PCP building blog

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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urgle the danish cow
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Fri Feb 03, 2012 5:27 pm

wyz2285 wrote:The sealing came from a co2 pin valve pin, about epoxy I used one with 360 bar rated.
so like the sealing face from a manufactured co2 gun? do you know the material?
also are your "valve pins" from a blowgun?
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Gippeto
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Fri Feb 03, 2012 5:52 pm

Uh huh.

Did you calculate what the fail pressure would be?


Edit: urgle...most co2 guns use urethane for seals.
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inonickname
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Fri Feb 03, 2012 10:05 pm

Gippeto knows what he's talking about.

Pressure test it if you want to actually be safe.

And by pressure test, I don't mean pump it up to 300 psi below the working pressure. I mean test it hydrostatically with a safety margin.

And trust me, it can fail.
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urgle the danish cow
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Sat Feb 04, 2012 12:44 am

Danke Gippeto
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wyz2285
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Sat Feb 04, 2012 6:36 am

And trust me, it can fail.
:? nobody said anything about Gun Freak´s gun...
CpTn_lAw wrote: :D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
dahakka
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Sat Feb 04, 2012 7:36 am

may be you should use some screws
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Gun Freak
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Sat Feb 04, 2012 8:53 am

My gun is held together by threaded fittings and carefully soldered joints and has a valve that has held 2,000 psi over night by another member here. :D
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Sat Feb 04, 2012 11:10 am

Gun Freak wrote:My gun is held together by threaded fittings and carefully soldered joints and has a valve that has held 2,000 psi over night by another member here. :D
3000 actually :D
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Gun Freak
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Sat Feb 04, 2012 12:40 pm

Gahh I didn't want to say 3000 and be wrong!!! :D
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wyz2285
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Sat Feb 04, 2012 1:39 pm

I belive my epoxy will hold more than your tin weld, it´s 3cm of epoxy in a 1cm2 area to hold only 70 bar...
CpTn_lAw wrote: :D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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Gun Freak
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Sat Feb 04, 2012 6:58 pm

I believe that is irrelevant because I only plan on using 400 psi :)
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Goats spudz
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Mon Feb 13, 2012 9:02 pm

Do you think Argon would be a suitable propellant gas?
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Tue Feb 14, 2012 2:35 am

Goats spudz wrote:Do you think Argon would be a suitable propellant gas?
It's denser than air so that will mean less performance for a given pressure than if you were using air or nitrogen, but it's less dense than CO<sub>2</s>.
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Tue Feb 14, 2012 8:45 am

I think ill use Nitrogen then, thanks :D
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wyz2285
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Wed Feb 15, 2012 2:30 pm

Some updates:
My epoxy leaked :( (plz don´t laugh at me), and I know it´s almost impossible to repair it (unless take the valve off, clean the epoxy and glue it again).
So I made a kind crazy decision: make my own valve, with o-ring seal. The advantage is obvious, I can fix the valve on the chamber with screws and when I have to repair the valve, I just have to unscrew it. Well, I made the valve out off nylon, because I don´t have a metal lathe, only my drill press.
Anyway, I made it :P , with 2 o-rings(still need to make the internals). Now I won´t be using 1000 psi, only 60 bar. The area is about 3.33 cm2, at 60 bar it will be 200.4 kg. I´m not worried about the valve blow up, but the screw part, where shout I place the screws?
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CpTn_lAw wrote: :D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
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