EVO Shifter Autonomous Without Stored Air

We are currently running EVO shifters and due to some long waits before matches actually start (think opening ceremonies, yes I know our leak may be excessive but it is hard to track down) we occasionally run our autonomous without having stored air. This causes unpredictable results as one or both of the dog gears may not engage (we don’t need to shift, just need them consistent). How do teams get around this? Any advice on tracking down the leaks I have done a little basic isolation but it is so hard to do at competitions with all the noise and limited time?

If you need any help with pneumatics I can swing by your pit when I get there in the morning to help you find any leaks?

Have you tried the tried and true hair spray bottle filled with soapy water? Spray any connection point and look for bubbles.

Other than that, the EVO shifter cylinder is spring-loaded, so it should default to a particular ratio with no air pressure. If you have 3 position valves, you can leave them in the neutral position until the air pressure comes up. That should guarantee the shifters match until you’ve built up enough pressure.

Thanks for the offer of help we would love any advice you could give!

I will get soapy water together now.

I thought that was true too but has not been my expierence so far. Maybe we don’t have something hooked up Wrong but I don’t know what it would be?

I’m not familiar with the EVO shifters, but I would imagine a small spring could be used to default the gearbox into a given position in the absense of air pressure. Generally the pneumatic cylinders used on AM gearboxes are more than adequate to shift the gearbox plus overcome a bit of extra resistance.

Thanks to the intelligent design of AM on this one you should be okay and the gearbox will lock into your “A” gear thanks to the am-3494. What you may be seeing is that the gear isn’t fully locked in when you set the robot down on the ground before a match. To make sure it is engaged, set the robot down and push it along the floor to verify both gearboxes are locked in. In terms of your leak, get yourself a proper tubing cutter, and redo all your cuts to make sure they are square. After that start looking at your threaded fittings. Best of luck.

If your robot is on the field for opening ceremonies, you should be allowed to tether the robot to your control system and refill your accumulators prior to the match (provided for in the exceptions of G06). You may not have this luxury after other delays, so fixing the air leak and/or making sure you don’t need air pressure to be in the correct gear would be preferable.

Make a stethoscope out of 3 pneumatic tubes connected to a pneumatic ‘T’. Use the same noise muffling ear protection you have in your shop, then put 2 of the tube ends up to each ear under the ‘cans’. Pressurize the system, then turn the robot off. Systematically start at the compressor and move the free end of the third tube through each and every fitting. You’ll hear (and sometimes feel) the air.

On our solenoids, the ports are held down by a screw. Make sure those are screwed on tight.

Came here to say this. And thanks for calling us intelligent. :slight_smile:

Sent from my desk at AndyMark

Soap bubbles or stethoscope are great ideas to hunt down air leaks.

Another option is to “Divide & Conquer”. Isolate half your pneumatic system. If it’s still leaking. Isolate half of that, etc. Soon you’ll find the offending fitting/component.

Replace the pistons with single-acting spring retract or spring extend. You will remain in gear even without air pressure. This is what we do, and we have never been stuck in neutral during a match the entire season thus far.

As a rule of thumb, if you drop below 60 PSI in 30 minutes, you have an air leak that’s only going to get worse over time, and you should fix it. See if you can bring the robot to a quiet area to listen for it, or try the soapy water trick.

Spring-return cylinders are a nice way to prevent lost air from immobilizing your robot, and they should be used for this application when practical, but be sure to solve the REAL problem here.

If you are using spring return cylinders, be sure you are not trying to shift. At low pressure you might be moving the cylinders just enough to put it between gears.

Much good advice on this thread for pneumatics. A couple things I would repeat/add or add to the list. Use good tubing cutter and cut perpendicular to the tube (repeat), push firmly into connectors and pull on the tubing to make sure it seated, buy high quality fittings and tubing (we prefer Parker). Some imported fittings and tubing do not fit together properly especially if mixed and matched (US and import) they don’t pull out but they don’t seal either.