The 3 shot cannon, just an idea.

[Jakal444]

I had an idea for a cannon that should be able to fire 3 shots semi-auto. It has one large pressure chamber (about 90 cm of 1" pipe), with three ball valves placed at regular intervals (about 30 cm). And a schrader valve at one end of the chamber and a two right angle fittings leading up to the barrel, which is about 30 cm of 1" pipe. The ball valve on the barrel is Fiveseven's design:

http://www.spudfiles.com/forums/viewtopic.php?t=1683&

In theory you would open the 2 ball valves closest to the schrader, fill to about 100 psi, close the two ball valves and your ready to fire 3 shots. To fire a shot first turn the loading valve once then open the first ball valve closest to the barrel, fire the next one by reloading and opening the next valve, and so on. Each shot will be the same pressure as you first pumped the gun up to, except that it will be one third the volume, the barrel is the same volume as one of the chambers to accomodate for this. I call it the M-30.
It can probably be modified into some sort of shotgun design.

[Benny]

tried it, i recon you could get more shots than 3, i made one but with my own idea, but with no hopper.

[Jakal444]

Really, how did it work? My freind already commisioned me to make this model for him and I have not even built a prototype!

[drac]

Each shot should get succesivley weaker because the pressure lowers as it occupies more volume.

[Jakal444]

Yes It would of course, but the question here is will it be a noticable difference?

I've seen many rifles on the forums where the air flow is directed through a maze of pipes before reaching the barrel and they seem to work fine.

Also remember the first shot is inline with the barrel and then the other two are follow the same path (there are no extra turns) just more volume to occupy but that is easily solved:

Pump each section individually!
Pump up the entire chamber, close valve one pump a bit more the next chamber, close valve two, pump up the last chamber a bit more.

[Pete Zaria]

As is, you have all three chambers in series, one after the other. What about making them paralell, next to eachother (instead if one after another), all directed into the same barrel? That would eliminate the problem of each shot getting sucessively weaker. Also, using this method, you could fire with a sprinkler valve, which would be much faster. Here's a very rough 5 minute Mspaint sketch of my idea:



Each pressure tank would have a schrader at the bottom. Keep the ball valves closed when pumping. To select a pressure tank to use, open it's ball valve. Then, fire the cannon with the sprinkler valve (box at the base of the barrel). Open the valve for the next pressure chamber, repeat. Try to keep dead space between the pressure chamber and the barrel as small as possibe. Keep in mind that with this design, you could also use two or even all three chambers at once for a more powerful shot, or use them one at a time. If I was going to build this design, I'd make it breech loading. This would make reloading much easier.

Peace,
Pete Zaria.

[saladtossser]

instead of having so many shrader valves, you can use 3 check valves and fill with only one shrader

[Jakal444]

Pete Zaria : Each time you would want to fire a shot from your design you would need to do three things, which is not really semi auto, also im assuming that each tank would need to be filled individually. Oh, and if you want there to be a sprinkler valve instead, you can use three sprinker valves instead of the three ball valves, not including the loading one which is used for loading.

Saladtosser: No need for many schrader valve or check valves, it all depends where you mount the schrader.

So by taking into consideration the above suggestions I have come up with a new model, the M-90.

You fill it once using the ONE schrader and close the ball valves.
Turn the loading ball valve to load a shot.
Open any one of yhe three ball valves to fire a shot.
Re-load.
Open another valve.

[rna_duelers]

Thats alot of weight to carry around and its realy bulky,but there would be a less noticable power drop unlike your first design.But i like Pete Zaria design better and you would only need one filling spot just open all the ball valves(not the barrel venting one) and have filling point anywhere you want and with a sprinkler valve it would work fine but the loading of the ammo into the barrel would be the hardest part to make it semi auto.And i have had a few two many drinks sorry if this doesnt make complete sense.Pease out!

[Jakal444]

Thanks for your input, but I'm not sure if you have noticed the ball valve on the barrel with a tube sticking out of it, this is how it would reload semi-auto, read the very first post of this thread to see how it works.

[Pete Zaria]

I think we're onto something very cool here.

My design could easily be modified to use one schrader to fill all three tanks. I like the ball valve on each tank, because this allows you to use one, two, or three tanks at once.
Also, using one main sprinkler valve to fire the cannon is more cost effective, and makes the launcher overall less complicated.
The barrel needs to be breech-loading for sure, but a bolt-action golfball system would be awesome. Any ideas on that?

I've built several combustion cannons but never a pneumatic. I think I might build this thing. A 3-shot semiautomatic golfball cannon sounds amazing.

Peace,
Pete Zaria.

[Jakal444]

Im happy to be an inspiration to you, especially if I managed to switch you over to the pneumatic side....

[Pete Zaria]

Jackal, I do appreciate the ideas.
I've never really been on the combustion or pneumatic "side", I've only built combustion cannons because they seemed easier (though more fickle). I also didn't have an air compressor when I first started building spudguns.

Speaking of that, my air compressor is a 2.5HP that goes upto 125PSI. Is that enough for this project?

I think I'm going to build the design we've discussed, but modified a little bit. I want to put the 3 pressure chambers under the barrel (over and under style, obviously) with one schrader (is there a better fill valve?) for all three tanks.

I'll admit, I've never made a breech loader before. What kind of union/fitting is best for this? I'd like to be able to use SDR21, 1.5", and 2" barrels.

Peace,
Pete Zaria.

[Jakal444]

Well asking me about the type of fittings that you have is rather pointless, since over here it is a different system (gray PVC), but im sure some one else can help you. You can mount the tanks anyway you want, the reason they are positioned like that in my picture is for clarity's sake.

125 PSI you say? Yes, thats definately enough, I like to fire my cannons at around 100 so yours will be fine.

No better fill valves are available I think, maybe a female quick connect for an air compressor will work though.

And finally I was kidding about the sides thing...or was I?... I dont know, I just prefer pneumatics due to their nearly unlimited upgrade potential and because I hate the smell of burning fuel!