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Air gun valve vs. QDV @ high pressures

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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Air gun valve vs. QDV @ high pressures

Unread postAuthor: auxiliary » Fri Sep 04, 2009 6:01 pm

I have been thinking about making an gun similar to the XM2. I want it to mimic the actions and looks of a pellet gun, but be in a greater caliber such as 0.5 inches. I was originally planning on making a miniature QDV for the gun (I have made a 2.5" diameter QDV in my 4" coax and I love them), but I was wondering if I could get away with a much more simple valve such a a poppet valve and hammer which is commonly used in pneumatic pellet guns. My reasoning is that I will be using high pressures (400-800 psi) through an on board pump so the pressure will be comparable if not more than a manufactured multi-pump pneumatic pellet gun. Poppet valves seem to have been working well with air guns for quite some time and I think this is because with the high enough pressures, the valve is forced open for a substantially longer time period than if it was opened with lower pressures (100-200 psi), enough to not make much difference if the valve was extremely efficient like the QDV.

Would the increase in performance created by a QDV be worth the extra work especially with such high pressures?

Image



Pellet gun valve ^^^
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Unread postAuthor: tghhs » Fri Sep 04, 2009 6:20 pm

Hmm, well very amature like me wouldn't know, but i'll still say my bit.

Do you plan on getting more then 1 shot with the poppet valve? if you dont i very much doubt that would match the performance of a QDV.
(where's technician?)
As u'd know they open extreamly fast and have no flow restriction like that created by the stem of a poppet.
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Unread postAuthor: inonickname » Fri Sep 04, 2009 6:26 pm

The only real advantage of a hammer valve is that they can be opened by a sear/hammer(a QDV could be as well) and that they allow multiple shots. Otherwise, a QDV will offer better performance in nearly every way.
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Unread postAuthor: THUNDERLORD » Fri Sep 04, 2009 6:36 pm

Hmm, well very amature like me wouldn't know, but i'll still say my bit.....


Statement like that, Helps me know you're not full O' Sh!t :P ,
and take in the info you do have!
(I do the same when I'm not sure, "I think", "IMO", "IDK" , "Not for sure" ETC.) 8)

I don't see where there'd be restriction with the hammer piloted poppet?
The hammer piloted poppets on airguns might (oh, also "might") be that way for easier trigger and bolt configuration.
And seem more advanced IMO..."IMO". 8)

...The only real advantage of a hammer valve is that they can be opened by a sear/hammer(a QDV could be as well) and that they allow multiple shots. Otherwise, a QDV will offer better performance in nearly every way.

Someone seconded my opinion (on easier triggering/ bolt config.) while I was replying! :shock: 8)
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Unread postAuthor: Technician1002 » Fri Sep 04, 2009 7:32 pm

(where's technician?)


I have a life. :D

The angled inlet is very great. A large area transitioning to a smaller area will help flow over a flat face orifice. That part should be good for flow.

Now to rip it to shreds.. No offense.. just my eval.

1 large dead space. Unless launching life savers into your thumb. :D

2 I assume the button won't be in the middle of the barrel, so I would assume another bend in the outlet before the barrel. Extra bend is bad.

3 The rod occupies some of the outlet space, so to get the same flow, either a larger valve is needed or the flow must go faster to deliver the same flow into the barrel.

4 The valve has the added moving mass of the rod that moves with the disk. This could possibly be less than the mass of the full QDV piston so the jury is out on that.

5 Pushing against the chamber pressure is much harder with higher pressure and larger orifices. I would not be strong enough to open a 2 inch version at 100 PSI.

This is my eval. Please don't hate me for it. :D

This is basically the same valve used in some blowguns.
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Unread postAuthor: Ragnarok » Fri Sep 04, 2009 7:55 pm

Technician1002 wrote:I have a life.

You don't want one of those mate. Losing your life causes you to die.
But... not having a life means you can't lose one. And hence, I have proven that being a geek or nerd makes you immortal.

Q.E.D. :D
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: THUNDERLORD » Fri Sep 04, 2009 9:14 pm

Here's an interesting pic that POLAND_SPUD posted in the other QDV (sp.?) Thread the other day:
Image

It seems to add rapid fire possibility to the QDV.

Seems like a hammer activated QDV would be possible too.
8) 8)
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Unread postAuthor: jackssmirkingrevenge » Fri Sep 04, 2009 11:56 pm

Technician1002 wrote:This is basically the same valve used in some blowguns.


Indeed, most airgun valve are the same design, just struck by a hammer. If it wasn't for the multiple shot benefit nobody would be using them. Look at the performance some spudders get with 400 psi launchers when commercial pneumatic airguns need 1500-3000 psi to get anywhere close.
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Unread postAuthor: Brian the brain » Sat Sep 05, 2009 3:50 pm

So how about my 35 bar push button thingy then?


It could be converted into a pressure independant ( therefore easy to scale up) hammer valve.
Just the springforce needs to be hammered...
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Unread postAuthor: POLAND_SPUD » Sat Sep 05, 2009 5:06 pm

as JSR has mentioned hammer valves have poor performance, so you need something else...

btb is probably right that his push button is what you are looking for

btb's push button valve and far cry's push button valve


ohh here is a simple way to open the QDV via hydraulic system (aka JSR syringe fetish syndrome) :wink: sorry for crappy quality but I don't have much time ATM
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