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mini pneumatic

Discuss miniature cannons built from things such as pill bottles and pen caps.
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mini pneumatic

Unread postAuthor: knappengineering » Tue Sep 18, 2007 10:42 pm

I'm looking to make a mini pneumatic that is capable of more that one shot before re-pumping. I was thinking of using a small regulator like this http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90590
to regulate it down to a second firing chamber but i'm looking to make it as small as possible! any ideas? btw, i was thinking of using a 1/2"pvc barrel but i'm not sure about the valve, i'm thinking anything small and easy to make. thx.
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Unread postAuthor: Lentamentalisk » Tue Sep 18, 2007 10:58 pm

well there is always that idea that i posted to you a few days ago, but what ever, incase you lost it, here it is
http://www.spudfiles.com/forums/firing- ... rt,15.html

why dont you just use a ball valve to empty from a larger tank at the same psi?
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Unread postAuthor: knappengineering » Tue Sep 18, 2007 11:01 pm

i made a larger gun with the ball valve design ur suggesting but i haven't tried it yet because the glue is still curing but i want to make this one super small. i thought i might use a blowgun for a valve. just not sure about the chamber design cuz now that would be the only large part.
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Unread postAuthor: f.c » Tue Sep 18, 2007 11:12 pm

go ahead but the largest thing you could fire from it would be 6mm bb's. though at 100 psi with a 6mm barell (50cm long) i could imagine it doing some decent damage.
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Unread postAuthor: knappengineering » Tue Sep 18, 2007 11:18 pm

i was thinking of using adapters to get up to a half inch barrel. I might use a 1 inch high pressure chamber thats regulated down to a 3/4" low pressure firing chamber. would that work for firing foam pellets and frozen mini marshmallows?
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Unread postAuthor: jimmy101 » Wed Sep 19, 2007 12:11 pm

Couple thoughts;

1. Large chamber at moderate pressure, perhaps 150 PSI.
2. Small chamber, also at 150 PSI.
3. The large and small chambers are connected by a very small ID hose, perhaps less than 1/16"ID.
4. Small chamber connected to an electrically activated valve, like a sprinkler or dishwater valve.
5. Valve connected to breech mechanism and barrel.
6. When you fire, the small chamber depressurizes and propels the ammo. The small bore hole between the two chambers restricts gass flow enough that little of the big chamber's air is used.
7. When the firing valve is closed the big chamber repressurizes the small chamber in a few seconds.

Another method would be to just use a poppet valve (IIRC what a paintball gun uses). The valve is opened by striking it and it auto-closes very quickly.

You might want to take a look at the RC Warship gun designs;
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Unread postAuthor: knappengineering » Wed Sep 19, 2007 11:49 pm

thx, i'll check it out
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