Ball bearing motor
A ball bearing motor or ball-race motor consists simply of a small ball- bearing assembly with provision for passing current radially between inner and outer tracks to produce circular motion. Explanation A ball bearing motor is an unusual electric motor that consists of two ball-bearing-type bearings, with the inner races mounted on a common conductive shaft, and the outer races connected to a high current, low voltage power supply. An alternative construction fits the outer races inside a metal tube, while the inner races are mounted on a shaft with a non-conductive section (e.g. two sleeves on an insulating rod). This method has the advantage that the tube will act as a flywheel. The motor rarely starts without assistance, having effectively zero static torque, but once rotation begins the motor will accelerate until it reaches a steady speed, the direction of rotation is determined by the initial spin. Although ball bearing motors can reach reasonably high speeds they are very inefficient. Producing significant torque typically requires so much power that the bearings are heated to several hundred degrees. Theory There are multiple explanations of the effect, see the large bibliography in McDonald's work. In 1965 Electronics and Power magazine published