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Budda's Belch

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Budda's Belch

Unread postAuthor: jr » Sun Dec 05, 2010 12:28 pm

Hmmm.... Where to start...

Well I have decided to go big...giant.... OK Gigantic!

I'm going to launch pumpkins! Thats right 8-10LB PUMPKINS!

I found out that there are a few local meet here in Washinton. A friend of mine is on a team with a trebuchet. They are cool but not my style.

I have a few ideas...but am looking for all the input I can get!

I'm thinking of a Low Pressure, High Volume design but that is just a thought. The basic design will be a 200+ gallon propane tank (chamber) valve assembly and a 10 inch barrel (thinking about 20 feet long). And it will be mounted to a trailer.

I want to start with the valve body. I could use a 10-12 sprinklers :lol:
But I was first thinking Piston! Any one seen a 6 inch piston!! Or would a BDisc be better?

Any thoughts are greatly appreciated!
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Unread postAuthor: ramses » Sun Dec 05, 2010 12:33 pm

burst disk is supreme, as long as it doesn't exit the barrel(against the rules) or break the pumpkin with the shock.

Butterfly valves are commonly used becasue of their slowness; this protects the pumpkin. There was some talk of a captive sabot that would protect the pumpkin recently.
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Unread postAuthor: Lockednloaded » Sun Dec 05, 2010 1:02 pm

JSR proposed design to protect the pumpkin from the BD with a captive bolt, I'd go for that if I were you
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Unread postAuthor: saefroch » Sun Dec 05, 2010 2:14 pm

The designs proposed here are pretty well the best you'll find. Using the proposed system, a fast valve is suggested, since the spring will decrease the initial acceleration of the pumpkin on the captive sabot.
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Unread postAuthor: Labtecpower » Sun Dec 05, 2010 2:27 pm

@ramses:

The burst disk D-Hall used on Vera doesn't release any shrapnel. maybe you should take a look at it.

Also, wouldn't it be great to organise a punkin-chunkin event with "unlimited class"?

You could build a massive hybrid then :D
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Unread postAuthor: saefroch » Sun Dec 05, 2010 2:53 pm

That burst disc design is a serious valve possibility if using the captive sabot, but it would probably require a lot of experimentation to get it to burst just right.

A massive hybrid would probably make pumpkin mist... There's sadly not much place for hybrids in throwing vegetables since they don't survive the massive accelerations.
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Unread postAuthor: jr » Sat Dec 18, 2010 4:14 pm

I like the B-D for the simplicity of its design, but I fear it will damage the shell of the pumkin.

I read a thread on a double B-D design... one in front of the other to allow more psi in the chamber. So that got me to thinking.. if I used a ball valve in-line with a B-D. Then the pumkin would start to move with the opening of the B-V and when the psi dropped on the barrel side of the B-D then it would release the rest of the pressure, thus accelerating the pumkin.

I will be building a "mini" and I think bell peppers will make a similar projectile.
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