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 Post subject: my plan
 Post Posted: Wed Jul 16, 2003 9:00 am 
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Originaly posted by robertjuric,
hey, can yall give your opinions on my plan for a pnuematic launcher? I wanted to use a bigger co2 bottle(not the small 12grams), and a regulator of course. I wanted to use 2' of the 2.5" tennis ball barrel, and 20" of 3" pipe for my air resevoir. should give me about a 3:1 ratio. and the solenoid sprinkler valve.

What I wanted to do, was run the co2 from an on/off asa, to the reg(maybe through an xpansion chamber), into the resevoir, let it fill at 100psi, then cut the asa off. I was just thinking, this would be a good way so that I can shoot the same amount of air everytime, and not waste any.

Just wanted to get opinions before I start purchasing parts.


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 Post Posted: Wed Jul 16, 2003 11:00 am 
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Originaly posted by mta,
That's an awfully short barrel. You'd get better performance shortening the chamber by 10 inches and adding that ten inches to the barrel. You'd get twice as many shots per CO2 bottle, as well.

What kind of valve are you planning to use?


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 Post subject: he said solenoid...
 Post Posted: Wed Jul 16, 2003 12:00 pm 
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Originaly posted by andeh,
so I assume an inline sprinkler. Mod it to pneumatically actuate.


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 Post subject: What size?
 Post Posted: Wed Jul 16, 2003 12:00 pm 
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Originaly posted by mta,
Size matters.


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 Post subject: mistake
 Post Posted: Wed Jul 16, 2003 1:00 pm 
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Originaly posted by robertjuric,
messed up my math, I actually need a 5" dia resevoir instead of the 3".

and I was going to use the sprinkler valve electronically.


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 Post subject: how would that help?
 Post Posted: Wed Jul 16, 2003 1:00 pm 
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Originaly posted by robertjuric,
how would that help with shots per bottle?


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 Post subject: volume
 Post Posted: Wed Jul 16, 2003 1:00 pm 
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Originaly posted by mta,
A chamber half as long (10" vs. 20") would have half as much volume, and you'd get twice as many shots per bottle.


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 Post subject: 5" ?
 Post Posted: Wed Jul 16, 2003 1:00 pm 
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Originaly posted by mta,
5" pipe is hard to find, and 5" fittings even harder. A 20" x 5" chamber has a volume of almost 400 cu. in. That's huge. You'd be getting only a tiny increase in velocity by using a chamber that large vs. a 3" chamber, and you'd be using almost 3 times as much C02 per shot.

I'd go with a smaller chamber, longer barrel, and supe up the sprinkler valve. Pneumatically activated sprinkler valves are a lot faster than solenoid ones.



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 Post subject: so..?
 Post Posted: Wed Jul 16, 2003 2:00 pm 
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Originaly posted by robertjuric,
so stick w/ the 3" pipe but take 10" off the length and put it on the length of the barrel? and use the sprikler valve pnuematically.


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 Post subject: That'll work
 Post Posted: Wed Jul 16, 2003 2:00 pm 
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Originaly posted by mta,
That'll work. The gun will be the same length, you'll use half as much CO2, and it will be a little bit more powerful. Suping up the valve will help also.

If you haven't already done so, download GGDT (Gas Gun Design Tool) It lets you try out different barrel and chamber dimensions and see the effect on muzzle velocity.

http://www1.iwvisp.com/thehalls/paintball/ggdt.html

For your gun I assumed a Cv of 7.5 for a 1" valve, 10 ms open/close time, 1000 ms dwell time. Tennis balls weigh 58 grams.




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