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Quick Dump Valve

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: jeepkahn » Thu May 07, 2009 1:32 pm

What you have made is basically a manaully operated "Parsoneault" valve... the valve used in avalaunchers and pneumatic pitching machines...

Something you may try as opposed to the reset pin is a spring...Calculate the actual opening force required when empty and preload the spring to just above that(you'll have to figure springrate as well to make sure it's not going to prohibit opening), that way the piston won't be able to act on the trigger rod(turning it into a missile itself)

And I could definitely see this in very high pressure applications(like my soon to be built copper gun)....with the above mentioned mods so that I can make a trigger to actuate the piston/rod...
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Unread postAuthor: Biopyro » Thu May 07, 2009 2:04 pm

I'm looking to put it into a high pressure copper gun, just need to sort the piston. It's a good valve, and I see it being used quite a bit in co-axial cannons in the future, however I wish we could quantify it's performance against other valves, particularly the toolie.

I haven't heard of the parsoneault valve, nor could I find much on google about it - do you have a good lik explaining it or something?
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Unread postAuthor: jeepkahn » Thu May 07, 2009 2:22 pm

Biopyro wrote:I'm looking to put it into a high pressure copper gun, just need to sort the piston. It's a good valve, and I see it being used quite a bit in co-axial cannons in the future, however I wish we could quantify it's performance against other valves, particularly the toolie.

I haven't heard of the parsoneault valve, nor could I find much on google about it - do you have a good lik explaining it or something?


http://avalanchemitigationservices.com/ ... lution.pdf

you won't get diagrams and such unless you do a patent search, I'll attach the patent pdf in a few minutes...

Crap, can't post pdf...
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Here's a Kickin' Air Cannon...It'll throw 4 pounds over 2000yds...

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Unread postAuthor: Technician1002 » Thu May 07, 2009 2:50 pm

jeepkahn wrote:What you have made is basically a manaully operated "Parsoneault" valve... the valve used in avalaunchers and pneumatic pitching machines...

Something you may try as opposed to the reset pin is a spring...Calculate the actual opening force required when empty and preload the spring to just above that(you'll have to figure springrate as well to make sure it's not going to prohibit opening), that way the piston won't be able to act on the trigger rod(turning it into a missile itself)

And I could definitely see this in very high pressure applications(like my soon to be built copper gun)....with the above mentioned mods so that I can make a trigger to actuate the piston/rod...


Google is showing a lot about the inventor, some on his cannons, some on his projectiles, but pretty much zip in the valve detail. It's hard to compare my design to a black box. :(

I have toyed with a spring. Finding one the right size is a problem. I operate over a very wide pressure range and the recoil tends to launch the piston past closed which would require a stop of some sort in the flow path causing a ridge for turbulence and a smaller aperture. In competition, the mass of the spring adds to the moving mass. Getting the triggering rod out of the way before the valve re-closes is the other consideration. I wouldn't want pinched fingers where the trigger suddenly yanked itself forward as the piston smacked it on the way back closed. The spring was considered, but rejected as impractical.

Biopyro wrote:I'm looking to put it into a high pressure copper gun, just need to sort the piston. It's a good valve, and I see it being used quite a bit in co-axial cannons in the future, however I wish we could quantify it's performance against other valves, particularly the toolie.


I've been trying to match it also in the valves in GGDT. Using my in barrel travel times and working backwards, it seems to best match a burst disk. We have been trying to do that in this thread.
http://www.spudfiles.com/forums/ggdt-and-in-tank-quick-dump-valve-performance-t18090.html
It has the flow of a piston valve, but due to the impact opening, it has the time approaching a burst disk. Something I'm still trying to figure out is why it appears more efficient than a burst disk. It may be because the burst disk has remnants causing turbulence and the plumbing between the disk and chamber that the DQV lacks.

At pressure, my measurements are pointing to an opening time of about 1 ms or less.
A traditional piston valve has a delay getting started because it starts at rest before any pressure is released into the barrel which pushes on the face of the piston. At the point the piston cracks open the accelerating force is near zero as it is in transition in force from forced closed to forced open. This slow start, and slow acceleration leaves the valve at mostly closed for a ms or two until it gets over the power hump and pops open in about 3 ms or more for most piston valves.

The QDV while not having a flat sealing surface like a piston is struck with a moving rod to initiate motion and has some travel distance before the o ring seal is broken open. On my big cannon, the golfball trigger rod assy has a 2 inch acceleration zone before the piston is struck. The critical initial cracking open of the valve is at much higher speed, therefore the total opening time is drastically reduced.

For these reasons, the QDV performance is close to a burst disk.

Crap, can't post pdf...


From the description, the valve design without a patent used in commercial declogging is the piston QEV. A piston QEV is a Barrel Sealer Piston Valve with a close ratio of seat diameter to piston OD. This ratio keeps the valve sealed until the trigger pressure is very low so when the face is exposed, it avalanches open independent of the pilot speed.
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Unread postAuthor: jeepkahn » Thu May 07, 2009 3:12 pm

After doing some number crunching and research, one of the main reasons your QDV opens so quickly is because the closer the sealing face is( in your case the forward o ring) to the piston diameter(in this case the rearward o ring) the faster the valve will actuate, Rag or another vet can prolly cite the actual nomenclature... Your flow rates are similar to burst disc and toolie designs because of the direct airflow path from chamber to barrel, and some may argue but I think sometimes in a pneumatic a toolie or design such as yours will perform better thatn a burst disc because a burstdisc the pressurized air is overcoming an obstruction to begin the flow, where as a piston valve on opening creates a momentary vacuum that allows the pressurized air to accelerate before slamming into the projectile( but a non toolie piston creates flow restriction and turbulance after the initial opening, decreasing their performance)...

If you look at this modified toolie diagram, the smaller you can make the piston on the pilot side, the faster the valve will open...

and you could actually make your piston with a sealing face for the barrel, and totally remove all the materiel between the ports and it would still work, as long as the piston "tube" is stabile...
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Unread postAuthor: Biopyro » Thu May 07, 2009 3:21 pm

It's good, that's what I know, and definately deserves it's own wiki page!
You sure know how to write a good post!!!
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Unread postAuthor: Technician1002 » Thu May 07, 2009 3:23 pm

jeepkahn wrote:
If you look at this modified toolie diagram, the smaller you can make the piston on the pilot side, the faster the valve will open...



I thought this too and it is true as it moves from an air piloted valve into the realm of a QEV. Continuing in GGDT trying to model my valve (GGDT won't permit a seat = piston diameter) I started getting the ratio very close to 1:1 in size. As you approach a QDV, the time in GGDT start to increase again due to the very slow initial acceleration force. The slow acceleration causes a slow valve opening limiting acceleration.... An impact start gets it way past this slow start portion of the curve directly into the power accelleration zone. A good project would be to find the best diameter to seat ratio for a fast piston QEV.

To see this extreme, model a 2.1 inch piston with a 2.0 inch valve seat in GGDT. I did this trying to model my valve.
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Unread postAuthor: jeepkahn » Thu May 07, 2009 3:29 pm

What vent diameter are you using???

Try using 2" sealing face, 2.1" piston diameter, and 2" vent... Look at the valve position on that.

i'm showing 1ms to full open...
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Unread postAuthor: Technician1002 » Thu May 07, 2009 3:39 pm

jeepkahn wrote:What vent diameter are you using???

Try using 2" sealing face, 2.1" piston diameter, and 2" vent... Look at the valve position on that.

i'm showing 1ms to full open...


In GGDT I told it 3/4 inch for my model. It is the size though the bumper into the LONG stopper assy. The actual exit clear back by the golfball isn't very large, but the volume in between would never reach even 5% of the chamber pressure due to compression.

The "Vent" is large to permit room for the piston reset pin to retract into it. I used that size as the pilot area doesn't really slow the piston much even if it were sealed. It doesn't provide much opposing force until the piston is over halfway open where the opening force is near maximum.

I'm showing curves that support a full open valve in 1 ms or less. :D

Biopyro wrote:It's good, that's what I know, and definately deserves it's own wiki page!
You sure know how to write a good post!!!


Hubb017 wrote:Hey, Technician1002, why not make a wiki article on this valve?


***EDIT***
What does it take to write an official Wiki Page? I could recycle some stuff from the already written page on the t shirt launcher competition. These are a couple pages I have already written elsewhere.


http://inteltrailblazerschallenge.wikispaces.com/Barrel+length+trim+method
http://inteltrailblazerschallenge.wikispaces.com/The+brag+zone
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Last edited by Technician1002 on Thu May 07, 2009 4:24 pm, edited 2 times in total.
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Unread postAuthor: jeepkahn » Thu May 07, 2009 4:04 pm

But I guess you're starting to see why the piston/sealing face ratio effects openingg speed greatly...
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Unread postAuthor: Hotwired » Fri May 08, 2009 8:00 pm

I really hate the way patents are written.

Yes they have to be exceptionally precise about it but dam is it a female doggy to read.

To sum up after ignoring 90% of the patent diagram which is in fact irrelevant:

A Parsoneault valve is the spool valve piston you have there, using o-rings either side of the chamber port.

The major differences are:

1) It has the piston secured by means of a spring to prevent the piston from moving until fired

2) Firing is achieved by pulling back the piston with air pressure.

Other than that all is effectively the same.

The rest of the patent mainly covers a throttling device to limit the gas flow into the barrel... which we're not really interested in... (why would we want to limit flow here?).


It's a new valve for the spudgun library but not for the world.

Heck, no spudgun valve is unique, best to hope for is to be first to claim it for spudgunning :)
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Unread postAuthor: jackssmirkingrevenge » Sat May 09, 2009 2:43 am

Speaking of avalanche launchers, there's a variation of Tech's deisgn uses the projectile as the "valve", as in this patent.

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Unread postAuthor: Technician1002 » Sun May 10, 2009 11:33 am

Hotwired wrote:I really hate the way patents are written.

Yes they have to be exceptionally precise about it but dam is it a female doggy to read.

To sum up after ignoring 90% of the patent diagram which is in fact irrelevant:

A Parsoneault valve is the spool valve piston you have there, using o-rings either side of the chamber port.

The major differences are:

1) It has the piston secured by means of a spring to prevent the piston from moving until fired

2) Firing is achieved by pulling back the piston with air pressure.

Other than that all is effectively the same.

The rest of the patent mainly covers a throttling device to limit the gas flow into the barrel... which we're not really interested in... (why would we want to limit flow here?).


It's a new valve for the spudgun library but not for the world.

Heck, no spudgun valve is unique, best to hope for is to be first to claim it for spudgunning :)


In particular,

2) Firing is achieved by pulling back the piston with air pressure.


This is a QEV that is held mechanically closed because the two sealing surfaces were not the same size. Mine is NOT held mechanically closed and there is no opening force until it is moved mechanically.

His is a QEV with a mechanical release. Mine is a Quick dump with an impact start. Patent officers would note they are not the same.

It's a new valve for the spudgun library but not for the world.

The closest match to my valve in the real world is used for liquid tanks to dump the contents quickly. It's adaption to a spudgun and a slide hammer start is the only thing unique about the design apart from the original quick dump valve used on chemical rinse tanks.
http://www.processregister.com/Quick_Dump_Valves/Suppliers/pid16655.htm
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Unread postAuthor: Hotwired » Sun May 10, 2009 12:59 pm

Technician1002 wrote:In particular,

Hotwired wrote:2) Firing is achieved by pulling back the piston with air pressure.


This is a QEV that is held mechanically closed because the two sealing surfaces were not the same size. Mine is NOT held mechanically closed and there is no opening force until it is moved mechanically.

His is a QEV with a mechanical release. Mine is a Quick dump with an impact start. Patent officers would note they are not the same.


The valve does not appear to be patented, the Avalauncher for example failed to get a patent on its valve and it was made with the help of the valve inventor who had previously been using it for a pneumatic pitching machine.

I've coloured the patent diagram to make it much easier to follow, click for full scale:

Pipe #20 fills the chamber.

Pipe #32 fires the valve by allowing air pressure to overcome the spring

Image

It's the same balanced spool valve your design is and as I said the only difference is that it uses (essentially) a pneumatic ram to unbalance the piston.

Actually now that I've used the phrase balanced spool valve I recall some paintball guns use that as well.
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Unread postAuthor: Technician1002 » Sun May 10, 2009 4:44 pm

Hotwired wrote:
Technician1002 wrote:In particular,

Hotwired wrote:2) Firing is achieved by pulling back the piston with air pressure.


This is a QEV that is held mechanically closed because the two sealing surfaces were not the same size. Mine is NOT held mechanically closed and there is no opening force until it is moved mechanically.

His is a QEV with a mechanical release. Mine is a Quick dump with an impact start. Patent officers would note they are not the same.


The valve does not appear to be patented, the Avalauncher for example failed to get a patent on its valve and it was made with the help of the valve inventor who had previously been using it for a pneumatic pitching machine.

I've coloured the patent diagram to make it much easier to follow, click for full scale:

Pipe #20 fills the chamber.

Pipe #32 fires the valve by allowing air pressure to overcome the spring

Image

It's the same balanced spool valve your design is and as I said the only difference is that it uses (essentially) a pneumatic ram to unbalance the piston.

Actually now that I've used the phrase balanced spool valve I recall some paintball guns use that as well.


Thanks for finding a diagram. It's the first one I have seen. 3 o rings and what looks like a pop off valve in the outlet air stream (maybe the pitch speed regulator). The main valve does look like mine, but much smaller aperture in relation to the barrel. It is very long. It does not have a mechanical decoupling from the trigger to the main valve to reduce the mass being accelerated.

That valve while reasonably fast suffers from excess length (mass) and small diameter (flow). The 3rd section with an o ring doesn't help the friction. The pop-off in the outlet doesn't help flow, but may help with the opening force to compensate for the excess mass and small aperture.

Again, thanks for finding the photo of the valve and adding the color.
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