very bad motor problem, need assistance

I made a claw that grabs a ball and pushes it against the robot and wedges the ball between the robot and the claw, completely holding the ball in place. We started off with a semi-used motor that worked perfectly. After a few runs of this mechanism, the motor became extremely delayed to any input and eventually moved extremely slow. It shifted between working fast and perfect to working slow, jerky, and delayed.

The motor got extremely hot during use. We changed this with a BRAND NEW motor, and after only about 3 runs of doing the same thing basically the same problem happened except without the jerky motions. Also, when i try to spin the motor in my hand, there is a LOT more resistance than compared to a brand new, fully functioning motor, and i opened up the bad motor and found no apparent problems.

There is a clutch on the motor, and a torque gear ratio to move the arm. In order to keep the ball completely wedged, the motor must be applying a constant force in order to lock the ball in (aka we’re holding the button on the controller down, sending a constant input to push in with the arm so that it will not unlock and let the ball go).

Im thinking maybe this constant input without any motion of the arm is causing it to overheat. If anyone has any idea, please let me know because I don’t want to ruin another new motor. Also, if anyone knows how i can fix my broken motors, please respond!

Thank you

nevermind, i looked on the forums and found this:

I guess i’ll have to put a limit switch to know when the arm is closed and to reduce the power to 10%.

Anyways, does anyone know how to fix the “overheated” motors? they still work, just jerky and slow.

you may want to use a servo instead, those are commenly used for the holding of things, but still should get cooled down occationally

We tried servos but they didn’t work. even though they lock their position, the gears slide slightly without the motor actually turning, and the programming of them NEVER works as intended, so we switched to motors.

Try adding a Vex Optical Encoder to the motor and use it to keep track of the motor position.

the overheated motors should regain power after it cooled off. If it still doesn’t work, then the gears inside may have been disrupted or broken. Worst case is you fried the chip module.

Since it appears that you want to be holding something most of the time, build your claw so that the “Default” position is closed. You could use some sort of tension to keep the claw closed and use the motor to open it. That way you are using the motor only for a little while every so often.

If your motor is still “jerky” when cooled down, try replacing the gear system,:smiley:

Its not as much as the motors are jerky, but the fact that when i spin the driveshaft in the motor without it plugged in, it has EXTREME resistance. I opened up and the internal gears are fine. Did the chip burn out?

I think we’re going to have a mechanical lock mechanism rather than a motor lock, and we’ll slightly hold the motors for a little as the robot turns and try to not do it too much so that it can cooldown