How Does a Magnetic Repulsion Machine Work?

[Guineafowl]

TL;DR Summary

How would you characterise the energy transfer when changing the reluctance between two opposing magnets?

Someone on a machining forum is proposing a curiosity machine.

Imagine two magnets, constrained to move along one axis, set N to N. They will move apart. If you insert a piece of steel in the gap, the magnets will move towards it.

The input of the machine will be a rotating toothed disc/rotor, which will alternately present a gap, then a steel tooth, between the magnets, so causing them to reciprocate, and this motion will drive the output.

The load on the output and friction of the mechanism will, of course, be felt in the ‘cogging’ of the input rotor, but he’s asking for a more in-depth, mathematical explanation of the power transfer as the flux is switched.

If the toothed rotor were simply turning between fixed opposed magnets, I could explain the build-up of magnetic potential energy as one tooth is spun out of the field, which is then returned as the next one is attracted in. But this machine is doing work on the magnets. How would that work be calculated?

 

[Baluncore]

But this machine is doing work on the magnets. How would that work be calculated?

What constrains the movement of the magnets? That movement multiplied by the force is the work being done, the energy flowing from the rotor to the undefined output.

 

[Guineafowl]

Here is his drawing. It’s posted on a public forum so I’m sure he won’t mind my reproducing it here:

As I say, a curiosity device rather than anything useful.

Work done being $Fd$, but how is the force characterised when it involves alternating repulsion and attraction by changing the reluctance of the gap? I can recall dipole moments in a uniform field, as when a compass needle is turned in line with a magnetic field, but this is somewhat different.

 

[Baluncore]

There is no load on the output, so no net energy flows out, or in.

As I say, a curiosity device rather than anything useful.

Please don't drag crap out of the sewer.
If you drop it here, someone will have to clean it up.

 

[Guineafowl]

There is no load on the output, so no net energy flows out, or in.

Please don't drag crap out of the sewer.
If you drop it here, someone will have to clean it up.

The forum he’s posted on is full of pragmatic mechanical engineers, so we’ve all jumped in to check this isn’t a free energy device.

He may or may not build it, but it’s at least an interesting thought experiment, in that if you did put a load on the output, it would couple through to increased effort on the input.

I can’t find any way of calculating the forces involved in this ‘switched reluctance’ situation.

 

[berkeman]

Please don't drag crap out of the sewer.

Agreed. We do not discuss/debunk PMMs or free energy devices at PF. @Guineafowl -- please do not post like this in the future. Thread is closed.