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air chamber dilemma

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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air chamber dilemma

Unread postAuthor: Major Collins » Wed Mar 02, 2011 4:40 am

ok well i have two air chambers to choose from
the first being a 20mm copper pipe about 70mm long
the second stainless steel also 20 mm but about 50mm

and my barrel is 1meter long (same as stainless just a whole 1m piece)
for those who need chamber to barrel ratio

which would be better ?

other notes you might need to know are im soldering the joins so dont know if it will be as well on the stainless steel
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 02, 2011 4:54 am

What is the wall thickness of those pipes, and what pressures do you intend to run at? If they are both suitable for the pressure you intend to operate, then the only difference is volume. If you're pumping manually and care about noise, go for the shorter one. If MOAR POWAH! at any cost is the priority, go for the longer one, as long as its still suitable for the construction you're using.
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Unread postAuthor: Major Collins » Wed Mar 02, 2011 5:41 am

the thickness of both pipes is either 1.5 or 2ish mm
for the time being only 150 psi but maybe up to 350

so you say i should go with the longer copper piping?

and im more for power
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 02, 2011 5:46 am

If it's power you want then more chamber volume is always a good thing.

It will take significantly more than 350 psi to burst 1.5mm wall thickness 20mm diameter copper pipe, you should be quite safe.
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Unread postAuthor: Major Collins » Wed Mar 02, 2011 6:00 am

alright copper pipe it is .. :) will be soldering that on tomorrow

and i was wondering if i could make a decent semi auto with the pipe by cutting it two halves .If you answered yes to this ... what ratio would i cut the pipe? .. eg 30 mm firing chamber to 40 filling chamber ?

would i get a decent semi auto ?

and i don't have the problem of letting air from behind the piston because i have a spring that pushes the piston back up against the barrel
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 02, 2011 6:38 am

In general I would disagree with having separate chambers for semi-auto, unless you were feeding HPA through a regulator.

I'll preempt POLAND_SPUD and suggest a DCV as a feed/pilot valve :)
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Unread postAuthor: Major Collins » Wed Mar 02, 2011 6:46 am

alright then thankyou for that
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Unread postAuthor: POLAND_SPUD » Wed Mar 02, 2011 9:16 am

I'll preempt POLAND_SPUD and suggest a DCV as a feed/pilot valve

POLAND_SPUD agrees with your statement
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