Flywheel Trouble

We believe we have eliminated all sources of friction, but our single flywheel will ramp up and gradually slow down in 3 intervals. Our flywheel is using a 35:1 gear ratio using 2 5" wheels and 6 393 motors. We believe the PTC’s are causing the problem, even though we have split the motors as following:

  • Two motors in Port 7
  • Two motors in Port 4
  • Two motors through a power expander in Ports 5 and 6
    We have also lubed our gears with graphite in order to reduce friction, and ruled out any error in programming by using a program thats only goal is to turn on the shooter. When our motors turn off, any other motors in that PTC section still run normally. As we are entering a competition tomorrow, any solutions would be appreciated. Thanks.

Are they turbo motors? If so, that gear ratio might be too high. My team uses 5" wheels as well (3 of them, on a single flywheel), and a 28:1 gear ratio overall (35:3 with turbo motors). That is with 4 motors. It works fine for us, and it shoots full court at about 70 power.
Also, check to make sure that all of your metal is aligned, you have bearing flats or drilled out holes any time an axle goes through metal, and your axles are straight. We tried a 6 motor flywheel at one point, but because we managed to offset the metal structure slightly, the extra motor mounts were not aligned properly, and were slightly bent inwards. This added a lot of friction, and we found that 4 motors actually works better as a result. We have also found that metal can get shaken loose and get misaligned, and that, too, adds friction.

I think that you have a motor controller issue. My team had a staged spin down and our problem was that we had two motor controllers that were dead. Also do you Y off and then have two separate motor controllers, or do you use one motor controller and then Y off?

6 motors on a 1:35 should be fine, although a admittedly a little higher than necessary. We had this exact issue with the first five iterations of our flywheel in November. The culprit is friction. Not much, but it’s enough to cause the motors to slow to a stop. Definitely check motor controllers and the cortex though.

We do have one motor controller Y-ing off to two separate motor, would that cause this issue?

You should have 2 motor controllers, since y-cables have 3 wires per motor. They go before the controller/H-bridge (the thing in ports 1&10, why they have 2 wires), and that is the most likely at least part of your problem. If you put the y-cable before the motor controllers, you will see at least improvement, if not a full solution.