The Duowheel is a MOC inspired by the JK Brickworks Monowheel. The original Monowheel uses a motor driven counterweight to steer, whereas the Duowheel uses tank style steering which is more sensitive.
The wheels are driven by two L motors with torque limited by two 76244 clutch gears on each axle to prevent the mechanism flipping over (most of the time, anyway). The battery box is mounted low and also helps minimise flipping.
I originally tried to alter the original Monowheel outer wheel design by splitting it in half, but had issues with the edges falling off. The current design came to me when I was playing around with some tank treads and turned them inside-out. The reversed tread is held on by two axles that are joined in the middle by a 36 tooth gear for support, which then connects to the driving axles.
While it can be a bit tricky to get started (you need to give it a bit of a nudge, then you can get going), the Duowheel is very fun to drive and quite sturdy (apart from occasionally tipping over).
Instructions on how you can build your own Duowheel are available from the store.