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Magnetism in gears

  1. Aug 30, 2015 #1
    If you put magnets in a gear (like in an Internal Permanent Magnet motor), what effect would the gear's teeth have on the magnetic fields?
  2. jcsd
  3. Aug 30, 2015 #2
    Not sure if I understand the question but, assuming the gears are metallic/conductive they will resist rotation in presence of the magnetic field due to magnetic damping
    Which is due to the eddy currents produced in the conducting material.
    The effect is surprisingly pronounced and has been used for breaking systems as well as slowing falls from tall buildings.
  4. Aug 31, 2015 #3
    Yes, you understand correctly. The gear is a conductor. Let's see if I understand correctly.
    If you put magnets in a gear, the gear won't turn, because the magnetic fields interfere with the contact area of the gear teeth against each other?
  5. Aug 31, 2015 #4


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    Magnetic fields will pass between gears through the moving contact areas on the teeth, but the possible repulsion will probably not prevent physical contact.
    Metal particles may be picked up by the magnetic gears and moved to the contact area where they can do most damage.

    You really must better specify the number of teeth on the gear wheel, the number of magnets and their orientation with respect to the teeth.
    What effect are you contemplating ?
  6. Sep 1, 2015 #5
    Let's say the gear has 18 teeth and the magnets are set up as in the image below.
    Basically I want to know, what effect would a magnetic gear have in a gearbox...

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  7. Sep 1, 2015 #6


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    Are the magnets bar magnets? Which ends are the N poles and which are the S poles.
  8. Sep 1, 2015 #7
    Yes, bar magnets. Every second magnet's north pole is facing outward.
  9. Sep 1, 2015 #8


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    The magnets would attract abrasive particles to the very worst place possible and so reduce the life of the gears.

    Meanwhile, the gear wheel would exhibit an effect like “cogging” due to the alternation of magnetic polarity.

    Nothing good will come of magnets in gears.
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