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65: Wanted – Homopolar Motor

Posted on Mar 5, 2019 by in Active

Wanted: A simple direct current motor made from just magnet spheres kissing a battery sitting on a surface. The bounty is currently $

A homopolar motor is a type of electric motor, specifically one that uses direct current to power rotational movement. Typically, a simple homopolar motor requires a wire, a magnet, and a battery.

The goal of the March 2019 contest is to make a homopolar motor with only magnet spheres, and a battery. No wires. Or rather, the magnet spheres themselves must be used as both the source of the magnetic field, and the conductor of current.

This contest is over if/when a Homopolar motor is successfully made. Bounty: $200 + $50 per month after Mar 2018, up to a maximum of $1000 on Nov 2020. Winner takes all. If this post is still up, the solution has not been found, and the contest is still live.

You can – and may need to – use multiple brands of magnets. Electroplated magnets like Zen Magnets, Micromagnets and Electroplated Neoballs all conduct electricity, while Polymer Neoballs will insulate electricity. Thus through a pattern of conductive magnets and insulating magnets you can control the shape of the “wire”.

As far as battery selection, make sure it’s one we can easily obtain in order to confirm your design. You should probably just use some consumer grade alkaline battery, but being that we have no idea if this this possible, we won’t limit you. Just don’t pick a battery (like an 18650 or other high current lithium) that may cause an explosion. (Pro-tip, if searching “short circuit” with your battery size on Youtube results in a bunch of explosion videos, pick a different battery!) It would probably be easier to use one small coin battery than multiple big D cells, but that’s just a guess.

No jigs, frames, or non-magnet sphere supports allowed. Your motor should be nothing except magnet spheres and a battery sitting on a surface (no restriction on material or conductivity of that surface). Lastly, there must be some resemblance of stability in your motor. If magnets start flinging off and collapsing within moments of activating an electrical current, then it’s not quite a motor yet. Your motor must not self destruct, at least for 30 seconds.

If you think you’ve got it, take a video and shoot us an email with “Contest 65 Entry” in the subject line. We’ll reproduce your work to confirm it’s legitimacy.

Summary of requirements:

  • No other magnets except neodymium magnet spheres.
  • No wires, mounts, jigs, or fixtures that aren’t made of magnet spheres.
  • Just magnet spheres kissing a battery sitting on a surface.
  • Battery must be consumer available. (Don’t use a lead battery you brewed in your lab)
  • Design must be reproducible.

Everything you submit for this contest goes into the public domain. As always, the first and foremost requirement is that you have fun!