Three inline wheels better than two?

Published: 16 April 2009

A Paris-based bike designer has come up with a new form of motorcycle – with three inline wheels. The idea is to keep all the fun and manoeuvreability of a two-wheeled bike, but make it harder to crash.

"The basic layout of a bike has hardly changed since it was invented," says Julien Rondinaud. "Riding a bike remains very dangerous: there’s lots of power and only a small contact patch with the road. On a traditional bike, a loss of grip on either wheel usually produces a crash."

Rondinaud's solution uses a reversed KTM Super Duke motor and three 14 inch wheels to create a 50% bigger tyre footprint. The first two wheels are very close together for agility, with the third trailing wheel adding stability. All three wheels use independent swing arms and suspension units, and single disc brakes. But to understand how it works you have to go a bit deeper.

The front wheel uses mechanical hub steering like a Bimota Tesi or Yamaha GTS. The mid wheel puts down the power, but because the front-to-mid wheelbase is shorter with the engine reversed, the drive sprocket is itself driven by a belt and pulley, to get the correct drive direction back.

The rear wheel is in another steered hub, but there's no connection with the handlebars. Instead, it simply follows the lean and degree of turn dictated by the front two wheels.

"Obviously, at different speeds the rear wheel needs to steer a different amount. The castor effect of the steering angle in the rear hub means this happens naturally, with a hydraulic damper smoothing out the action," explains Rondinaud.

There’s more on this incredible machine in next week’s MCN. To see a computer-generated video of the bike working, go to www.julienrondino.com.

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