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Brush DC Motor Science Project HELP

  1. Jan 18, 2013 #1
    So I have a Gr 11 Physics Science project. I need to build a Brushed DC motor.

    I already build an armature with coils. I have a copper commutator and copper are connected to it. Lastly, I placed electric tape on the wood body

    The problem is that I don't know how to make an effective Brush Motor. I tried sheering a copper wire and using the end of it as a brush, but it had too much resistance.

    I also tried 2 copper sheets but that had even more resistance. Someone please help!

    http://img221.imageshack.us/img221/1546/img20130118181038.jpg [Broken]

    http://img824.imageshack.us/img824/958/img20130118181032.jpg [Broken]
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Jan 18, 2013 #2

    Simon Bridge

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    I take it the copper track does not go all the way around... it's broken in two places right?

    You want anything with a good electrical contact - I've used copper-wire with the insulation stripped from the ends - bent so they are held tightly against (in your case) the copper track by spring force ... use the sides of the ends of the wire rather than the tips, and use an abrasive to make the sides shiny. Try holding the wires so the "brush" ends press hard against the track.

    If you hit the end of thick wire with a hammer you can flatten it out - or you can use a braided copper wire and frey the ends out in a literal brush.
  4. Jan 19, 2013 #3
    Use a higher voltage power source. It not a very efficient solution, but it doesn't look like maximum efficiency is really one of your objectives ;-)
  5. Jan 19, 2013 #4
    If you can use some manufactured parts maybe you could just take an old synchronous motor (the one with commutator and windings on the rotor part as well) and use the brushes from that motor on your copper two side commutator. That would be better , safer and easier then trying to stick two naked wires to a copper commutator , as I believe the wires would scratch and destroy your commutator pretty fast also the brushes would have better electrical contact and more reliable operation.
    Also the brushes from commercial motors have springs inside them which push them close for better contact.
    Yes Simon asked that one is important are your commutator really electrically insulated the two parts as to each parts goes to it's winding.

    Sorry if you already know this but sometimes pointing out the simple things helps to not forget about them.
  6. Jan 19, 2013 #5
    Thanks for the advice, Ill keep at it!
    Last edited: Jan 19, 2013
  7. Jan 19, 2013 #6
    Use the copper sheet, but get some scissors and cut the end into about 10 or 15 fingers, each about 1/2 inch long.

    The reason the copper sheet had high resistance is because it is probably only making contact is one spot. They are called "brushes" for a reason. The idea is to make sure there are lots of points of contact.
  8. Jan 20, 2013 #7


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    Perhaps try making brushes from the braided outer screen of a coax cable?
  9. Jan 20, 2013 #8


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    Just make sure that each brush leaves off contacting one half of the commutator before it makes contact with the other half of the commutator.
    Otherwise, your machine's efficiency will nosedive. N3OrO.gif
  10. Jan 20, 2013 #9
    Thanks to all of you!

    It works now!

    Here's the link!

    Last edited by a moderator: Sep 25, 2014
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