Piston Valves Explained Visually

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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BigDeutcher
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Wed Sep 18, 2013 10:46 am

Okay, I am playing catchup with all this information. In the first shockwave file with the equalization hole, would there be any benifit to adding a light weight spring in the pilot area behind the piston to ensure quicker resealing?

Great illustrations!

Sorry about the bump had to ask the question .... my mind is reeling with ideas.
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Gippeto
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Thu Sep 19, 2013 11:19 am

Unless you're attempting a multi shot version...no benefit to the spring.

A check ball in the piston to prevent flow back to the pilot section would IMO be of benefit.
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lonniev
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Tue Oct 29, 2013 7:03 pm

The closed-cell foam used as a sealer on the inside and the outside of my piston valve cup compresses nicely to form a seal but it is a little fragile and gets torn by the air pressure. I am wondering what PSI is adequate to begin to experience the impulse effect: where the cup slides back and the pressurized air in the coax chamber rushes out the barrel rather than out the pilot/back valve.

At 50 PSI, I don't get the effect: the air still goes out the back.

On this first attempt cannon, the current piston is made with a durable, smooth plastic cup about 2.75" in diameter that fits over the inner 2" barrel and slides freely but not sloppily within the 3" PVC outer pipe. So, it is very light compared to a metal, epoxied plug.

Any clue on what PSI should be the transition region (yet won't shred the foam out of the piston cup?)
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sharpshooter
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Thu Oct 31, 2013 1:54 pm

Pics are broken now... perhaps on the forum change? Just in case some new guys need the info
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jrrdw
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Thu Oct 31, 2013 2:52 pm

These should open in IE8,9 or 10. I haven't tried with other browsers...Click on the file name, save as to a folder of your choice, open with IE.

[The extension swf has been deactivated and can no longer be displayed.]

[The extension swf has been deactivated and can no longer be displayed.]

[The extension swf has been deactivated and can no longer be displayed.]

Look if you must.
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sharpshooter
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Thu Oct 31, 2013 2:56 pm

Ahhh. I have only tried with chrome.
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dart guy
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Thu Oct 31, 2013 3:06 pm

Yea chrome doesn't get it but if i go to E 8/9 then i will get yelled at for bad spelling and punctuation.
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Thu Oct 31, 2013 3:10 pm

dart guy wrote:Yea chrome doesn't get it but if i go to E 8/9 then i will get yelled at for bad spelling and punctuation.
I was going to delete this but you seem to want to get complained about...BOOM!
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calif94577
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Wed Jul 15, 2015 11:46 pm

Question, I am building my first spud gun and I had to already sledge hammer out my barrel because I accidentally shoved it in too far. Then when I re-set it, I thought I had it the right distance let it cure and found out that the barrel is now too far forward... sigh. How important is it to have the piston and the back of the barrel to meet in the middle of the T? Currently I have it quite forward of the middle, as in barely visible from the bottom of the T. Image attached with hand for size reference. Will this still work? I really don't want to have to re-sledge hammer it back out, I don't think it will come out now that it has cured almost completely...
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matti
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Fri Jul 17, 2015 3:50 am

calif94577 wrote:Question, I am building my first spud gun and I had to already sledge hammer out my barrel because I accidentally shoved it in too far. Then when I re-set it, I thought I had it the right distance let it cure and found out that the barrel is now too far forward... sigh. How important is it to have the piston and the back of the barrel to meet in the middle of the T? Currently I have it quite forward of the middle, as in barely visible from the bottom of the T. Image attached with hand for size reference. Will this still work? I really don't want to have to re-sledge hammer it back out, I don't think it will come out now that it has cured almost completely...
If your piston can reach the barrel and seal it then it will be ok. I think it's more a flow thing to have the port in the middle of the T fitting. But you can use it yes..
kitharington44
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Thu Jun 23, 2016 7:33 am

A device used to control the piston valve it's motion of fluid along the valve.If the tube or pipe means by the linear motion chamber.
Luke31
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Tue Oct 20, 2020 7:59 pm

I came across this video of a piston valve air cannon bursting.


All of the pipe appear to be schedule 40, they even said it only had 90 PSI in it, which is very concerning.

Someone please shed some light on what might of happened. I was about to build a similar sized cannon with a 3'' barrel.
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