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Idea for pneumatic gun using CO2

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: -T0OL- » Tue Oct 03, 2006 6:37 pm

Image

from what i have read and seen this is how a piston cannon is designed...

a few questions though:

1. Whats the ideal distance for the piston to be able to move?

2. Whats a reasonable size for the equilization holes?

3. Would it make sense to put one way valves on the equilizer holes?

4. Whats the ideal C:B ratio?
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Unread postAuthor: MrCrowley » Tue Oct 03, 2006 6:46 pm

so your building a co-ax now

1:there is no ideal distance just keep it small-ish enough room for everything to fit in really.
2:correct me if im wrong but i think its 1/16" cant remember for a co-ax.
3:no,theyre too big to fit in and could break when it actuates and slams into the end cap just put small holes.
4:for pneumatics there is none just stay between 1:5:1 and 4:1 and thats a safe bet.
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Unread postAuthor: -T0OL- » Tue Oct 03, 2006 6:51 pm

alright thanks... when i was thinking one way valves i was thinking just taking a flap of rubber and screwing it to the piston on one side with only one screw... but if the holes are only 1/16" its kinda pointless isnt it?

just one equilizer hole or two?
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Unread postAuthor: MrCrowley » Tue Oct 03, 2006 9:01 pm

two, but double check the 1/16" thing i use the metric system and 1/16" for some reason poped to mind when i thought of co-ax eq holes.
it might be 3/16" not sure but i remember it from this site so just search it.
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Unread postAuthor: -T0OL- » Tue Oct 03, 2006 10:02 pm

in my diagram above the piston is in the shape of a bottle cap. but after thinking about it a bit, im starting to think it would be better if it was solid so that there is less air waisted in the pilot area.
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Unread postAuthor: MrCrowley » Tue Oct 03, 2006 10:32 pm

yeah pistons arnt hard to make just use something random and it usally works :roll:
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Unread postAuthor: -T0OL- » Tue Oct 03, 2006 11:55 pm

here is what i've been planning to make...

The red lines are what it would look like idealy, the rest is labled.... First priority is to get it to work, then to get it to look right and add features like semi-auto.

Image

EDIT::

any suggestions on what would work best for something like this:

what i have so far is:

galvanized steel for chamber
copper for barrel
piston??
air compressor blower for handle/trigger (dunno technical name)
9oz CO2 tank from walmart
Regulator (gotta check PB store nearby)
this:
http://cgi.ebay.ca/Paintball-Gun-Remote ... dZViewItem
for the On/Off switch and to connect regulator to chamber (hopefully)

and i think thats all i've come up with so far.
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Unread postAuthor: POS » Wed Oct 04, 2006 4:48 pm

3 : You could make one way valves on the piston by just making the rubber disk bigger, so it covers the holes. The pressure from behind will push it away, so the chamber will fill. The pressure from the chamber will seal the holes when the gun is fired, the chamber pressure will puch the rubber against the holes, sealing them off, when the pilot pressure drops.
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Unread postAuthor: -T0OL- » Wed Oct 04, 2006 10:59 pm

ooh, i never thought of that thanks POS... by doing that less pressure will be lost out the pilot area right? though it probably wont be enough to notice...

EDIT:: when i put my sketch into GGDT i get this after calculating the performance:

WRN: Barrel potentially choking flow
WRN: Barrel choking flow

what would i do to fix that?
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