Instructables

Build a Pneumatic Cylinder

Picture of Build a Pneumatic Cylinder
I needed an electronically controlled pneumatic cylinder for an upcoming project that I'm currently designing. I looked into purchasing one, but it turns out that they're way beyond my budget. Looking through the garage got me thinking that I might be able to build one out of some plumbing bits and bobs, and hook it up to my compressor.

After hours of explaining exactly why this was so important, my wife agreed that I should do it. Well, actually, that didn't happen. I explained it to her, and she looked at me like I have two heads, and quietly accepted that I was going to do it anyway.

This is a preliminary build of the cylinder, just as a proof-of-concept. I built it to be able to be disassembled (nothing is permanently glued). I had thought that this might make the final product weaker, but it turned out to be stronger than I had anticipated. I may end up using this method to build the final one that matches the size requirements, so that I can re-use as many of the parts as possible if the need arises.

For this build, there are a few parts that are must-haves, but everything else was cobbled together from what I had kicking around in the garage. Feel free to modify, substitute, and improvise if you're going to build one yourself.
 
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jj.inc2 months ago

I don't know how you did your math bit you won't be lifting 2500lbs at those air pressures. Your pipe is 1 and 1/2 inches the actual surface area on which linear force is applied is only the end in the cylinder which is .75 squared times pi time 30 psi. That comes to about 50 pounds. I could see you accidentally coming up with 100 but 2500 isn't even logical

padbravo4 months ago

I am on the same quest: a couple of projects need some strong movement... and the air is an option over an electric linear actuator... its fast, its powerful, its somehow easy to control... So I will make some experiments about a pneumatic cylinder... cooper pipe, nylon as piston...

How your final project ended? this cylinder was a good solution?

boa snakes6 months ago

Great idea! I am making a pneumatic powered exoskeleton for heavy lifting. Do you think it will work for the legs?

heathbar642 years ago
Also Loved your tapered bolt to regulate air flow. that's a simple but effective trick I will use someday.
jptrsn (author)  heathbar642 years ago
Can't take credit for the idea, but I can't cite my source, either. I saw it somewhere a long time ago and thought "Hey, that's really neat! I'm going to use that somewhere some day."

Thanks go out to the brilliant, anonymous person who showed the technique wherever it was that I saw it, and to the person that originally thought up the idea!
heathbar642 years ago
If i'm understanding correctly, the inner pipe is open to the air pressure. this is why you need the seal around it. typically, an air cylinder is sealed at the piston and no seal at all is needed at the outboard end. How about using a leather or rubber cup type piston like was used in the old bicycle pumps.
I one time made a low pressure cylinder from an all plastic caulk tube. I just pushed the piston out and sanded it down to fit a little freer. then used a long bolt for the piston rod.
jptrsn (author)  heathbar642 years ago
I decided to use the entire unit as an air chamber to add a bit of cushion to the action of the piston. I had thought about using an inner seal that traveled up and down the cylinder body, but I was inspired by the reducer part.

I have an old bicycle pump with a rubber disc sandwiched between two pieces of steel. The whole assembly is on a threaded rod, and the fit between disc and cylinder is fine tuned by squishing the disc by tightening down the nuts to compress the rubber. This seems to work well, and in my next build, I might try to do something similar.

Thanks for the comment!