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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: jackssmirkingrevenge » Mon Aug 17, 2009 3:19 pm

gabeb123 wrote:hey you guys are all so hostile chill out.


Au contraire, I think we're mostly quite reasonable, and only to happy to share advice based on our own experiences and research. If this happens to disagree with what you believe, that can hardly be construed to be impolite. This is a discussion forum, there'd be no discussion if we all agreed all the time ;)
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Unread postAuthor: gabeb123 » Mon Aug 17, 2009 6:12 pm

good point.

hey so i got a 1.5"pvc barrel that is about 4 feet long and a 3" chamber that is 33 inches long is that good
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Unread postAuthor: MrCrowley » Mon Aug 17, 2009 10:22 pm

gabeb123 wrote:good point.

hey so i got a 1.5"pvc barrel that is about 4 feet long and a 3" chamber that is 33 inches long is that good

If good means efficient, no.

Cut the chamber down to 12"-15", that's all you'll need.
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Unread postAuthor: Technician1002 » Mon Aug 17, 2009 10:35 pm

MrCrowley wrote:
gabeb123 wrote:good point.

hey so i got a 1.5"pvc barrel that is about 4 feet long and a 3" chamber that is 33 inches long is that good

If good means efficient, no.

Cut the chamber down to 12"-15", that's all you'll need.


For very low pressure stuff such as 6-10 PSI, the ratio is good and effecient. For very low pressure cannons, a very fast valve is not required. A well lubed ball valve provides good flow.

If you intend to use higher pressure then a smaller chamber will be needed for high effeciency. Use GGDT to model your chamber and barrel at your working pressure. An oversize chamber can provide a small velocity increase at the expense of using more than twice the air. For hand pumped stuff, smaller is much less work to pump up.
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Unread postAuthor: gabeb123 » Mon Aug 17, 2009 10:36 pm

will it hurt anything to have a bigger chamber because i have a big compressor so it takes like 20 seconds to fill it

also what are most sprinkler valves pressure rated too? i've been doing 60 psi because im afraid to go any higher
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Unread postAuthor: MrCrowley » Mon Aug 17, 2009 10:39 pm

It wont hurt performance, it will just waste air from your compressor, so if you're happy with that, leave the chamber at 33". Though you might have trouble if you use a track pump to pump it up.

Most sprinkler valves are rated to 125PSI, safe enough at 150PSI.
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Unread postAuthor: gabeb123 » Tue Aug 18, 2009 11:51 am

next im going to modify the sprinkler valve and im going to make a new bigger barrel for it im thinking 2" because i have tons of empty caulk tubs laying around.
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Unread postAuthor: Technician1002 » Tue Aug 18, 2009 12:19 pm

gabeb123 wrote:next im going to modify the sprinkler valve and im going to make a new bigger barrel for it im thinking 2" because i have tons of empty caulk tubs laying around.


I love screw on barrels. The ammo variety increase is fantastic.
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Unread postAuthor: Willdebeers » Tue Aug 18, 2009 1:04 pm

Technician1002 wrote:
gabeb123 wrote:next im going to modify the sprinkler valve and im going to make a new bigger barrel for it im thinking 2" because i have tons of empty caulk tubs laying around.


I love screw on barrels. The ammo variety increase is fantastic.


Nice paint job! :D You could always use a piston valve, as they are very powerful and open very quickly. *Cough Destroyer MKII Cough*
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Unread postAuthor: noname » Tue Aug 18, 2009 1:14 pm

If you do make several screw on barrels, remember to use female threaded adapters. Not many people seem to do this, but those who do realize that it is an extremely easy way to breech load. :wink:
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Unread postAuthor: gabeb123 » Tue Aug 18, 2009 1:47 pm

its allready set up for screw on barrels i just only have one barrel the female threads are on the barrel
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Unread postAuthor: Willdebeers » Tue Aug 18, 2009 2:05 pm

Nice. But what's the point of having threads when you only have one barrel?
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Unread postAuthor: gabeb123 » Tue Aug 18, 2009 9:52 pm

im going to make more barrels eventually i want to make a tennisball barrel so i can launch a tennis ball into one of my fields and have my dog go get it for me i could do that all day.
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