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Good 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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Good C:B Ratio?

Unread postAuthor: Gidney14 » Sat Aug 06, 2011 5:56 pm

Just finished my tennis ball cannon, and realized that my C:B ratio was probably way out of whack. ATM: MY 4'by 2.5" barrel has a volume of 235 CI, my 3' by 3'' chamber measures in at 254. For a combustion the best ratio is between .6 and .8, What would it be for a pneumatic? about the same?
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Unread postAuthor: Gun Freak » Sat Aug 06, 2011 6:07 pm

It is fine.....
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Unread postAuthor: Gidney14 » Sat Aug 06, 2011 6:08 pm

Gun Freak wrote:It is fine.....


Thanks.
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Unread postAuthor: MrCrowley » Sat Aug 06, 2011 6:26 pm

You can simulate any cannon design you want and receive estimated performance for such design using a program called GGDT. Any information you require about using the program can be found on the site so be sure to read it over before asking for help with it.
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Unread postAuthor: Gidney14 » Sun Aug 07, 2011 9:58 pm

Last stupid question, what would you select for valve type if using a modded sprinkler valve?
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Unread postAuthor: Mr.Tallahassee » Sun Aug 07, 2011 10:01 pm

Search the GGDT site. Depending on what model and size you have, there should be an accurate representation for the valve. I think it's under the "Archives" section.
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Unread postAuthor: Gidney14 » Sun Aug 07, 2011 10:07 pm

Mr.Tallahassee wrote:Search the GGDT site. Depending on what model and size you have, there should be an accurate representation for the valve. I think it's under the "Archives" section.


Found it. Thanks.
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Re: Good C:B Ratio?

Unread postAuthor: velocity3x » Sun Aug 07, 2011 11:35 pm

Gidney14 wrote: For a combustion the best ratio is between .6 and .8, What would it be for a pneumatic? about the same?


For high pressure, I prefer a CB of 1:1
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Unread postAuthor: Technician1002 » Sun Aug 07, 2011 11:53 pm

For low pressure, you want larger chambers. For high pressure, if the compressor supply is not an issue, large is good, but has diminishing returns. For hand pumping, a smaller chamber can reduce performance a little while cutting the workout on the hand pump to a managable workout.
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