Pneumatics Activations

Hi,

I’m curious about robots that use pneumatics. I’m interested to find out many activations (where in and out would be considered separate activations), you can get with a single tank (pumped up to 100 psi) and a single double acting piston.

Thanks

Eric, Programmer for Team 3129A

If you read the information on the product page for the double acting pistons kit, it says that you should get 45 activations from 100 to 25 psi. However, you can also squeeze out a few more activations from 25 psi downward. They will just be weak, which depending on your application might be ok. Also, I think you can use the pressure regulator to make it so your activations are slower, but because you use less pressure you have more of them.

I will admit though that my team is somewhat new to pneumatics, so it’s possible that I’m not 100% correct. You might want a member of the forums who is more familiar with them to verify what I said.

How many activations you get also depends on the leakage in your system. At 100 psi, we typically got ~20 activations on a claw, but I also know that we had leakage that we weren’t able to eliminate (if we pumped up, then waited 30 minutes, the pressure was pretty much gone). By using the on/off switch at the halfway notch (45 degrees), we could increase the number of activations to ~30, which was enough for a 2-3 minute match. As a result, we always pumped up within 5 minutes of a match, sometimes using our hand pump while waiting in the queue.

Friction and load in the system will also affect the number of activations – you’ll get fewer strokes if each stroke has to work against forces that oppose it.

Each stroke uses a certain amount of air, not dependent on the force on the piston, unless of course it is not being extended fully, but then it will use even less air because the cylinder is not filling all the way.

I’m not sure why we noticed a difference in loaded vs. unloaded performance, but I believe that our significant leakage was at fault. Unfortunately, we did not find good solutions to this problem, having tried the “obvious” fixes (re-cut and re-insert tubing). This improved, but did not optimize the system.

I also re-read the OP more carefully and realized that it refers to “activations” as a single action, not a complete cycle. By that definition, we were actually getting 40-60 activations, or 20-30 complete cycles.

Did you try using teflon tape to cut down on the leaks?

No, but that’s a good suggestion for next time around – thanks! Do you have any suggestions for how to apply it? Do you only use it on the metal-to-metal joints, or on tubing joints as well?

I’m not sure tape would work so well on the non screw-in parts. Besides, the rule is:

For the tubing, try putting a tiny dab of grease at the joints to decrease air leaks.

I am bring back this thread because my team is going to be getting pneumatics for the first time and the question was never really answered.
How many full strength strokes can you get with one piston and one tank?

40ish, but if your worried about running out of air, the SMC website sells entirely legal 25 dollar reservoirs. If you were at worlds, you might have seen a psychopathic middle school team with eight reservoirs, that would be me.:smiley:

Good Luck

That was so messed up, I remember seeing that and I was like :eek::eek::eek::eek::

did you do the train drive system that used pistons

What mechanisms were piston powered?

Can you post a link? We may want an extra tank, and I can’t find reservoirs on the SMC site.

Is this what your looking for?

Hmm… I’ve never really needed to do this before but is it possible to hook multiple reservoirs to a single piston?

Of course it is :slight_smile:

If the reservoirs are hooked up to each other, they will all have the same pressure, and each will have the same amount of air. When you use this air to power a single cylinder (piston), all the reservoirs will lose a little air.
*

If you’re trying to power a cylinder with different reservoirs, but want to keep the reservoirs isolated, then you would have to use two solenoids (one from each reservoir) and a T fitting that output to the cylinder.*

Ok. I thought it would work but wasn’t sure. So basically you could get more actuations if more than one reservoir was used, correct?

Yes. If you have twice the volume of storage (twice the number of reservoirs), you will get twice the number of actuations until you are at the same pressure.

i would like to also add that the pistons will use less air the closer the solenoid is to the piston (because the air in the tubing adds up)

I did the math on this a few months ago and it turns out that in order for a length of tubing to have the same volume as a cylinder, you need like 30 feet of tubing (I can’t remember the exact number, but it was way more than you would even think about putting on a VEX robot).

Although the loss is minimal, it is a loss, and it will add up. To reduce air use, you can also put a pressure regulator between the reservoir and the solenoid (if you don’t need the full force of the 100psi).