One obvious conclusion from the hypothesis that the torque of the
ball bearing motor is primarily due to hysteresis in the balls and
races, and thus is proportional to i^2, is that the most efficient
motor will, all other things being equal, have a shaft with the least
possible resistance. This implies the following conclusions
regarding the shaft:
1. copper is better than iron or steel
2. silver is even better
3. shorter is better
4. solid bar is better than pipe
5. good electrical contact between the shaft and the inner race is
important
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
