EVO Shifter not shifting correctly

Hello all,

This offseason, our team decided to build a west coast drivetrain that we plan to use for our practice bot. We are using AndyMark’s EVO Shifters (2 CIM, 2 Stage), and we are having trouble shifting. Both gearboxes shift from slow to fast smoothly, but only one is able to shift back while the drivetrain is in motion. For the other one to shift back, we have to stop moving. Does anyone else have this problem, and can anybody offer a solution?

Hmm, im not 100% sure in your situation, so does your EVO shifter cylinder have auto retract, auto extend, or double acting? This could help narrow it down.

Other than that the only thing I can think of is some sort of deformation in the dogs that makes the one side not want to retract, I would try manually trying to create friction by pulling the gear, and have someone else pushing the dog gear against the gear’s dog and seeing if there seems to be too much friction. If it seems smooth still like the other side does, then you know your problem lies in your cylinders.

Our team did not have this problem last season. Are you using a double-solenoid to forcibly retract, or are you relying on the spring? If you’re relying on the spring, I recommend retracting under pressure.

Have you contacted AndyMark? They are always quick and helpful. Contacting the the manufacturer should be the first thing you do with any product issue.

Check your plumbing and make sure both cylinders are getting the proper air.

Try this:

Adjust the amount of thread engagement between the 1/4-28 cylinder rod end and the shifter block. This adjustment should be so that the dog does doesn’t bottom out against each adjacent gear. Another trick is to loosen and tighten the two screws for shift cylinder plate. If that plate is out of alignment, then the cylinder rod is in a bind and doesn’t want to move freely.


What is your working pressure? This year, on our shifters (custom gearboxes), we were having a similar issue. We just needed more pressure, so we set up a branch circuit in our pneumatics such that one branch had 60 PSI going to just our shifter cylinders and the other was at 45 PSI for the rest of the system. After we did that, the dogs engaged just fine on the fly.

Out of curiosity, why not use 60 PSI across your whole robot?

Because every actuation uses air. I’ll leave it to you to calculate how much you lose at 60 when you only need the force that 45 psi will generate.

This. We did not use an on-board compressor.

This type of adjustment has fixed every dog-shift issue we’ve ever had.

Actually a single-solenoid, 4 or 5 port valve will will work fine to forcibly extend & retract a double acting cylinder. You just need to maintain a signal to the solenoid to keep it shifted. Don’t worry about draining the battery; it’s only pulling a half watt.

I believe he really meant that you should use a double-acting cylinder, not a double-acting solenoid.

Thank you for your help. The shifting was finally fixed when we started actuating the piston in both directions rather than relying on the spring to retract.