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Unread 03-07-2012, 21:01
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Mentor (1114), Alumni (772)
AKA: Aaron Koscielski
FRC #1114 (Simbotics)
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Join Date: Jul 2010
Rookie Year: 2006
Location: LaSalle, Ontario, Canada
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Re: CIM Motor Failure

Quote:
Originally Posted by Richard View Post
The CIM motor data sheet indicates that the motor is designed for intermittent duty. Its specified test load is 64 oz-in running from a 12V supply, which corresponds to 4320 RPM on the motor's speed-torque curve -- the mechanical load is about 204 Watts and the motor is dissipating about 76 Watts as waste heat (in its armature windings and brushes) at this load.

Its specified test cycle (for endurance) is:

3 minutes at the above rated load, counterclockwise, followed by
2 seconds off, followed by
3 minutes at the above test load, clockwise, followed by
30 minutes off,
and then the cycle repeats, until the motor has run 1000 cycles.

So the motor is designed to run for about 100 hours at 200 Watts mechanical output from a 12V supply, with 16% duty (i.e., 30 minutes off for every 6 minutes running). Exceeding this load and duty will overheat the motor. Seems like that is what Al's team did.
In the case of it being a drive motor, would only turning it the one way (counter clockwise) and hardly ever turning it clockwise reduce the life of the motor?
I sure hope this wasnt a 2012 CIM.
Also do you usually reuse CIM's from previous bots (competition bots) or only remove them from the Practice bots? We have previously destroyed some of our robots and reused CIM's but in the last few years (2011, 2012) I wont let them touch the robots. Though our practice bot will be taken apart and reused for spare parts and probably prototyping in the years to come.
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