Claw and Arm stall half the time?

We have finished our robot and everything seems to be working fine. But then every once in a while our claw will begin opening and closing very slowly and our lift will just completely stop moving. We dont think its mech or programming as it works again after we restart the robot. Any ideas?

Pics below
Claw powered by smaller gear
For the lift one set of that gear train on each side

It looks like your lift is made out of steel c-channels. Is that right? If you’ve got a full-length (or very long) steel c-channel with a claw and motor out at the end of it, you could possibly be asking more of your motors than they can give, even if you have 2 on each side.

The behavior you’re describing is pretty classic motor stall/overload. This article might help:

Also, do you have any elastics or similar helping lift the arm? Maybe I just missed them, but I didn’t see any. You want “neutral buoyancy” in your robot’s arm, meaning the weight of the arm is countered without using the motors, so the motors only have to handle the motion and what is held. If you do it really well, you can get the elastics to also handle some of what is held without accidentally lifting an empty arm.

As what I can tell, you don’t have any bearing flats on most of your gears(Since the distance is pretty far from your motors to your gears on your tower I’d suggest adding bearings too). Also, some good information is to never use a bearing attachment rivet(The plastic things that snap into the bearing flats) on your robot, they really don’t last long without coming loose. It’s very hard to attain a 36:84 gear ratio on your lift, so I’d suggest something more like 12:60 or 12:84 gear ratio. For your claw, make sure you use bearing flats as well, and make sure you don’t constantly apply too much power with the claw motor when holding a cone. With the claw, you can simply fix your problem by adding a small rubber band that stretches from the left arm of the claw to the right arm of the claw, so there’d be force applied when you tell the motor to have a power of 0. By the way, I think you should remove the slider(assuming you’re using it for support) and replace it with a rail. Those sliders are heavy.
To simplify the things as a checklist:

  • Add bearing flats to the lift and claw
  • Replace the rivets with screws
  • Change your gear ratio to a more sustainable one
  • Add a rubber band to your claw
  • Replace your slider with a rail

Ok, Thanks guys. We used all your tips and its working great now!