Robot Slowly Stops Moving During Middle of Match

The AKHS VEX Team 5600 went to out State competition this past weekend. Our first robot was working perfect until it go to the finals. In the Finals, it would slowly stop moving. The vexnet, battery, and all motors (except for the ones on the wheels would still function fine though. The motors on the wheels stopped. Our Back 2 wheels are connect to ports 1 and 10 and it was those two wheels that would stop moving. My question is, what do you think was wrong with it because once the driver left it alone during the match for a couple of seconds, the robot would move for only another couple of seconds and then stop moving again. This actually was the reason why we lost finals! Please Help, Thanks!

Sounds like your motors are overheating…
Inside each motor, there is a thermal breaker that protects the motor from heating up enough to hurt itself. After a long day, many competition robots can trip this breaker. Motors heat up the most when in stall condition.

To mitigate this problem, try:

  1. Placing more torque on the drive system. Do this through adding motors or changing the gear ratio.
  2. Making your robot lighter weight. (This puts less strain on the motors)
  3. Change your driving habits. Don’t get in a pushing fight with another robot… (speaking from experience)


How heavy is your robot?

Are the motors 393’s or 269’s?

What is you exact drive train configuration? (ex. "we have 4 393’s on our drivetrain at a 1:1 gear ratio and it is 4wd)

You might want to check all of the axles of your drive train for unnecessary friction.

And lastly were you pushing another robot? or straining you drive in any way?

This happened to me once in the finals on my drive too. First it was because the it was only operating on 2 393’s (the other two burnt out without me knowing) and I had done 10 matches, so my robot was getting revenge for the “harsh” treatment ;). We had to take a timeout to wait for the motors to cool down. Maybe we should have brought an ice pack…

This is some nice info from all of y’all, thanks a lot!

(Andrew) What would the best torque be for speed yet durability?

(DpBailey) Don’t know how heavy it is. We have 4 269’s on our drivetrain at a 1:1 gear ratio and it is 4wd. The axles are fine and the driver wasn’t coming in contact with robots at all.

(Team Viper) Our driver was driving pretty smoothly, so when it happened, we really didn’t know what to do.

I’ve also heard that ports 1 and 10 aren’t really recommended, could this have contributed as well?:confused:

It really depends on the entire construction of the robot–what types of wheels, the weight, etc. Here’s a video (someone on here made it) that explains choosing the best gear ratio for your drive:

What types of wheels do you have on your robot?

The reason that ports 1 and 10 “aren’t recommended” is because they use a built-in motor controller inside the cortex. The rest of the ports use the external motor controller. If you blow the controllers in 1 and 10, you can’t replace them. Of course, it’s fine to use 1 and 10, but they should probably be the last ports you use.