James Bruton loves to experiment with unusual vehicle drive systems and configurations to find out how they perform under the dynamic conditions of real-world use. Internal combustion engines and driveshafts don’t tend to fit in those vehicles, so Bruton often utilizes electric motors. He usually turns to Arduino to control the motors and read the sensors in his contraptions. That remains true for his newest project: a strange two-wheel steering e-bike.
Imagine a bicycle, but with a rear wheel that also steers, and you’ve got a pretty good idea of the concept. But it would be really hard to steer both wheels at the same time, so Bruton came up with a unique control scheme. The front wheel has free steering, like a typical bicycle. The back wheel has active motor-driven steering. An encoder monitors the angle of the front steering so the back steering can rotate in response. There are three modes: one that locks the rear wheel to mimic a standard bike, one that matches the rear steering to the front, and one that mirrors the rear steering relative to the front.
An Arduino Uno board handles all of these functions. Both the front and rear wheels have hub motors, and the rear wheel has an active steering motor. The Arduino controls those through ESC (electronic speed controller) modules. It spins the two hub motors according to a signal coming from a standard e-bike throttle on the handlebars. Power comes from a LiPo battery pack. Bruton constructed the bike’s frame using a combination of steel tube and 3D-printed plastic parts, with heavy duty bearings for the steerer tubes and regular bicycle saddle to sit on.
Bruton reports that this configuration handles quite poorly and it probably isn’t something you’d want to build. But that’s okay, because this is just another experimental vehicle in Bruton’s garage and we’re always happy to see those.