Piston Valve Help

[idespisecats]

I'm looking at building a large scale pneumatic cannon to launch t-shirts with, and am thinking a piston valve would be better because the barrell is going to be so large anyways. How would I mod one to launch right or what kind should I use? or would I just be better off using a sprinkler valve?

[Gnobbes]

How big a barrel do you think you'll need to shoot a rolled up T-shirt??

I would think an unmodified sprinkler valve would be fine to launch t-shirts. You just need to lob them into stands, not blast people with them.

Where are you planning on using this thing.
And what are you gonna use to charge it. Compressors charge fast, but aren't very portable.
CO2 is more convienient, but you'd need to invest in a regulator, and use materials that could withstand very low temps. The sprinkler valve probably wouldn't be a great idea with CO2.

[MrCrowley]

How would I mod one to launch right or what kind should I use? or would I just be better off using a sprinkler valve?

what do you mean "how would you mod one"?you just build them,for this design you should go with an over-under barrel sealing as a co-ax youll need one huge chmaber b/c of the barrel bore and a over-under chamber sealing piston needs o-rings and is slightly harder then a barrel sealing.

if your just launching into stands go with a modded sprinkler valve if you want distance or destruction go with the BSP(barrel sealing piston) over-under design,3" barrel 3' long,2" tee for the piston then a 4" chamber 4' long.

[zeigs spud]

quote from Gnobbes"How big a barrel do you think you'll need to shoot a rolled up T-shirt??"

really? lol...i'd just make a normal spud cannon if u want a piston then mkae a bit larger piston cannon (havn't ever really seen big ones, well normal size compared to and sprinkler valved canons)

[Velocity]

Yeah, you don't want to blow holes in people...

I blew a hole in my desk with my piston-valved cannon at 20 PSI. I didn't even notice it until a few minutes after! You can see it in this <a href="http://s94.photobucket.com/albums/l112/ ... ">video</a>

[MrCrowley]

lol i saw that video yesterday didnt realise you broke the desk though

[idespisecats]

Thanks for the advice, 2 more quick things though, how big should I make the reservoir? and I keep hearing people talking about using epoxy as a sealant. What kind of epoxy is it and what do I use it on? I was going to just use regular blue pipe glue.

[MrCrowley]

1:i would say 4" pipe 3-4' long
2:use primer AND glue to join the pipe.