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[brogdenlaxmiddie]

(Deleted Post)

[FeLeX]

Probably mauler valve. QEVs work good. But you said LOTS of air so Id say mauler.

[DYI]

The fastest valve is a burst disk, for any given size, but piston valves are far easier to use once they're built. QEVs are good for small cannons, as they are essentially store bought piston valves. The Mauler is one of the fastest piston valves of a decent size.

[brogdenlaxmiddie]

(Deleted Post)

[DYI]

Mauler valves can be bought from BCarms, but for a cannon that size you may want to do a homemade piston valve in a 4" tee (or a 6" tee, but that would cost you your life savings)

[Velocity]

Hmm... a large cannon of that size using some type of burst disk setup would be very cool... problem is, it would be difficult to use two burst disks, because they would burst at different pressures and therefore only one would really be the valve.

It would need to be SCH 80.

I can find you a 3" PVC SCH 80 socket weld union for $27... PM me if you are interested.

[DYI]

You could always buy a 4" socket weld union from Mcmaster (if you have the money). I'm pretty sure it would be classified as a Weapon of Mass Destruction then though. As far as sheer power, a 6" porting piston valve would be the way to go.

[boilingleadbath]

It is more logical to size the barrels by the size of barrel you are using than the size of chamber you have.

[mark.f]

Where are you planning to get your 6"? I've got 9' of the stuff under my house right now. I was not that fun trying to find, and I bought it off my friend because he only needed around 15" of the stuff.

Depending on the size barrel you have, (and I'm guessing around 3" or 4" for that size chamber), you may not be better off searching for a VALVE that dumps that much air, but rather some VALVES that dump a combined total of air large enough to work.