Chamber size question

Brooner115 · Sat Apr 28, 2007 10:53 am

How big of a chamber would I have to have to support a 60" long 1 1/2" barrel??

I only have 3" pipe so if you could tell me how long of 3" pipe I would need that would be great

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I'm thinking I need around 18"s to get the best performance out of it but I'm not sure could someone pleaze help?? I'm a complete retard when it comes to c:b ratios and good performance. oh ya its a combustion cannon.

super spuder · Sat Apr 28, 2007 10:58 am

um. is it pneumatic or combustion?

Brooner115 · Sat Apr 28, 2007 11:03 am

damn it!! I knew I forgot something its a combustion sorry about that.

hi · Sat Apr 28, 2007 11:07 am

you will have to have it be about 2 1/2 feet long.

Velocity · Sat Apr 28, 2007 11:36 am

The optimal chamber to barrel ratio for a propane powered combustion is 0.8:1.

Your barrel is 1.5" x 60"; the volume is therefore about 34pi

You need a chamber with a volume 80% of that, or 27.2pi

Divide 27.2 by 2.25 (which is (3/2)^2), and you get about 12

Your combustion chamber needs to be about 12" in length

hi · Sat Apr 28, 2007 12:31 pm

rmich, there is no way thats right, a 12'' chamber will be way to small. A 12'' chamber is good for about a 35'' barrel, not a 60''.

Velocity · Sat Apr 28, 2007 1:31 pm

Well...
Barrel: ((1.5/2)^2)(60)(pi) = 33.75 pi cubic inches
Chamber: ((3/2)^2)(12)(pi) = 27 pi cubic inches

This creates a chamber to barrel ratio of 0.8:1

hi, keep in mind that each inch of 3" pipe has 4x the volume of each inch of 1.5" pipe... and the calculations don't lie.

SpudBlaster15 · Sat Apr 28, 2007 1:32 pm

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Brooner115 · Sat Apr 28, 2007 4:42 pm

Ya guys its gonna be a hairspray combustion and thanx to all of you for helping me out I think i'm gonna go with a 18"-20" chamber in between what all of you where arguing about thanx a bunch

Whats OP mean? is that a complement or a nickname or are you making fun of me? lol

SpudBlaster15 · Sat Apr 28, 2007 4:58 pm

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boilingleadbath · Sat Apr 28, 2007 10:48 pm

One note:
The discussion that has occured up to this point gives you the smallest chamber that can keep the spud from slowing down before it leaves the barrel - not the chamber that will give you the most muzzle energy.

To maximize muzzle energy with a fixed barrel length, you generally want a chamber bigger than their calculations suggest.