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new type of 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: jimmy101 » Mon Sep 01, 2008 6:23 pm

POLAND_SPUD wrote:no sorry but it is a piston vavle... a piston valve can be acctuated using pilot valve or you can move the piston using your muscles or electric motor... whatever...

the fact that someone has called something does not mean that it is a push pull valve or whatever... it just means that some guy from some site has called it like that...

... and of course, POLAND_SPUD is also just "some guy from some site" so just because he says it should be called something doesn't necisarily make that correct either. :D

I would say it is a "new enough" design to be called unique. Can anyone point to old posts here, or elsewhere, describing it's use in a spudgun type setting?

Seems to me though that this valve is going to be very slow, an unmoded sprinkler valve would probably be better.
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Unread postAuthor: QuaziGNRLnose » Mon Sep 01, 2008 7:52 pm

well from what ive tested its pretty damn fast, and a spinkler valve isnt really in my budget, also the speed at which it opens depends on how force you use to pull it, id say its not as fast as a sprinkler valve, but it can close alot faster.letting go of it will close it in under 15 ms. you can pull it open when you have a good handgrip and trigger in about 20-30 ms, depending on how strong you are (i can open it in about 80 by hand, and theres not much from stopping you to do faster my time is slow cause well i have no surface are to grip and im not using my grip strength to close it, im using my whole arm pulling it while i hold the assembly). its basically gonna work with a ratchet which closes the valve as soon as its fully opened. so as little air will be wasted. a human hand can close pretty fast, so if it only had to close 1-1.5 cm then you see how fast it can close. opening time isnt my issue really, any minor slowness can be reversed with a longer barrel. i think the only issue might be flow. but its not shooting anything big so its fine. a sprinkler valve in a bb/paintball gun do they make them that small anyway? remember i want good air management, a 1" valve is way to big.

also thank you that you think its original :D
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Unread postAuthor: jimmy101 » Tue Sep 02, 2008 1:44 pm

QuaziGNRLnose
So, you might be wondering; "just how fast does the valve need to open anyway?". Is 100mS fast enough? 10mS, 1mS ...?

Here one way to think about what the opening time should be.

How fast do you want / think the gun shoots? (the muzzle velocity)
How long is the barrel?

Assume the average velocity of the ammo in the barrel is half the muzzle velocity. So, if the muzzle velocity is 300 FPS then the average velocity in the barrel is 150 FPS. If the barrel is 3 feet long then the time it takes for the projectile to transit the barrel is;
(3')(second/150') = 20mS

You would like to get the valve completely open well before the round has left the barrel. In this case, a valve opening time of perhaps 5mS or so would be nice. A faster valve won't increase the performance all that much and the performance difference between a 1mS valve and an 0.1mS valve would probably be unmeasurable.

If your valve takes 50mS to open then the ammo is long gone by the time the valve is fully opened and the valve is significantly choking air flow and reducing the gun's performance.

If the valve has to move 1cm to trigger and you want a 5mS opening time then your hand will have to moving at 1cm/0.005S = 200cm/S (6.6FPS) which sounds possible.
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Unread postAuthor: QuaziGNRLnose » Tue Sep 02, 2008 4:48 pm

wow thats a thoroughly thought out post! i'm actually saving what you said so i can use it to optimise my valve (tweaking spring and gaskets so they can open quicker while still giving their required performance) ill use a stop watch to time some things when i build the trigger assembly.

also you can account for the fact that when the valve isnt fully opened so the projectiles speed will be lower in the first few milleseconds than the fully opened time, so it starts off at around 10 FPS, and then fully accelerates to 150FPS in the barrel when the valve is fully opened. meaning the projectile might take longer than 20ms to transit. a faster valve can make the maximum time it takes to reach 150 lower, but in theory if u were to add a foot of barrel you could have a valve opening at 10 or even 15ms. all this is just theory, but as soon as i complete my trig assembly i can start testing things out,

once again thanks, i never would of thought it out that way
oh yea
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Unread postAuthor: jimmy101 » Wed Sep 03, 2008 3:00 pm

Quasi: Exactly, my treatment is very approximate and you can probably do the math in your head. It just gives a rough idea of how fast things need to happen. It's really meant to answer the 100mS, 10mS, 1mS... question, not the 5mS vs. 4.5mS question.

You can always play around with GGDT and get much more accurate results. GGDT might let you model the flow restriction through the partly opened valve.
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Unread postAuthor: Hailfire753 » Wed Sep 03, 2008 3:36 pm

Hmm, some very useful info here. Nice to see an idea backed up by a working model! I do think it is an original idea; wish you luck.

The semi-auto design on nerf haven would be good to fill/pilot a QEV. It seems like a variation of a sleeve valve or spool valve.
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Unread postAuthor: QuaziGNRLnose » Wed Sep 03, 2008 3:40 pm

sorry for my slight noobiness i understand alot of the concepts here and such, just ive been wondering what a QEV is, im still quite new , i know its something that paintball guns use but im unsure excactly what it is
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Unread postAuthor: Hailfire753 » Wed Sep 03, 2008 3:48 pm

A QEV, or Quick Exhaust Valve, is basically a 3-way variation on the piston valve.

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When air comes from the source (1) , it closes the barrel (3) and goes to the chamber (2). When the pilot is vented, the piston opens the path from the chamber to barrel, firing the gun. It needs a three way valve to fill and pilot it for semi-auto efficiently, or a snap-valve.
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Last edited by Hailfire753 on Wed Sep 03, 2008 3:48 pm, edited 1 time in total.
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Unread postAuthor: trollhameran » Wed Sep 03, 2008 3:48 pm

its a quick exhaust valve, its basically a ready made piston or diaphragm valve.
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Unread postAuthor: QuaziGNRLnose » Wed Sep 03, 2008 3:52 pm

looks excactly like a piston valve, but it seems the flow would be just incredibly low, with all those constrained curves, oh yah is it fired by releasing a pilot volume into the atmos or some other way?
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Unread postAuthor: Hailfire753 » Wed Sep 03, 2008 4:06 pm

No, it has better performance than a sprinkler, but less than a piston. QEVs are awesome because of their fast opening time. The difference is that it closes immediately after firing. It is fired by cutting off input of air and releasing the air from that area.

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Replace the "temporary air reservoir" with the fill side of a QEV, and your set. Fits my design so perfectly, you might think I planned it. Thanks Quazi, I was having a hard time finding the right valve. I saw that picture before, but seeing it again just made my mind click.
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Last edited by Hailfire753 on Wed Sep 03, 2008 4:12 pm, edited 1 time in total.
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Unread postAuthor: QuaziGNRLnose » Wed Sep 03, 2008 4:10 pm

ur gonna use it on ur semi, that'd be awesome, add some variety to a sea of generic valves on this site
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Unread postAuthor: Hailfire753 » Wed Sep 03, 2008 4:13 pm

Yeah, I think I will. Dang, gotta get to home depot.
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