Pneumatic powered cannons.

[Ronald_raygun]

I've been considering ;aunching promotional items at various sporting events held at our school. However, I'm not too sure how to go about the pneumatic launcher.

We have a variety of valves possible including the usual ball valve, a diaphragm, and piston valve

And a final design similar to these cannons. (the top has a separate air chamber underneath the barrel, the bottom has the barrel inside the air chamber)




With regard to the diaphragm and piston valves, would the kit solenoids help at all?



For those that don't know how a diaphragm or piston valve work allow me to explain.

Two barrels, one smaller than the other, are coxially aligned. A diaphragm is placed so that then the air behind it is pressurized, the diaphragm is pressed against the inner barrel.

Air leaks around the edge of the diaphragm and into the rest of the pressure chamber (Remember, the air doesn't go out of the barrel because the diaphragm has sealed it. )

Once the pressure chamber has been filled to the desireable PSI, the air behind the diaphragm is vented out. With the unequal air pressure, the air in front of the diaphragm pushes it backwards. Now that the diaphragm is sealing the fill valve of the air chamber, the pressurized air instead goes out of the now open barrel end accelerating the projectile that was placed inside.

The for operation fo a piston valve, simply replace the word diaphragm in the description with piston.

[jrocket567]

not nearly advanced as your plan, but very simple--bummin around in the back lab, we took two accumulators, hooked them together, and then to the compressor- out the other end we stuck a tube into the bottom of a 1/2" (i think) diameter PVC pipe about 4 feet long-- we shoved a tootsie roll down the pipe, and with the regular bulky relief valve, turning it as fast as we could, launched it about 75 yards- you might not have to go through all of them fancy valves and stuff to make it work- KISS

[Tytus Gerrish]

did you guys ever hear of My "gator gun" witch i launched a nut and bolt asembly, nearly missing 4 engineers and shattering our shop window?


http://www.chiefdelphi.com/forums/sh...ight=gator+gun



http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=4251&direction =DESC&sort=date&perrow=10&trows=10&quiet=Verbose

[KenWittlief]

If this is something you are going to use at public events, and I assume pointing at people in the audience, then my inclination is to remember that 'entertainment' is 95% illusion and deception!

I would make something that is spring loaded: pull the spring back, put the tee-shirt (projectile) in the barrel and release the spring. Two moving parts, very easy to ensure nothing can break off and become an unintended projectile.

But, entertainment! you can make it look like its air powered, stream powered, or a quantum rail gun, and have pressure tanks and gauges and lights and valves and a night vision scope, even have it shoot out CO2 vapors when it fires, and only you and the school board (and their lawyers) will know its all smoke and mirrors, with a small spring inside doing all the actual launching. :^)

In fact, with this approach you will probabally end up with something more impressive looking than if it really were air powered.

[jdhawg]

Do you mean something like this?

http://www.chiefdelphi.com/forums/sh...ad.php?t=39324

Team Fusion built this and have modified it several times. After Hurricane Katrina, our t-shirt supply was gone, so a quick change to the barrel allowed us to shoot Hot Dogs into the stands during a pep rally.

[Andrew Blair]

Hers an example of what we did.

http://media.putfile.com/T-Shirt-Cannon <<<VIDEO!!!!!!!!!

http://www.chiefdelphi.com/forums/pictures.php?s=&action=single&picid=12036&directio n=DESC&sort=date&perrow=3&trows=3&quiet=Verbose


We simply used, as per the Team fusion gun, a piece of 3 inch PVC to make a take with a large release output (Something important that you can't get with the kit accumalators; you have to use multiple 1/4" inputs like tytus then.), a rainbird irrigation valve from Lowes, and two kit compressor to do it all. We also use the old pressure transducer from the kit to gauge the pressure we're using. T-shirts work, hot-dogs are on the way!

[Ronald_raygun]

I would make something that is spring loaded: pull the spring back, put the tee-shirt (projectile) in the barrel and release the spring. Two moving parts, very easy to ensure nothing can break off and become an unintended projectile.

ts all smoke and mirrors, :^)

The smoke and mirrors idea I like. But with the spring, any sources? And material of the barrel? Largest springs that I can find and replace easily are the kind found on those retractable pens not exactly useful mind.

Team Fusion built this and have modified it several times. After Hurricane Katrina, our t-shirt supply was gone, so a quick change to the barrel allowed us to shoot Hot Dogs into the stands during a pep rally.

I've been following that thread and I think I was the last person to post with an absolutely crazy idea to use a cho-ko-nu (ancient china) to launch the t-shirts. You mentioned video before Hurrican Katrina hit. Do you still have it? May help spark some ideas.


Finally, a couple of you mentioned launching hot-dogs. How exactly does that work?

My understanding is that you wrap the hot-dog in some sort of foil or plastic wrap. Shove it into the barrel, and let it fly. What does the hot dog look like when it lands in the crowd?



Thank you for the quick response everyone. This will make for an interesting spring season.

[KenWittlief]

Originally Posted by Ronald_raygun

The smoke and mirrors idea I like. But with the spring, any sources? And material of the barrel? Largest springs that I can find and replace easily are the kind found on those retractable pens not exactly useful mind.

hardware store: screen door springs

or surgical tubing!

or if you want to launch a whole box of tee shirts into the crowd with one shot: garage door springs! :^)

BTW, a couple years back, the game with the soccer balls: we were looking at shooting the soccer balls using a pneumatic cylinder from the kit. The problem we ran into was the valves could not release air fast enough into the cylinder to get any distance with the soccer balls.

The solution is: you have to let the cylinder extend about half of its travel, and hold it back with a mechanical block (trigger). You pressurize the cylinder, then you release the mechanical trigger. If you build something like this also remember you cannot let a pneumatic cylinder slam into its end of travel over and over - the end will eventaully break off the cylinder. You need a mechanical stop (a bumper) at the end to limit its travel.

[NoodleKnight]

Originally Posted by Ronald_raygun

With regard to the diaphragm and piston valves, would the kit solenoids help at all?

Are you asking if it will work? If so, yes. You only need enough flow rate to keep a constant pressure difference between both sides of the diaphragm, just don't leave too much space on the fill/trigger end of the diaphragm since there's only so much cfm the little solenoids can release per second (ideally you want to just dump all the air on that one side so that the air in the "firing" side can just dump out).

Also, I'd go with the diapgragm/piston valve. Using a sprinkler solenoid limits you to the max cfm rating and psi rating of the sprinkler solenoid (which for some is a good thing, because it's better to pop the spinkler solenoid's diaphragm than the PVC pipe). Ball valve, well, you just have to be quick with turning a knob.

Hope this helps.

[Ronald_raygun]

Originally Posted by NoodleKnight

Are you asking if it will work? If so, yes. You only need enough flow rate to keep a constant pressure difference between both sides of the diaphragm, just don't leave too much space on the fill/trigger end of the diaphragm since there's only so much cfm the little solenoids can release per second (ideally you want to just dump all the air on that one side so that the air in the "firing" side can just dump out).

Hope this helps.

The idea behind using kit solenoids is to dump the trigger pressure so the firing pressure can propel the projectile. My question is whether or not that is possible.

Being the freshman last year I did most of the grunt work. "I want you to cut 40 bars of stainless steel by hand!!!" I was sore after the 5th and I'm glad it was "only" .25" thick. And therefore I didn't have too much experience with the "specialty" jobs.

[NoodleKnight]

Originally Posted by Ronald_raygun

The idea behind using kit solenoids is to dump the trigger pressure so the firing pressure can propel the projectile. My question is whether or not that is possible.

Being the freshman last year I did most of the grunt work. "I want you to cut 40 bars of stainless steel by hand!!!" I was sore after the 5th and I'm glad it was "only" .25" thick. And therefore I didn't have too much experience with the "specialty" jobs.

Sorry if I wasn't too clear with my first answer: Yes using the kit solenoids will work.