Piston Valve Airgun 3/4"

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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DerpWithAGun
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Sat Jul 30, 2011 10:23 am

Hey guys I'm new here :)
I just built my first piston valve airgun and it didnt turn out well.
im wondering if anyone can give me some advice.
i dont have any pictures but my piston in housed inside a 3/4" brass tee and i made a piston out of hotglue. When i put pressure in the gun the piston will not slide forward, instead air leaked around the piston even though it was a tight fit inside the 3/4" connector. My piston valve is also a barrel sealing one, mine looks very similar to this one: just skip to 0:08 seconds and watch him assemble the thing. Mine has a ball valve instead of blowgun trigger (but i would like to know also how he attached it like that D:) so once again i repeat this my piston is sitting a little tightly in the housing and air will just leak around it. i also pushed my piston with a rod all the way into the barrel part and the air will still leak around it and go through the barrel. it would be nice to see a tutorial on this forum for a piston valve housed in 3/4" parts
please help me thanks for reading
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warhead052
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Sat Jul 30, 2011 10:27 am

Not bad, did you follow MRR's piston valve tutorial for it?
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DerpWithAGun
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Sat Jul 30, 2011 10:29 am

Yes i watched him build it a long time ago but his video got deleted, all i can watch now is that animation that doesn't really help with making a piston valve at all. i already fully 100% understand the concept for this type of airgun just building it is a pain
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Gun Freak
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Sat Jul 30, 2011 10:30 am

Try to remake your piston, make sure it is smooth and can slide freely when you push on it with your finger. Lubrication helps.
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DerpWithAGun
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Sat Jul 30, 2011 10:33 am

ok i just took a look at my piston and i think what happened was i screwed in the rubber gasket with a short but fat screw and it seems that it has warped the piston slighty (made it fatter at the top) which could be the problem why it wont slide, i greased up the connecter with a ton of grease ( vividly remembering MRR tutorial from months ago) but this still does not explain why air can leak around the piston. D:
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Gun Freak
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Sat Jul 30, 2011 10:37 am

Air is supposed to leak around, but your piston needs to be able to slide better. Try taking it out, cleaning the inside of the cylinder really good, and remake your piston. Keep it as smooth as possible.
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DerpWithAGun
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Sat Jul 30, 2011 10:39 am

alright thanks for the help, could you give me any advice on how to make the piston slide better and make it as smooth as possible? and what would be more efficient for the connector? Lube or Mobile grease? (grease for cars)
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Gun Freak
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Sat Jul 30, 2011 10:42 am

Any slippery stuff you have :P
Maybe you could pick up a rubber stopper at the hardware store and use that for a piston, if not, lube the cylinder a lot before you cast your piston and let it dry before you take it out. When you put in the screw try not to warp the piston.
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DerpWithAGun
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Sat Jul 30, 2011 10:55 am

ok i will make a new piston tomorrow i just broke the seal for my schrader valve and got a GIANT leak will fix tomorrow aswell. I might make a tutorial for this eventually and maybe make a tut for encasing your pipes in a nice wooden stock aswell as putting rifling in a PVC barrel. btw Gun Freak could you look at my very first post on this topic and have a look at the youtube vid? the way he connected that blowgun trigger to plumping parts seems impossible to me. Would it be possible to enlighten me on how he did it? i live in australia and parts are abit limited here, i went to my local hardware store today and asked one of the people there how to connect a blowgun trigger to a plumping part like that and he said the only way is to machine your own. and i dont have a mill or any machine to do so
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Gun Freak
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Sat Jul 30, 2011 11:11 am

I saw the video... all he did was thread the blowgun onto a nipple...
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DerpWithAGun
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Sat Jul 30, 2011 11:18 am

a nipple? ok thanks ill check out some the next time i go to hardware store i appreciate all help you've given me, this is slighty off topic but has anyone invented a bullet for a air gun that has buckshot inside it? i have some idea to make it possible.
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MRR
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Sat Jul 30, 2011 12:04 pm

Here you go. I set the video to not listed because in my opinion it is not appropriate for some people on YouTube.
[youtube][/youtube]
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DerpWithAGun
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Sun Jul 31, 2011 3:19 am

ok thanks everyone for the help and most thanks to MRR for that video :)
i finally completed the whole thing, remade the piston ect. i tested it out and the piston shot forward and had a 100% perfect seal on the barrel. i just finished solvent welding my PVC chamber (temporary chamber) and ima see if it works tomorrow. thanks for the help everyone :D

EDIT: My Piston won't seal the barrel anymore. It will shoot forward but air escapes around it and goes through the barrel. Also, when I test fire it the piston only shoots backwards half way and i must shove the piston back with a rod after every shot. Someone please help.
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Gun Freak
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Sun Jul 31, 2011 9:14 am

Screw the hot glue piston and go with a bolt/washer piston with orings.
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Golf Ball Cannon "Superna" ■ M16 BBMG ■ Pengun ■ Hammer Valve Airsoft Sniper ■ High Pressure .22 Coax
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DerpWithAGun
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Sun Jul 31, 2011 4:31 pm

What do you mean bolt/washer? Is there a tutorial on this forum or some pictures i can check out?
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