GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: Motorhead on January 08, 2020, 05:26:05 PM
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My times a little short and will return with more specific info later this evening ... so here a taste of whats cookin ???
The first photo is a design of what we are currently seeing and using with JSAR SS 2 / Raptor ( Tho these are custom built, design holds true to original )
This being a double end poppet, stem side seals the valve throat setting on the seat, other male end up within balance chamber which is held up on the intake grate at entrance to valves internal space.
The second photo is my redesign which has inverted the placement having the poppet head setting on seat the same, but has the balance chamber on the other end. All that is attached to the intake grate is a stem with the sealing o-ring on it down within the poppet heads balance chamber.
Original version must use an INTERNAL spring and be deep enough to allow for the length of the spring, be deep enough that when spring coil binds you can still achieve the required lift.
Redesign version uses an EXTERNAL spring and has no effect on chamber volume allowing one to have a volume ONLY THAT of the poppet lift distance. * Small volume is really important here !!
Next advantage to the redesign is the Path distance air travels from the bleed holes on stem to get into the balance chamber .... The Redesign is @ 1/2 the distance resulting in less wasted volume and faster filling.
Another being with NO HOLE in the portion of poppet that seals the balance chamber, the o-ring groove is now stronger in the redesign version, where weaker in the original because of the hole passing threw the minor diameter of the o-ring groove.
Also now the intake grate holes can be MUCH larger increasing the in-flow.
Last on my mind being .... NOW we can adjust spring preload via the threaded intake grate, while based upon poppet stem pushed in flush with body from hammer strike can dial down the chamber space to ZERO !!
which will create a much faster closing valve if wanted.
More later ....
Scott S
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Way over my head Scott but I'm going to follow this so maybe I can learn a thing or two.
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nice, youve kinda flipped the traditional design on its head.. and this does alleviate the coil bind issue on the balance chamber.
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Nice work, I like the adjustment feature.
Made a BV about a year ago with a similar external balance chamber spring.
If I make another BV I'd like to try the spring on the outside of the valve.
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Yep makes perfect sense and always a way to build a better mousetrap with the right tools and patience for attention to details.
I just hope eventually these innovations make into individual valves for most common platforms for us tinkerer/modders to be able to purchase separately from complete guns.
BD
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Ok I'm back ...
On the 4th picture we see BOTH style poppets side by side with the stems vent holes aligned.
The original design air path is @ 1.2" threw the stems .055" hole traveling further within the male stem before it exits into the chamber. The Revised design a mere .6" or exactly half.
When put on a scale BOTH weight 4.3 grams so we have given up nothing in cyclic mass / weight
As too the external spring it has a few immediate advantages, with one long term ........ Being spring only need clear the stem going into chamber( I.D. of spring ), differing spring rates / stiffness's can be used for further tuning.
With an internal spring your very limited to ones choices being spring is small and coil bind is against you !! An internal spring also drags against the inner chamber wall and will in time gall or wear away on the same surface the o-ring is moving and sealing against ( long term bad ) Where an external spring can drag and wear all it wants because it is now BEHIND the o-ring and never contacts inner bore of chamber. ( Long term no damage )
Further elaborating on the portion with stem & o-ring attached to the intake grate being able to thread up / down within the grate ( Last pic show threading ) we achieve a unique tuning ability that is two fold. So long as the internal volume / depth of the chamber is such we get some range of in/out adjustment ? As we screw the stem inward we add preload to the spring while at the SAME TIME are reducing the volume within the chamber. * these two effects added together amplify the effect on valve wanting to close and i see this as a huge advantage with not only high power tunes but low as well.
As too the o-ring, in both designs the pressure within the valves interior space is attempting to get past this o-ring and enter the chamber, pass down vent hole and exit out barrel !!! Only thing keeping this from happening is this o-ring. Sadly in both designs the pressure is pushing on the o-ring towards the end of the chamber stem and will if material is too weak ... TEAR THE END RIGHT OFF sending it into the chamber with catastrophic failure of the system.
Thus in the Revision as stated in the first post NO LONGER has the venting hole passing under the o-ring groove with a resulting much stronger ring groove and end being less likely to fail.
Any who .... Revision parts shown were just a proof of concept quickly done bit of parts. While it will work I see dimensions needing tweaks to truly fulfill the advantaged noted.
Great time to be into PCP's .... the innovations we can marry together is pretty mind boggling from where we were not 5 years ago .... Cool stuff !!
Scott S
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Following. I’ve been thinking about trying my hand at a balanced valve.
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It looks like it should work.... My initial thought was that stiction would be an issue by turning the design inside-out.... However, you are also moving the O-ring to the other side of the balance chamber (front instead of back)…. so that should work OK.... I'm looking forward to your results....
The last drawing I made in the thread for the "Simplified Balanced Valve" also went to an external valve spring.... for the same reason you quoted.... You can reduce the volume of the balance chamber....
(https://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Balanced%20Valve%20External_Spring_zpscg16atbi.png) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Balanced%20Valve%20External_Spring_zpscg16atbi.png.html)
As you say, turning that inside out will shorten the length of the passage in the valve stem.... which should be an improvement.... 8)
Bob
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Ok ... made one more tho this time around changed materials and specs as to make a valve that had the specs of this one: https://www.gatewaytoairguns.org/GTA/index.php?topic=160999.msg155792422#msg155792422 (https://www.gatewaytoairguns.org/GTA/index.php?topic=160999.msg155792422#msg155792422)
Above Referenced thread and that valve opening with a mere 43% opening force of conventional valve, able to use a 20 gram hammer, easy one finger cocking etc ... had to see if a valve built to the REVISION specs would work the same ?
I used a JSAR SS 1 valve body that has a throat of @ .320" with .250 big port transfer. Specs here are about identical to a modified WAR valve in above Ref: thread.
This time tho the poppet head was 100% Glass filled acetal rod that when assembled tipped the scale at just 3.8 grams being lighter than OP version.
Chamber bore opened up to .250" and poppet O.D. at .365" giving us @.022" sealing margins.
The chamber stem attaching to intake grate now aluminum and got an o-ring groove for "006" series o-ring * Tho used a QUAD RING which is ideal for this dynamic application.
Exterior spring design stayed intact, as did the adjustable preload / chamber volume threading.
Put it all together adjusting the chamber rod to just bottom out at near zero volume when poppet stem is flush to body. Total available poppet lift @ .170" ( Amount extending out for hammer to strike )
Aired up with a slight leakage until @ 600 psi and then it stopped once above that. Man does it open easy !! being just like the WAR valve, near identical too.
Assembled the WarP with the light hammer, light spring SSG and an extension on striking tip to destroke hammer travel, along with a taper choked transfer port at .165"
2000 psi reg setting and first shot with 21.3 barracuda .. 1070 fps, 24.8 Nielsen slug 960 fps. That was too easy !
QUIET TOO being IMO sounding as if using even less air than previous where my RAPTOR spec valve had been previously and indeed quieter than the modified WAR valve.
YES IT WORKS turning the valve around aka: "REVISION" and in the future think I'm going to stay the course and make them this way from now on ... it is actually easier to fabricate too !
Scott S
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Those poppets look like aluminum? What is your sealing surface? Are you just cutting a groove and using a oring? Thanks for sharing your work in progress.
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Those poppets look like aluminum? What is your sealing surface? Are you just cutting a groove and using a oring? Thanks for sharing your work in progress.
Yes both in OP were Aluminum poppets that sealed against Acetal seats. o-ring used are 90 duro buna. My valve used this morning has an aluminum seat surface so the poppet head was Glass filled acetal.
Either seat or poppet can be the softer and sealing part where Acetal / Delrin, PEEK, PET-P among others are common.
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May I point out that you no longer need to drill the valve stem with this design. A simple hole through the valve face works just as well.
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May I point out that you no longer need to drill the valve stem with this design. A simple hole through the valve face works just as well.
Huh .... that makes life easier yet for those w/o access to getting or creating a drilled stem. faster filling yet going past our current .052" stem hole in .125" stems
Thanx !!
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Something to keep in mind.... I tried a "near zero" clearance (IIRC about 0.020") inside a balance chamber.... and I LOST power because the poppet was bouncing off the coil bound spring.... even though the valve stem length would not allow the poppet to be driven that far by the hammer.... Apparently, the poppet's own momentum carried it deep enough into the balance chamber to drive the spring to coil bind, and it rebounded, reducing the dwell.... I had to leave "a bit" of additional clearance (I think I added about another 0.030") not needed mechanically, but necessary for the "dynamic" travel....
It's kind of like a hammer bouncing off the back of a valve and losing velocity as a result.... An unintended consequence of trying to take things to the limit.... ::)
PS, I really like the idea of not having to drill the stem, but just drilling through the poppet head adjacent to it, into the "cup" in the poppet.... Talk about a SHORT air path.... 8)
Bob
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A practical question, how thick walls do we need for that poppet "cup" if we use PEEK? Will 1mm do, i.e. 6.5mm poppet and 4mm plunger inside or do I need to expand the poppet diameter once the hollow inside starts?
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A practical question, how thick walls do we need for that poppet "cup" if we use PEEK? Will 1mm do, i.e. 6.5mm poppet and 4mm plunger inside or do I need to expand the poppet diameter once the hollow inside starts?
I have been using PEEK on & off for the Cup / Chamber and not seen any crush or collapse at @ .065" wall. Pressure crushing a cylinder from the outside inward is a lot different than pressure on the inside pushing outward.
Also used Glass reinforced Acetal with same results ... fwiw
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The bigger the OD, the thicker the wall needs to be (in direct proportion).... You would need to know the tensile/compressive strength of PEEK to calculate it....
I can understand the reason for wanting to use PEEK or Delrin for the poppet.... not having to make a seat insert for the valve to use a metal poppet.... One less part to make, and one less O-ring to leak (seat to valve body)…. On the other hand, then you have the structural problem of mounting the PEEK poppet head/cylinder onto the metal stem.... without having it thrust through on firing.... ::)
Bob
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The bigger the OD, the thicker the wall needs to be (in direct proportion).... You would need to know the tensile/compressive strength of PEEK to calculate it....
I can understand the reason for wanting to use PEEK or Delrin for the poppet.... not having to make a seat insert for the valve to use a metal poppet.... One less part to make, and one less O-ring to leak (seat to valve body)…. On the other hand, then you have the structural problem of mounting the PEEK poppet head/cylinder onto the metal stem.... without having it thrust through on firing.... ::)
Bob
Thats whats so cool about the balanced design in general .... You no longer need to really strike hard at the poppet stem to get valve opened. The issue of driving the stem further into the poppet head becomes so much less likely.
I was working on a third one last night that is a PEEK head on a drilled stem ( .052" hole ) and ALSO has a .063" hole in the body of poppet angled inward slightly it entered cup I.D. right on the edge of bore.
Hold the poppet and cup end in your mouth you can actual breath softly threw it. It flows massive amounts of air and should be VERY very responsive to throat pressure driving it back down towards seat ... violently so I'm figuring.
As an abstract thought .... If we look at the valve ONCE POPPET IS LIFTED and pellet or bullet is yet to move, we have the pressure within valve throat going TWO directions. One being out the transfer port and other filling the balance chamber. With larger venting to the balance chamber the poppet itself becomes a projectile too getting basically Shot back towards the seat. ( While this is HOW the valve works anyways ) With larger venting this effect is going to be really really fast and violent. Tho, it has little effect on the initial opening effort.
Dwell will be less no doubt and i'm wondering if the closing effect being super fast via large venting, or somewhat slowed down via smaller venting become a further tuning parameter as what I've decovered using smaller transfer ports to create more back pressure within throat.
My thoughts are ... By increasing the venting size to balance chamber the need or desire for a strangled transfer port may very well become unnecessary ??? Being each by in large are creating the same end result of getting the poppet to shut quicker.
Thoughts ?
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You have to remember that the closing force can NEVER be greater than it would be for a conventional valve of the same poppet (seat) diameter.... In a conventional valve, the entire poppet is surrounded by HPA.... In this version, the pressure inside the balance chamber can rise to ALMOST the same pressure, but can never exceed it.... The pressure in the balance chamber can never exceed the throat pressure, which will always be slightly less than inside the valve.... The best you could ever hope for is a valve that opens easier and possibly faster than a conventional valve.... and closes at nearly the same rate....
Increasing the diameter of the balance chamber reduces the hammer strike required to crack the valve.... Eventually, if you make it too large, there may not be enough force remaining to seal the poppet when the valve is closed.... That will limit the minimum hammer strike required to cycle the valve.... It is important to remember that if the inside of the balance chamber remained at atmospheric pressure (not vented to the throat), the valve would blow open and stay open until the reservoir drained.... It requires venting to the throat so that the pressure inside increases and that pressure allows/causes the valve to close.... You start with a net opening force, and end with a net closing force....
Reducing the volume inside the balance chamber, and/or shortening the air path from the throat.... actually decreases the dwell of the valve, because it blows open for a shorter time before the force reverses and becomes a closing force.... The slower that chamber fills, the longer (and further) the valve is "blowing open", with the result that less hammer strike is required to develop enough dwell to produce a given FPE.... As you decrease the chamber volume, and increase the fill rate, you actually need MORE hammer strike to get back to the same dwell you had before.... This is an important thing to remember....
These were the problems I faced when developing the "Simplified Balanced Valve" last year.... Originally, my valve opened very easily, but it was difficult to tune for a bell-curve because it was blowing open, because the chamber was filling too slowly.... This created a valve that cycled nearly like a Cothran, either working or not, with nearly a cliff between, and a very narrow tuning range.... I made the chamber smaller, and the vent larger and shorter to get the pressure to equalize faster.... which resulted in a valve that could be tuned better.... HOWEVER, and this is very important to remember, those changes required an INCREASE in hammer strike to get back to the dwell required for a given FPE level.... Yes, the hammer strike was still a lot less than for a conventional valve.... but it INCREASED as I made the balance chamber fill faster, because I was losing some of that "blow open" assist....
I can see that turning the balance chamber inside out (which reduces its volume and shortens the air part) would have greatly reduced those issues.... However, you will end up needing MORE hammer strike to maintain the dwell you need, because the valve will no longer be blowing open because the pressure in the balance chamber will be rising so quickly.... The valve will be shifting from a net opening force to a net closing force almost instantaneously.... You may, in fact, find that the increase in hammer strike required to get back the lost dwell, may not be worth the tunability of the design.... and a compromise may be necessary....
Please note, I am not trying to discourage the development of this idea, far from it.... I am hopefully pointing out the pitfalls before they bite you....
Bob
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Ok ... made one more tho this time around changed materials and specs as to make a valve that had the specs of this one: https://www.gatewaytoairguns.org/GTA/index.php?topic=160999.msg155792422#msg155792422 (https://www.gatewaytoairguns.org/GTA/index.php?topic=160999.msg155792422#msg155792422)
Above Referenced thread and that valve opening with a mere 43% opening force of conventional valve, able to use a 20 gram hammer, easy one finger cocking etc ... had to see if a valve built to the REVISION specs would work the same ?
I used a JSAR SS 1 valve body that has a throat of @ .320" with .250 big port transfer. Specs here are about identical to a modified WAR valve in above Ref: thread.
This time tho the poppet head was 100% Glass filled acetal rod that when assembled tipped the scale at just 3.8 grams being lighter than OP version.
Chamber bore opened up to .250" and poppet O.D. at .365" giving us @.022" sealing margins.
The chamber stem attaching to intake grate now aluminum and got an o-ring groove for "006" series o-ring * Tho used a QUAD RING which is ideal for this dynamic application.
Exterior spring design stayed intact, as did the adjustable preload / chamber volume threading.
Put it all together adjusting the chamber rod to just bottom out at near zero volume when poppet stem is flush to body. Total available poppet lift @ .170" ( Amount extending out for hammer to strike )
Aired up with a slight leakage until @ 600 psi and then it stopped once above that. Man does it open easy !! being just like the WAR valve, near identical too.
Assembled the WarP with the light hammer, light spring SSG and an extension on striking tip to destroke hammer travel, along with a taper choked transfer port at .165"
2000 psi reg setting and first shot with 21.3 barracuda .. 1070 fps, 24.8 Nielsen slug 960 fps. That was too easy !
QUIET TOO being IMO sounding as if using even less air than previous where my RAPTOR spec valve had been previously and indeed quieter than the modified WAR valve.
YES IT WORKS turning the valve around aka: "REVISION" and in the future think I'm going to stay the course and make them this way from now on ... it is actually easier to fabricate too !
Scott S
would I be correct in assuming you did the mod to .320 throat diameter? and by the sounds of it, turned your own poppet?
cheers,
Douglas
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Yes Douglas .... Throat changed from .280 and all the parts fabricated.
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Yes Douglas .... Throat changed from .280 and all the parts fabricated.
I need one like that...:)
cheers,
Douglas
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Bob S .... If you will ?
What about the cause & effect of the strangled transfer path and not seeing much loss in power ( Previous thread ) and dwell becoming less because of the back pressure within throat ?
And now increasing the chamber venting to speed up the filling ?
Both create an increased fill rate and decreasing dwell. What your thoughts on with larger venting & if we keep the transfer size larger will it act similar to less venting and a strangled transfer ?
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I think that with such a short vent path and large vent that the "blow open" phase will last only a fraction of the total dwell.... The pressure may, in fact, equalize when the poppet has hardly cleared the seat.... The result of that will be that you will need more hammer strike to keep the valve opening, and get the lift and dwell you need to flow enough air to get your desired FPE.... I think if you compare it to the original simplified balanced valve design, with identical throat, poppet seat, and balance chamber diameters, you will need a heavier hammer, more spring, or both....
You can only open up the transfer port until it matches the smallest port area somewhere else, be that the barrel port, or the bore area minus the bolt probe area, or the valve exhaust port.... Going bigger than that should do nothing, other than drop the pressure in the entire system because you are creating extra volume for the air to expand into before it moves the pellet.... IIRC, your largest port in that previous thread was larger than the chamber (bore minus probe) area.... which is why you didn't lose velocity when you went a bit smaller.... Once you went small enough, the FPE dropped, and because you were using less air, the report was less.... I'm sure backpressure had some effect of course.... but I wasn't all that surprised by your results.... It was, however, an additional tuning method that worked well....
What I'm saying is that your design may work TOO WELL.... By creating a small balance chamber and venting it to the throat with a short, large vent, the "blow open" part of the cycle will largely disappear, and then the full closing force, as experienced by a conventional valve, will take over.... That will require a heavier hammer and/or spring, or you will lose power....
Bob
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Thank you .... Have 2 of them made now, one is in the WarP being the .22 slug shooters and seems to work great !! It being the Revised with just the .052" vented stem as is typical.
Second one with the additional vent hole will be going into a Custom bottle converted .25 cal m-rod in a week or so. * Lloyd is just finishing up the machining this weekend.
We will know more on this large vent path variant within a couple weeks.
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https://www.youtube.com/watch?v=krD4hdGvGHM (https://www.youtube.com/watch?v=krD4hdGvGHM)
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Do put up a pic or three, and how it shoots. Always love seeing another Bottle 'Rod in action. I am re-barreling my .25 with an LW polygon, and would be quite interested in a valve that does not need as big a spring as I can fit in.
cheers,
Douglas
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Do put up a pic or three, and how it shoots. Always love seeing another Bottle 'Rod in action. I am re-barreling my .25 with an LW polygon, and would be quite interested in a valve that does not need as big a spring as I can fit in.
cheers,
Douglas
Let me know how your polygon shoots I’ve had no luck at all with them unless I put a monster choke on them so I stopped using them.
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Ok, we have looked over the REVISED design quite a bit, received some excellent suggestions and come to a resolve of was is IMO the simplest configuration that utilizes all I know of PCP valves over the years.
This one uses a TAPERED seat shape ( Cone if you will ) which captures the poppet head around the O.D. being very similar the what BSA has done for years while creating great flow around poppet head.
Made two poppet heads, 1 being PEEK that got the additional .063 vent hole being spoken of a few posts back. Other made of Glass reinforced Acetal which of late has been my material of choice. Both have .250" balance chamber at @ .350" deep. Both use a drilled stem with a .052" hole. * Valve assembled with the Acetal poppet first to get base line of operation.
Figured out the dimensions to keep the chamber plunger just out of contact with chamber roof when valve stem went flush and just permanently set that attaching it to the intake grate. In this picture you can clearly distinguish the use of a QUAD RING in lieu of an o-ring to seal the chamber.
For the spring I used a .040" wire spring, heated and flattened the ends then grinding ends flat. Over all length of spring such that it fit and plunger bottoms out before going into coil bind. Assemble prior to going into body it looks like this.
Once assembled the view from the valves intake side.
Look down transfer hole with the stem vent holes mid throat/port exit position.
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Here just a preview on the entire firing system to be used with the above valve that's going into a custom .25 m-rod build.
Hammer uses the "Threw bolt" type SSG devise. Modified end cap with gap adjuster screw. Poppet striking end has had the cap screws wrench pocket inserted with a PEEK plug to silence the impact.
The poppets lift and keeping parts internal to valve from bottoming out, we are using a #212 Teflon o-ring as a buffer. This still allows more than enough poppet lift ( @ .180" ) where the poppet w/o it can go @ .215" This buys us @ .035" of space cushion within the balance chamber.
* Spring rates on the SSG yet to be finalized until we get some testing done on the assembled rifle ... When that happens, actually will start another thread on that Custom build here in the next couple weeks and back reference this post as relative ;)
Think I'm done with this thread unless further conversation is required. Thanks for following along ...
Scott S
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Looking good Scott, but I can't see how you would be adjusting the spring tension once the gun is fully assembled.
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Looking good Scott, but I can't see how you would be adjusting the spring tension once the gun is fully assembled.
This version is a take it out and play with it ... once set install and forget about it. * M-rod is a BOTTLE conversion using an adjustable output regulator, should provide plenty of speed adjustment.
If it creates an issue ??? redoing with an External SSG is easy enough and a painless alternative.
Again .. this is just R&D and nothing is ever cast in stone ::)
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Do put up a pic or three, and how it shoots. Always love seeing another Bottle 'Rod in action. I am re-barreling my .25 with an LW polygon, and would be quite interested in a valve that does not need as big a spring as I can fit in.
cheers,
Douglas
Let me know how your polygon shoots I’ve had no luck at all with them unless I put a monster choke on them so I stopped using them.
The one in my .22 Bottle Rod is stellar. As in silly. On a calm morning at the range, it will keep up with both my Anschutz 1813 SuperMatch, and my son's 40XBR( both eating premium ammo ). The one I helped fit to an FX500 in .25 gave me fits at our next gathering/competition.
cheers,
Douglas
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Looking good Scott, but I can't see how you would be adjusting the spring tension once the gun is fully assembled.
This version is a take it out and play with it ... once set install and forget about it. * M-rod is a BOTTLE conversion using an adjustable output regulator, should provide plenty of speed adjustment.
If it creates an issue ??? redoing with an External SSG is easy enough and a painless alternative.
Again .. this is just R&D and nothing is ever cast in stone ::)
Thanks! Also gap adjustment will work as well.
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All of the “blowing open” stuff with these valves is caused by the cute little circles of air flow holes that direct the air around the poppets . That in turn creates a slight low pressure up in front of the poppet . I have a valve shroud on my conventionaly valved .58 that has the same effect.
I can mess around with the adjustable hammer striker and get it to dump 3000 psi easily.
The balance valve i built in back in 2002 has full air airflow around the poppet and is vented to the atmosphere not the port , and it would reset perfectly till it dumped .
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Any test results yet about the valve with extra hole in the poppet? I'm about to build one of these and would like to know if very good breathing is a good idea or not.
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Great thread Scott. Yes I totally get the 0.053 through the poppet, in the plastics. I was sitting at the dinning room table and heard a discharge. Ran to the shop and discovered the WARP discharging. The poppet broke from the bottom of the groove right into the .053 hole. And discharged the 500cc tank. Fortunately it was through the 0.053 hole, so it was a "Controlled" Leak!
Thanks for Sharing
Michael :- )
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I don’t know how I missed this one. I have struggled with the drilling of the stem on the last two I built and that in turn had negative effects on performance . I just couldn’t get a big enough hole to get the valve to close. Now this looks real simple to make. I’m going to have to look at my parts bin , I hope I have a disco valve on hand.
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I don’t know how I missed this one. I have struggled with the drilling of the stem on the last two I built and that in turn had negative effects on performance . I just couldn’t get a big enough hole to get the valve to close. Now this looks real simple to make. I’m going to have to look at my parts bin , I hope I have a disco valve on hand.
Yea I thought that I had it down to a science. Then after 4 with no problem broke 3 bits on the next one. Must have hit a hard spot. I'll be glad not to buy so many bits!
Michael :- )
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Really like the idea of an aluminum poppet head...I really do. 8) Making the poppet is SO much quicker and easier this way than turning it from a piece of stainless. Not doing the revised poppet this time, but won't rule that out for next time.
Fun stuff to play with, thank you for posting Motorhead.
Al
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The additional hole along the side of stem ( with stem also drilled ) had valve wanting to close much faster. This compounded by the fact I use really light hammers that really don't have the mass / weight to hold the poppet off the seat for very long. Adding more hammer weight tho LESS spring driving it is a work around to a heavily vented balance chamber IMO. Sadly as hammer weight is increased you can get the valve to over dwell Very very easily.
JSAR uses a buffer to limit poppet lift height which is effective over a broad tuning range & power. ( kind of a do all design )
I really like a single venting path of less area using a lighter hammer and heavier spring driving it, then choke the transfer port to get a longer duration pressure rise within the throat which helps the poppet get a tad more dwell before the chamber comes up to pressure and poppet slams closed. ( This with a balance ratio more 60/40 ) being pretty easy to crack open.
Wish I had the time and fortitude in creating a cause & effect chart for these Reduced opening force valves. Charting out the cause and effect of Ratios of opening forces, effect light and heavy hammers have in achieving the wanted lift and flow without the valve over dwelling it self. In my mind I have a pretty good grasp on the physics involved and understand too a point what is happening. Sadly to really get a handle on all of this the parts and pieces thus far have needed to be custom purpose built. These valves are Very very reactive in that one change effects another function or requirement much more so than a conventional knock open poppet valve.
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I'm not surprised that you are finding that with the short, large vent and small internal volume the "blow open" phase disappears in a hurry, with the result that you need more hammer strike to get back the dwell.... That is what I suggested would likely happen back in Reply #23.... A chart showing how all the various factors interrelate would be great, but I think it might end up being "valve specific", in that the trends would be similar, but a valve of different proportions might act quite differently.... At this stage about all we can reasonably expect is to get a handle on the trends, IMO.... Just too many variables....
The buffer is a great idea for a regulated PCP, and can be made to work unregulated as well (eg. bstaley mod)…. but it tends to knock the top off the power in either case (by limiting lift and dwell)…. It all depends on what you are after, efficiency and shot count, or lots of power.... as they are to some extent mutually exclusive.... and certainly the balanced valve design requirements are quite different....
Bob
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So a balanced valve is easy to open but getting the dwell correct can be a problem.
I'm thinking that a balanced valve combined with an electronic striker (solenoid) would be a great combination. The dwell of the solenoid is easy to control electronically.
We just need a balanced valve that opens easily and quickly. With sufficient valve spring to close it (not blow/stay open).
The solenoid plunger would need just enough momentum to crack the valve, and then just enough holding force to keep the valve open against the spring(s). The solenoid could have an adjustable millisecond timer in order to set the dwell.
The FPE is adjusted by setting the dwell. That would give the most efficiency possible, regardless of FPE settings.
Imagine a valve that fully opens easily and near instantly. It stays fully open only as long as we want it to. And then it closes instantly. That's what we could have.
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If you can get the resolution of the solenoid down to 10 microseconds or so, that could be a good solution.... The entire shot cycle is only 1-2 mSec.…
Bob
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If you can get the resolution of the solenoid down to 10 microseconds or so, that could be a good solution.... The entire shot cycle is only 1-2 mSec.…
Bob
The solenoid coil firing voltage is variable. As is the capacitor properties and overall capacitance of the reservoir that will discharge into the coil. A film/foil affair is going to behave differently from an electrolytic, yes? Then we can also tweak the inductance of the coil. Am thinking it ought to be pretty low, and able to stand a substantial amount of amperage...which would be tuned by capacitance and firing voltage. We can for sure get a MOSFET capable of 100A to fire in well under a microsecond with a robust gate driver.
Just recall, there is no violating the conservation of energy; the hammer is fed from a battery. Lead-acid need not apply...:) But let's look at the numbers; a 3.5 A-h 18650 is going to be able to deliver about 40,000 Joules of energy. Even at 25% delivered to the hammer, that is 10,000 shots on a charge.
And then the usual suspects come into play, hammer mass top among them.
cheers,
Douglas
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If you can get the resolution of the solenoid down to 10 microseconds or so, that could be a good solution.... The entire shot cycle is only 1-2 mSec.…
Bob
The solenoid coil firing voltage is variable. As is the capacitor properties and overall capacitance of the reservoir that will discharge into the coil. A film/foil affair is going to behave differently from an electrolytic, yes? Then we can also tweak the inductance of the coil. ...
An advantage over strictly mechanical is that dwell does not depend on hammer mass. The valve can be held open electronically. Dwell is easy to control. I played with a 12fpe electronic build. An easy opening balanced valve would make the electronically controlled hammer more advantageous.
https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0)
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If you can get the resolution of the solenoid down to 10 microseconds or so, that could be a good solution.... The entire shot cycle is only 1-2 mSec.…
Bob
The solenoid coil firing voltage is variable. As is the capacitor properties and overall capacitance of the reservoir that will discharge into the coil. A film/foil affair is going to behave differently from an electrolytic, yes? Then we can also tweak the inductance of the coil. ...
An advantage over strictly mechanical is that dwell does not depend on hammer mass. The valve can be held open electronically. Dwell is easy to control. I played with a 12fpe electronic build. An easy opening balanced valve would make the electronically controlled hammer more advantageous.
https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0)
If you guys want I can help with coils we wind our own at work. The price is stupidly low.
Michael :- )
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If you can get the resolution of the solenoid down to 10 microseconds or so, that could be a good solution.... The entire shot cycle is only 1-2 mSec.…
Bob
The solenoid coil firing voltage is variable. As is the capacitor properties and overall capacitance of the reservoir that will discharge into the coil. A film/foil affair is going to behave differently from an electrolytic, yes? Then we can also tweak the inductance of the coil. ...
An advantage over strictly mechanical is that dwell does not depend on hammer mass. The valve can be held open electronically. Dwell is easy to control. I played with a 12fpe electronic build. An easy opening balanced valve would make the electronically controlled hammer more advantageous.
https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0)
a solenoid directly driving the stem on a balanced valve might actually work.. might not even need a hammer mechanism... Assuming the poppet was soft enough to seal in a very balanced state ( like 85% ) . Could be run by arduino and externally adjustable.. ( im getting carried away
the solenoid itself could reside in the tube , meaning a marauder would be an ideal base for less restriction on size. to add to this , I actually test some overbalanced valves, but when the seating force got too low , the valve would cycle itself
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If you can get the resolution of the solenoid down to 10 microseconds or so, that could be a good solution.... The entire shot cycle is only 1-2 mSec.…
Bob
The solenoid coil firing voltage is variable. As is the capacitor properties and overall capacitance of the reservoir that will discharge into the coil. A film/foil affair is going to behave differently from an electrolytic, yes? Then we can also tweak the inductance of the coil. ...
An advantage over strictly mechanical is that dwell does not depend on hammer mass. The valve can be held open electronically. Dwell is easy to control. I played with a 12fpe electronic build. An easy opening balanced valve would make the electronically controlled hammer more advantageous.
https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=96617.0)
a solenoid directly driving the stem on a balanced valve might actually work.. might not even need a hammer mechanism... Assuming the poppet was soft enough to seal in a very balanced state ( like 85% ) . Could be run by arduino and externally adjustable.. ( im getting carried away
the solenoid itself could reside in the tube , meaning a marauder would be an ideal base for less restriction on size. to add to this , I actually test some overbalanced valves, but when the seating force got too low , the valve would cycle itself
On my 12fpe solenoid gun with a conventional valve, I was never able to push the valve open directly. I only needed to give the plunger a running start of 0.09" before contacting the valve stem, though it worked best at about .120". Even a little bit of momentum can make up for the high force needed to crack the valve.