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Advanced Combustion Chamber To Barrel Ratio?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Advanced Combustion Chamber To Barrel Ratio?

Unread postAuthor: spudkilla224 » Tue Nov 25, 2008 7:19 pm

hello, i'm planning on building a advanced combustion cannnon using metered propane. and my question is "what's a ideal Chamber To Barrel Ratio for a and advanced combustion"?

i want to figure that out before i go and buy the pvc.

Thank You
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Unread postAuthor: jimmy101 » Tue Nov 25, 2008 7:29 pm

There is no such thing as an "ideal Chamber To Barrel Ratio for an advanced combustion" gun.

Read the SpudWiki on combustion gun's CB ratio.

Get a copy of HGDT and fiddle with it. Decide what you want to trade for better muzzle velocity.
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Unread postAuthor: MrCrowley » Tue Nov 25, 2008 7:37 pm

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Unread postAuthor: LCTChamp » Tue Nov 25, 2008 7:53 pm

I always use about a 1.5:1. I read that that was the so called "ideal ratio" somewhere, but I could be wrong.
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Unread postAuthor: starman » Tue Nov 25, 2008 10:22 pm

Go to Burnt Lake's Siteand read the performance data gathered on various sized c:b ratios. He found .8:1 was roughly an ideal ratio. However you can go on up to 1.5:1 or so with very little loss of efficiency...which is really what you're measuring.

However, as a general rule of thumb, for any given chamber, a reasonably longer barrel will almost always improve performance AND for any given barrel, a larger chamber will almost always improve performance to some degree.... 8) Did that make sense?

So it really boils down to a compromise on size and weight and handling of the gun you want to build.
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Unread postAuthor: psycix » Wed Nov 26, 2008 2:37 pm

Only drawback on larger chambers is that burn time may increase, so multiple spark gaps would surely help.
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