somewhat new cobustion?

[haulinick]

I found an old combustion sitting in my garage that i made a long time ago. When i made it i could never get the damn thing to work. Its made out of a 36" sch80 3/4 in barrel and a 17" sch80 2in chamber. I finally got smart yesterday and through the numbers into that caculater (sry i forgot the name) and it turns out that in order to get a good c:b i would hav to shorten my chamber to 7" long. i was thinking that i might as well use my first propane set-up on this since it just happens to be all sch80 which wont scare my parents shitless. I was just wondering if anyone could check my math for the c:b cause I had trouble getting to where I am now.
And also, is it necessary to have a pressure regulater on a meter set-up? I dont know what an average psi for a full propane tank is.

[benstern]

psi for a propane tank varies with temperature.

[LucyInTheSky]

Make your barrel 120inches.

This will give you a 0.79:1 Ratio, ideal!

I got this using RATCALC from http://www.burntlatke.com

[haulinick]

That would be pointless. Its not worth it since it would cost alot for another sch80 barrel. I am tryin to keep the sch80 theme going without spending anymore money.
All I want is small rifle kind of combustion. A 10' barrell would mess that up.

[Atlantis]

So you want to change the chamber to fit the barrel. I did the math for a C:B ratio of 1.5 to 1, I got 7.6" for the chamber, I wrote a C:B calculator program on my graphing calculator, it's very useful.

36" 3/4" Barrel
7.6" 2" Chamber

[haulinick]

Thanks alot Atlantis. That helps!

[SpudStuff]

that barrel is $5 that is not expensive. you can get it as a sptinkler riser.