The Wildest Electric Bike You’ve Ever Seen

James Bruton is probably known best for his unique robots, but his innovative vehicles are arguably even more impressive. Over the years, he has built many vehicles that could be very loosely described as “electric bikes.” In a video posted about six months ago, he showcased his attempt to build a bike with mecanum wheels oriented perpendicular to the direction of travel. But that didn’t work very well, so Bruton went back to the drawing board. Now he’s back with the wildest electric bike you’ve ever seen.

It is difficult to come up with a concise term to describe this vehicle. It is rideable like a bicycle or motorcycle and has a drivetrain built around electric motors. But it has four mecanum wheels directly underneath the rider and all of them seem to be facing the wrong way. Bruton calls it a “screw-bike,” because the wheels spin in opposite directions, kindle of like a screw-drive tank.

To understand how this moves, it is best to imagine a standard mecanum-wheeled vehicle with the typical “four corner” arrangement. When it spins its wheels counter to each other, it can move sideways like a crab. This bike does the same thing, but the wheels are all in a row. Of course, that means it can tip to either side and so Bruton also implemented self-balancing capability similar to a hoverboard. Together, those attributes let it stay upright and move in a straight line in any direction. The only thing it can’t do is make a clean arcing turn like a conventional bicycle. Instead, it performs more of a drifting type of turn.

Like most of Bruton’s project, this makes heavy use of 3D-printed parts. But it also has a welded steel frame for strength. The mecanum wheels were all made specifically for this project.

Powerful ODrive motors turn the wheels and a Teensy 4.1 development board controls those via beefy drivers (also from ODrive). An IMU tells the Teensy if the bike is tipping over so it can perform counter movements. This utilizes a PID (proportional-integral-derivative) algorithm, tuned for this specific vehicle. A hand throttle with a mode toggle switch lets the rider move the bike in whatever direction they like.

Many of Bruton’s vehicles tend to perform... erratically in the real word. But this screw-bike seems to work very well. In his parking lot testing, Bruton was able to control the bike without issue. The self-balancing worked as intended and the unique drive system makes this vehicle capable of maneuvering in ways that nothing else can.

We call that a success! And as always, this is open source. We can’t help but hope that some manufacturers jump on this idea...