Our cim motors are getting very hot after a few practice runs.
Does anybody know where we can get the specs on this year’s cims?
Does anybody know what the maximum operating temperature for them is?
How dangerous is it if we do overheat them?
It is normal for the CIMs to get very hot after 2 minutes (match length) of heavy use. If you are operating for longer than a match length, they will be very hot, but I’ve never seen a CIM quit working from getting too hot. In my experience, you can drive a robot the length of a parade route (1/2 mile and 1 battery change) with 1 CIM per drive gearbox and they’ll be really hot, but that’s about as much as I’d drive them without a break.
When you change your battery, it’s a good idea to let your motors cool down a bit before continuing. That’s my rule of thumb.
I don’t have any numbers to back up the way I do things, I just try to play it safe since I don’t have any official data.
They do get very hot in a minute, on our robots we usually put atleast one computer fan near the motors to cool them down.
Good Luck:)
Our robot in 2006 actually managed to severely decrease the cims performance from them getting too hot. This happened after the first finals match on galileo when a piece of tread came off preventing our drivetrain from spinning, hence a toasted cim. Due to that the next match drivetrain response was ultra shotty and cost us the next match.
we actually made a rating system for that robot placing the cims as <1,2,3,4, or indefinite judged by how long you could hold your hand on it, when practicing we stopped just above 2.
Watch the heat, it cost us einstein
The CIM motor data from 2005 is here.
Note that the normal load specified for this motor is 64 oz-in torque, and the specified current draw at that load is 27 Ampere. Note also the endurance test conditions specified (under the heading Special Features near the bottom right of the drawing):
So the CIM’s manufacturers indicate that motors of this design were tested by running the following load cycle:
- Apply +12V between the red and black leads and load the shaft at 64 oz-in for three minutes,
- Remove the voltage for two seconds,
- Apply -12V between the red and black leads and load the shaft at 64 oz-in for three minutes,
- Remove the voltage for 30 minutes,
and then repeat steps 1 thru 4 until 1000 cycles are complete.
My understanding is that the CIM was developed as a winch motor. In that application it is often operated intermittently beyond its normal load.
Thanks to everybody who responded. We actually fixed this problem and another issue we were having with base control by just changing our driving gear ratios. After a few runs they still get warm, but the difference is significantly better. 