Gearbox

The gearbox is the scooter's muscle. It consists of all of the parts that make the scooter move under its own power: the motors, gears, sprockets, chain, axles, bearings, and rear wheel. At full power without any load, the CIM motors spin at 5330 rotations per minute (~90 times a second!), but they have little torque behind them. By attaching the motors to a 11:84 spur gear reduction, the shaft now spins at 11.5 rotations per second, but with 7.5x more torque. A 15:36 chain reduction further reduces the speed to about 5 rotations per second. This is the speed that the wheel spins at. A 6 inch diameter wheel spinning at ~5 rpm will travel linearly at 7.6 feet per second. Once the wheel is put under load, however, the motors can no longer spin at their free speed. Any load will give some amount of reduction in speed, but the more torque the motors have, the less change in speed for a given load. If the motors were not put through any speed reduction, they would stall, or not be strong enough to turn. By adding the speed reductions, the motor torque is increased and the change in speed is reduced, giving a final loaded speed of 6.2 feet per second.