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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: mega_swordman » Tue Apr 10, 2007 1:43 pm

atreverse12 and I (I know him personally) are having a dispute about a pneumatic rifle and I was hoping (much smarter about this that us) could help resolve it.

The question is as follows: Is it better the have an in-line sprinkler valve on the bottom of the cannon, near the chamber, or is it better on top near the barrel?
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Unread postAuthor: deusXmachina » Tue Apr 10, 2007 1:54 pm

I personally prefer it on top....wait wrong discussion XD

The less restriction you have between the valve and the barrel, the better. So in your case I guess it would be having the inline on top, inline with the barrel. The logic being if you have the U-bend before the valve, it is just air under pressure that isn't moving that fast, but if you have the U-bend after the valve, you have high-flow air moving through a restriction. How much of a difference that makes, I dunno.
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Unread postAuthor: Blitz » Tue Apr 10, 2007 2:11 pm

I concur with deus.

The more direct path air has beyond the valve to the projectile and the atmosphere, the more efficient.
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Unread postAuthor: jssizzle » Tue Apr 10, 2007 2:14 pm

Like deus said, it is definitely better to have the valve closest to the barrel, in this case before the "U". If it was closer to the chamber, it wold create what we call dead space, making the air travel a greater distance before hitting the projectile in the barrel.
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Unread postAuthor: mega_swordman » Tue Apr 10, 2007 2:16 pm

Hmm yes. That means I win. Thank you very much, now if you excuse me, I'm going to show atreverse12 that he is wrong.
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Unread postAuthor: rad14701 » Tue Apr 10, 2007 4:57 pm

The dead space issue is definitely the determining factor... The closer the chamber pressure is to the barrel, the better... Pressurizing dead space slows the firing process and reduces the overall velocity generated within the barrel...
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Unread postAuthor: spudthug » Tue Apr 10, 2007 5:04 pm

although this is true that a valve traveling that far is dead space but also if u have the valve at the top it has to go throguh the bends....say u have 1 inch bends on a 4 inch chamber it has to be restricted greatly..most people prefer the sprinkler valves at the bottom of the gun..
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Unread postAuthor: mega_swordman » Wed Apr 11, 2007 4:38 am

However, with the stock(?) of the rifle, and no good way to block the flow from entering the excess pipe, I feel it is better to have pressure on the joints than to have air flowing through unneeded pipe length.
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Unread postAuthor: Scope » Wed Apr 11, 2007 5:23 am

Closest to the barrel from what i see... it adds to your chamber volume and does not have airflow restrictions after the valve has opened
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Unread postAuthor: paddo » Wed Apr 11, 2007 5:32 am

id say barrel. exact same reason as above. you get more chamber space (good) and the air in the bends is pressurised so the turning will have much less effect.
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