Ball bearing motor


A ball bearing motor or ball-race motor is an electric motor consisting of two ball bearings assembled on a conductive common shaft with provision for passing electric current between two outer bearing races. The motor is usually not self-starting and must be given an initial rotation to start. When a large current is passed through the device, an electromechanical effect, called Huber effect, causes the motor to maintain the rotation. The effect is a complex physical phenomenon, its nature was still subject of a scientific debate in the early 2020s.
A macroscopic scale ball bearing motor is "completely impractical", as heating and sparking will cause it to self-destruct in seconds if operated in the air.

History

Huber effect

Jacob Huber had discovered the eponymous electromechanical effect in 1959, when he investigated wheelsets moving on rails: if a voltage differential is applied to the rails then the initial rotation of the wheels causes a force to appear that supports the initial motion. Huber assumed the force to have an electromagnetic nature, but it is not borne out by the experimental results.

Ball bearing motor

A ball-bearing implementation spinning at 1000 RPM was made by R. A. Milroy in December of 1959.
Kosyrev et al. in 1963 proposed a single-bearing design where the voltage is applied to the inner and outer tracks.

Explanation of Huber effect

There are multiple explanations of the effect, see the large bibliography in McDonald's work.
In 1965 Electronics and Power magazine published a letter by RH Barker asking for an explanation of how this type of motor worked. At the time various explanations had been offered. S. Marinov suggests that the device produces motion from electricity without magnetism being involved, operating purely by the resistance heating causing an asymmetric thermal expansion of the balls in the bearings as they rotate. The same explanation is given by Watson, Patel and Sedcole for rotating cylinders. However, H. Gruenberg has given a thorough theoretical explanation based on pure electromagnetism.
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.