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Copper QEV gun w/damage pics

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Copper QEV gun w/damage pics

Unread postAuthor: skyjive » Wed Dec 10, 2008 3:31 pm

This is a pretty simple but powerful pneumatic I finished a while ago, but my recent acquisition of a CO2 system really kicked it up a notch. Some pics:
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The gun sitting on my ping-pong table. Its about 7 feet long so getting the whole thing in the shot was a headache

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The pilot/fill area with blowgun pilot and quick-disconnect

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The QEV and union loading

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The regulator gauges. There's a lot more room for higher pressures if I have the nerve.

The gun has a 1/2" copper barrel and 1" copper chamber. The barrel is 66" long and has a volume of 13 in^3, and the chamber is 75" long and has a volume of 59 in^3, for a C:B ratio of about 4.5:1. Since I have plenty of available gas filling capacity I decided to go for broke on the C:B ratio to maximize power. I used a McMaster 3/4" QEV and a blowgun pilot valve.

The ammo I used was a steel-tipped dart made of steel, wood, and (as always) duct tape. The center of mass is slightly forward of the midpoint, and the duct tape wrapping allows it to fit snugly in the barrel and places the center of pressure at the rear. The dart always strikes tip first. The photo is of a 3/4" dart and this gun used a 1/2" dart, but its the same except for the thickness of the duct tape tail.
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And now for some damage pics (all from one shot):

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The target before the shot (actually reassembled afterwards, but you get the idea). It is two halves of a model tank I made when I was little placed back to back.

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After the shot. The front half was completely split in half and flew apart. The back half mostly survived.

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A bit blurry, but shows that the wood is slightly over 3/4" thick.

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The steel tip of the dart fully penetrated the second layer as well, but did not shatter it in the same way as the first layer. The dart completely disintegrated, all I could find was a splintered section of the wooden middle bit.

I would include GGDT data but I don't know how to model a QEV.

I plan to up the pressure if I can convince myself the gun isn't gonna disintegrate.
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Unread postAuthor: mark.f » Wed Dec 10, 2008 3:53 pm

Looks good!

Although I would inquire why there is such a large amount of copper used to form the 90 degree bend going into the Q.E.V. cylinder port.
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Unread postAuthor: jackssmirkingrevenge » Wed Dec 10, 2008 4:05 pm

Nice, and if you're confident about your soldering, why not take it higher :) an alternative gas to the rather heavy CO<sub>2</sub> would bring about better performance for the same pressure too.

Also, set your camera to a slightly lower resolution ;)
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Unread postAuthor: Hotwired » Wed Dec 10, 2008 4:16 pm

Common copper plumbing pipe has at least a working pressure of 300psi in those sizes ^^

I don't think a lower res will help but finding the macro button certainly will for the close shots :)
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Unread postAuthor: skyjive » Wed Dec 10, 2008 4:31 pm

@mark: The reason there is such a long length of pipe between the two turns is so I have room to screw and unscrew the union.

Regarding the QEV, it says on the website that it is only good for 125 psi, but I suspect that it can go much higher. Has anyone tested McMaster QEVs at high pressures?
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Unread postAuthor: FishBoy » Wed Dec 10, 2008 5:40 pm

I noticed that the the high pressure guage on your reg reads slightly over 500 psi, when the smaller one reads just over 200, something's not right there. Perhaps you went over the lower ones limit and messed it up?
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Unread postAuthor: VH_man » Wed Dec 10, 2008 6:16 pm

Nice Cannon. That barrel length will do you some serious goodness.

Just a Thought, Why not clean up the "stock" area with some 45degree elbows and a 90 degree, letting the chamber run along under the barrelw ith a minumum of direction changes, Instead of that 90degree and long pipe thing youve got there. It might actuall even improve preformance, and improve astetics, In my mind.

Anyway, Sweet gun. And that damage is freaking sick.........
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Unread postAuthor: Hotwired » Wed Dec 10, 2008 9:59 pm

FishBoy wrote:I noticed that the the high pressure guage on your reg reads slightly over 500 psi, when the smaller one reads just over 200, something's not right there. Perhaps you went over the lower ones limit and messed it up?


Or maybe.

The high pressure gauge is reading the pressure of the gas cylinder and the low pressure gauge is reading the outgoing pressure from the regulator.
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Unread postAuthor: VH_man » Wed Dec 10, 2008 10:05 pm

Heh... Just a side-note-threatening-to-get-things-off-topic.....

I have the same 0-600 PSI guage on my Shock pump :D

And to be on topic: Doesnt Co2 give off far more than 600 PSI?

Edit: Heh..... The one on the right is 0 to 3000... not 300.... God im tired.
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Unread postAuthor: Hotwired » Wed Dec 10, 2008 10:12 pm

Yes up to 852.8 @ 70*F, now go to sleep, you're rambling :P



Dam. Quarter past 3. I need some sleep too :shock:
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Unread postAuthor: jackssmirkingrevenge » Thu Dec 11, 2008 3:14 am

Hotwired wrote:I don't think a lower res will help


It will help with the page not taking half an hour to load ;p
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Unread postAuthor: mark.f » Thu Dec 11, 2008 12:34 pm

I've used McMaster Q.E.V.'s up to 300 PSIG without failure, but I wouldn't recommend it.
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