Flywheel Problems

Hey fellow vex members! I am a member from the Vex team 80R and this is my first time doing VEX. (Though that’s not the case for a couple of my fellow teammates.)

Our team decided to use a two-wheels flywheel mechanism, where the wheels sit side by side. We are having a problem with one of the flywheels just suddenly stop spinning.
Does anyone have a similar problem, and does anyone know any possible problems/solutions?

  • 80R-Vexgirl

If one of the wheels on your flywheel doesn’t turn when starting up, it is likely that one of your motors are the wrong way round, and is turning against the other motor, and thus the wheel cannot turn.

However, if one of your wheels suddenly stops after launching a few balls, it is likely that the PTC’s on the motors powering that wheel are tripping. The most likely problem is friction on the gearing at that side, so check that shafts aren’t bent, bearings are aligned properly, gears are meshing together well etc.

there is one other possibility as well as the ones LEER mentioned above, if you are using velocity control programs make sure that the encoders are linked with the correct wheels. I know this sounds obviouse but we had problems with this earlier, and it causes realy weird symptoms. to be specific, make sure the readings from wheel # 1 are actualy being used to control wheel #1’s velocity. This could be a problem with code or encoders being in the wrong ports

We were having similar problems earlier in the year. As @LEER said, it’s possible that two linked motors are turning against each other, resulting in no net movement. We found that having all the motors connected to motor controllers in the same orientation (i.e., red to red or red to black) dis not necessarily mean that they spun in the same direction. So I would first try reversing some motors (either physically or in software) and seeing if that solves the problem.

We also ran into problems tripping PTC fuses. In addition to the PTC fuses in each motor, the cortex has 2 PTC fuses: one for motor ports 1-5, and another for motor ports 6-10. So each motor is protected by 2 fuses: one on the motor and another on the cortex. The arrangement and values of these fuses is such that four or five motors running near (but below) their maximum current draw can still trip the cortex PTC fuse. So if you have all four flywheel motors running through the same cortex PTC fuse that could cause problems. Probably a good idea to have one flywheel on each cortex PTC fuse to mitigate this problem.

See also this thread which I opened when we were first playing around with flywheel building, and having similar problems.

First, one of the main things that needs to be checked is the amount of friction in your flywheel. This is most likely the cause, since anything slightly wrong can influence it. Check to make sure your gear box and mounting system is very rigid and can not bend in any way. Next, make sure that your spacing and washers are good. Too much spacing can cause unnecessary friction. Also, check to make sure that your gears are all in good condition and dont have major issues with half-missing teeth or something like that. If you are able to, take your flywheel off of your robot and that way you can check if the mounting influences friction. We had this problem earlier, and a sturdier mounting system was necessary.