I'm a n00b...

[CuddlyBurrito]

hmm sounds like this will be an interesting cannon. do you have any pics of the pipe and/or fittings? how big are you planning to make this thing? oh and how much money are you willing to sink into it? (sounds like a lot. haha)

answer these and we might be able to help you more

oh and combustions are for cavemen??? hah! your hilarious. but oh well its your opinion not mine...

unless you want 1.3 megapixle phone pics then u wait till saturday. I am willing to pour about 100 bucks into this thing (for everything, glue, valves, fittings. since i have only used pvc for plumbing i dont have any glue laying around). and when i said combustion are for cavemen i ment the kind my dad use to make... not the really cool hybrids

[CuddlyBurrito]

ok i'm going out at lunch look at some local stores and if i dont find anything jus buy a valve from lowes, and otherthings!!!

what should the barrel to chamber ratio be?

[jrrdw]

ok i'm going out at lunch look at some local stores and if i dont find anything jus buy a valve from lowes, and otherthings!!!

what should the barrel to chamber ratio be?

A good rule of thumb is twice as much chamber then barrel.

Here's another good one for ya -- no more double posting, theres a edit butten at the top of your post once it is summited. Just go back and edit, beleave me i'm saying it nicely, others probly wont, it all depends on what kinda mood their in.

[Zippster]

As far as Schrader valves go, I've had some good luck with buying a couple of tire stems for $1, then shoving one onto a 3/8" barb and hoseclamping it over a bunch of teflon to not tear the rubber up. The only problem I've ever had was when it popped off once, but that was easily fixed by chucking mercy out the door and getting out the powertools to tighten the hell out of that thing. Cheap don't-have-to-order-online solution, and mass producable too.

[DYI]

Assuming a fixed chamber size and the use of ~120psi, the barrel should have about 5x as much volume as the chamber for maximum performance (0.2:1 C:B).
Assuming a fixed barrel size, increasing chamber size will always improve performance to some extent.

[King_TaTer]

I'm not sure about the C:B ratio for pneumatics, not too familiar with that class. well you kind of left my questions wide open but thats alrite, it's understandable . Also you might want to let your dad help you with you with glue job unless your absolutely confident with yourself. I say this mainly because its your first powerful gun and glueing is of great importance when dealing with high pressures. I was at my buds one time and he had a cannon similar to the one your building. We had it up to about 115 psi then suddenly one of the endcaps on the chamber blasted off blowing through his porch railing. Not kool haha.

[CuddlyBurrito]

.....suddenly one of the endcaps on the chamber blasted off blowing through his porch railing. Not kool haha.

lol thats sounds bad.. i dont live with my dad i live in a dorm room, i'm 18. so i am confident i have used pvc before (plumbing, my uncle is a plumber..) so i'm good btw i finished today and going to post in the cannons section in about 10 min i gotta take some pics.