This Motorcycle Has Circus Balls for Wheels

Despite what your mother said when you expressed interest in them, motorcycles are actually very stable. At speed, it is difficult to make a bike tip to one side or the other. And that tipping is necessary to turn, which is why motorcycle racing is a physically taxing sport. But what if you didn’t have to tip the bike to turn? And what if the bike could move in any direction? Such things aren’t possible with conventional wheels, which is why James Bruton put circus balls on his electric bike.

This bike’s wheels are “walking globes,” which you might recognize as those circus ball thingies they have under the big top for performers to strut around on. They’re big, quite round, and very sturdy, which makes them ideal for a project like this.

Bruton put those wheels in the normal bike locations: one in front and one in back. But because they’re spheres instead of rings, they can roll just as easily in one direction as any other. That is, however, difficult to keep stable for exactly the same reason, which is why we’re impressed when circus performers balance on them. In the case, Bruton put three omni wheels between each ball and the bike’s frame. Together, each trio of omni wheels can push their ball in any direction. When both balls can move in any direction, so can the bike — it can move sideways, pivot in place, cruise at an angle, and so on.

Unlike a conventional motorcycle, however, this is incredibly unstable. A rider could never hope to keep the bike upright without electronic assistance. Fortunately, Bruton has a great deal of experience in this area, as the problem is similar to other balancing contraptions that he’s made in the past. A Teensy 4.1 development board performs the balancing calculations, using an IMU module from SparkFun to understand what “upright” means and when it is in danger of losing that status. The Teensy then, in turn, controls the motors through ODrive modules via a CAN bus connection.

Structurally, the bike is mostly aluminum extrusion and 3D-printed parts, with a few aluminum plates custom-milled by PCBWay.

After adding a handlebar, controls, and a headlight, Bruton tuned the balancing performance of the bike and then headed to a basketball court for some testing. While it wasn’t perfect, the bike performed quite well. And it is quite a sight to see, as it doesn’t seem like a vehicle that should be able to move around without toppling over.