Old Motors

At my school we have around 60 393motors for 4 teams. Some of these motors are well over 4 years old. We have lately had the problem that some of these motors don’t work as well as others {new motors} OR the motor does not even work. Does anyone have a fast and easy test that we could do in order to find the best ones? Maybe a test that could measure the torque of the motor?

Any suggestions???

A quick (but not definitive) process we used at our school to get a ballpark idea before more rigorous testing was to place an axle with a 60 tooth gear into the motor, which was wired into the #10 port on a cortex we knew was functional. We then allowed it to spin in both directions and observed its performance. It may not find every fault, but some motors will have obvious difficulty or move slower, sometimes in one direction but not another. One can also tell (with a bit of practice) by the sound of the motor. I’m afraid I cannot describe what a healthy motor sounds like as opposed to a broken one, but you can run a motor you know is healthy and compare. Once again, this is NOT definitive. It just gave my team a ballpark idea of what bin to put motors in to be tested/ sorted later.

Some of your motors may have a chipped tooth on one of the internal gears. If the chip is small enough, the motor will still function, but poorly.

I wouldn’t suggest testing old, questionable motors on ports 1 or 10 of the cortex. If there is an internal short in the motor, you run the very high chance of permanently damaging the cortex port. Better to use a motor controller and ports 2 - 9. That way, if you lose something, it will be a $10 motor controller, not a $250 cortex.

To answer the original question, our students built a small motor test bed with a shaft encoder and calculated the motor rpm. Not as good as a test under load, but better than nothing.

You could take that and make a pull a weight up on a string test fairly easily from that to add a bit of load. Not sure how much weight though. That would put some strain to get through.

Thanks “MikeHS”. I did not think about testing them in motor ports 2-9 over 1 and 10. I should have!! We have had 2 Cortex in the last past 3 weeks blow. I think that you might have found the problem. Thanks