How does this unusual motor work?

[mariost]

CAN ANYBODY EXPLAIN HOW IT WORKS? I made it after following the instructions from a video in the net and actually it works. I cannot understand how it happens.
In this motor there are no coils , magnetic fields, magnets, and brushes.There are only two bearings connected by a metal axis.
The current flows through the first bearing, the axis and then the other bearing. The electrical power supply is connected to the outer rings of the bearings.

MOTOR PROPERTIES:
1. the engine must be first started. Cannot start alone with the current.
2. the motor rotates in either direction.
3. the engine is working both direct current and alternating current.The power is approximately 5 to 12 Volts with very strong current , about 20 or more Amps.(this is a short circuit and after a few seconds everything is too hot.)
There are different explanation. One of them is :
"In the ball bearing Motor" the current passes through inner race of one side ball bearing , then to the shaft , outer race of other ball bearing , then to inner race , causes a temporally expansion of each ball , deforms it to elliptical and adds pressure between inner & outer race then cause a moment of rotation , for that reason , it needs a prime movement to sustain rotation , by the way it doesn't matter whether the current is DC or AC , it just used to heat up the balls. YOU CAN WATCH THE VIDEO HERE:

 

[Asymptotic]

"In the ball bearing Motor" the current passes through inner race of one side ball bearing , then to the shaft , outer race of other ball bearing , then to inner race , causes a temporally expansion of each ball , deforms it to elliptical and adds pressure between inner & outer race then cause a moment of rotation , for that reason , it needs a prime movement to sustain rotation , by the way it doesn't matter whether the current is DC or AC , it just used to heat up the balls.

No.

It looks like a homopolar motor. What is the disk material?
https://en.wikipedia.org/wiki/Homopolar_motor

 

[mariost]

The homopolar motor uses a disc from neodymium magnet. Here the disc is from simple iron.

 

[Dr.D]

From the video, it is evident that this motor is not self-starting; it apparently develops no torque when at standstill. This provides some clues as to how it works, but on the whole, it is not obvious.

Is it possible that the Earth's magnetic field is sufficient to be the operative magnetic field?

 

[Asymptotic]

The homopolar motor uses a disc from neodymium magnet. Here the disc is from simple iron.

I'm not sure why this motor works, but would experiment to answer the following questions.

1. Remove the disc. Does the shaft still rotate?
It ought to if motion is caused by heating balls in the bearings.

2. Try using a nylon washer instead. Does it rotate?

3. In this demonstration the disc, which appears to be a large diameter general purpose steel washer, is painted black (or has a black corrosion resistant coating). The ID bore of a washer of this OD size is larger than the OD of the threaded rod, and in combination would suggest the disc is electrically isolated from the rod. Does the motor rotate if an unpainted plain steel washer is used instead?

My guess is @Dr.D is right, and the rotor assembly is interacting with the Earth's magnetic field.

 

[jim hardy]

I think the answer is interaction between
B field surrounding current in the axle , circular lines of flux in space
and the left to right current inside the disc.

QV cross B inside the disc gives current flowing across the disc's thickness a radial push toward center,
imparting a swirl to it (curl?)
and that swirling current by right hand rule makes an opposing flux resulting in a small torque that aids rotation.

But I'm too terrified of vector calculus to attempt a proof.

 

[DaveC426913]

Question: Can this motor provide useful output?
Some devices can run quite a while by conserving the energy first put into them (like a pendulum clock), but they can't provide any useful torque to do work. Many ostensible perpetual motion machines tend to "work" this way.

 

[256bits]

the usual explanation for the motor is the heated bearing.
Low voltage but the high current will heat the bearing parts touching along the balls and race making kind of a hill for the balls to roll down, producing a torque. Since the motor runs on AC as well as DC, and is not self starting, but needs a push in either direction to get it going, that does seem to be a plausible explanation.
The disk should be acting as a flywheel to keep it turning. Things are supposed to get really hot - a prolonged endurance test run should either melt the wires or seize the bearing IMO.

Yet, on the Wiki page,
https://en.wikipedia.org/wiki/Ball_bearing_motorthere does seen to be an electromagnetic explanation as well.

S. Marinov suggests that the device produces motion from electricity without magnetism being involved, operating purely by thermal means.[1] The same explanation is given by Watson, Patel and Sedcole for rotating cylinders (instead of balls).[2] However, H. Gruenberg has given a thorough theoretical explanation based on pure electromagnetism (and neglecting the thermal effects completely).[3] 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.[4]

 

[jim hardy]

Yet, on the Wiki page,
https://en.wikipedia.org/wiki/Ball_bearing_motorthere does seen to be an electromagnetic explanation as well.

googling those two Greek authors turns up several paywalled IEEE papers
and this non paywalled one
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.434.8909&rep=rep1&type=pdf
which says there's a torque developed in the rollers , not the disc as i thought.

I suppose one could thread a piece of #6 wire through a wood axle cut from a broomstick, affix a ball bearing apply current and give it a spin.

That'd test the hypothesis of heating the balls .

old jim

 

[256bits]

good catch.