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ADVANCED TUNING for the JSAR Raptors as well SS-2 Balanced Valves

Forums PCP Airguns PCP Airgun – Discussion ADVANCED TUNING for the JSAR Raptors as well SS-2 Balanced Valves

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    Motorhead
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    United States
    Accuracy: +81

    Let me start with saying what I'm going to disclose myself and Travis Whitney of JSAR had discussed Many times in the past 6+ months or so as the R&D behind the scenes was happening.  We had the conversation that at some time these tuning traits should be brought to light and shared.  In the past 6+ months further testing and tuning with an Actual Raptor valve ( SS-2 in function ) retrofitted into my WarP , have got to get some really good data and more importantly some Cause & Effect when changes are made in TRANSFER PORT SIZE … which for now will be the focus of this thread.

    To recap on how these valves work … simply put is by having a DUAL use poppet head, one larger diameter side sealing the valve throat as is typical, Other end being reduced in diameter and extended into a sealed tube / chamber and sealed via an o-ring.  * What has happened is the pressure within the valve internal space bearing down on the closed poppet has had PART OF IT'S TOTAL AREA isolated by having the opposing end up in the o-ring sealed chamber. THUS the pressure exerted on the poppet seat is greatly reduced and the valve will break free and open far easier with not only LESS hammer weight, but less strike energy as well ( Softer hammer spring, less hammer stroke etc ..   )

    While this sounds all good & fine we all like easy cocking fast cyclic actions  8) there is now the issue of getting the valve poppet to close quickly and this by design utilizes a partially hollow valve stem that goes from just under the poppet head within valves throat up into the end of the poppet within the chamber.  * So at any time when valves pressurized the chamber at the upper end of poppet is at atmospheric pressure being vented via the poppet stem into throat, then out the barrel. Yet there is pressure surrounding the poppet that is kept from escaping via the o-ring mentioned earlier sealing it.

    Here is where we're going …. WHEN THE GUN IS FIRED there is a spike in pressure filling the valves throat and ultimately launching the pellet or slug.  In that very short time span that released pressure travels up threw the partially hollow valve stem and INTO the chamber pressurizing that space.  In this instance the poppet which has traveled inward within the chamber via the seat side being lifted is now acted on by the pressure filling chamber and is quickly pushed back down the chamber violently closing the seat.      Crazy stuff !! and now with this base knowledge to chew on we will address the purpose of this thread  ;)

    Understanding the hammer that opened the valve, it's weight mass etc is also holding the poppet from closing very fast being reliant on the Balance chamber to push back so hard the hammers lift on poppet can be stopped with hammer forced to then go back the direction from which it came and allow poppet to close again.   This is the tuning trick that for those incline will find HUGE efficiency gains, lower muzzle report and less air used in general at any given power level.

    Because these valves have such generous port values, huge throat and transfer path they BREATH SUPER WELL releasing mass volumes of air that produce Really big power !!
    Controlling there DWELL ( How long the air is flowing is dwell ) and this is controlled by HOW EFFECTIVE THE BALANCE CHAMBER is to sense the mass flow and SHUT IT DOWN !!!
    For once the pellet or slug is underway and moving 1/2 the barrel length or less, releasing more air IS NOT DOING A THING or very little and somewhat caliber & projectile weight dependent.

    TRANSFER PORT SIZE MATTERS and is a MAJOR major tuning parameter with these valves and Bigger IS NOT better in many instances belief it or not ???
    AS WE CONSTRICT THE OUTFLOW or air leaving valves throat we are INCREASING the amount and strength of the air that makes it into the balance chamber / tube and gets the valve to close.
    Valve opens EASY and breathes volumes, but control of getting it shut down is paramount to Efficiency & a Low muzzle report.

    Below is a test recently done while shooting NSA .22 caliber slugs. hammer weight, stroke, spring tension never changed ONLY TRANSFER PORT SIZE.  * Barrel is @24" with an elongated transfer port offering FULL caliber port specs so it to breaths to the bores caliber 100%.  Pressure regulated at 2200 psi.

    BIG transfer port at .250" being slightly greater than caliber @ 935/940 fps
    >Caliber spec transfer port at @ .210" @ 980 fps
    Smaller yet transfer port at .175"  @ 980 fps
    Smaller yet transfer port at .160"  @ 960 fps
    Smallest transfer port tried at .140" @ 915 fps

    Whats really interesting is listening to the gun fire with the top 4 tests especially ( All Shots are exceeding 50 ft lbs ! ) in .22 caliber too.     NOISE, that of the residual after the shot released air that is the heard muzzle report.

    The largest port arguably having excessive volume poppet to slug and the least efficient with a good WOOOSH sound upon firing. * Still making great power !!
    With the .210 transfer the report was notably quieter and as a tuner you know the dwell was reduced. YET it making MORE power … kewl !
    With the .175 transfer the report becomes a muffled SNAP and is quieter yet again.  Whoa same power too ! Now I know we're wasting less air and dwell has really been cut back.
    With the .160 transfer the report sounds like a 12fpe pcp with LDC … Sounds like a cricket farting being weirdly concerning the guns power had tanked, yet we only lost 20 fps.
    Finally  the .140 transfer … about like the above just less power tho still FLINGING these 24.8 slugs with authority !

    With all my testing coming to light in this shared manor, I not going to get into efficiency number beyond a recent check I just did a few days ago.  That being when the .210 port was fitted and thought I was done and giggle happy. Efficiency numbers crunched at 1.29 fpe/cu in shooting the NSA 24.8 at the above speed which was Awesome.   Having just run these smaller transfer port tests just hours ago … IT'S EVEN BETTER and going to keep the .160" transfer in place for now and see just what the efficiency does.  * Have a fun shoot next weekend and will be shooting the gun quite a bit and able to really gain some extensive real world numbers.

    Hope this all makes some sense, was not overly long winded and you gain some knowledge from it  ;)

    Scott S

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    Papy_Yosh
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    United States
    Accuracy: +16

    Scott,

    Thank you for the added knowledge. That is a piece of really interesting information when you compare it to the usual saying that says "the bigger, the better".

    Papy_Yosh

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    Hobbyman2007
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    Canada
    Accuracy: +11

    This is really good information Scott . I don’t have or plan on getting the valve or gun , but this is somewhat in line to a failed balance valve attempt I had had made a year or so ago. I may just have to revisit that one , I just couldn’t get it to close fast enough . 

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    FelixS
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    Very nicely written; I appreciate the CAPS that were strategically used and enough information provided to drive home the points!!

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    Kinetic45
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    Accuracy: +14

    Thanks, concise explanation of function let me visualize it quite well.

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    BH
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    Accuracy: +24

    Thanks for sharing your findings – very cool.

    Are the various TP sizes available as options on the Raptor / Mini Raptor (i.e. can the .22 gun be ordered with the .160)?

     

     

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    Motorhead
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    United States
    Accuracy: +81

    BH

    Thanks for sharing your findings – very cool.

    Are the various TP sizes available as options on the Raptor / Mini Raptor (i.e. can the .22 gun be ordered with the .160)?

     

     

    At this time NO … What I'm sharing is with no direct affiliation with the folks at JSAR.      Having been in the R&D loop for several years have got to validate findings, take side trips and other directions adding input here and there …. Be Shared with and returned findings of learned stuff I never knew or understood previous.

    Understand these valves are primarily focused on MAKING POWER ! …. If your application can be well served by a conventional valve at low to modest power there is little point to go this route IMO.

    As too ever smaller transfer size, there is a limit quickly reached that happen sooner with a heavier hammer and increased tuneablity with a light hammer.
    This simply because at any given pressure within the valve and throat, and that pressure threw the small hole / path connecting to a given area balance chamber … can and will only exert a given amount of push back based on the pressure / area within the chamber.

    As a hammer gets heavier the inertia it carried via the hammer spring throwing it to open the valve is less effected by the closing forces created by the chamber getting pressurized.  Lighter the hammer greater is the ability to influence its motion by the opposing force created by the chamber / poppet pushing back. 

    Yes some stuff going on no doubt … Cause & effect, just keep whats doing what and it starts to make more sense.

    The limit of reduced transfer size becomes relative to being able to stop the hammers LIFT and reverse its direction with any control.   As you go smaller it is still somewhat GREY to really get a handle on IF OR NOT ? the power finally drops away because DWELL is so controlled/ chopped ? … Or the Restriction in flow controlling the power potential ?  * I think this has a large bearing on a hammers weight where a heavier hammer over powers the closing effects of the chamber less so than a light hammer.

    ying – yang to be sure ….

     

    THE PRODUCTION JSAR RAPTOR uses a different weight hammer, different operating pressure, different caliber etc etc etc ….  This post if for those who wish to TUNE there guns or valves based upon there specifics at hand.  There is no way to have paint by numbers give me this size transfer etc without a whole lot more folks having them and giving tangible input as to what they find optimal ..  We understand it, can cover the mechanics / pneumatics, but shy of a sure fire cook book.

     

    Scott S

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    Broken_WV_Guy
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    So it's like a variable air spring? Variable depending on the back pressure generated from the TP and reg pressure?

    Sorry, just reading this for the first time.

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    Motorhead
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    Accuracy: +81

    Broken_WV_Guy

    So it's like a variable air spring? Variable depending on the back pressure generated from the TP and reg pressure?

    Sorry, just reading this for the first time.

    In simple terms Yes ….

    Tho the pressure exerted on the contain area of poppet via the venting WILL NEVER exceed the same pressure seen on a conventional poppet system.

    Trick is the fact you can OPEN the valve so much easier, use a lighter hammer and weaker spring to do it.  All said less cyclic vibration along with valve that wants to breath mass amounts of air netting big power !

     

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    Roachcreek
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    United States
    Accuracy: +9

    Interesting.

    My JSAR ti tube and SS valved Bulldog never gave me problems with a .27 tp.  Once I had it reamed to .30  I had valve dump, violent valve dump, as in destroying end ca0s. At the same time velocity dropped. It also started leaking after that.

    The expensive ti tube and valve have been sitting on my gun room floor for months, perhaps the larger .30 port is why.

    If I get a new barrel with a smaller port, say .25, will the valve dump stop?

    Regards,

    Roachcreek

    • This reply was modified 1 year ago by Roachcreek.
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    Motorhead
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    Accuracy: +81

    Valve dumping typically from having PRELOAD on the stem.  If the force created threw pneumatic action pushing the poppet closed can not overcome the hammer and spring energy that opened the poppet and reverse the poppet towards closing the valve will indeed dump !!

     

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    Roachcreek
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    Mystery solved…I hope.

     

    Thanks,

     

    Roachcreek

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    mtnGhost
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    Not sure how the heck I missed this thread, but thank you very much for taking the time to post this!!!  

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    Roachcreek
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    Scott,

     

    On my my Bulldog,should my transfer port be smaller, back to the .27 from the .30 it is now?  I have the lighter spring also.

     

    Roachcreek

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    Motorhead
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    Accuracy: +81

    All I can tell you is this ….

    In all my fiddling with balanced valves in .177 threw .30 caliber using lighter hammers and SSG devises is THAT …. I found the ability to REDUCE transfer path size quite a way down from bore caliber with nearly No reduction in power and when finally getting very small in transfer area the power only gradually fell away with further size reductions.

     

    So while I can't know what size to recommend ? will suggest making a few different sizes and see at what point the power actually starts being effected ?

    It is at that point where transfer choking just starts to effect power where closing effect of the balance chamber will be the greatest & best efficiency will be found IMO.

     

    Scott S

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    Springrrrr
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    Anything close to this??

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    Motorhead
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    Drawing above is a type / style I'm unfamiliar with.

    What JSAR as well my own version of the concept is more of this flow configuration ….

     

    https://i.imgur.com/Nza44hJ.png

     

    Actual parts on a personal WAR valve conversion like this:

     

     

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    Springrrrr
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    That picture was just one of a few that showed up on a page from Hard Air Magazine and I thought it may be close to the one you were working on.

    Keep up the fine work, it is a benefit to us all.

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    Scotchmo
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    Motorhead


    BIG transfer port at .250" being slightly greater than caliber @ 935/940 fps
    >Caliber spec transfer port at @ .210" @ 980 fps
    Smaller yet transfer port at .175"  @ 980 fps
    Smaller yet transfer port at .160"  @ 960 fps
    Smallest transfer port tried at .140" @ 915 fps

    Scott S

    The Mach number through the transfer port cannot be greater than 1. As you increase the port size, you reduce the flow velocity through the orifice. Once the calculated Mach number goes below 1, there is nothing to be gained by going to a larger transfer port.

     

    • This reply was modified 1 year ago by Scotchmo.
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    Motorhead
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    Makes perfect sense … and no matter at this point being all my PCP's with balanced valves have reduced area tapered throat transfer tubes in them.

    It really upped the efficiency and chopped the muzzle report doing so.

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