Two days ago, I thought of this device, which may seem to rotate indefinitely(in all 3 directions). I have two questions.

  1. Is this perpetual motion machine already known? If it is, could you please give some references?
  2. What is the exact mechanism that makes it stop? By this, I mean an explanation, not simply "because it would break energy conservation". Of course energy conservation is true, and of course cannot rotate indefinitely. But for any known (presumed) perpetuum mobile, there was an explanation, usually based on showing that the force generating the motion is balanced by another force.

I made a model in COMSOL of my device(first picture shows a view from the right side of the device, while the second shows it from above).

View from the right side of the device View from above

The device consists of a big magnet, a sphere and an insulator of magnetic field. The idea is to block the magnetic field around half of the sphere, so that only the other part of the sphere will be pulled. Everything is built with Armco iron.

The sphere is with radius 2 meters, and the information, which the program provides about the forces on the sphere are:

Axial torque (N*m) = -0.08622111144594605

Electromagnetic force, x component (N) = -1.069911296291055

Electromagnetic force, y component (N) = -1063.7242803838271

Electromagnetic force, z component (N) = -166.95389061849949

Torque, x component (N*m) = -17.99053531174359

Torque, y component (N*m) = 5.067797194981982

Torque, z component (N*m) = -0.08622111144594605

I would like to make some observations.

  • I don't consider an enough explanation simply to refer to the energy conservation. I am interested in an explanation showing exactly how the magnetic forces making it rotate, are balanced.
  • If the forces are balanced, only then friction will make it slow down and stop. I don't think that we can explain only by referring to friction, which in principle can be made as small as needed. There has to be a balance of forces.
  • Why spending time trying to understand or explain something that admittedly can't work? Well, even though perpetual motion machines cannot actually work, I think they may be interesting as puzzles.

closed as off-topic by Carl Witthoft, ACuriousMind, CuriousOne, Kyle Kanos, John Rennie Mar 28 '16 at 15:15

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  • 3
    $\begingroup$ Aside from friction, what about electromagnetic radiation? $\endgroup$ – Armadillo Jim Mar 27 '16 at 13:26
  • $\begingroup$ I cannot understand your devise, you have to label the figure. What is the mu metal, what is the sphere that turns, what is the magnet where is the axis . If energy is taken from the field, demagnetisation will be a problem. $\endgroup$ – anna v Mar 27 '16 at 15:30
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    $\begingroup$ "theoretically..." is not true, nor is it a representation of how magnetic materials actually behave. And just where are you going to get a perfect vacuum? $\endgroup$ – Carl Witthoft Mar 27 '16 at 15:41
  • $\begingroup$ I don't have the slightest idea what I am looking at. Please describe this machine in detail with a suitable drawing. Where is the extra energy supposed to come out? $\endgroup$ – CuriousOne Mar 28 '16 at 9:26
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    $\begingroup$ If you want it deleted, press the flag button and use the custom flag for the moderator. Tell them you would like it deleted. Do not deface the post. $\endgroup$ – tpg2114 Apr 1 '16 at 22:30

I think I know what you're trying to say. Lets try to simplify it. Lets say you have a ferromagnetic wheel, a magnet, and some magnetic shielding. It would look like your picture but with a cylinder instead of a sphere.

When the part of the wheel that is closest to the magnet rotates into the magnetically shielded area it will be pulled towards the magnet and create clockwise torque. For other parts of the wheel which are approaching the magnet they will create a counter-clockwise torque. These will cancel each other out and the wheel won't start spinning faster. Thus, this wouldn't be a perpetual motion machine.

Hope I helped. :)

  • $\begingroup$ I think the counter term in your answer is not there. The part of the sphere shielded by the mumetal will not get a torque. What you describe is an unshielded wheel. $\endgroup$ – anna v Mar 27 '16 at 18:44
  • $\begingroup$ I don't see how that configuration would make those torques arise. I think it's a glitch in the program. Try making it in real life. $\endgroup$ – Laff70 Mar 29 '16 at 1:17
  • $\begingroup$ In both the sphere and the cylinder, the center of mass of the unshielded part is somewhere left of the axis of rotation. At first glance it appears that the magnet is pulling down on the center of mass so the wheel should move, however, the center of mass never moves since a new part of the sphere or cylinder would emerge from the shielded area. Therefore, the wheel would never move at all. $\endgroup$ – Peter R Mar 30 '16 at 20:19

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