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Valves, the difference opening time makes.

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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Unread postAuthor: bigbob12345 » Sat Jan 19, 2008 12:15 am

Im not that sure but I think they open a littel faster and if there is any one that has a QEV gun that is willing to do the suggested test It would be appreciated if you could perform it.
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Unread postAuthor: Hotwired » Sat Jan 19, 2008 12:33 am

I have a 14mm 1/2" QEV cannon which isn't too far off the 15mm of Zen's cannon.

I'll try in a few hours time, 5am isn't the best time for me to be blasting anything about :wink:

I'll take point blank to be muzzle touching but not forced against the paper.
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Unread postAuthor: Zen/// » Sat Jan 19, 2008 12:36 am

Oh yes, the copperhead.

I thought it was a piston cannon lol.
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Unread postAuthor: bigbob12345 » Sat Jan 19, 2008 12:37 am

Great I will do similar tests on sunday
And its 9:30 at night here and I think Ill go to bed now Im tired.
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Unread postAuthor: Hotwired » Sat Jan 19, 2008 12:37 am

Well its a piston QEV so half right :)
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Unread postAuthor: Hotwired » Sat Jan 19, 2008 11:28 am

Double posting and I don't care 8)

70psi into a sheet of printer paper gave it a distinctly punched appearance.

Image


To emulate the burst disk fragments I added a shredded 1" square of tough plastic, also at 70psi:

Image
Image


Finally just for the hell of it I had a go at 240psi with just air. I eventually found where the paper went.

Image


Can't say how close a match the paper was to Zen's though.
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Unread postAuthor: bigbob12345 » Sat Jan 19, 2008 11:43 am

Great that looks good
were you using the QEV or burst disk because you talk of burst disk fragments.
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Unread postAuthor: Hotwired » Sat Jan 19, 2008 11:56 am

I was using a QEV but in the second shot I added some shredded plastic wrapping to mimic the plastic fragments from the burst disk in Zens cannon.
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Unread postAuthor: bigbob12345 » Sat Jan 19, 2008 12:42 pm

Okay Ill do the sprinkler,Ball,and piston test today if I get time
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Unread postAuthor: TurboSuper » Sat Jan 19, 2008 1:44 pm

This is interesting.

I guess the logical next step in this investigation would be to compare opening time vs. flow, assuming constant pressure.

One of the major arguments for using ball valves over sprinkler valves is that they come in larger sizes, thus providing greater flow to larger cannons...I always wondered how true this is.
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Unread postAuthor: ALIHISGREAT » Sat Jan 19, 2008 1:47 pm

One of the major arguments for using ball valves over sprinkler valves is that they come in larger sizes, thus providing greater flow to larger cannons...I always wondered how true this is.


i can't see a sprinkler 1" being out performed by a ball valve unless it was for something like a 2" bore...
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Unread postAuthor: bigbob12345 » Sat Jan 19, 2008 2:47 pm

This is What my tests came up with
Image
Ball valve 60psi


Image
Ball valve 100psi


Image
[u]Sprinkler valve 60psi



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Sprinkler valve 100psi


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Piston valve 60psi


Image
Piston valve 100psi

All test were done with a 2in diameter 36in long chamber and a 4ft long 1in diameter barrel(with no ammo of course)
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Unread postAuthor: bigbob12345 » Sat Jan 19, 2008 2:50 pm

Sorry for this pointless double post I did it accedently and Im having trouble with the delete function just ignore this.
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Unread postAuthor: SPG » Sun Jan 20, 2008 6:52 am

Obviously in the OP the reason the paper is torn is because the burst disc fragments have torn it. I'm not certain just popping some bits of plastic in the barrel will replicate this either as they're not forming a tight seal insdie the barrel and would allow most of the air to pass over them. This means they can't gain the same energy as the burst disc can from the pressurised gas.

The ball-valve, QEV and piston tests are more interesting though, as you've got a much more like for like comparison., they'd also suggest that using a ball-valve to actuate a burst disc isn't as good as using either of the others.

That said, paper isn't really a great testing material, if you look at a sheet closely you'll see the "texture" is hardly consistant between sheets or even across a single sheet. But it does give a graphic illustration.

Perhaps better to clamp the paper in a frame rather than just propping it up on the barrel?
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Unread postAuthor: Carlman » Sun Jan 20, 2008 8:16 am

can someone try a spring loaded ball valve so we can compare it to a standard ball valve, i would but my cannon is elsewhere, and the spring is still at bunnings :wink:
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