GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: skorec on December 21, 2018, 12:00:40 PM
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Travis Python valve concept let me idea for next similar valve concept .
Pleas let me comments and help me calculate particular dimensions for three times less hammer strike force then standard valve.
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Travis Python valve concept let me idea for next similar valve concept .
Pleas let me comments and help me calculate particular dimensions for three times less hammer strike force then standard valve.
First its a very cool concept. Now to get it to work. Area S1 is atmospheric until the valve poppet V1 opens then its driven to just below the HPA tank pressure due to expansion so getting poppet V2 to open using expanding gas is unlikely UNLESS you make a tiny version of the thimble and V1 poppet so basically two balanced valves in one.
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Functionally, that valve will work like an SS Valve.... In an SS valve, your second valve V2 is part of V1 and moves with it, and is sealed by an O-ring inside the thimble....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/6%20Stepped%20Poppet_zpsyklaxoxl.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/6%20Stepped%20Poppet_zpsyklaxoxl.jpg.html)
As soon as the valve cracks, the area between the O-rings in the SS Valve rises to nearly HPA pressure because of the rapid rise in pressure in the exhaust port.... In your valve, volume S1 does the same thing, as does this valve....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Balanced%20Poppet_zpsysyicmhc.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Balanced%20Poppet_zpsysyicmhc.jpg.html)
I realize your valve has an extended stem on the main poppet V1, which is supposed to open the secondary poppet V2 when it gets to nearly full lift.... What you may not realize is that "full lift" varies depending on how you tune the hammer strike, and also varies with pressure.... The valve opens further as the HPA pressure drops, and so would open V2 sooner at low pressure, the opposite of self-regulation....
Further, I don't think opening V2 would make any significant difference to the way the valve cycles anyways, because by the time that occurs, chamber S1 should already be nearly at HPA pressure through the poppet vent.... At least that is my opinion....
In terms of proportions, the two drawings I posted are designed to have 70% less opening force than a conventional valve with a 3/8" seat.... pretty close to your 1/3rd requirement.... actually slightly less....
Bob
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Don't see the secondary poppets purpose ???
When hammer strikes primary poppet and the throats fills with HPA with a portion back venting to get some balancing properties ..... The pressure within the valves interior space will ALWAYS still be above the pressure in the valve throat and balance chamber.
* With NO pressure differential biased to be GREATER in the balance chamber than the plenum/feeding pressure to the valve CAN OR WILL the secondary poppet come off it's seat.
** Now if mechanically the primary contacts secondary will it be lifted.
Anyways ... that is what I'm seeing as drawn ???
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That said ... how about this ?
As drawn ( Basic design wise ) we're good.
Now place an adjustment screw down the middle of the secondary poppet that has it extend into the balance chamber and stop just shy of contacting the back side of the primary poppet.
You end up with still having a sealed system w/o use of o-rings, but critical to BOTH poppets having good sealing dynamics.
As primary poppet is driven open and throat pressures up and transfers via bleed to balance chamber, you get that advantage. A tad further in the primary poppets lift the "Screw" in secondary poppet Adjusted in length so it is contacted lifting the secondary off it's seat for a small burp of air ( Likely all incoming + pressure to the balance chamber ) and some will head out the bleed hole to throat too.
As primary poppet falls away from max lift it allows secondary poppet to close. Now the system once more is operating in Cobra type mode and the primary poppet returns to seat.
This JUST thoughts of a thing to try .... based upon your drawings.
No further thoughts on this really at this time.
Scott
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I see what you are getting at, Scott.... As an example, set the gap between the poppets at some small value, like 1 mm, so that when the primary poppet V1 opens that far, V2 opens and the pressure in S1 rises instantly to HPA pressure.... The valve converts from a balanced valve to a Cobra valve at that instant, with the exception of any "air spring" effect.... a couple of thing to think about....
If you use a screw in the secondary poppet V2 for adjustment, it has to seal to the poppet V2 or it will leak.... I would suggest just carefully made parts with the proper clearance between V1 and V2 to get V2 to open when you need it to.... It may take a few before you get that gap right....
If you have a jet in front of V2 you may be able to gain back the "air spring" effect.... but on the other hand a small trapped volume may not raise the pressure in S1 high enough when V2 opens.... Probably not going to work with any Cobra effect, IMO....
I think if you go back to the original design, with a small gap between the parts, you may get a valve that functions OK, and in a similar manner to this one....
(http://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Balanced%20Poppet_zpsysyicmhc.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Balanced%20Poppet_zpsysyicmhc.jpg.html)
The difference is that it would act like that valve with a large vent, but with a delayed action allowing the main poppet to rise further from the seat before the pressure in S1 rises and closes the valve.... This can be arranged by the proper choice of the vent diameter, but instead of that you will have to get the gap just right....
Bob
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Your still going to have and oring on the main V1 poppet no way around that and I haven't seen any balanced valve designs without a dynamic oring.
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Inside of V1s poppet orifice we could put a long rod that when V1 opens the rod is shot forward knocking V2 open?
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In such R&D the screw and where adjusted for gap could be easily sealed via a low grade hold thread locker liquid & once found what gap works between primary & secondary, screw could be omitted and parts / poppet made to have said contact gap. * Or a blind screw within the balance chamber being threaded into the head of secondary poppet adjustable ONLY by removal.
Just work arounds ...
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Inside of V1s poppet orifice we could put a long rod that when V1 opens the rod is shot forward knocking V2 open?
Floating kinetic striker .... If it has sufficient energy to crack the secondary ??? Which to drive it ABSORBS energy that lifts and dwells the primary.
Slippery slope there ???
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Uff, You are too quick for me .
Ability of having the smaller vent hole inside poppet may able to reduce dependency of transfer port dimension ? The valve V1 is closing whit much higher force which can reduce valve cycles ?
Adjusing valve dwell is easier to do via Scot adujusting screw in the poppet of V2 then via dimension of venting hole or via jet ?
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I agree, you need at least one dynamic O-ring, the main poppet must be sealed inside the thimble.... In addition it must be stepped in diameter or it will never seal, with atmospheric pressure on both sides of it when closed.... The seat MUST be larger than the upper part that slides in the thimble....
I agree, a kinetic striker to open V2 would be hard to get to work properly.... although it would be assisted by HPA in the exhaust port coming into the vent....
I don't know about the "low grade thread locker" as a thread sealant.... I have used Loctite purple thread sealant on parallel threads with no success, it only works on tapered threads, in my experience.... which are basically "self-sealing" because of the taper.... Parallel threads have a helical path between the male and female threads providing an easy escape for 3000 psi air.... You could use a setscrew in a sealed pocket in V2, disassemble and adjust, until you get it working OK.... but I have a feeling any change in operating conditions may require a different gap.... Only building it would show you one way or the other....
Bob
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Just a design note:
The primary poppet stem where pressed into the poppet head will need to rest upon a shoulder. Not doing so the impact will just slide the stem threw the poppet head.
The secondary poppet could also be reversed as to which end has the stem & said stem could also be the adjuster miens to set contact gap. ( Not a double end poppet )
Or a simple Ball Check given a way to have adjuster in there too for contact gap.
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Peter, you have the idea.... but I think the gap between the end of the adjusting screw and V1 will have to be very small.... about 1 mm or so....
Now it's a matter of sealing up the three points, two poppets (one tiny) and one dynamic O-ring.... My experience with the SS valves has shown me that the dynamic O-rings are much easier to get to seal than the seat of the poppet.... Every time I have a leak, it traces back to the poppet seat....
BTW, as drawn you also have to seal the poppet head of V1 to the stem and keep it from moving on impact.... A press fit won't cut it....
Bob
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This design would be very expensive to produce and I personally cant see any advantage to building it though its really cool to see other new designs out there.
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This design would be very expensive to produce and I personally cant see any advantage to building it though its really cool to see other new designs out there.
It's Winter and we're all sitting around .... nothing wrong with an off season think tank.
Darn Mouse Traps anyways !!! ... gotta be a better way to trap them little buggars !
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It's Winter and we're all sitting around .... nothing wrong with an off season think tank.
AMEN to that !!!!
Bob
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OK thanks for your time.