Hello,
Even though I am a senior, and graduating, I’d like to know what people think good motor practices are. Such as how do you store them? Clean them? Do people need to break them in? Other interesting tips? I’m interested in both large and small AC and DC motors. I know obvious stuff like don’t stall them or overheat them, ect, but what about less obvious things?
Thanks!
CIM’s and other vex motors are pretty well sealed and hearty motors so they do not need a lot of care.
Banebot and Fisher price style motors tend to rust pretty easily in humid environments. They also do not like being dropped as thery will flex and the stator will hit the magnet often shattering it.
Brushless hobby motors tend to be higher quality motors and are usually anodized so they do not corrode easily. They often have small unprotected bearings that like to seize when they are not maintained properly.
I am not a motor expert, but I know there are posters on this forum that are acquainted with the inner workings of these things. I have a few questions to add on this topic:
Suppose I’ve run an AM/Banebots/Fisher Price motor in a near stall application and I saw a small bit of smoke and that characteristic smell of a melting motor. The motor still runs afterwards. What was physically damaged when the smoke was released, and how much was the performance of the motor affected? (It is noted that the plastic fan is partially blackened/melted and some of the windings are blackened after this stall period)
Is performance affected if I stall a CIM? No magic smoke is released in that case. What is physically damaged?
Often the smoke you see will be the insulative coating on the copper wire of the windings inside the motor when they heat up and burn. Sometimes the windings will short out afterwards depending on how hot it got and it may or may not affect performance but it is always a good idea to be cautious when it is part of a vital function.
The cims have a larger diameter wire than the Banebot/FP motors and a cooling jacket so it can dissipate much heat better than the smaller motors. If the CIM got seriously hot it may have been damaged but they tend to pretty hearty and reliable motors
I second what he said, we got a few CIM’s seriously hot and they still kept going. Common electronics practices should apply here, keep them clean don’t burn them out. Make sure they are in a place where they can stay cool. Make sure the correct voltage is supplied etc… Depending on the motor you can take them apart and relubricate it.
This may be helpful
https://www.santeecooper.com/portal/page/portal/santeecooper/mybusiness/energymanagementtips/motorsystemmaintenance-abest-practiceapproach.pdf
http://www.morganamt.com/us/files/Morgan%20Carbon%20US/MaintenanceConcerns.pdf
Long link
CIM motors can take a heavy beating before being damaged, Team 11 managed to shear half the face of one, and it still ran. Be careful though with the BaneBot and AM motors, as stalling them for too long will cause damage or deteriorate preformance
Make sure you don’t run them above the recommended voltage. Also, don’t overtighten the mounting screws, or if you have tapped screws in a gearbox, don’t tighten them into the motor on the other side. Please don’t drop them either, as that de-magnetizes the motor.
Be very careful if you try to press something onto the shaft or to press the raised ring on the end of the CIM itself into anything. If you press the shaft of any motor, it is hard not to ruin the bearings. If the other end of the shaft is exposed, you can support it and even use it to help hold the shaft perpendicular to the press by using a piece of metal with a dimple drilled into it to keep the shaft from wandering. The raised ring on the end of the CIM is part of the endcap which can be fractured pretty easily in a press – avoid any tight fits here.
Have you ever actually broken one? I have been part of a few ahem questionable mounting practices, including using a hammer on the end of the CIM to get a gear onto the shaft.
I’ve seen it done, both types of trouble. The minibot motors were fairly easy to mess up by pressing the unsupported shaft.
some past team member milled/hobbed a gear on the shaft of a CIM, I have no idea why but it still works.
Can you please explain how this works? I always tried not to drop motors for other reasons, but how does a drop affect magnetism?
A magnetic is comprised of many small magnetic fields called domains basically electrons spinning in the same direction with their poles aligned. This creates a magnets pull. When you drop a magnet these domains slowly become misaligned with each drop and eventually you no longer have a magnet.
Before the magnet losses its magnetic “power”, the motor will have mechanical damage like shaft gets bent or the casing cracks. With a bent shaft, the motor power is wasted, the bearing wears out and possibly seize and may result in motor stall and finally burn out. A cracked casing can be like a ticking bomb, you will never know when the guts or the whole motor falls out! 
The magnets themselves are brittle. Very tight clearance between the magnet and the rotor. Magnet flakes from being dropped will lock up the rotor.
You don’t see/smell the magic smoke from the cims because they are sealed. Al has posted pictures on another thread of what a smoked cim looks like.
A few links worth looking at:
Here’s a link to some details of how CIM motor’s heat up when loaded to their maximum mechanical power.
Here’s a link to some measurements my lab made of CIM motor starting current. Special thanks to Russ Ether for his help with that testing. Here’s another link to his white paper on how several FRC legal speed controllers limit the CIM motor’s starting current.
Here’s the link to Al Skierkiewicz’s thread (mentioned above) on failure of a CIM motor due to extended, hard practice driving. Don’t try this at home, or if you do then plan to replace the motors before your next competition.
Older CIM motors had a hobbed gear on their shaft. The last year I saw them was 2002. In 2003 they switched to key way. That might explain what you saw.