Ball Bearing Motor

The ball bearing motor has the advantage that the tube will act as a flywheel. The direction of rotation is determined by the initial spin which is usually required to get it going.

A ball bearing motor is an unusual electric motor that consists of two ball-bearing races on a common conductive shaft, with the outer ring of each race being connected to a high current, low voltage power supply.

An alternative construction fits the ball races inside a metal tube mounted on a shaft with a non-conductive section (e.g. two sleeves on an insulating rod). 

S. Marinov suggests that the device produces motion from electricity without magnetism being involved, operating purely by thermal means. The same explanation is given by Watson, Patel and Sedcole for rotating cylinders (instead of balls).

However, H. Gruenberg has given a thorough theoretical explanation based on pure electromagnetism (and neglecting the thermal effects completely).

Also, P. Hatzikonstantinou and P. G. Moyssides claim to have found an excellent agreement between the results from the electromagnetic theory and the experiments measuring the total power and efficiency of the motor