How-To: Make a pneumatic cannon with a 2" piston valve.

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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tomthebomb137
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Sun Oct 21, 2007 9:20 pm

when you say 2" piston valve do you mean for a 2" barrel, or is this the size of the piston, and the brl size is more like 1 1/2" because i need a piston vavle for a 2" brl
thanks so much
-tom
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battlemonkey
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Sun Oct 21, 2007 9:50 pm

i dont know if you can but if so get some umpy just bigger and cut it to size may need a lathe tho
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MrCrowley
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Sun Oct 21, 2007 10:19 pm

@tomthebomb

It usually refers to the size of the piston housing, which is the tee.

@battlemonkey

? :? Can you reword that please.
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tomthebomb137
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Mon Oct 22, 2007 2:05 pm

alright, then do you have any ideas for a 2in brl piston valve?
thanks again guys
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MrCrowley
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Mon Oct 22, 2007 2:11 pm

Same as my valve, just have the seat a smaller diameter then the piston, so maybe have a bushing as the seat instead of the 2" barrel.

If you have no idea what i'm talking about, do some more research there is plenty of info on this site.
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tomthebomb137
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Mon Oct 22, 2007 5:02 pm

alright so you mean put a 2" to 1 1/2" on the inside of the valve at the end of the barrel so the seat extends over the ends of the 1 1/2 bushing, il have a smaller face?
am i following you?
thanks again Mrcrowley
-tom
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MrCrowley
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Mon Oct 22, 2007 9:40 pm

Yeah, I think you got it.
anthony5640
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Sat Jan 12, 2008 8:27 pm

what do i make the piston out of?
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BigJon
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Sat Jan 12, 2008 8:38 pm

Well since its 2" pipe 1 1/4" endcaps fit pretty good. Basically anything that will fit, for example MrCrowley used a deoderent can i believe?
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MrCrowley
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Sat Jan 12, 2008 9:06 pm

anthony5640 wrote:what do i make the piston out of?
I'm not going to tell you, because it's all over my topic yet you failed to read it, even look at the damn pictures.

You obviously have no clue what you are doing, so learn how they work, how to build one, what the hell you are doing in the first place, then come back to me and you will realise exactly what I made it from and you will have no more questions.

Just learn what you are doing before asking questions.
nabu92
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Mon Jan 28, 2008 9:28 pm

I finally understand how pistons work. Thanks.
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MrCrowley
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Mon Jan 28, 2008 10:11 pm

Glad I could help.
niglch
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Sun Apr 13, 2008 8:07 pm

Ok, I have one more quick question:
If you make a serviceable piston housing using the 4 screws, do those screws also serve to stop the piston when it fires back with the bumper in between? I think that's what you meant, but it just seems like the screws would take a lot of the impact. Is there any possibility that this could crack the PVC that the screws are threaded through?
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MrCrowley
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Sun Apr 13, 2008 10:35 pm

Yes they do take the impact. I would actually never make a serviceable piston again using bolts. There are much easier ways that cost a bit more, but it'll save you in the end.

Bolts usually leak after awhile, and need sealing up, which destroys the point of the serviceable piston. Just use threaded fittings.

And yeah they probably could end up cracking the PVC.
niglch
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Mon Apr 14, 2008 9:56 am

Just use threaded fittings.
I feel like a total newbie asking this, but what is the proper way to put together threaded PVC parts? I tried using a threaded plug and female adapter the first time I tried building my housing but ran into some difficulties. I wrapped the male threads with about 3 layers of Teflon and tried to thread it into the adapter. However, the parts became locked up after only a few twists, and the end result was a cracked plug. Are the parts not supposed to thread completely into one another?
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