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Motor magnet retaining (mainly for Nick)


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DumHed
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Joined: 29 Jun 2004
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Motor magnet retaining (mainly for Nick)

Today I was rebuilding the starter motor for the race car, and noticed that the magnets are retained in an interesting way.
Apart from the usual sheet metal spacers between each magnet, there's actually a very thin tube between the magnets and the armature, which will make sure both the magnets and retainers stay in place under all conditions.

Since starter motors have a hard life, being subjected to harsh vibration and temperature differences, I think this setup must have been found to work pretty well!

http://robowars.org/forum/album_pic.php?pic_id=934

http://robowars.org/forum/album_pic.php?pic_id=935

The starter motor actually has a very tough looking single stage planetary gear reduction in it too, as well as some very strong bearings on the output shaft.
The actual motor shaft runs on tiny bronze bushings though, so I don't think it would last very long if used as a drive motor for any length of time.
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Post Thu Jul 21, 2005 2:52 pm 
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Nick
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Wow! That's really interesting, do you have any idea what the thin inner tube is made of? It looks to be metal, but the exact type would be critical to the motor performance. This would work really well if there is enough clearance between the magnets & armature in the Mag motor.
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Post Thu Jul 21, 2005 5:11 pm 
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Valen
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its probbly a non ferro magnetic metal
i'd gess aluminium,
you could probbly make one out of titanium nick ;->
you want something that is a poor electrical conductor if possible as the metal will get eddy currents induced in it, so perhaps stainless?
a fiberglass/kevlar version would be good methinks.

the eddy currents probbly arnet a problem in a starter as they typically have power to spare and dont run long enough to get hot (one hopes)
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Post Fri Jul 22, 2005 10:32 am 
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DumHed
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yeah I think it's stainless steel.

It's certainly stronger than aluminium anyway!
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Post Fri Jul 22, 2005 9:32 pm 
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