Building Coreless DC motor using with powerful magnets.

Discussion in 'The Projects Forum' started by duhdave, Feb 8, 2011.

  1. duhdave

    Thread Starter New Member

    Dec 6, 2010
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    Hi, I'm looking to build a motor using my two 2"x2"x1" N50 block magnets (each has 320 lbs pull force). I'm thinking coreless due to the power of the magnets, and since I'm not worried about heat too much (the motor would only run for short periods of time). It's more of a proof of concept project, high RPM is the highest priority. I have access to a ABS plastic 3D printer so fabricating a casing of any shape is not a problem. I'll be starting with a 6v lantern battery for power and moving up from there.

    tl;dr:
    What is the best design for this format? The only motor I've built before is a iron core tri-pole. Thanks.
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
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    By "coreless", do you mean an outrunner Brushless design?
     
  3. debe

    Well-Known Member

    Sep 21, 2010
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    The coreless motor ive seen there was no iron core for the armature, just copper windings set in a ressin & a comutator. The concept was low inertia for armature due to no iron core.
     
  4. debe

    Well-Known Member

    Sep 21, 2010
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    Pics of a coreless motor wth plastic armature & comutator, has magnet each side. They also come in convential looking motors.
     
  5. duhdave

    Thread Starter New Member

    Dec 6, 2010
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  6. wayneh

    Expert

    Sep 9, 2010
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    Handling these magnets is so much more dangerous than most of the topics here, that I think this topic may be forbidden by the forum safety guidelines. I have some similar magnets less than half this size and they scare the $hinola out of me.

    Don't believe me? http://www.geekologie.com/2009/02/guy_loses_finger_to_neodymium.php
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    I have seen a motor that had a very thick copper track deposited on what looked to be fibreglass substrate. The rotor was on the order of 6" across. It ran between the poles of a couple of horseshoe magnets. If you shorted the leads, it was almost impossible to turn by hand. That may be what you are looking for.

    There is a difference between the Wiki article's "fast acceleration" and absolute rotational speed. Whatever material you are using for the rotor has only so much mechanical strength. If centrifugal force exceeds that strength, the rotor will come apart.

    All the high speed motors I have worked with have conventional armatures and were series wound. Their bearings are made for high speed, and lots of time was spent drilling the armature for balance. The armatures were between 1 & 2 inches in diameter.
     
  8. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    1,571
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    the other problem with handling these magnets is unless you have an immaculate clean room, they quickly become polluted. I've worked the Kaman PA44 PM motors and they must have a clean room for disassembly.
     
  9. duhdave

    Thread Starter New Member

    Dec 6, 2010
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    Polluted? I'm not sure I understand.

    I am relatively experienced with magnets this powerful. I keep them in .5 inch thick plastic cases when I'm just messing with them, so if I do accidently crush my hand in them, it's only ~100 lbs, which will sure as heck hurt, but probably not enough to cause permanent damage.

    @beenthere: so are you just suggesting I stick with a regular tri-pole design and scale it up for the bigger magnets?

    Would a 6v lantern battery be powerful enough to overcome the magnetic pull of the blocks? I'm not sure of the amperage of these batteries.

    Thanks guys.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    Not at all - I am suggesting that the motor is not likely to be capable of exceptionally high speed. The armature has to do with that. You have not supplied any details about the design, materials, etc.
     
  11. duhdave

    Thread Starter New Member

    Dec 6, 2010
    13
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    I'm not very experienced with motor designs, that is the purpose of this thread.

    The motor I was referencing was the most basic design possible, similar to this: http://upload.wikimedia.org/wikipedia/commons/0/04/Electric_motor_cycle_2.png but with three poles. I don't know how to make any other designs thus the reason I am asking for suggestions.

    As far as the core goes, the first motor involved a stainless steel shaft, with a nut drilled and threaded on three sides where I screwed in each pole. (each separated 120º). The casing was laser cut acrylic with smaller magnets inserted, like the image above. The commutator was even simpler-- chunk of 1" oak dowel with the commutator plates. The brushes were applied manually.

    But I want to go back and make a (much) better one, so I have upgraded hardware and tools. This time a ABS 3D printer, so precision as far as the commutator and casing goes is not a problem in the slightest. All I'm looking for is a design that would be efficient for these types of magnets. I'm not asking for schematics, just a starting point.
     
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