Ebike friction drive unit

thingiverse

Update 24.03.2019 As the weather improves, I finally had the chance to put the e-drive through its paces in real-world conditions. This thing accelerates incredibly well with a 4S battery, motor, and ESC that's capable of handling 6S power. The test results show that the position of the drive unit relative to the wheel is crucial - if it's too high, the tires compress and can cause the vehicle to jump. To prevent this, I'll need an end stop or a small shock absorber, similar in size to those used in RC cars. The gear mesh is solid, and the gears are strong enough for this motor. This project is still in its early stages - only two sprints in - but it's already showing promise as a proof of concept. My design goal is to create a fully 3D printable drive unit that can be fitted to a mountain bike with limited space. It won't be suitable for long rides, but rather serve as a booster on short slopes. I'm testing the unit on an old 26" woman's bike, using RC hobby electronics that are readily available from many manufacturers in similar sizes and quality. Here's a quick video of the unit in action: https://youtu.be/5WURZFLKVwA The friction drive is self-locking in one direction and freewheeling in the other, solely dependent on its position relative to the wheel and the direction of rotation. No additional pressure is needed to push the drive gear against the wheel - no one-way bearing is used. However, at high speeds, oscillations occur due to the irregular circle shape of the bike wheel. To mitigate this, I plan to add a shock absorber between the console and the drive unit in version 3. For now, I'm using an RC car shock unit as a temporary solution. Currently, the ESC is controlled by a potentiometer (attached to the handlebar via a servo tester), but I'd like to develop a better solution if possible. The battery is also temporary - a proper battery box will be added soon, along with improved cable management. Here are the specs for my current setup: * Motor: Hobbyking Turnigy Aerodrive SK3 4240 620KV * ESC: Hobbyking Redbrick 60A * Battery: LIPO 4S (with as much capacity as possible - I might try a 6S battery if I can get one, since the motor and ESC can handle it).