'Simplicity'; simple to build and to maintain, the least of everything with a custom chassis and easily available, manufacturers 'parts bin', components.
Modern performance cars require high speeds to be thrilling; not our intention. This trike will be open, light, and quick, the driving experience will come from decent cornering and going up and down the gears.
WHY THREE WHEELS
Compared to a four wheeler, the theory involved in building reverse trike is complex but, put simply, the main problem comes down to where you put the single wheel. When a car corners fast, weight is transferred to the outside front wheel, if the 'trike' has a single front wheel, it will tip, but, a reverse trike, with two wheels up front, won't and, as the single rear wheel experiences no weight transfer, the vehicle will remain stable. Also reverse trikes do not need the torsional strength as a four wheeler.
With a 4 wheeled vehicle, suspension geometry and front/rear roll stiffness affects any tendancy to over/understeer by changing the weight transfer front to rear with lateral acceleration. With a 3 wheeled vehicle all weight transfer happens at the end with the pair of wheels. This leaves tyre selection as the primary variable in adjusting over/understeer.
For stability the front tire slip angles need to increase at a greater rate than the rear with increasing lateral acceleration (understeer), so the rear tire selection is the key to what you can do at the front.
Overall, reverse trikes have
- 30% less polar movement for better handling
- 25% lower rolling resistance, for lower energy consumption
- Fewer parts, for a quicker, cheaper, lighter build
- No differential, so the complexity of the rear end is reduced
There will be no wind tunnel testing or scale models, the overall style is a choice but, form will follow function, the shape will be dictated by the mechanicals, as the body will be a shrink wrapped envelope.
Two styles will be tried. First will be an 'open' cruising body, following will be a more 'modern' racy look.
The bike’s gauges and handlebar switches are extended forward to the dashboard. They come complete with the loom, are already calibrated and some newer bikes have fuel injection fault codes built in.
The bike’s clutch, gearchange, braking and throttle controls using the standard cables or rod linkages are routed to the car-type pedal box via additional rod links.
Note: Never forget to earth the side stand switch and check for any other ‘safety’ cut out switches.
There will be a problem as the engine is away from it usual, open environment. There must be a generous, ducted, air flow to any radiator or, if air cooled, to the fins, especially where the exhaust exits.
The bike cooling system will remain standard. Air ducted through lightweight aluminium ducting, hidden in the side pods, will direct air to the standard motorbike radiator, or directly onto the head, if air cooled.
A small thermostatic fan will be fitted to operate when the car is stationary.
Pedals will be mounted on a single cross rail, then onto an adjust-a-rail, dragster style. Remove a couple of bolts and set the pedals where the driver is most comfortable. This is good if more than one person drives the car or adds to car resale value.
GIVE IT A BADGE
- The least possible to do the job
- Use proven, understandable and practical technology
- Integrate the design - let one part do the work of two
- As light as possible - each part should be just strong enough
- As small as possible on the outside for a lower frontal area
- Keep it easy to build, servicing and maintain
- Single seat
- A minimum of comfort
- Minimum ground clearance - to minimize air flow under the car
- Slightly raked underside - to create low pressure under the car
- Minimum weight - for acceleration, braking
- Custom, self jigging' chassis (no tooling, or jigs, required for construction
- Use easily available, manufacturers 'parts bin', components
- No 'extras'; anything not making it stop, go, or turn, will not be there
- Aerodynamically clean - for less drag
- Pointy front - to minimize frontal pressure build up
- Decent power - for acceleration
- Good brakes - for deceleration
Adding 'tabs and slots' to joining parts drastically reduce the amount of time and effort required to build an accurate chassis. Together, they avoid any need to 'layout' and remove the need for jigs and other assemblies.
The benefits are immediate and simplify construction; if fact the chassis can be held together with bungees for welding.
Note: Everything has been done before. It's just a matter of 'cherry picking' the bits you want to incorporate!
Four-tube multiframe, based on two continuous beams, one either side.
To manufacture, the chassis sides are built flat, then self jig as they are joined together by cross pieces. Adding the dash, forward stays and roll hoop completes the chassis.
Aluminum panels will be added to increase chassis rigidity.
- Longerons - 50mm x 50mm x 2mm
- Uprights - 50mm x 50mm x 2mm
- Cross pieces - 50mm x 50mm x 2mm
Using a bike engine has pros and cons:
- Highly tuned car engines are expensive: a large motorcycle engine is a lot cheaper than a car engine of equivalent power.
- Sequential gearbox for a much simpler gear change mechanism
- Lack of low end torque
- Have no reverse gear
- Working life is reduced as they have to move more weight than designed for
- Clutch slip: a clutch designed to move 200 kilos, through a small tyre contact patch, now is moving 300+ kilos- The clutch will
feel much lighter and engine reaction is sharper as there is no large flywheel mass spinning. Maybe heaver clutch
springs to replace the light duty ones.
- Oil surge: bikes lean into corners, cars don't! When accelerating, braking and cornering, oil will move away from the pump pick up,
possibly starving the engine of oil. The solution for oil surge is to baffle the sump.
A single centrally mounted spring over an adjustable shock absorber provides the front suspension, operating with push rods to a small, pivoting, frame mounted on pillow blocks on the chassis main beams. The frame will/should act as an anti-roll bar. the aim is a roll rate of zero by the weight transfer to the outside wheel being offset by the same reduction of weight on the inside wheel.
The lower wishbone will be a single piece, and will be the reference for the fully ajustable upper, two part, wishbone.
The front will use normal car tyres and, as motorbike tyres have poor lateral stiffness, relying on camber for cornering, a car tyre will be used at the rear.
The Morgan three wheeler showed that you can generate high cornering speeds on narrow tires, and motorbike tyres have a minimal frontal area and rolling resistance, but it's important to get the tyre contact patch to match the weight distribution.
Limitations, using a bike tyre, will probably be wheelspin, due to the contact path, and high wear!
As 13in in the most common size, and worldwide availability, why would we use another size?
The choice of donor is down to the customer.
The front forks and top yoke are removed along with the hand controls, fairing, single headlight and instruments.
The bike is then mounted to the rollover bar using the headstock, bottom yoke and steering spindle.
Stabiliser tie bars link the front of the frame to the chassis, and side links from the chassis to the bike sides ensure torsional rigidity.
Mr Suzuki/Honda/Kawasaki have spent millions of Yen designing their bike so the donor’s standard rear suspension, exhaust system and fuel tank are retained in their original positions.