Our robot has recently started acting up. After 5 or so minutes of driving, the drivetrain locks up and will not move for another 15-20 minutes. Any ideas? Our robot uses 4 11W motors on a 6WD drivetrain, using the 3.25" traction and omni wheels.
This might be an overheating issue. What gear ratio are you using?
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The gear ratio is a 5:3, with the four drivtrain motors driving two 60t gears on each side. those gears then turn the 36t gears that are attached to the wheels.
Do you hear sounds? My first guess is overheating, it could be mechanical but if it fixes itself after 15-20 minutes it’s most likely an overheating issue. Try making sure your motors aren’t covered by too much aluminum or plastic. Allow heat to escape and you may see better results.
Try logging the temperatures of the motors to the brain or controller. If they are over 50° (it is in c), then they are overheating (well at least thats what our team uses). You could also try just feeling the motors and making sure they aren’t warm. In our team’s experience (with a green 4m drive), you definitely should never be driving for 5 minutes straight. We have a system where when the motors are overheating, it vibrates the controller with a specific pattern corresponding to the motor that is overheating (drivebase, cata, etc) so the drivers can know what system not to use. To get the temperature of the motors, in pros it’s motor.get_temperature(), with okapi it’s motor.getTemperature() and in vexcode it’s motor.temperature(celsius) (note: this only rounds to the nearest 5 degrees celsius). I hope this helps!
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333rpm should be more than fine to run more than 5 minutes, 2 of our sister teams have been able to drive around the field for around 15 before experiencing any loss in acceleration and speed due to over heating
i doing 450 on 66W yes you will overheat. it really isn’t that bad but bring chiller or canned air to competitions to make sure the motors are cool for matches.
Very nice, this is a great thing for teams to add to their code. Not a lot of extra code needed, but the feedback to the driver is really useful. I’ve seen teams log the max temp to the screen to check after a match, but the realtime info is a very ingenious idea.
@Steeltron0419 - You should make a pass through the drive train mechanicals. Bearing blocks everywhere? No bent axles? No wheels rubbing the frame? It’s the little amounts of extra friction that cause problems with a long term drive session. Is it a super heavy robot?
I agree with @stromboli_499A, you should get more than 5 mins of drive time. Just a reminder that those little vents in the plastic are just there to look cool, they don’t really vent any heat out of them.
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Did you get this fixed? If so what did you do?
We have not managed to fix the problem after checking everything on the drive train, so we’ve been testing to see how long we need in between running practice matches to keep the motors from overheating. At the moment, the robot works just fine, although it is rather heavy. We have used some bracing on the outside of the wheels for extra stability and to prevent the chassis from bowing out, and that has helped.
Check your no load amp/watt draw on the wheel motors. Hold chassis up in the air, turn wheels on, check readings for each wheel.
IIRC, you should read well under 1 watt of power.
If higher than this… you have a design/construction issue… which is a long way of saying ‘friction’.
Also, from memory, all the motors can supply, in s sustained manner, is around 5 watts. Much over that leads to RAPID overheating (<30 seconds).
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