Ball Shifters - weird shifting behavior

Team 4155 is using ball shifters as a ratcheting/neutral gear mechanism as a part of our catapult system like many other teams on CD are doing. However, the piston controlling which set of gears is engaged is behaving in a way I wasn’t expecting.

Basically, whenever our motor is activated and begins to wind our winch, the shifter unexpectedly shifts to the neutral gear almost immediately. We noticed that this problem can be delayed by providing more PSI to the piston itself (much more than 30 psi).

If you work the gearbox with your hand, it seems that rotating the axle on which the winch is mounted is somehow “pulling” the piston into the gearbox and switching into our neutral gear. You have to physically hold the shifter to keep this from happening.

Is this normal behavior for the ball shifters? I do not have any previous experience with them and was wondering if someone could provide some information in order to help us troubleshoot.

You need at least 40psi; 60 is best.

So it is normal that rotation of the axle causes the shifter to move? We just need more PSI on the cylinder itself to keep it stationary?

Did you rearrange the gears on the ballshifter mechanism, or is it still in the stock configuration? We had a similar symptom when we reassembled the ballshifter and mixed up the position of the gears and washers.

We’ve replaced a gear with a ratcheting wrench. During our troubleshooting last night, we noticed that we are actually missing a spacer that fits on the outside of the upper gears. We replaced it with a fabricated part last night but didn’t have time to test it.

I wonder if this might be the cause of our problems. I don’t know why it would cause the shifter to move, though.

Sounds similar to what we did. I believe that the spacer helps axially line up the grooves in the gear with the balls. Because it’s not lined up without that spacer the balls aren’t sitting inside the grooves fully, and so applying some torque will push the balls back inside and move the shifter also.

Take a look at this thread