While visiting Raleigh Electric in Simi Valley, California I was invited to take a look inside the Brose mid-drive electric bike motor with President Larry Pizzi. It was neat to see the famed Kevlar notched belt drive, which cuts down on noise and vibration, and understand how the sensors and gearing works to convert power. This centerdrive motor, along with Shimano, Bosch, Yamaha, and others, is designed to measure rear wheel speed, pedal cadence, and pedal torque up to 1,000 times per second for smooth efficient power flow that is also safe, because it starts and stops almost instantly as it measures your pedal input.
A small gearless canister drive spins at high RPM and is stepped down through a planetary gearing system and belt transfer to provide torque. There’s a high-precision cadence sensor inside as well as a printed circuit board that converts the different rider signals into motor operation and the whole thing weighs about 6.61 lbs which is very lightweight compared to other mid-drive motors.