SpudFiles

Hey Guys,

As the title says, I am looking to build a simple tennis ball cannon to play with in the park behind our house. I think it will be great fun with my boys and our dog. Besides, after building my metal cannons, a simple PVC cannon will be cheap, easy, and quick to build.

Anyway, I have found a couple sources on-line for the oddball 2.5 inch barrel material. What I am curious about is the best source for a 2 inch sprinkler valve. I have found a couple for $58, but I was wondering if anyone knows of a cheaper alternative. Also, I assume 50 to 60 psi is all I will need to really fire a tennis ball for distance. But, I have never fired a tennis ball before.

So, who has built one of these and what is your advice?

Matt

Big valves cost money. You will enjoy a large cannon.

Do you have a source for large volumes of air? Hand pumping large cannons is a serious workout.

With the high pressures you have access to and the short range you're hoping to achieve, I'd go for a small, high pressure launcher with an oversized tennis ball barrel. I've got pretty good ranges with a 3/4" QEV and a small steel chamber above 300psi.

Technician1002 wrote:Big valves cost money. You will enjoy a large cannon.

Do you have a source for large volumes of air? Hand pumping large cannons is a serious workout.

My two stage compressor has a 200 psi 3 gallon stage one tank on-board with an adjustable regulator with low pressure outputs. That tank charges in about 4 minutes from zero. So, with a 1 gallon tank on the cannon charged to relatively low pressures, I would think my compressor can keep up with repeated firing.

I have considered a high pressure system firing through a smaller valve. But, I really prefer a larger valve.

This should be a cool cannon for its intended purpose.

Can anyone tell me from experience what kind of performance I can expect from this thing at various pressures?

Matt

You can model it in GGDT to find out.

I bought four 50mm sprinkler valves for about $15USD. They were 25+ years old and had various things wrong with them but I managed to get three working valves out of them. If you're prepared to wait a bit, a good deal will pop up online sooner or later.

Tennis balls generally wont travel very far; maybe 400' maximum. They don't weigh very much in comparison to their size and the fuzzy exterior doesn't help with drag. Fill the with water and they will go further. They still pack a punch at short range though. I have a 2" sprinkler valve cannon with a 3' tennis ball barrel and a 3' 2" chamber that operates at 120PSI maximum and can get about 400fps muzzle velocity from a tennis ball. Muzzle energy approaches 1000 ft/lbs when shooting soda cans (which are usually the same diameter as tennis balls). Not bad for a basic, low pressure cannon; they're loads of fun.

This is the distances I got with a tennis ball in a lake using GPS for measurements. The far shot was with a ball cut open and filled with water. Shots were at 100 PSI. Launched from the green spot on shore into the lake. One landing wasn't found. It went over the dam. I wasn't shure I could reach that far, but did. Range for me is ~750-800 feet.

The pink line cross the parking lot was an antenna launch test towing a mason line with a bottle of water.

Cool, that is what I wanted to know.

Alright, I think I have settled on a design. I want this cannon to be able to sit as a mortar or hand-held (actually, it will be used as a mortar nearly 100% of the time). It will be fed by my compressor attached to my regulated "Pulsed" output. That output is regulated (0 to 150 psi) and run through a small solenoid valve so it only puts out air when a momentary button is pushed. So, the cannon will sit on the ground attached to the compressor and a tennis ball will be dropped into the barrel, the pulse button will be pressed to charge the tank and it will be fired. This will allow more repeated shots. I may need to setup a large secondary tank to allow more repeated shots before recharging.

This should be fun. I am so used to a cannon costing many hundreds of dollars and taking over 100 hours of time to build. This will take me one afternoon and about a hundred bucks max.

Matt

Be aware, I used a coaxial piston for those shots. Expect a little less range due to flow restrictions in the turns and twists inside a sprinkler valve. Do measure and post your results.

Be sure you use 2 inch or larger connections between your chamber, valve, and barrel. Small pipe really restricts flow and hurts performance.

Mine took close to 80 hours to build.

Well, for my purposes, I could deal with half that performance.

I just want to be able to fire balls into the park behind my house for my boys and our dog to run after and try to catch (fired high in the air, not fired at them).

Of course, the occasional 100psi power shot will occur as well!

As I mentioned earlier, I want this to be a really quick build.

Matt

OK, the cannon is finsihed and has dozens of shots from it at this point.

First, the tennis balls sure do fit tight into the 2.5 inch barrel. I was assuming they would slide right in. They really require a firm push to insert. No biggie, though.

Second, this thing is a riot! My boys and I have had so much fun with this thing. For starters, we have been using our bike tire pump. I did not feel like lugging my big compressor home. Plus I wanted to teach my boys how much energy was used with each shot. Letting them pump up the cannon themselves is a good way to demonstrate that.

So, at 70 psi (about 35 pumps), the tennis ball nearly disappears if shot straight up. I was shocked at the performance of this thing.

We tried numerous things with the cannon. One of the coolest things is to fire two balls at once. The second ball follows right behind the first and is dragged along in the draft of the first ball. You can see the second ball wagging back and forth in the turbulence behind the first. It has turned into quite a physics experiment. This is what this is all about, anyway--- spending time with each other and having fun. This saturday we go out and fire the all metal HPA guns and blow stuff apart. But, for today, we are having alot of fun just popping balls up in the air and trying to catch them.

Thanks for the advice on this gun.

Matt

Sweet but Y U USE DWV!?

Ha ha, good question.

First, AFAIK the only thing that is DWV is the 3 inch tank tube (how can you tell from the pictures, anyway?).

Second, I did not realize it was DWV until I brought it home. The wall thickness is the same as my pressure rated stuff, though.

I am ordering some pressure rated PVC for it. It is cheap enough. I tested this to over 80psi. I would not go any higher, though. 70 psi is best for our application anyway.

I have looked locally and no-one that I have found carries pressure rated stuff above 2 inch diameter.

Matt

The two 90° elbows and the bell reducer on your chamber are definitely DWV. You can tell by the socket depth.

As far as your 3" chamber goes, if you thought it was DWV then why did you use it? If it does not read NSF-PW in red or black ink along the side of the pipe, it is unsafe. You may be dealing with cell-core PVC, which is a big no-no for pneumatics especially, regardless of wall thickness.

Great looking cannon otherwise, would love to see it when it's rebuilt. We're all concerned about your safety here and since DWV pipe and fittings aren't rated for pressure, and known to fail, we're obligated to guide you in the right direction.

I am actually ordering schedule 80 pipe and fittings for it anyway. I used this only because it is what I had. I tested it beyond what I am pressurizing it to. So it is OK for now. But the rest of the cannon is good to 150 psi. So, I want to be able to hit that. Schedule 80 is what I will switch over to once it comes in.

I appreciate the words, though.

Matt