Problem with arm lift losing power

I am not sure whether it’s just my superstition, but our team have encountered unusually high number of motor issues this year. So far we have burnt two motors and experienced overheating quite frequently on both swing arms and elevators. I suspect then new firmware may have something to do with it.

I’d take a look at my three favorite issues, too much friction, requiring too much torque, too much weight. All point back to bigger design issues.

Care to post a picture of your bot? Tell us which motors have burned out or are running hot.


Not to hijack this thread, but we seem to be having the same issue where our 4-bar link arm performance degrades with time - it takes longer for the arm (with a cube) to come all the way up, and the motor starts feeling warm to the touch. I’ll post pics later tonight, but the motor is connected to a 12-tooth gear which in turn is connected to a 36-tooth gear connected to the arm. Here’s a snippet of the code we use to raise the arm to its highest position:
The velocity is set to 70% and the torque is set to 100% elsewhere in the program.
Manually moving the arm up and down, we don’t feel any excessive friction. Can’t comment on torque/weight, since it’s our first mechanism.
Any clues?

Most likely it’s the motor overheating. We have seen the same symptoms where it starts becoming difficult to raise and lower the lift. A 1:3 ratio on a lift is more than enough to lift up the cubes.

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So is that an indication of a faulty/dying motor or is the root cause elsewhere?

No, I don’t think it means the motor is faulty. The Vex motors have built in current and over heating protection. So, it’s more a symptom of that kicking in. You just need to let it rest and cool down.