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Calculation problems

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Calculation problems

Unread postAuthor: Mr_SBC » Thu Mar 30, 2006 10:41 pm

Hi, I am building a pb gun and I have a question.

1. I am trying to calculate the proper ratio, and trying to find what set up is the best.

I am using EVBEC v 1.2 at the moment and it is the calculater for combustions. Will it work the same for pnuematics? Will the ft/s be the same?

For example... Im going to be using a 5.5" x 2" sch 40 chamber to a 3/4" sprinkler vavle to a 40"x .75" barrel. Will this set-up be in the 450 ft/s range? GGDT is working for me right now, otherwise i would just use that. Any suggestions are appreciated.
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Unread postAuthor: boilingleadbath » Thu Mar 30, 2006 11:36 pm

You can try using EVBEC to model a pneumatic if you want, although I don't recommend it. You might try multiplying the output velocity by sqrt(pressure/30 or 40), although that's going to be inaccurate in this case due to valve flow issues.

As to that specific cannon, I guessed at some values for a modded 3/4" sprinkler valve, and it gets ~450 fps at 55 psi.
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Unread postAuthor: zvallance1 » Thu Mar 30, 2006 11:39 pm

for a pnuematic cannon, you're best bet would be to use the GGDT (gas gun design tool)...Its available along with some notes, from this link
http://www.spudfiles.com/spud_wiki/index.php?title=GGDT


best of luck!
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Unread postAuthor: boilingleadbath » Fri Mar 31, 2006 3:13 pm

Zvallance1, he stated in his post that the GGDT wasn't working for him.

Which is a horrible situation... Mr. SBC, what type of machein are you using? ...and are you logged on as a administrator?
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Unread postAuthor: zvallance1 » Fri Mar 31, 2006 5:04 pm

boilingleadbath wrote:Zvallance1, he stated in his post that the GGDT wasn't working for him.


well, thats weird, I must have missed that when i read it...how embarrasing :oops:

Anyways, Mr_SBC...if you post the information about your gun, I (and im sure almost everyone else here) would be glad to help you out
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