Drive Stalling

Our team has been having issues with our drive. After about 30 seconds of driving, our drive stalls. This only happens on the competition foam tiles and we checked for excess friction. Our drive is an all omni-wheel direct powered with 393’s set to torque. We suspect that we are tripping our breakers.

Is there any way to fix this? Help would be very greatly appreciated.

If the cortex is tripping, you want to try spreading out the motors over the different circuit breakers. On the cortex, ports 1-5 are on a separate breaker than ports 6-10, so if you balance drive motors between those (and a power expander if you have one) that might help.

You REALLY shouldn’t be seeing this problem. A 4 motor torque base can move over twenty pounds.

Are you sure that your motors are all plugged in, going the same way, and set to the same gear ratio?

If those motors are more than 2 years old, or strained with a previously faster ratio, they probably degraded to the point of replacement. The only way you can fix that is to replace the motors. How many motors do you have on the drive train, and what is your weight(approximate if needed)?

We put two of the motors on the cortex, and the other two on a power expander

We just got our motors on Wednesday and have only used them to practice

We have four motors on the drive

Our robot is approx. 15 pounds

We have checked for all of these, and since we have a direct drive, we do not need to worry about having different gear ratios.

That’s not true. Earlier this season, I put one high speed motor on one side of the drive, and a normal speed on the other side. Kept burning out until I swapped out the low speed to be another high speed.

Based on what you’re telling us, there is absolutely no reason for your drive to be burning out. Which means you’re missing something. Is it possible your intake tray is dragging on the ground? Are the motors on your intake dragging? Anything like that?

We made sure nothing was dragging on the floor to reduce friction.

Our motors came straight out of the box, and to my knowledge, the “factory setting” for all new 393’s is torque.

Yeah, you’re right about that.

Is it possible that you have too many spacers on the axle, causing friction as it spins? You might not see that if you tested for friction like we sometimes do, before everything is spaced correctly.

Are you using Delrin Bearings? That helps a little bit.

Are your wheels cantilevered, or braced on both sides? We’ve had problems with drives stalling in the past when we cantilevered the wheels.

Our wheels are using two spacers each, and are braced on both sides.

I am not sure which ones the Delrin bearings are, but we have the standard ones (if it’s those).

My drivetrain guy wants me to test your motors, just to make sure those aren’t the problem. Here’s the way he suggests.

Take the motors one by one off of the wheels on your chassis, and put an axle with just a wheel on them. Power the motor with a backup battery by plugging the ports into the Backup Battery Cable. Stop it by hand, and see if any of them die really quickly. After they’re stalled, wait five seconds and see if they start spinning at full speed again. If one spins less than the others, then there’s your problem. If they all go back to full speed immediately, then we move onto something else.

I’ll let you know what happens as soon as I finish testing it.

After testing each of the drive motors, we found that none of them exhibited this problem.

I did find however, that it got increasingly easier to stall the motor after the first time.

Good, that’s what you should see. That right there is why after the first time you stall your base, it happens more and more frequently. So now we need to figure out why it happens the first time.

Does it burn out crossing the bump, or even just driving across the flat area of the middle and goal zones?

EDIT: Can you just post a couple pictures of the base? That might make this easier.

You have a friction issue! We had a 27lb. robot our first season using 4 393’s geared for torque and didn’t stall. Are you using omni wheels, mecanums, or high traction wheels? Also is your base square? When I say square I men if you measure from one corner to the other diagonally on each side is it the same for both measurements? Are you in League City already? I assume you are competing there tomorrow and not driving in from the Valley in the morning.

He said Omnis, claimed there was no excessive friction.

My bad, I overlooked the omni’s. Spinning the wheels does not rule out friction from extrinsic factors such as wheel camber or asymmetry of the base. That is about all I can think of, I cannot imagine 4 HT 393’s stalling that fast. I would wonder if the wheels are all powered and turning the same speed. Our scissor lift weighed 19-1/2 lbs and never stalled with 4 393’s.

I will post pictures in the morning, we are reassembling the drive train right now

I do have a square base and I am already in League City, after we passed inspection we tested it on the practice field. This was when we noticed our problem.