How to test motors?


I was wondering if any teams have a good method for testing old motors, as my team has accumulated several dozen over the past two years, which we have taken off for a variety of reasons, and I would like to put some back into circulation, however, when we took them off we were in a rush and didn’t label them, so there is no way to tell why we took them off.

I’m sure this has happened to other teams, and I am wondering if any teams have a good solution to test motors under strain to see if they slip and are need of repair. We could put the motors on our robot to test them, however, this would be time-consuming to do for more than a few motors as they are hard to reach.

Does anyone have a good system to test this, and is it adaptable for High-Speed motors, or only the stock VEX ones?

Thank you!

get the backup battery cord and hook it up to a 9-volt battery. then plug the motor into the cord. Black to black. this is just to see if motors work and can turn. if you want to see the opposite direction, then flip the connection.

That works for just testing to see if the motor can run, but what I’m really interested in is a strain test for the motors.

Take a look at this thread: Build a Dyno

You can develop a pretty good “feel” for motor performance with an axle and wheel and your hand. Sort of a “human dyno”, you can feel if the PTC is tripping too soon. To get started, “calibrate yourself” with a new motor to learn to feel how much torque is typical, and how easy/hard it is to stall the PTC. Finding weak or worn out PTC’s is pretty easy, the motor stalls without much effort–these become spare parts.

We have a “test rig”: a spare cortex, hand controller, MC29, digital readout, and shaft encoder all hung on the wall, along with a piece of axle with a wheel attached. “No-Load RPM” on the readout tells if the gearing is Torque, Speed, or Turbo. If it doesn’t fall withing 5-10% of a standard RPM at no-load, something is gummed up.

@kmmohn How long was the training process for team members to understand the differences between worn out motors or good motors? I like the idea, but if it’s a hard skill to learn, it may be worth building an electronic system instead

All the team members are too busy building bots to fix motors, so I’m the only one that does it. It’s certainly not quantitative, but it does sort out bad PTC’s pretty easily.