Drivetrain Losing Power

Hi all,
Whenever I tell my robot to strafe, the robot strafes for a little bit then loses power and is very slow from that point on. It takes a while for it to recover. The same happens after I drive for around 10 minutes straight; the motors lose torque and they take a while to recharge. This is especially detrimental in programming skills, since I rely on strafing for accuracy in lining up. Any suggestions?


This is most likely because the PTC thermal fuses in either the motors or cortex are tripping from too much load. What is your drive train setup, gear ratio, motors, wheels, etc?

It is a 4 motor drive train with mecanum wheels. The motors are internally high speed and are chained (1:1) externally to the wheels.

How heavy is your robot? It sounds like the PTCs in your motors are tripping when you try to strafe.

I’d say it’s around 15-20 lbs.

How far does the robot strafe before burning out?

I haven’t tried continuous strafing actually but I know it contributes to burning out the motors more. I would approximate it to be around 5 - 10 seconds of strafing until the motors weaken and strafing starts to pivot the robot due to reduced power in the motors not allowing it to strafe straight.

Ya mecanum wheel strafing is incredibly prone to stalling on a heavy robot because the rollers spinning requires the wheels to rotate in place. With too much traction this can be incredibly hard on the motors. Also mecanum wheels in general are worse in VEX due to their weight. I would suggest using all omnis in just about every scenario in VEX.

That is a strange issue you are having. We have a direct drive high speed mecanum drive and it has not stalled on us once yet. In fact, we still have more than enough torque to push other robots. Our robot weights about 18 pounds by the way. I do not know if this would help or how much it would help, but try having the motors directly driving the wheels and not using chains. The way I see it is that having chains or gears causes more friction, so if you have a 1:1, you might as well use direct drive. However, I do not know if what I am theorizing is true or if the friction is even significant enough to make your motors stall. Perhaps you could post pictures of your drive and if there is a physical issue such as friction, others would be able to help. What ports do you have your motors connected to right now? You should split up the four drive motors so that two are on ports 1-5, and the other two are on ports 6-10. This way if you are tripping a PTC, you will spread the load of the motors on two PTC’s and it should not trip anymore. Sorry I could not be of much help. :confused:

Maybe the drive is cantilevered? Pictures might help.

I’ll send you pictures later today.