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help with C:B ratios.

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help with C:B ratios.

Unread postAuthor: A-98 » Mon Mar 12, 2007 12:38 am

ok, first off, im good at math, but im terrible with ratios, so could omeone help me?

i have a chamber with a volume of 301 cubic inches, and a barrel with 63 cubic inches.

i sorta did the math and i came out with .79:1....but i know thats terribly wrong.

any help would be appreciated.
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Unread postAuthor: SpudBlaster15 » Mon Mar 12, 2007 12:41 am

Divide the chamber volume by the barrel volume to find the chamber to barrel ratio. Your C:B ratio is ~4.7:1.
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Unread postAuthor: A-98 » Mon Mar 12, 2007 12:48 am

is that crazy big for a pneumatic?( at ~100 psi)

i dont want this thing to wake up the neighborhood
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Unread postAuthor: SpudBlaster15 » Mon Mar 12, 2007 1:25 am

It is quite overkill and will be very loud. For a pneumatic launcher at 100psi, I usually suggest a C:B ratio between 1.5:1 and 2:1. Larger ratios will give you very slight increases in performance, but they are not worth the extra air comsumption in my opinion.
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Unread postAuthor: joannaardway » Mon Mar 12, 2007 7:20 am

Huge C:B ratios are usually best avoided, unless you're trying to break the sound barrier, or make a racket. If you can, halve your chamber size.
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Unread postAuthor: A-98 » Mon Mar 12, 2007 10:07 am

ill think about changing the pipe size from 4" to 3", and also chaning the length from 24" to 18". ill plug in the #'s and see what i get.
thanks for all your help!

EDIT: ok, i plugged in the #'s and i got a C:B ratio of 2.01:1

could someone check that for me?
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Unread postAuthor: noname » Mon Mar 12, 2007 5:40 pm

Or you can just make the barrel longer. :D Better performance, but reducing chamber size and increasing barrel length will make it possible to have a chamber still big, but not as big, and you can still come out with a 1.5:1 or 2:1 ratio.
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Unread postAuthor: A-98 » Mon Mar 12, 2007 8:57 pm

well, im not sure if pimp has cut the pipe, but im going for a 3' golfball barrel, And the max length shippable is 5'...ide have to do the math....i might do some optimization. also i have the price figured out so that it comes to 80$, and i dont want to mess that sexy # up :D
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