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Old Feb 25, 2011, 01:22 PM
Fly long and land softly
Jim_Marconnet's Avatar
Madison, Alabama USA
Joined Oct 2005
5,378 Posts
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Any heatsinks for uM motors?

Anyone know of sources for or a way to make a very lightweight heatsink for the brushed motors used in the uM Sukhoi, Mustang, UM4-Site, the UMX Extra 300, etc.?

Seems that if these motors could be kept somewhat cooler, they would have lower wire resistance, give higher performance, and would possibly last much longer.

Or possibly some sort of air intake/shroud could direct airflow right over the motor and cool them better?

Jim
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Old Feb 25, 2011, 01:34 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,425 Posts
Jim,
I've never heard of any. It could be a good idea. Or, it might not be that effective. I'm not really sure.

That said, the brushed motors that had heat sinks used were often GWS and similar "can" motors. In those can motors the magnets were around the inside of the can, touching the casing. The Parkzone motors are coreless motors. The magnet is a cylinder magnet in the middle of the motor, that is attached only at its front end to the casing (meaning that's the only heat transfer point). And, the windings surround the magnet and spin, touching neither the magnet or the ouside can. The can does serve to contain or focus the magnetic flux, and is why a coreless motor will not develop as much power if its can is removed.

Here is a picture from the March 2004 Inside Story Column where I tested 6mm coreless pager and similar motors when we first began using them.
http://www.rcgroups.com/forums/showthread.php?t=210688
I took apart both a coreless 6mm motor and a traditional 6mm can motor and took pictures.

The caption underneath the picture reads: "In a coreless pager motor the windings rotate around a stationary magnet. In a traditional cored motor the cored stator rotates inside a set of magnets."

So, I'm just not sure that a coreless motor lends itself to a heat sink the way a can motor does. I suspect that most of the heat transfer to the outside casing occurs up in the front of the motor where the magnet is attached. But, that is the part of the motor that is pressed into the gearbox and not accessable for a heat sink. The aft end of the motor is what's accessable, and I suspect less heat transfer to the outside casing occurs there due to the lack of a direct metal to metal connection.

Maybe someone who knows more about coreless motor design than I do will know the answer for sure.

Gordon
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Last edited by Gordon Johnson; Feb 25, 2011 at 01:45 PM.
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Old Feb 26, 2011, 07:31 AM
Fly long and land softly
Jim_Marconnet's Avatar
Madison, Alabama USA
Joined Oct 2005
5,378 Posts
Gordon, thanks for sharing. I did some searching and reading, and of course, you nailed it totally!

I was also surprised to read how fast you can destroy one of these motors by overheating it. Just a few more reasons to go brushless if possible.

Jim
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