tennis ball cannon, flak style

[Gene]

How about 3 tennis balls?

[fdodge]

How about 3 tennis balls?

That would make it a blunderbus or a shotgun!

We launched 2 at a time. Still couldn't see them until they were pretty far out there. Both went really far. I'd be afraid of the breech exploding if there were 3. Most of the balls need a little push to get them down the barrel. Not much, but they are slightly snug fitting. We do have 1 ball that will roll down on it's own.

[AndyC]

Cool one



Andy

[Nick Carraway]

I'd like to see someone try to return that with a tennis racket. Take that Pete Sampras!

[MauserCollector]

Projects like this are way cool nicely done aswell

Best
Morten

[fdodge]

So on the second outing, the knife gate failed at 60+psi and I installed a 3" ball valve. It turned out to be a huge disappointment. We fired multiple shots from 60 psi to 100 psi and we were only getting maybe 150 yards. The problem is that the ball valve takes longer to open than the previous valve did. The pressure needs to enter the breech very suddenly and at it's maximum.
So we're going back to the knife gate, which is rated at 5-9psi and we were getting about 55 psi out of the last one.
Also notice that we lowered the barrel angle from 45 to about 37 degrees and added a piece of schedule 40 3" to slip over the lower barrel and breech to add weight to help control recoil and for protection in case the thinner walled barrel fails.
The photos were taken yesterday late afternoon. This is the 3rd time we have tested this thing. Some little kids volunteered to chase down the balls for us but we noticed they disappeared when we were wrapping up and Wes had to chase the little buggers down to get our ammo back! They were headed home!

[blinky]

One tiny bit of advice based on experience: You might not want to have a knee or an ankle right behind the cap when you're pressurizing it. It'll probably crack open before you'd have a catastrophic failure and have it pop back into you but why chance it.

Next weekend we're going to build one based off of your design....it seems like good cheap fun!

[fdodge]

I'm into this thing for $250. now. Just the 3" tee fittings alone are $20. apiece. You'll notice the addition of a coupling at the very front. I had to split the 2 sides to change the valve section. Now I use threaded instead of glue in valves

[fdodge]

Here's the 3" slide or "knife" gate valve to replace the ball valve. It is duplicate of the first valve we used and we won't go over 55 psi. Remember, this valve is rated at only gravity to 9 psi so we're living on the edge here.
You can see that the valve comes apart for servicing and we'll apply vaseline to the rupper flange faces and apply silicone rtv sealant to the pvc valve faces. Without doing so air escapes around the rubber and out the sides of the valve body at about 50 psi.
This cost me about $30. with the 3" female adapter to attach to the male threads on the cannon and the 3" X 2 1/2" bushed female adapter to accept the barrel. We will dope the threads and fully tighten the 3" female adapter to the cannon before gluing the valve so that the valve's handle points straight up.

[fdodge]

With adapters......

[fdodge]

And here's the test head. I use this at work to pressure test all kinds of underground irrigation and gas lines before burial or gas lines in houses before put into service. It works great in this application.
I should also note that this cannon will never be carried or transported under pressure as pvc is brittle and if dropped could explode and the plastic shrapnel could cause great injury.