Vex motors overheating every 4 minutes

Hello, our robot is overheating way to quickly within a couple minutes, what’s the best way we can cool them and what can we do to prevent this from happening? Our motor has a 36 tooth gear on it, and the wheels have an 84 tooth gear with blue cartridges for 257 rpm.

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how many motors are on your drive? our robot uses the same thing with 6 motors and i can run it for a lot longer than 4 min while doing a regular driver control. Also are your drive motors set to hold, brake or coast? If they are set to hold then set them to brake or coast its better for preventing overheating. also make sure your using bearing flats on all axles. test your drive for any unnecessary friction.

I have a four motor drive, we have a button that switches between hold and coast for balancing on the platform in tipping point.

Address friction… the drivetrain MUST spin freely. Check ALL shafts so that they spin freely without being ‘notchy’. If they are… your bearings are damaged.

Shafts can be out of spec dimensionally. Check them. Sand if needed. If a shaft does not spin perfectly in a NEW/UNDAMAGE bearing, the shaft is bad. I’ve had entire packages of brand new shafts be too large.

Check amp draws against a free running motor and against a known good drivetrain from a different bot. Anything greater than maybe 25% increase is cause for concern.

Make sure shafts are supported properly so nothing is binding (friction).

You should NOT have a heat problem at 4 minutes. Something is wrong.

A 60/84 gear gets wheel rpm of 280 using a normal cartridge.

Try using brake instead of coast/hold.


Ok I’m testing the friction right now, what’s the difference between having the wheels in coast vs. brake?

Coast allows the motor to freewheel when not being driven… no resistance other than internal mechanical/friction.

Brake slows a motor down in a predictable way without the shock of going straight to hold.

Change your code and see the differences… and write a notebook entry during it all.


This won’t help with the source of the overheating issue but something I’ve seen teams use is compressed air/gas to cool the motors down at queuing and the pits. Might be worth checking out.


Even with evaporative cooling it takes ~10 mins to cool them down. If they have back to back matches they are toast.

They have to find the heating source.

I would do some data logging:

  1. define 5 variables amps_lf, amps_lr, amps_rf, amps_rr, amps_counter
  2. set them to zero
  3. query the 4 motor’s amp draw
  4. if >.25, add the current reading to the corresponding variable and increase the counter by 1
  5. divide each total by the count to get an average
  6. display ALL these to the brain
  7. compare to a bot that does NOT overheat

If you are seeing averages > ~1.5… that’s trouble. Peak is capped at 2.5… but in my experience, averages over 1.5 mean quick overheating.

This makes a GREAT notebook entry also.


Cooling spray, more commonly known as keyboard dusters or air dusters. Works like a charm, once you start to overheat just spray your motors for a few seconds each and you should be cooled down enough to drive one match. I use them during eliminations when our matches are continuous with little to no breaks to rest the motors in between.

The vex motors are notorious for having bad ventilation and ways to distribute and get rid of heat, but something that will definitely make you overheat faster and have more problems is friction. Make sure that your wheels are able to spin freely when not connected to the motor, if your spacing is too tight they will spin a bit and stop almost instantly but if you have your spacing right there will be just a slight area for the wheels to move around allowing them to spin freely and not cause as much friction. There are other ways to prevent friction as well so I would recommend researching that as too much friction is the number one guaranteed way to overheat your motors.

Also make sure to not drive continuously for more than 4-6 minutes at a time as running for longer than that will put stress on the motors and make them overheat. If you have to run for long periods of time use cooling spray like i mentioned earlier but when possible only drive for 4 or 5 minutes at a time then give your robot and the motors a few minutes to cool off.


if you need to cool down your motors, use compressed air. its basically useless when used properly but if you turn it upside down and spray it, it will freeze the freon and make basically a liquid nitrogen cold spray that will help cool down your motors alot.


Need a way for people other than the orginal poster to mark posts as a solution. @turbodog made a posts on how to FIX the problem. Not using frozen air (a popular band aid) but how to fix it. Then a post on how to do on brain instrumentation to give details on how to narrow down what is going on in order to FIX it. And a reminder to put all of this in your notebook to make the judges go wild since they eat that up.

FIX the issue, don’t band aid it!! Now go back up in the thread and :heart: the Turbodog posts because this is the way to FIX things, not just sort of mess around with them,


Properly running 4 motor drivetrain, in my experience, will run a medium weight bot around a field for 20-30 minutes without overheating on direct drive 200 rpm cartridges.