SpudFiles

This is the first actual spud cannon/tennis ball cannon I have built, but I have mechanical experience. My question is, disregarding convience and such, which valve would be better? I have yet to find a 2" sprinkler valve, maybe I'm not looking in the right place, but I'd like to keep my valve price under $20. I am planning on using a barrel that is 3 feet long. Thanks in advance!

Just buy a 1" sprinkler and put adapters on both sides.

I am not one hundred percent sure, but I would say the 1" sprinkler valve. By the time you get a ball valve half open all the air from the tank would be emptied. You would get better performance with a longer barrel, but it would be less portable/harder to hold.

Edit: Every once in a while you can find a 2" sprinkler valve on Ebay, but the cost would be at least 40 dollars.

Would it really be worth getting a 2 inch sprinkler valve? What kind of ranges could i expect with a 3ft 2" barrel, 40-50psi, from either a 3" or 4" 2' air tank?

I'm not much for pneumatics but GGDT may answer a lot of your questions.

With a 3 feet barrel, pick the sprinkler.
Ball valves are only good on very long barrels (or very heavy projectiles)

You could also look into building your own 2" diaphragm or piston valve.

This probably dosen`t help but i would look into burst disks.

mrcrouse1 if you are by any chance in australia i have a 3" sprinkler rated to 220psi laying around somewhere.

My 2 cents, PVC 2" ball valves are super annoying to open/slow.
Metal ball valves are pricey so unless you have one hanging around, I saw them going for like 45$ at Lowe's. My 1" sprinkler valve was 15$ I believe.
I honestly think you should build your own piston valve, for price and efficiency they are amazing.

Go with the 1" sprinkler, it'll out perform the 2" ball valve. Not only will the muzzle velocity be better with the sprinkler valve but you also have a much better chance of actually hitting anything smaller than the county you live in.

Build the first gun with the un-modified valve. If you think you need better performance you can mod' the valve later. Cost $5 to $10 to mod' the valve unless you have an extra compressor blowgun laying around.

Ok, thanks to everyone who has responded. What about a 2 inch piston? I think I finally understand the concept pretty well. It would be nice though, if some people could post some pictures of them. I tried to look around to find some specifics, but wasn't too sucessful.

Piston Valves

As far as piston pics, there are several, several, pics here. Also, check the wiki.