393 Motors Stop Spinning For Flywheels

We have two motors connected to flywheels and what happens is that the wheels start spinning bust stop after two seconds. The code on RobotC says that the motors should spin longer than what it is spinning for now. We are certain it is not friction, because we have put in bearings, and the fact that it actually starts spinning. We dont know if it is a problem with the programming or the motor. However, we have replaced both motors several times to check, and it is still not working.

Well, I am actually quite certain it is friction. Bearings have friction as well. Most likely it could be the PTC tripping.

How do you control the duration of the spin? By timing?
To troubleshoot, maybe you can try putting in a very large number to see if the spin duration is affected.

If it is still trpping at around 2 sec, then it should be the PTC tripping (i.e. the 2 motors are overworked).

It is most likely a problem with your gear ratio or build quality. There are plenty of threads with many recommendations for gear ratios that work well for a two-motor dual-flywheel setup.

If you are using one of those gear ratios, then make sure you check to make sure everything is aligned properly and none of your shafts are bent. Without the motor attached, your gearbox and flywheels should be able to spin for around 10 seconds or longer before stopping when spun by hand.

The problem you are having is caused by the motors stalling under the heavy load, drawing a large amount of current from the cortex. A mechanism inside each motor called a PTC “trips” and prevents the motors from overheating, which could cause damage, by stopping the motors from running.

Hope this helps.

Do you mean we should try spinning it without the motor to check? @Bpalms


What should we do if that works for 10 seconds and it still stops working after we put the motor on? Is that possible? @Bpalms

Anything is possible, but I don’t think it’s likely unless you’re using too high a gear ratio. What ratio are you using?

While running the code have the motors debug window open (provided you’re using controller plugged into the computer to debug) and keep an eye on the motor values, this way you will know for sure if the motors are being given power. You can also post your code if you think it could be an issue with the program, but as others have said it’s most likely due to tripping the PTCs.

84 tooth gear is connected to the motor which drives a 36 tooth gear which drives a 12 tooth gear

Is that a bad gear ratio? @Bpalms

That gear ratio should be fine. Just make sure everything is aligned and try the hand-spinning test as I have already said. If you’re still having problems, definitely try Kevin’s advice as well, as it could also be an issue with your code.

When things don’t line up just right adjusting the size of the bearing block hole via a 3/16" drill bit can help a ton.