Motor stall

Hi, a couple weeks ago I made a post asking about motor stall at a competition. The reason then was because we had turbo motors. Now we have regular 393 motors with no gear ratio. Even still sometimes the motors will stall within 10-20 seconds of driver control. It’s a 4 motor base with a power expander. Are there any tips to keep our motors from stalling?

Are all those motors in the one power expander? Split them between the three ptc’s. If they’re all on the power expander, move one to some port 1-5 and another to some port 6-10.

When we are practicing and put our driver on a 1:45 time limit to simulate the match the robot works fine it in our last match after autonomous, the motors completely stalled for the whole match after 5 seconds. We can run it for a minute straight but in a real match it sometimes will run for 20 seconds, sometimes the whole match, and sometimes for 5 seconds.

We have both sides of our motors in two separate ptc’s. The intake and lift are also distributed equally.

Map four buttons on the controller, one for each motor, and test 1. if the motors work at all and 2. whether some of them have a ridiculous amount of friction or something that causes them to be less efficient.
Do NOT put all four drive motors through the power expander. That is a one way trip to stall hell. Split the power expander between your lift motors and your drive motors.

We have our motors split, two in power expanded and two in cortex. Our motors all work as they are supposed to. Since it only happens on the competition field, is there any chance static could be a factor. Another team here had the same problem as us. It has really messed us up since we are at state comp.

Yes, I can say I’ve seen more ptc issues on the competition field than in practice, including practice on actual fields. But I suspect some of this may also have to do with the extended use the robot sees in one day. The thermistor may not cool down enough. You might try lowering the temperature between matches by using the motors less between matches, giving space for air flow, and maybe even manually cooling (compressed air, ice, etc.).

We had such an issue many years ago with a solar car we’d brought to a race in Florida. It usually raced in the north and hadn’t had trouble. The high ambient temperature in Florida caused problems. Our quick fix was to tape a sealed plastic bag of ice onto the motor controller.

Anyway, no guarantees. Just some more thoughts.

Thanks for the tips guys. It seems like a major factor was the amount of static on the field. After qualifications I think they sprayed the field with anti static spray and our robot worked fine. We ended up winning state so it all good :slight_smile:

Congrats. You’ve also let us know VEX will be around for quite a while with 999 more state titles to come for you. :wink:

Oh hey guys! Congrats on state champion! I also want to say callen is right, there are about 999 more state titles for you. Keep up the good work!