All that’s old is new again.
Three-wheeled cars are enjoying a huge resurgence in popularity in recent years, perhaps unmatched since Karl Benz built the very first mass-produced automobile (the 3-wheeled Benz Motorwagen) in 1886. Trikes can offer many of the benefits of a motorcycle (speed, good fuel economy and reliability) with some of the stability attributes of a car. However, you might want to think twice about building a copy of your Dad’s Volkswagen-powered cart.
If you want to know why three-wheeled cars aren’t more popular, you need only look at how weight transfers. When going around a left-hand corner, the vehicle’s weight transfers to the right-front corner. This isn’t a problem in a car, but a traditional “Delta” shaped trike doesn’t have a wheel at that corner to lean on. End result: hit the brakes while turning and the trike rolls over on top of you. The simplest and most obvious solution is to put two tires at the front and one at the back. This “backwards” design is colloquially known as a “tadpole,” and is simply the safest and best performing three-wheeled design on the planet.
Tadpole trikes suffer from the opposite problem that Delta trikes do; they can flip over backwards under a combination of acceleration and cornering. Not only that, but powering a single rear wheel and turning with two front wheels is simply asking for snap-oversteer (sudden spin-outs).
The best way to safeguard against either of these happening is to make your tadpole trike front wheel drive. Under cornering, a front-wheel drive car lifts the outside front wheel, which will limit your trike’s ability to put power down in the twisties and act as a “weak link” in the chassis dynamic capabilities. In short, you shouldn’t be able to put down enough power to flip the trike while cornering.
Engine and Chassis
Here’s the simplest and most effective recipe for a FWD tadpole trike: a Volkswagen transaxle mated to an 1,100 cc V-twin motorcycle engine with an adapter bellhousing. Volkswagen transmissions are fairly light and their bellhousings face backward, allowing you to put the engine closer to the center of mass for better handling.
Connect the VW’s half-shafts to any front-wheel drive car’s suspension (Acura RSXs have an excellent front suspension), and tie it all together with a custom-built tube chassis. Stick a huge 15-inch wide street-tread drag tire (both Indy and Mickey Thompson make them) out back on a hard-tail suspension and you’ve got yourself a basic chassis.
Car vs. Bike
At this point you can go one of two routes, car or motorcycle. You can install a single or two side-by-side bucket seats and some fiberglass or aluminum body panels to make it a car, or you can install a single or tandem saddles to make a motorcycle. Either way, the torque and horsepower of that 1,100 cc V-Twin will provide plenty of motivation for your under-1,000 pound ride. A side-by-side car-style setup simplifies the steering linkage (which will require a chain-drive for center-mount applications), but will make the trike much heavier on one side than the other.