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Proper valve: Small, handheld launcher

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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Proper valve: Small, handheld launcher

Unread postAuthor: Col. Kurtz » Tue May 25, 2010 5:22 pm

I'm building a launcher that's meant to replicate the shape and style of an M79 "Thumper" grenade launcher, breakaway barrel and all. However, there are a few logistics to work out, especially including the valve. The last cannon I made was a basic, 3"X1.5' tank - converters down to 1/2" pipe - half inch ball valve, half inch barrel. Using a bike pump, got up to about 115 psi.

This build has a much smaller tank made of two lengths of 1" pipe put together with a 45 degree T, and my concern is that the ball valve will not be nearly fast enough for such a small amount of air. I can post rough designs to show the positioning, but it's my understanding that a normal T shape QEV wont fit the design.

(this is using a small, inexpensive hand bike pump expected to get between 40-60 PSI before it leaks.)
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Attachments
m79.jpg
Replicating this, more or less. the valve would be around the same place as the trigger on this one. The two 1" tanks will be contained in the faux stock, barrel will be the barrel, etc.
m79.jpg (32.74 KiB) Viewed 510 times

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Unread postAuthor: metalmeltr » Tue May 25, 2010 5:33 pm

A QEV may work if hidden in the stock.
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Unread postAuthor: Col. Kurtz » Tue May 25, 2010 5:41 pm

metalmeltr wrote:A QEV may work if hidden in the stock.



That's what I was thinking, and, granted, I have yet to go looking for QEV's that would fit, but the basic T shape will not work for the design.

Edit:
After looking at it, I now see what you're saying. If the pilot is pointing up, with the QEV backed into the stock, I think I can still make it look like a continuous 1 1/2 barrel.
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Unread postAuthor: Hubb » Wed May 26, 2010 7:14 am

Goat did it a while back and used a pressure washer handle with unregged CO2. It seemed to work pretty good and made a rather nice piece of work.

http://www.spudfiles.com/forums/goats-mcs-t12488.html

Maybe you can get some ideas from his design. Also, search the forums for his other one. It uses a sprinkler valve, but still has the break barrel thing going on.

Good luck and I'm looking forward to the end result.
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Unread postAuthor: Brian the brain » Wed May 26, 2010 1:10 pm

A modified sprinkler valve would do the trick.
Smallest cut up blowgun as the trigger.( Saw off everything after the blowgunvalve)

Then use two 45 degree elbows and a capped off pipe to form the stock.

The rest can be done with bondo and sandpaper, some beige paint and a big brush of darker brown to mimic the wood.

Don;t mess with CO2 unless you know what you are doing.Seriously.

I do however suggest you paint the tip of the barrel bright orange to make sure nobody can mistake it for the real thing.
You could get in serious trouble.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Col. Kurtz » Wed May 26, 2010 4:10 pm

Yeah, I saw goat's, those were pretty cool. However, those have handles attached to the bottom, coming down, instead of just an in-stock trigger. I suppose it could work if I turn it sideways, but I'm still working on the basics right now. Thinking that I'm going to get the pipe tomorrow, then get the stock pieces machined this weekend. Thanks for the advice all, updates laters.
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