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Chamber Lengths

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Chamber Lengths

Unread postAuthor: Grignacke » Wed Dec 22, 2010 9:00 pm

Hey guys,

I currently have a 2' , 2" chamber with additional reducing couplings on the sides (to fuel, and to barrel). I've noticed this is a pretty long and thin barrel, which the wiki said is conducive to DDT. Would you all recommend I shorten the chamber? I mean I could get more reducing couplings and have a large diameter chamber as well, but that might get pricey. Of course, if a long, thin chamber = terribad performance, then I'll consider it.

Thanks, and have yourselves some happy holidays :)
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Unread postAuthor: saefroch » Wed Dec 22, 2010 9:19 pm

Probably no danger of DDT unless you're running a high-mix oxy-propane hybrid. Probably not much of a performance loss either, but you may consider going for a shorter, fatter chamber just to make it easier to hold.
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Unread postAuthor: Grignacke » Wed Dec 22, 2010 9:23 pm

Gotcha. Thanks!
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Unread postAuthor: Technician1002 » Thu Dec 23, 2010 12:18 am

A shorter fatter chamber tends to perform better as the flame has less distance to travel to ignite all the gas. There is less wall in contact with the gas so there is less cooling of the hot gas.

The most efficient shape to contain any volume of gas is a sphere.
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