SpudFiles

I am in the planning stage of a new cannon. I want it to be built of steel, with a 4"x14" air chamber and a 2"x 96" barrel. I plan on using the gun at about 500 PSI via a SCUBA tank. What kind of valve could I use that will handle the pressure?

I would go with a burst disk. I have no idea what material to use though. Maybe a couple layers of soda can. Just an idea.

sounds like this will get some really good power(might even rival the SCTBDC)
And a triggered burst disk setup would be ideal(if you dont know what i mean by the triggered part look it up)
And for the disks i would reccommend aluminum foil. You will go through a lot with a union that big but atleast it will seal well

I haven't read anything on the burst disk valve, I just glanced over a few illustrations, but aren't they one time use? I need something that will facilitate fairly rapid fire. I'm considering a steel 2" ball valve actuated with a pneumatic ram, has this been done before?

How bout a piston valve(again look it up if you dont know)
a ball valve will deacrese performance hideously even if you put a pnuematic ram on it.

a ball valve will give you disgusting performance, you should use a burst disk (if your going for power) for speed you could use use a piston valve as bigbob stated but I think you would need to do some welding for that.

Welding is no problem, that's why I'm doing it out of steel.

Okay then a piston valve is your best option
Do you understand how they work if not here is a link for you
http://www.spudfiles.com/forums/piston- ... t8157.html
I would reccomend a barrel sealing valve in a 3in tee with a 2in porting.

why not a 4" tee sice he probably can get it? then a 2" ball valve for pilot.

mabe he even make a 4" tee :=)

He's going to need a really long barrel to get optimal performance out of that thing..... but I bet those potatoes will get a taste of the stratosphere.... 8)

I would recommend a burst disk because:
-Optimal performance
-Easy breach loading (dont want to push something ALL THE FKIN WAY DOWN would ya?)
-Its not that hard to reload, its just a disk of alluminium foil or similar in an union holding the air, then bursting coz it cant handle the presure anymore and giving full flow.

Because you are unscrewing the union to put a new disk in you will also be able to easily put a new projectile in the breech at that time.
DONT use a ball valve, atleast use a piston valve or else a burst disk.


@ Jared:
He IS using a really long barrel.

Busrt disk isn't going to happen for me, too little control. I think I will try to use 2 pneumatically actuated 2" ball valves and a larger chamber to compensate.

psycix wrote:@ Jared:
He IS using a really long barrel.

Just glancing at GGDT, I would think it might need to be a tad bit longer than 96 inches... More like around 30 ft for best performance?...

Dirigo wrote:Busrt disk isn't going to happen for me, too little control. I think I will try to use 2 pneumatically actuated 2" ball valves and a larger chamber to compensate.

Dirigo... build a piston valve. It only takes a few dollars to build, and its not that complicated. At pressures you're wanting to use, ball valves might not work to the best performance for you.

burst disk can have control. Just build a controlled burst disk.

If you want ease of use, just build a piston valve. The only reason that I use a TBD setup is that I don't really have the motivation to build a proper piston valve ($$$) for the SCTBDC.

If you're looking to build a good medium pressure piston valve, you'll likely need a lathe, and welding capabilities. If you have those, and the right materials, it can be done quite well. The only reason I haven't done it yet is because I don't yet have a lathe.