Water cannon

[jdpete]

Has anyone made a compressed air cannon using water as the projectile? I recently built an air cannon and plan to use a length of 16" 4" pvc with 1-1/2" reducer as the end piece on a 96" connection of 1-1/2" pipe connected to tank. I'm using a 3/4" QEV. I roughly modeled with GGDT and got a 1000 ft lbs of energy at 90 ft per second with muzzle velocity of 90 ft per sec. and 200ms travel time. I'm just not sure if this setup would create any inherent problems with water weight of 3000 grams.

[D_Hall]

Yeah, we had one at the office that shot a rather sizable slug. About 800 gallons. The "barrel" was a 12' length of 48" diameter pipe. It used five household propane tanks for air storage (200 gallons each?). Muzzle energy was on the order of 640,000 ft*lbs.

Well, technically, we still have it, but we haven't fired it in about 20 years.

[jdpete]

Whoa! That's a cannon

[jimmy101]

Should work... but 1000 ft*lbs of recoil is pretty significant.

[jdpete]

Yeah the recoil was my big concern. I may have to really secure everything.

[jdpete]

Charged the water cannon today with water and blew the 90 degree elbow apart on my 36" barrel. I believe, and maybe someone knows the answer, that since I only filled it half way with water that the sudden change from 4" to 1-1/2" and the headspace above water is the reason. I will fix and try again with a full water load and remove elbow.

[D_Hall]

"Water hammer" is not your friend.

[jdpete]

For anyone interested I attached a schematic for a variable speed trigger controller. Range is 18ms - 1200ms. Ignore the pc board diagram. That was for my benefit. A friend designed and built it for me. I'll try to answer questions, just don't get to techy.