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Optimum C:B ratio

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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Optimum C:B ratio

Unread postAuthor: Jolly Roger » Tue Aug 29, 2006 2:57 am

Hey just wondering what the optimum chamber to barrel ratio is? I tried using that GGDT tool but personally I don't think its very accurate. I change the outside diameter of the chamber and the velocity goes up??? WTF? I didn't realise when first entering my numbers but the piston diameter was larger than the chamber diameter and it still tried to chuck out results..? WTF? Oh well, yeah what I'm trying to figure out is the perfect ratio for a piston exhuast cannon at about 100psi..
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Unread postAuthor: MrCrowley » Tue Aug 29, 2006 3:05 am

the guy that desgined it is a weapon enigineer for the US army. correct me if im wrong. the O.D thing is weird, make the O.D the I.D and set the I.D as 0.
there is no best ratio for pneumatics but a good one to start at is 1:5:1
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Unread postAuthor: LucyInTheSky » Tue Aug 29, 2006 4:30 am

The ID is for co-axal chambers.
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Unread postAuthor: killagorrila99 » Tue Aug 29, 2006 5:12 am

it was designed by a weapon designer? wow lol i didnt no they used spudguns in the army...




jks
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Unread postAuthor: mark.f » Tue Aug 29, 2006 5:19 am

Actually, I believe he's Navy... so....

GO Navy!!! BEAT Army!!!

I think any ratio above 2:1 is good. Just don't get too extreme, like 6:1, or you're just wasting money for what little extra velocity you gain.
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Unread postAuthor: noname » Tue Aug 29, 2006 10:31 am

Oooooo mememe! I made one that was 9.5:1! I probably should have put a bigger barrel, it wasn't intentional.
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Unread postAuthor: MrCrowley » Tue Aug 29, 2006 3:37 pm

yeah i think it was navy but thats not the point he designed weapons for stuff...
here this is from his site:"My name is David Hall. I'm a Mechanical Engineer employed at the Naval Air Warfare Center, Weapons Division, Ordnance Test & Evaluation Branch. I started my career writing flight simulations. These days I test bombs, rockets, and guns. Combine those two assignments and voila."
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Unread postAuthor: Jolly Roger » Thu Aug 31, 2006 12:07 am

So despite his extremely specific calculations to obtain the perfect C:B ratio, it doesn't really matter as long as it is between 1.5:1 and say 6:1...
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Unread postAuthor: killagorrila99 » Thu Aug 31, 2006 3:10 am

id go 4:3


works good for pneu's
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