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Im working on a school project using stationary magnets to cause the rotation (torque) of a drum with magnets adhered to it. I have skimmed through an electrodynamics textbook but I am finding it very difficulties to know what I am searching for without attending a formal class on electrodynamics.

Setup: I have a drum mounted such that is can rotate about its center axis. I apply a triangular magnet onto the drum, with the triangle pointing tangentially. I mount a stationary magnet in a position that it can interact with the triangular magnet. The stationary magnets wants to spin the drum until it meets the widest part of the triangle.

Now I want to be able to calculate the attraction between these magnets. How would I begin to calculate this?

Magnets

The stationary magnet is black, blue is the magnet applied to the drum.

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Doing those calculations by hand is hard, even for people trained in that art. There may be a computer simulation program or an app available somewhere that does the calcs for you instead.

But it appears that you are trying to put together a rotating motor with nothing but permanent magnets in it. If this is indeed the case, then it would be useful for you to know up front that no such scheme can be made to work. I am not saying this to discourage you or disparage your efforts but only to save your time.

You can try searching this site or the web for "magnetic motor" or "permanent magnet motor" to learn more about why this is so.

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  • $\begingroup$ I understand a purely magnet driven motor is impossible but what Im ultimately working on is improving the efficiency of the magnet drive. The magnets are attempting to keep it in rotation, while I use a DC motor to kick it over every once in a while. Im attempting to harness the output of that torque in the most minimal way. Again, im not expecting an output greater than input. I have a license to a high end electromagmetism software, but it is being requested that I run the math before I make the simulation. Im fighting to derive equations on a very difficult subject to grasp. $\endgroup$ – Ricky Nov 1 '18 at 5:25
  • $\begingroup$ well, good luck with your project... $\endgroup$ – niels nielsen Nov 1 '18 at 5:54

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