SpudFiles

im new here and working on my first cannon. i plan on having a diapram
valve but i just dont know how long i should have my barrel . the materiel i have is 2.5 inches in diameter. any input will help

30." Nice easy size.

thanks cause i really didnt know

for a coaxial, homemade diaphragm valve? A barrel sealing valve? Or like a sprinkler valve? Can you give a little more information?

Considering that your chamber is large enough, go as big as you want!

Coaxial Diaphragm as a first gun is a little too much unless you've researched all this for quite a while. Sprinklers are barrel sealing, and a chamber sealing diaphragm is extremely hard to make. So most likely barrel sealing, probably a sprinkler.

well its going to be a home made barrell sealing valve. i have a couple of pipes laying around and because i dont want to be spending to much money i want to make sure i dont screw up and have to buy new stuff.
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If you want to make sure that you don't screw anything up then start with something a little less complicated. Try a simple combustion or if you're dead set on pneumatic try a sprinkler valve instead of making your own valve.

Believe me, barrel sealing valves are really hard as a beginner.

ya today i decided on building a combustion and i think i can finish it up tommarow

Ya know, if I published all my mini-rants here as a book, I could probably make money.

Noname, stop misleading people in efforts to get buisness.
My first cannon ever was a large barrel sealing diaphram valve. Worked fine, first time, every time ('till it was retired due to DWV fittings).

"as a beginner"
That phrase is pretty meaningless. Sure, as a beginer to diaphram valves, it's possible to mess up. Building a combustion doesn't help you any, though.
Thoroughly research it, and a "beginer" could build a hybrid. (although, I'll admit, practice helps with the "gluing large fittings" skill.)

If anyone wants to make sure that they don't screw up, they should build simple. Anyone.

I'm not trying to get business, I'm simply telling him that barrel sealing diaphragm valves are hard as your first cannon.

i built a basic combustion and thats it and i can build a barrel sealing diaphragm, its all down to how muc you know,your skills and how much research youve done all though building cannons does help

Don't knock it. I built my first pnuematic six weeks ago and since I've built a diaphragm and a piston (chamber seal). I'm working on coaxial at this time and hope to test fire it tommorow. My only advice is this, know the basics (See the animations available on this site) and read the instructions on the solvents/glue/epoxies you use. A dead amateur can build it if they are determined enough.

My only other bit of advice is this. Make your gun in implemets that you can seperate. This way you cut down on cost if you screw something up. Once you are sure it works, then go back and build as a single piece. Threaded couplings are your friend.