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blow forward pop-off valve

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: wyz2285 » Fri Nov 18, 2011 3:50 pm

Ah now I understand it! very nice! I think the ammo won´t move significantly before the valve opens, but why not try it? this looks like a good way for full auto
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Unread postAuthor: MrCrowley » Fri Nov 18, 2011 3:57 pm

I'm a little lost, does the design rely on air getting behind the yellow piston thingy to move it forward?
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Last edited by MrCrowley on Fri Nov 18, 2011 4:23 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 18, 2011 4:15 pm

MrCrowley wrote:I'm a little lost, does the design rely on air getting behind the yellow piston thingy to move it forward?


Pretty much, the "yellow piston thingy" is held by the spring. Air from the blowgun leaks into the pilot area and starts to overcome the spring strength, pushing it forward until it eventually leaks and pilots the main piston.

Again, it leaks more than pops but as long as LeMaudit is happy with the TAKTAKTAKTAK, hey... :D
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Unread postAuthor: LeMaudit » Fri Nov 18, 2011 5:31 pm

It does POP quite a bit in fact :D
If I'm not mistaken looking at the 1000fps video, the valve vent its pilot volume in 2 milliseconds and fully open in 2 more milliseconds. That's 4 to 5 milliseconds to goes from fully closed to fully open. How does that compare to other valves? Numbers anyone?
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Unread postAuthor: MrCrowley » Fri Nov 18, 2011 6:09 pm

I believe typical piston valves are between 5-10 milliseconds and spring loaded ball valves about 25ms. Just off the top of my head, can't be certain on those figures.
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Unread postAuthor: jackssmirkingrevenge » Fri Nov 18, 2011 6:35 pm

LeMaudit wrote:It does POP quite a bit in fact :D


My explanation is that spring + weight gives the bolt a fair bit of intertia, so when it finally gets going, it's really going :)
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