Shooter Motors Cutting out

We are having an issue with our shooter motors. Every time we run them, they will run for about 30 seconds and then one side cuts out. We have tried to switch out the controllers and switching ports on the Cortex. It seems that some of the ports may be failing. Is their a way to actually test the ports for failure, or is it merely a trial and error guess. And if it is a bad Cortex, can they be rebuilt or do we have to fork over $250 for a replacement?

Are you using flywheels? This sounds like your motors are drawing too much current and the PTCs (thermal protectors) are shutting down the power. Motors will draw too much current if they are suffering from too much load, or too much friction on their shafts. If you’re using flywheels, check that your flywheels can spin freely when they are physically detached from the motors. Also, if you are using dual flywheels and the flywheels are too close together, you might be overly compressing the balls when you shoot them and this can put excessive load on the motors, too. It’s important that the bearing mounting and overall structure of your shooter is rigid and not bending and causing shafts to bind up, grind, etc.

yes, we are using flywheels. They do rotate freely. If we change the wires around on the cortex, the other side cuts out. So actually both sides cut out depending on where they are plugged in. Even when using a power expander the motors will still cut out. The motors will cut out even when the motors run without any balls being fed though it. Because one side or the other cuts out because of where it is plugged in is why I am looking at the Cortex as being faulty.

What is your definition of freely? How long does the flywheel spin for if you spin it with your hands (without the motors)?

We had a similar issue… friction!

Each motor has a built-in PTC but the Cortex also has a PTC on each side. The Power Expander also has its own PTC, which is the same type as that inside the Cortex (I think). The Cortex PTCs are rated for more current than the individual motor PTCs. It sounds to me like the motors ganged together are drawing more current than the Cortex or Power Expander PTCs can handle. How many motors are you using on each side of your flywheel?

Yes, in my opinion, this is one of the notorious problems with flywheels. They have to be built quite well and their supporting structure needs to be rock solid. And good luck controlling their speed.

You can’t slob around with flywheels.

It does sound like a problem with friction as many have been stating above.
Maybe try plugging in motors you aren’t currently using to see if they can still spin continuously without the flywheels. If they do, it’s either a problem with the flywheels themselves (friction!!) or maybe the motors you’re using.
You should then try taking off the motors and spinning them in the same way. If they work normally, then it’s the flywheels.

Almost everything should work theoretically in my mind, which is why Vex is a game with a lot of trial and error. Over… and over… :wink:

We had the same problem for a while and it did end up being friction. We placed one of the really thin spacers between the metal and the shaft collars wherever weight was being placed on the shaft collar, and if that doesn’t work, I’d try loosening it and making sure that the shaft collars aren’t as tightly against the metal as possible, leave a little space.

What gear ratio are you using? Prior to the change we were having problems like yours, but the change eliminated the problems. You might want to changing the gear ratio on your shooters.

If you could attach a picture that would be great. I’m assuming you have at least two motors on each side, in this case it is possible that one of the motors is going the wrong way. Also it could be that one side of the metal that has the axles on it is off center therefore, creating friction.

Make sure that you have half of the flywheel motors in ports 1-5 and the other motors in 6-10 so you don’t trip circuits

So if I understand you properly, you, for example, put the left flywheel assembly on ports 1-5 and the right on 6-10 and, the left fails. And then, if you put the right flywheel assembly on 1-5 and the left on 6-10, the right fails. So that it is always the side associated with ports 1-5? If this is the case, and you make no other changes, then yes, it sounds like the PTC for 1-5 in the Cortex is the issue. Try putting them all on 6-10 and see if they will at least run without balls being run through it. It does seem strange that it fails with the power expander though.

If the scenario ChrisR presented is correct, perhaps it takes more current for the PTC on motor ports 6-10 to trip out compared to motor ports 1-5 or the power expander, so maybe you don’t see ports 6-10 trip out because the flywheel is using an amount of current just below 6-10’s trip out level but just above 1-5’s trip out level. These PTCs can vary quite a bit in their behavior.

Exactly!! Thank you :wink:

If this is the case, and you can’t keep the flywheel launcher running by having all the motors on the above average PTC, then you still need to reduce friction OR try several power expanders until you find another above average PTC.