Layout of the Rear Wheel

While initial work on converting a bicycle to use a high speed motor went well, little details came back to haunt the prototype.

1. Although a great amount of attention had been given to making sure the go kart sprocket that was bolted to the Sturmey Archer hub didn’t cause chain interference problems and the newly built up wheel fit in between standard drop outs, one detail was overlooked: adding a sprocket on the drive side caused the rear wheel to be offset to the left just enough that the axle did not protrude sufficiently from the drive side drop out to thread a nut.  Gary on Endless Sphere forums who did a similar build earlier in 2009 used a steel framed bicycle.  Our bike uses a lighter aluminum frame.  Aluminum is less dense than steel and so the drop outs are about three times thicker. Oops.
2. The magnets in the RC motor are very strong and picked up metal shavings from the shop.  These shavings got into the gap between the outer rotating magnets and inner stator.  To avoid damage to the motor, the motor was disassembled and cleaned using duct tape and fine tweezers.  It is advisable that if the motor will be stored in the same room as metal working equipment such as grinders and mills that all openings be taped off or the motor be stored in a sealed box or bag. Wash your hands before handling it. These magnets are STRONG!
3. The sensorless Shenzen Sucteam controller was damaged yet again when applying full throttle from a stop.  This is the third failure so far.  The usual failure mode is that a MOSFET (an electronic switch) on one of the three phases fails and gets stuck on or off.  This manifests itself as a stuttering when the motor turns.  The 3 phases are arranged around the hub so that each phase covers 120 degrees of the hub.  The controller should turn the phases on and off to make the wheel rotate, but instead a phase is stuck on or off and either the motor shakes back and forth or has no power in part of its rotation.  The Shenzen Sucteam sensored controllers have been rock solid so far, but RC motor’s don’t come with sensor.  There are only two solutions: a) find a more reliable controller or b) attach sensors to the motor.

Tags: Hot Rod Scooter Alpha 1, RC Motor Drive
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