Pneumatics Help

Yes, (yet) another thread about pneumatics. :rolleyes:

My team has recently acquired a Pneumatics Kit 2, and I have hooked up a piston to the tank. (Basically the demo picture, but without the “T” - only one piston.)

I’ve pressurized the system, hooked it up, and programmed it - but when I command the piston “open,” it opens really slowly. It closes at a somewhat faster rate, but it’s still slow…

All the tubes are cut basically perpendicularly/straight, but I’ve only tightened the little brass/steel connections with my fingers. Is there anything I should try now?


P.S. I seem to remember seeing a thread that had a tutorial pdf in it about pneumatics - but I can’t find it. If anyone knows where that thread is, I’d be very happy to know as well… :slight_smile:

Here is the pdf you were talking about. I found it under the pneumatics product page.

Are there any leaks? I would say leave the pump attached to the system so you can verify the pressure while you’re testing it. Are you using a pressure regulator? That could be limiting the pressure you’re putting into the cylinders. Is the piston easy to move by hand? That will tell you whether it’s in the piston (like a bent shaft) or in the air flow/pressure.
The solenoids are either open or closed, so that shouldn’t be the problem. Finger-tight has always been tight enough for us.

Sorry for late(ish) response, haven’t had time to experiment in a little while…

I don’t know… The pressure decreases fairly quickly when the pump is plugged in (it’s an old bicycle pump, and it doesn’t form a perfect seal when filling :o). How would I find out if there are any leaks?

Yes, but it’s configured to route as much pressure through to the cylinders…

It’s easy to move (as long as there’s no pressure in the system).


Thanks for posting this… :slight_smile:


The L-shaped 1-touch connectors for the pistons have a small airflow adjuster on them that you can adjust with a flathead screwdriver.

Well there’s a good chance that’s your problem. The way I like to check for leaks is to disconnect fittings and clamp the tubing until the leaks stop. It may be that you’re just not getting very much pressure into the system.
Before checking for any leaks however, I would fire the cylinders while someone is maintaining the system pressure at close to 100 psi. That will tell you for sure whether it’s a lack of pressure or another issue. If the cylinder does fire quickly and with force, try disconnecting your bike pump and check the force with which the piston is extended. If it drops quickly, you’ve got a leak.

I am new to robotics. What are pneumatics? I saw them under vex products but what can that do for a robot? Is it like hydraulics?

Yes, pneumatics are like hydraulics, but they use gas instead of liquid.

i was wondering this too i know how they work and everything but i was wondering if you program them to “open” and “close” slowly (just like a hydraulic cylinder)rather then fast. because i havent seen anybody with this and was wondering if it was possible. also what is the max load for a pneumatic piston, 2??

Ok, I’ll try that…


The solenoids used to control pneumatics are either open or closed. You can regulate the pressure with the pressure regulator, but there is no way to control just how much air you are letting in, except by reducing the firing distance of your piston. Hydraulics use a pump to move slowly, but VEX pneumatics have one reservoir, and that’s all the air you’re going to get in a match.

Cylinders, when fired at 100psi, have about 12lbs of force. Kit 2 pneumatics have the same force when extending, but slightly less when retracting.

I found the problem! (Just posting in case anyone else has the same issue…)

The nut on the tire pump fitting was just thick enough to prevent my pump from pressing in the pin in the fitting… So, the system was never really pressurized. :o Oops…

Moral of the story: if your pump reads 100psi after about two strokes, and the system doesn’t act pressurized - make sure air is actually passing the tire fitting!

I do have another question - both pistons in my kit open slower than they close. (They take about 1sec to open, ~.5 sec to close). Is this supposed to happen, or is there something else I should be looking for?

Thanks again,

If the cylinders are unloaded, they should both go very fast (much faster than half a second). If you are using them to move something, I would think that the problem is in what you are moving (it “wants” to go one way or another so the cylinders have to work harder one way). Do they have the same force both ways? That’s always a great way to tell if it’s the air pressure or something inside the cylinder.

The MSU college team had a similar problem to this that they were asking about. I wonder if they managed to pressurize it fully?

i think that your sulinoid is hooked up backword. i think that you have attached you pistion to the vent outlets.

I LOVE YOU:D…we had the same problem tried this, and it works perfectly now