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QEV pop-off guns plus trigger

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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QEV pop-off guns plus trigger

Unread postAuthor: Gaderelguitarist » Tue Apr 28, 2009 8:10 pm

So it has hit me like a sack of bricks that QEV pop-off guns are the hot ticket these days. However I've noticed that all of the one's I've seen use a fill valve as a trigger.

I would like to get a general opinion on whether it would be smart to place some sort of push-button or blowgun valve in between the QEV and the pop-off.

Granted, these valves are not the most reliable for high pressure applications, however wouldn't the closer proximity of pressurized air to the pop-off valve result in a faster trigger response?
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Unread postAuthor: twizi » Tue Apr 28, 2009 8:13 pm

i used a bv that was connected to the qev pop off then to a quick connect and used the bv as a trigger
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Unread postAuthor: Gaderelguitarist » Tue Apr 28, 2009 8:17 pm

A ball valve at the fill source is just common sense so as not to waste pressure when switching connections.

What I'm suggesting is a valve in between the pop-off and the QEV for a more sudden response and a potentially more ergonomic operation.
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Unread postAuthor: twizi » Tue Apr 28, 2009 8:30 pm

oh sorry miss under stood
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Unread postAuthor: covey12 » Tue Apr 28, 2009 8:42 pm

i dont get how these guns work, does the pressure have to rapidly build up so it is piloted out by the popoff then repeat?
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Unread postAuthor: Gaderelguitarist » Tue Apr 28, 2009 8:47 pm

That's exactly how they work :D

However what seems to be a trend is directly connecting the pop-off to the QEV so the moment the chamber pressure exceeds the pop pressure, the gun with begin to fire.

It seems to me to be similar to the firing of a burst disk cannon, where there is no 100% guarantee that the gun will fire when you think it will.

Again, its only a few milliseconds, but I'm picky about designs :wink:
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Unread postAuthor: SubsonicSpud » Tue Apr 28, 2009 10:49 pm

I have not had a proper trigger on mine, mainly because I am still developing the weapon, the final version will have a trigger close to the pilot area, this would probably be the same case for the rest of the guys . The air in the hose is not really wasted because it is usually only just below the cutoff pressure of the popoff valve and doesn't just get vented out, this also means there is not much of a delay once the valve is opened to fire again.

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Unread postAuthor: jackssmirkingrevenge » Tue Apr 28, 2009 11:56 pm

What I don't like about these designs is that aside from the fact that pilot volume is wasted, you still have a flow into the pilot chamber during firing. It's probably really not that much of a loss in terms of total air usage but the idea irks me.

Custom pop-offsFTW! :D
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Unread postAuthor: Technician1002 » Wed Apr 29, 2009 12:18 am

jackssmirkingrevenge wrote:What I don't like about these designs is that aside from the fact that pilot volume is wasted, you still have a flow into the pilot chamber during firing. It's probably really not that much of a loss in terms of total air usage but the idea irks me.

Custom pop-offsFTW! :D


Probably not a near future project, but in looking far into the future, I have been brainstorming on a possible custom Pop Off to use with the "Gumball Machine --- Gun"

The common flaw with pop off valves are they are DESIGNED to open at one pressure and close at another. Often the closing pressure is very close to the pressure required to pilot a QEV, so the combinatin is hit and miss to get it to work.

The MOD
The mod would be designing a pop off not for opening and closing pressures, but as a full cycle all the way up and all the way down valve to cycle a QEV at high speed.

To do this, the 2 steps in a typical pop off would be eliminated. The spring would be longer and at a much lower tension, and instead of a flat seat, it would be a cylinder much like a piston valve. The valve core would be made heavy to make it slow.

Here is how it would work. At rest the piston would sit in the cylinder about 1/2 way to the bottom but sealed. When air is applied, the piston moves up to where the piston cork is ejected. The moving mass tends to keep it open longer than a typical pop off valve. This permits lower than normal pressure drop before the spring returns the slow massive piston.

Now that the pilot pressure has depleted way down, the spring drops the piston way down into the pilot hole and mass carries it further than the normal at rest position. As the spring rebounds and the pressure builds, the piston reverses direction and is ejected again to repeat the process.

This would make a (can't quite call it a pop off) vibrating cycle valve operate over a wider pressure range than a typical pop off. The fire rate is set by the mass spring resonant frequency, not the pilot fill speed. If the pilot volume and resonant cycle valve are tuned to each other, very high air usage efficiencies can be achieved.

Any thoughts? Will it work? Too many projects, too little time.

Maybe later I'll sketch it up with a typical cheezy quick drawing.
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Unread postAuthor: SubsonicSpud » Wed Apr 29, 2009 12:44 am

Technician1002 wrote:
jackssmirkingrevenge wrote:What I don't like about these designs is that aside from the fact that pilot volume is wasted, you still have a flow into the pilot chamber during firing. It's probably really not that much of a loss in terms of total air usage but the idea irks me.

Custom pop-offsFTW! :D


Probably not a near future project, but in looking far into the future, I have been brainstorming on a possible custom Pop Off to use with the "Gumball Machine --- Gun"

The common flaw with pop off valves are they are DESIGNED to open at one pressure and close at another. Often the closing pressure is very close to the pressure required to pilot a QEV, so the combinatin is hit and miss to get it to work.

The MOD
The mod would be designing a pop off not for opening and closing pressures, but as a full cycle all the way up and all the way down valve to cycle a QEV at high speed.

To do this, the 2 steps in a typical pop off would be eliminated. The spring would be longer and at a much lower tension, and instead of a flat seat, it would be a cylinder much like a piston valve. The valve core would be made heavy to make it slow.

Here is how it would work. At rest the piston would sit in the cylinder about 1/2 way to the bottom but sealed. When air is applied, the piston moves up to where the piston cork is ejected. The moving mass tends to keep it open longer than a typical pop off valve. This permits lower than normal pressure drop before the spring returns the slow massive piston.

Now that the pilot pressure has depleted way down, the spring drops the piston way down into the pilot hole and mass carries it further than the normal at rest position. As the spring rebounds and the pressure builds, the piston reverses direction and is ejected again to repeat the process.

This would make a (can't quite call it a pop off) vibrating cycle valve operate over a wider pressure range than a typical pop off. The fire rate is set by the mass spring resonant frequency, not the pilot fill speed. If the pilot volume and resonant cycle valve are tuned to each other, very high air usage efficiencies can be achieved.

Any thoughts? Will it work? Too many projects, too little time.

Maybe later I'll sketch it up with a typical cheezy quick drawing.


Sounds like a bit of a cross between JSR's rattlesnake valve, and my hammer valve/piston repeater. Definitely worth a try, but I think there would be a hell of a lot of factors to juggle to get it to cycle :shock:

A diagram would be god to get a better idea of the concept


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Unread postAuthor: Technician1002 » Wed Apr 29, 2009 1:19 am

SubsonicSpud wrote:Sounds like a bit of a cross between JSR's rattlesnake valve, and my hammer valve/piston repeater. Definitely worth a try, but I think there would be a hell of a lot of factors to juggle to get it to cycle :shock:

A diagram would be god to get a better idea of the concept


SubsonicSpud


Noted. No way to scan resize and send at this computer. Will need to submit the cheezy quick sketch in the morning when near the scanner.
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Unread postAuthor: SubsonicSpud » Wed Apr 29, 2009 2:05 am

Technician1002 wrote:
Noted. No way to scan resize and send at this computer. Will need to submit the cheezy quick sketch in the morning when near the scanner.


Windows Paint? :D
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Unread postAuthor: Technician1002 » Wed Apr 29, 2009 3:07 am

SubsonicSpud wrote:
Technician1002 wrote:
Noted. No way to scan resize and send at this computer. Will need to submit the cheezy quick sketch in the morning when near the scanner.


Windows Paint? :D


OK cheezy Windows paint. Think it will work?
The idea is for the piston to make the pressure to operate the QEV. It does not need to wait for the feed air to pressurise the pop-off valve. It simply vibrates saving air.
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Resonant vibrating mass QEV modulator.
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Unread postAuthor: i-will » Wed Apr 29, 2009 4:10 am

i'm too tired to understand what is being discussed in detail but i have my own idea that i think u should consider. it's a plug that stops the pop-off from popping which keeps it from firing. pull the trigger to pull the stopper which will let the pop-off go crazy as long as u hold it down. it allows u to set ur pneumatics once and trigger the piston mechanically. u won't have to worry about flow valves or leaking o-rings on moving parts. if it matters u can fit a regulator to the source so that first shot of a burst won't be to strong leaving the pop-off hangin open longer(this happens cuz u r keepin the pop-off from doing the regulating when blocked) it'll also make your shots more instant. instead waiting that half a second for the piston to pressurize after opening the flow it'll fire immediately cuz the piston will already be pressurized and waiting to be piloted. i think it'll increase the simplicity of the whole pop-off piston craze and at the same time making it feel more like a real trigger mech and not like a blowgun. u know wat i'm talkin bout.

this is not to scale. i drew the pop-off too small. i think.

<a href="http://s90.photobucket.com/albums/k273/PROGRESSKATE/?action=view&current=pop-offtrigger.jpg" target="_blank"><img src="http://i90.photobucket.com/albums/k273/PROGRESSKATE/pop-offtrigger.jpg" border="0" alt="spud trigger pistin pop-off"></a>
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Unread postAuthor: SubsonicSpud » Wed Apr 29, 2009 4:55 am

i-will wrote:i'm too tired to understand what is being discussed in detail but i have my own idea that i think u should consider. it's a plug that stops the pop-off from popping which keeps it from firing. pull the trigger to pull the stopper which will let the pop-off go crazy as long as u hold it down. it allows u to set ur pneumatics once and trigger the piston mechanically. u won't have to worry about flow valves or leaking o-rings on moving parts. if it matters u can fit a regulator to the source so that first shot of a burst won't be to strong leaving the pop-off hangin open longer(this happens cuz u r keepin the pop-off from doing the regulating when blocked) it'll also make your shots more instant. instead waiting that half a second for the piston to pressurize after opening the flow it'll fire immediately cuz the piston will already be pressurized and waiting to be piloted. i think it'll increase the simplicity of the whole pop-off piston craze and at the same time making it feel more like a real trigger mech and not like a blowgun. u know wat i'm talkin bout.

this is not to scale. i drew the pop-off too small. i think.

<a href="http://s90.photobucket.com/albums/k273/PROGRESSKATE/?action=view&current=pop-offtrigger.jpg" target="_blank"><img src="http://i90.photobucket.com/albums/k273/PROGRESSKATE/pop-offtrigger.jpg" border="0" alt="spud trigger pistin pop-off"></a>


That one has been done by Mitchza89 on his QEV pop off gun, not a bad way to trigger the system and gives full control. The only problem is when you are using a high pressure air supply, the chamber and all the components have to be rated to the supply air pressure, not just what the popoff pressure is set to.

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