengers. These are not toys.

Rotaries. A sensible alternative to a jet engine is a multiple rotor wankel. (Mazda)
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, if somewhat overly complex 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.

Sound. (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.

Looks. (Style.)
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 air days and spare parts are still easy to get. (I recently asked a Supermarine Spitfire owner if engine parts were hard to get - he said 'about 24 hours'.) 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 available and 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.
Some Alfas.
Citroen SM with dated V6 Maserati engine, be prepared to get lost in the plumbing. If you chose this, I will happily attend your meeting with Madame Guillotine.
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 the optional 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 lobotomy.
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 too.
Jaguar V12's. Sheer music, but how far will a tankful get you? (It still works 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) offers 200+HP.
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 day.
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 usually as supplied.
Mopeds only suitable for kiddies trikes.

Other engines.
Honda Gold wings and modern Rocket Three's 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.

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, nor will ever equate to dollars, - it depends upon skill.

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 - not for power, but just to be better). 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 balance, and how and where you are going to sit.

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 in chalk 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.
Use that chalk: The reader may not consider themself a designer, but this is a genuine hands on design process.

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 appropriate.
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 my preference to Lightwave. As the trike is basic engineering, the design can be seen primarily as an art form.
I always run a trike design though Lightwave before building, to see where further refinements can be made. An example is shown here, when asked about access for a disabled triker from wheelchair to riders seat.

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 which can be viewed from all angles.
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 routings.
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.

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 when building.
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.
Even if you failed hand painting in kindergarten, you can still use a pencil and paper: Do it.

If you get stuck, feel free to email your ideas to me - but no more than two small, compressed jpeg sketches - for a free assessment and a few hints. emails no bigger than 15kb.
I do not expect works of art, just a chance to see where the problems may be.

First get the engine and rear wheels suitably positioned, then position the forks or steering to get a sensible amount of weight over the front wheel.

The structural part of the frame is the most important and is designed first. This will decide how you will mount the engine, 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 mountings etc.

The following is what you need to understand your design more closely.

It is assumed the scrapyarding and early drawing stage will have helped decide the best engine and the other main components such as rear axle. It does not give hands on feeling for the overall effect, as paper and pencil is only a part of the game.

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. If other bits are still hanging off then tidy them so you can see the main parts. 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.
If you have forks, prop them on a chair or hung from the roof to be in the approximate position for good overall balance.

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 for a shortened prop shaft. Strip, inspect and decide just how short it can be. 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 car engines, there is often little to do. On trikes using front engined cars, 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 distribution.

Take your time laying out the bits.
Adjust, look, contemplate.
Then adjust, look, contemplate.
Then repeat many times.
Now 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 later.
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 bumps.
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 Porche or 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 for show trikes. The Porsche engine can be repositioned nicely much closer to the rear by minimising the high speed prop shaft between clutch and excellent design of 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, Then use an intermediate mounting plate between the back of the engine and the transmission bell housing. In some cases it may be necessary to machine the flywheel to take the correct starter ring or more easily by simple modifying of the starter motor mounting to fit the standard starter ring. The clutch plate for the transmission will sit happily between the engine clutch clamp plates. Some fore to aft alignment may be needed, but not very often, as the splines can take up much of this minor misalignment.

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. The ford splined clutch plate sits happily in the VW clutch housing.

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.

Another problem when looking at the bits laid out neatly in the garden, is the rear suspension, especially 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.
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 and as shown in the piccie. Today, the extremely common suspension mounting on front wheel drive transverse engines is the McPherson strut, 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.

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. Many car suspension parts are made from stamped steel and look awful, so cosmetic rebuilding is often important after final testing.

This is an interesting example of a VW trike.
I dislike the VW engine because it hangs out the back and causes poor handling, but the rest of this otherwise fine example is worth a look. The frame is minimalist and phenomenally sleek, possibly just two scaffold tubes used with excellent artistic flair. - It stands out from the crowd.

The front suspension is also a work of art, being one piece fork legs pivoting on parallel linkages with adjustable shock absorbers. Although the front end unsprung mass is fairly high, it is far better than most trike front ends. (I have not ridden this machine, but looking at the massive amount of trail, looks to be a tad heavy to steer at speed through twisty lanes and may well be designed thus to compensate for the VW rear end.)

Of a lesser note is the motorcycle riding position, which is rare on trikes, as it looses the opportunity to restrain the sideways body forces with a car seat.

Finally, the gear change is the standard VW unit, and it looks as if the designer had problems integrating the standard gear change into the design. Never allow any mechanical item to dictate the trike design, as nearly all items can be redesigned and modified to make a better machine. But with a little work, could have been extended forward a little to be closer to the handlebars for faster gearchanges. If the clutch is on the left handlebar, then the gearchange could extend slightly to the right for ergonomic convenience rather than sitting under the riders belly.
If the seat was lowered and forward footrests added, then the gearchange could be rotated to extend out to the side, or simply extended forward to be nearer the handlebars.
I would have had the gearlever to the left and added a secondary hand operated clutch lever on the gearchange for one handed, slicker movement. And if the clutch was not modified and rather heavy, I would include a small vacuum or solenoid servo unit.

Common car chassis components.
As found siting carefully on the garage floor.
If wanting to have a more commonly available engine, then the front transverse engine is a world wide design started in modern mass produced cars by Alec Issigonis at Austin Motors.

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.

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, WW2 Tiger Tanks 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. Tosrion bar suspension can make an incredibly lean suspension setup, but end stops and movement dampers must also be employed, such as remote dampers acting through tension/compression struts as per F1 cars. If using remote compression struts, then it is still better and neater to use concentric coil springs to support the mass of 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.
(Luckily, for engineering reasons, this gearing is similar to motorcycle chain drive and shaft drive gearing.)

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 Panhard rod on the top of the solid axle prevents it from moving left or right, while still being able to move vertically.

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.

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 arms.

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 many modern 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 problem.
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 sprocket 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 heavily modifying sprockets to fit differentials, then drill the mounting holes as needed, then grind away most of the inner sprocket as needed, with just the areas near the mounting holes used for alignment. Use a vernier caliper between the base of the teeth and the mounting face on the alignment point to make life easier. By having to only file the sprocket alignment at four or six places, they are much easier to make and fit by hand. )

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 wraparound 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. Alternatively build a suitably large box structure to support the differential bearings, and clear the sprocket, which would also integrate into or be a removable part of the trike's rear chassis.
Before cutting the diff housing, fit and weld up the external support brackets and when cross braced, remove just enough to clear the chain and sprocket. This can become ugly, but must be strong. The ideal would be a strong, bent steel tube along the horizontal plane, but as the diff is normally removed from a large plate in the rear, then the rear supports should be above and below this removal zone. The cross bracing tubes can be flattened along the ends to weld directly to the axle tubes. Secondary tubing will be needed above and below and another running in the front, between the upper and lower chain runs.

The open area where the rear sprocket runs, 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.

Because a trike differential and sprocket are often removed from the rear, then the front section where the chain runs, can be moulded into tunnels to give the chain weather protection and keep the oil in the differential.

Make sure the chain and 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 six 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 does less work than the wheel axles which run in grease, so greasing the main brarings 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 regularly lubricated by graphite motorcycle chain lube or drip feed with a thick oil.

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 and can be brought very close to the engine for better overall balance.

A design example.
If new to this game you may well be confused by the conflicting needs of fitting a differential to a trike. You are not the first, nor last to face trike rear ends.
This is just one example of making your own engineering solutions, to show how you may wish to approach the engineering problems. for classic reasons, the example has a car differential with independent suspension and a chain drive, just to make the example as difficult as possible.
It is not simple DIY, but needs a reasonable degree of good engineering skill, rather than any expensive engineering machine shop solutions.
Done badly, it can be very dangerous, so take your time and don't skimp the problems.

First of all, the differential can be removed from a modern car such as an Escort Mk 3 or 4 fiesta or Vauxhall, they are al the same under the skin. Then mounted into its own metal cradle subframe 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 taking the Escort gearbox and diff unit from the scrapyard and strip.
Remove the original large diameter crown gear which leaves a nice mounting face for a sprocket.
Machine the diff ring gear area to take a standard bike sprocket of the same size as the original bike or relative in diameter to match the new rear wheel relative to the original bike tyre outside diameter. The bike rear wheel and the trike rear wheels are often of a very similar outside diameter.
Later, you may need to slightly 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 frame. Such bearing cups can be made by steel tube, split to fit and welded to be a snug fit over the bearings. Then an end plate added which has a hole just big enough for the prop shaft to fit through. The cups are tack welded, removed and fully welded, then take a hand grinder to ensure the bearings will fit in them snugly.
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 to hold the diff in position. The belville washer will be partiality compressed when the assembly is built in the trike, so the taper roller bearings will be securely preloaded.
Check the chain alignment and adjust as needed.
Place the rear wheels where desired relative to the rest of the trike, - be it just an assembly of parts on blocks or a partially finished trike.
Lay the differential and sprocket on the garage floor and draw the chain rub, then measure the offset of the differential from the trike centreline. The rear frame and sub frame will be deigned to align the differential to this overall arrangement. The differential will also be mounted on blocks further above the wheel centreline, by half the distance of the suspension movement.
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, with few engineering skills.
To ensure the differential can be removed, one of the bearing cups can be fixed into the trike frame, with the other securel