GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: triggertreat on October 09, 2018, 01:21:41 AM
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I got my SS valve back after sending my older version in to JSAR for the latest upgrades to it. Man am I happy with the initial tune results I got today.
I ran the same hammer and spring setup I used for my signature tune that I ran many months ago and was able to repeat it and even better it by a little bit. I did use a smaller jet this time (Mikuni 87.5) .0370" verses the .0600" I used before, which increased the efficiency from 1.45 to 1.49 FPE/CI. The ES is slightly lower too at 1.96% compared to 2.08%. The average FPE is the same as before at 55.94 compared to 55.92 FPE.
The cocking effort is about the same, but I am running a shorter dwell with the smaller jet so I am impressed that I can reach the 56 FPE mark with a shorter dwell time using the same hammer and spring setup. My spring lengths are customized by me. I use the original TSS and I also have a gap on both springs. I customize the lengths only because I want my TSS adjustments flush with the end cap as I use my thumb to cock the gun. They are heavier rated springs than most use, but I use what it takes to allow a gap, reach 56 FPE, use a lighter than stock hammer and have a smooth thumb press. It's still fairly easy to cock with all of that going on thanks to the balanced valve.
I don't know everything that was done to the valve. I know some work was done to the seat area and the spool. I did notice it sealed up immediately as soon as I cracked the tank valve open which is different than the old valve which took near 2000 psi to seal. I bet this one doesn't leak, but am testing overnight to be sure. I'll also be checking for first shot sticksion issues coming up, but am feeling good about that too as I was checking by hand every few hours before installing it. Very pleased overall so far.
Looking at the string, I'm fairly confident I could come close to a 40/50 tune under a 4% ES, but am not really interested being it's used as a long range hunting gun.
I've got to thank JSAR for all of their efforts in upgrading my SS valve. It was a fast turnaround and I was notified that it was on the way back to me by Jason I think it was, and Travis also checked to make sure I had received it Very good support from the JSAR staff!
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That's great news and really great if the sticksion issue is no longer !
I'm real close to revisiting my SS valve soon as my Nielson sampler pack of .177 slugs get here later in the week.
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Looks good Keith!
Scott you know I will be watching with interest. My .257 barrel is with them now for an O ring groove in the breach. Looking forward to see what it will do in the Rainstorm. It was very accurate in the Talon/Dor with heavier bullets, Soooooo--- ;) ;)
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Sweet the mods are working! Im going to change the CNC program to incorporate this in future valves.
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Cool I'm glad the upgrades are help you. I believe I'm running the same jet in mine 87.5 let us know about the sticktion
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The good news is my gun hasn't lost a drop of air overnight and all day today with the new SS valve. I'm very happy about that. It's been awhile since I've seen that.
The bad news is I got water in my chronograph today and it's not working correctly to test for sticksion issues. All I can say for now is the first shot sounded like the second and so forth. I do have the display working again, but I get errors still when shooting across it. I will continue to try and dry it out.
What happened to the chronograph? When I was unlocking my shed, my sippy cup tilted and poured water down into the sensor. Stupid mistake, but I'll press on.
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Sounds like one of my days.
My Wife set up the package for JSAR, and left the check out for the shipping return. I need to apologize and call for instructions. GRRRRRR!!!
Just as much my fault as hers. Well, mostly mine. LOL!!!
I got kinda fed up with my old Chrony, and sorta shot it. By accident I swear!
The new Caldwell is much better. I enjoy it, and particularly the seeming lack of errors showing up. The old Chrony gave as many errors as readings. LOL. ;D
Knife
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Sweet the mods are working! Im going to change the CNC program to incorporate this in future valves.
Travis ,
SS Balanced valve is perfect and it is also improving day by day but unfortunately you have forgotten to send me some upgrade for my Puncher valve. Also I have no any PM answers from you.
Probably you are too busy ?
Peter
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Sounds like one of my days.
My Wife set up the package for JSAR, and left the check out for the shipping return. I need to apologize and call for instructions. GRRRRRR!!!
Just as much my fault as hers. Well, mostly mine. LOL!!!
I got kinda fed up with my old Chrony, and sorta shot it. By accident I swear!
The new Caldwell is much better. I enjoy it, and particularly the seeming lack of errors showing up. The old Chrony gave as many errors as readings. LOL. ;D
Knife
I have the ProChrono Digital. I like it, but if I can't get it going, I may order a Caldwell. A lot of people seem to like them, and I wouldn't have to manually type out my numbers anymore. The Free Spreadsheet also has a FPS filter for the Caldwell.
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+1 for the Caldwell vs ProChrono.
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+1 for the Caldwell vs ProChrono.
Have you had both, and if so why is the Caldwell better?
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Were there updates to the design to avoid stiction?
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Keith, if you need to you can borrow my Caldwell, I'm not using it at the moment. You can get a free app for a smart phone or Ipad and plug the chony right in to it, I use it with my old Ipad.
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Keith, if you need to you can borrow my Caldwell, I'm not using it at the moment. You can get a free app for a smart phone or Ipad and plug the chony right in to it, I use it with my old Ipad.
Thanks Tom! I may do that if I can't get mine going today. I want to answer the stiction question we all have.
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Keith, buy this one and don't look back!
https://www.amazon.com/Caldwell-Ballistic-Precision-Chronograph-Rechargeable/dp/B01B7OYNJG/ref=mp_s_a_1_3?ie=UTF8&qid=1539188032&sr=8-3&pi=AC_SX236_SY340_FMwebp_QL65&keywords=caldwell+chronograph&dpPl=1&dpID=41eA3hjGWZL&ref=plSrch (https://www.amazon.com/Caldwell-Ballistic-Precision-Chronograph-Rechargeable/dp/B01B7OYNJG/ref=mp_s_a_1_3?ie=UTF8&qid=1539188032&sr=8-3&pi=AC_SX236_SY340_FMwebp_QL65&keywords=caldwell+chronograph&dpPl=1&dpID=41eA3hjGWZL&ref=plSrch)
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Ok, my chronograph is back in business. Thanks for the offers and suggestions!
First shots this A.M.Shots four hours laterSo there seems to be a little stiction, but not too bad. It may very well be the heavy silicon grease I applied to the O-rings. Also, these O-rings are brand new and have at most 50 shots on them since I got the SS valve back from JSAR. Time will tell. personally I am very happy with this new valve. I will continue to test the first shots a few more times.
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This stiction thing is maddening. It doesn't matter too much for plinking, but it sure does for hunting.
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i haven’t followed all the details leading up to this point so this may be a dumb question but is this stiction symptom present with unregulated setups?
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Yes, it can be.
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i haven’t followed all the details leading up to this point so this may be a dumb question but is this stiction symptom present with unregulated setups?
Good question, but I couldn't say. Mine is regulated.
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Okay thanks, I was just thinking it could be a combination of stiction and regulator creep.
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Starting to wonder if this is going on with mine, too. I have a huma regulated jsar valve at 1750psi. I only shot a few shots to tune it to jsb 15.89@890fps, and didn't do a full shot string.
Shooting it though, I'll get flyers and then groups tighten up as I shoot more. I'll have to get the chrony and do some periodic testing as well, and report back.
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Okay thanks, I was just thinking it could be a combination of stiction and regulator creep.
I can say, at the moment, my Huma is rock solid and without creep. I did fight with creep until I rebuilt it months back. Now it's the last thing I'm concerned with as it's the same every time I check it.
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Mine is a Huma regged .25, and I did not have much luck with stability until I got close to around 2000 psi. It is currently set at ~2100 psi for a fairly high power tune (about 52 FPE with JSB 34 grain pellets), and have had it this way for over 6 months, and I checked the velocity a few weeks back and it was stable on the first shot. It probably has about 600-700 shots through it at this set up, so the o-rings are well set, and it holds air with no leaks over weeks.
This is my second Huma regulator - the other is in a .22 Marauder. That one was rock solid for about 5 years then I had to rebuild it as it started to creep - and it is back to rock solid again. I will take that maintenance schedule.
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i haven’t followed all the details leading up to this point so this may be a dumb question but is this stiction symptom present with unregulated setups?
I am running it not regulated for now and first shot handicap is a little bit les by using it around 3000 PSI. I reduce/adjust the power rader via choking air transfer way at my Puncher mega .177
Also when I clean and lube entrance of SS valve with Teflon spray first shot handicap is a little bit less. Approximately after one month first shot velocity handicap return back .
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Why the orings could not a person get enough of a seal to leave them out to get rid of sticktion problems . Or does it have to be sealed up on that end to make it work . Otherwise you could adjust the jet size to help with some leak by . What am I missing
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Must be sealed up x2 ...
The cobra tube requires a seal so the captive pressure minus what bleeds off via the jet actually forces the poppet to close. If this o-ring leaks or is absent it allows air into the balance chamber.
The balance chamber is connected to the throat via a drilled passage threw the poppet stem and if this o-ring leaks the containment pressure within valve takes that path exiting out barrel.
The balance chamber uses the Cobra tube o-ring at one end & has the primary poppet o-ring at the other end.
BOTH must be in place and offer 100% seal integrity for the system to work.
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Thanks for explaining helps me understand the valve better
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I have mentioned here already the idea to recompense front jet chamber by some spring but it is probably stupid idea because no one react on it .
If I understand front jet chamber right it acts as high air pressure flexible bumper at open phase and then as blank holder of poppet to stay closed enough.
Am I wrong ?
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I have mentioned here already the idea to recompense front jet chamber by some spring but it is probably stupid idea because no one react on it .
If I understand front jet chamber right it acts as high air pressure flexible bumper at open phase and then as blank holder of poppet to stay closed enough.
Am I wrong ?
The Cobra chamber as you state ALREADY CONTAINS A SPRING ... that is in place so an empty gun can be filled, it overcomes the static sticktion of the o-rings pushing poppet against the seat.
Compared to the closing force of the captive high pressure air within the tube, the springs actual contribution is very very small.
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I have mentioned here already the idea to recompense front jet chamber by some spring but it is probably stupid idea because no one react on it .
If I understand front jet chamber right it acts as high air pressure flexible bumper at open phase and then as blank holder of poppet to stay closed enough.
Am I wrong ?
The Cobra chamber as you state ALREADY CONTAINS A SPRING ... that is in place so an empty gun can be filled, it overcomes the static sticktion of the o-rings pushing poppet against the seat.
Compared to the closing force of the captive high pressure air within the tube, the springs actual contribution is very very small.
.[/color]
YES I know.
You are meaning probably front chamber with jet if you have written cobra chamber.
I am thinking that :
1. Cracking/opening force is proportional to calibre of front chamber and air tube pressure plus inside spring force.
2. Start closing force is proportional to calibre of front chamber and higher air pressure plus higher spring force + poppet calibre and air tube pressure.
3. End closing force is proportional to calibre of front chamber and air tube pressure plus inside spring force + poppet calibre and air tube pressure.
If the jet of front/cobra chamber will be much larger we lose only :
a, flexible bumping effect
b, higher start closing force
Am I wrong ?
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I have been checking for stiction in my new SS valve and it doesn't look like it's going away anytime soon with my current hammer and spring setup. It's not real bad, but my .25 is a hunter and I can't have any stiction issues. I do believe I can fix the issue and will be playing around with different spring setups and maybe a different hammer as I have others to play around with. I really don't blame the valve, but blame myself for how I have it setup knowing how the valve is designed. I keep setting it up like a traditional valve and not a state of the art balanced valve. I love this valve and I don't whine or give up so easily.
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I love this valve and I don't whine or give up so easily.
I too.
Yesterday I have polished/lapped bough chambers with rottenstone , change O-rings and lubed with teflon spray . The first shot velocity handicap decrease a little bit again.
I am thinking that use lube which is stable ( some non drying oil especially at HPA area ) is most important.
I am not sure at all if the Teflon lube is the best !!!
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If reducing O-ring stiction is the goal, it looks like FEP is the material of choice:
https://web.wpi.edu/Pubs/E-project/Available/E-project-102112-214155/unrestricted/NAG1202-Investigation_of_O-ring_Adhesion_in_Space_Mechanisms.pdf (https://web.wpi.edu/Pubs/E-project/Available/E-project-102112-214155/unrestricted/NAG1202-Investigation_of_O-ring_Adhesion_in_Space_Mechanisms.pdf) (refer to page 37)
https://en.wikipedia.org/wiki/Fluorinated_ethylene_propylene (https://en.wikipedia.org/wiki/Fluorinated_ethylene_propylene)
If that's too hard to find, this article claims Viton (FKM) to have low breakout friction:
http://www.o-rings.com/would-slippery-o-rings-or-seals-improve-your-product-performance/ (http://www.o-rings.com/would-slippery-o-rings-or-seals-improve-your-product-performance/)
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Thanks,
I have read that Viton swell by air pressure. :o
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That maybe the fix we need ptfe encapsulated or fep encapsulated o-rings I searched them and there are a few companies that offer them just no pricing
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I truly hope we can ban together and resolve this issue. I don't know the sizes of the O-rings. Lubes I assume will deteriorate eventually. I'm going to dabble with an oil lube along with some preload. I know the valve can handle some preload without efficiency loss. I'm also going to try a much heavier hammer. None of this may work, but the stiction is not real severe in mine. It's just enough to disappoint, but not enough to throw it in the dirt.
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No I agree there has to be something that can fix it other than that one shot it's great I'm going to stay running it I might try to find some viton orings and give that a go I don't know the oring sizes either but that would help
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Does anyone know oring sizes in the ss valve would like to try a couple different types but need the sizes
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Yeah I hope you guys can get it sorted out. I sympathize with the importance of first-shot reliability in hunting situations.
Since Viton is easy to obtain, I would be tempted to try it and run a before and after trial to see if it shows some improvement...and if so, then work on sourcing the FEP. Perhaps burnish a dry lube onto the O-ring and its mating surface. I imagine PTFE would be one of the best for this purpose but I wouldn’t hesitate to try graphite. For example, I know if you smear graphite onto a piece of rubber, it loses its grip against a smooth surface. Like you said, I’m not sure how long it will last but surely long enough for a test over a few days’ time.
Regarding Viton swelling, yes that’s what I’ve observed but compared to the pressure forcing it against its mating surface, the added friction component would be academic I think.
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Allorings.com has fep encapsulated o-rings ptfe encapsulated and several different cores that are encapsulated so if anyone know oring sizes for SS valve that would be great
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4.5mm x 1mm and 5.5mm x 1 mm
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Thanks Travis
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Is this "stiction" only observed when using regulator?
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Is this "stiction" only observed when using regulator?
most prevalent with heavy hammers and softer springs ...
If you use a light hammer with a heavier spring the impact and motion of the poppet within valve is so fast you get far less sticktion effect.
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No observed both regulated and unregulated
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First shot is still enough to change point of aim for a hunter I don't want to have to burn a shot hunting
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Other than that I like this valve alot once I got it to seal up
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I have been testing daily since my posted string. I'm getting 809 to 815 on the first shot. 855 to 860 on the 2nd shot. I'm using a 50 gram MDS with a 12.5lb primary and a 14.8lb inner spring. Basically, the primary spring is flush (no preload) The inner 14.8lb is a 1/4" shorter than the primary spring. If I add any preload to the primary spring, I would have to back off on the inner spring even more. I don't no if adding a heavier spring in the mix will work, but worth a try. I'll pull the valve and clean the thimble again and see if any rubber residue is in there. I have seen some in the past with a new poppet.
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Did you try a tune with a smaller jet? I solved it for now on my Bulldog with a .015 jet, and more spring, along with a tune that expects the stiction, so a bit extra spring.
I am interested in FEP oring results, as I would like to go back to my higher power tunes, but then I need to open the jet up again. I asked Travis about FEP in one thread about the stiction, but didn't get a direct answer if he had tried that specifically.
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Did you try a tune with a smaller jet? I solved it for now on my Bulldog with a .015 jet, and more spring, along with a tune that expects the stiction, so a bit extra spring.
I'm using a .037" jet. The jet only affects the closing speed. I was using a .060 jet, but dropped it down seeing's how the cocking was still doable. 56 FPE with a 50 gram MDS is a tall order and requires a lot of spring already, even ported at .220 with a 2225 set point.
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Yes it is a tall order I'm using a 30 gram mds hammer and 12 spring with a good amount of preload and am getting stiction . I put out for a quote at allorings.com for price and availability for fep encapsulated o-rings and a couple other orings . They also have xrings but I would imagine they wouldn't help any being more sealing surface
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I have never understood the stiction thing.
Do you guys think that first shot is harder to open and not getting the lift?
Or
The valve does open and the valve closes faster (Dwell)?
Is there a possibility that the poppet to thimble o ring is leaking.Just going to through this out there, what happens if you don't use o rings on the poppet?
Check out this website about dynamic o rings.
http://www.applerubber.com/hot-topics-for-engineers/what-you-need-to-know-about-dynamic-seal-applications/ (http://www.applerubber.com/hot-topics-for-engineers/what-you-need-to-know-about-dynamic-seal-applications/)
I wonder if something like this is happening where the o ring is extruding and hanging up.
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I think Huma regs use a HARD square o ring on the pressure adjustment screw ?
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I wonder if PTFE coating the inside of the thimble would decrease the stiction ?
I have been working a lot lately with electropheric polymers as a conformal coating. At only 8um/10um film thickness I would be curious if the poppet/oring would still fit.
On Monday back at work, I will be working on a PTFE version.
Instead of coating the inside of the thimble, can one make a thin wall Teflon insert ?
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I think it's opening harder on the first shot some lubes have helped for a bit
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If extrusion is a contributing factor, what would help is some combination of a higher durometer O-ring and/or reducing the gap between the parts.
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Some of the powder burner guys will embed a dry lubricant into the bullets, or the barrel. I don't know the physical layout of the valve, but is it possible to treat the metallic components with a dry lubricant like HBN (hexagonal boron nitrate) or molybdenum di something?
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I think Huma regs use a HARD square o ring on the pressure adjustment screw ?
Nope ... they just get Hard and Square after a year or more.
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https://www.theoringstore.com/index.php?main_page=index&cPath=14 (https://www.theoringstore.com/index.php?main_page=index&cPath=14)
here is a thought from my monkey brain..a backup ring on one side of the o-ring :-\
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IN noticing several mentions of Graphite, remember, it is corrosive to bare aluminum.
Knife
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https://www.theoringstore.com/index.php?main_page=index&cPath=14 (https://www.theoringstore.com/index.php?main_page=index&cPath=14)
here is a thought from my monkey brain..a backup ring on one side of the o-ring :-\
I’ve always wondered why no one used backup rings . Works wonders with proportional hydraulic systems . I have a good assortment and will do some testing on my cobra setup once I get a chance.
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I kick myself in the butt for not sending mine in yet, I was going to do it at least a week ago but I've just got so many irons in the fire so to speak right now. Seems like I'm always testing pellets, working on other guns and the list goes on. But still at the top of the list is getting out hunting with them. I'll be out shooting my DAR25 later this morning, the thing is just shooting the 26 grainers so nice I can't stop.
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Knife, isn’t that a galvanic corrosion between dissimilar metals? Like where aluminum is against steel? It would not apply to an O-ring on aluminum.
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I believe that FEP orings, square orings, higher durometer orings, and backer orings are 4 possibilities that warrant testing.
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IN noticing several mentions of Graphite, remember, it is corrosive to bare aluminum.
Knife
My thimble is brass.
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We've tried to source coated O-rings with no luck so far and many companies have stated that the coating wouldn't last long anyway.
Brake caliper pistons use a square cut o-ring to pull the piston back into the bore, don't think that'll help here.
And yes, all the thimbles are brass.
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What is a "Sticking Point" ... yes pun intended.
Is that a conventional poppet valve is a passive devise where as the seal containing the high pressure is that of a simple cork over hole design. There is no o-rings within the valve that controls or seals exit & flow of HPA to the pellet other that the transfer path.
So now we enter the realm of a valve where the design has not just 1 but 2 o-rings that keep the poppet from leaking HPA having nothing to do with the seat seal that ultimately controls HPA flow to the pellet :o
These o-rings just sit there in a STATIC position and bear the load upwards of 3000 psi. They will deform wanting to be smashed against the groove / gland just like every other o-ring that seals the HPA containment !
When the gun is fired these 2 STATIC o-rings are required to do a DYNAMIC sealing function too and really feel this is where the design problem runs into a compromised situation :(
An o-ring that is no longer semi round bearing a pressure load simply can't act the same as the same o-ring in a static load with no pressure bearing against it.
I'm really not sure if there is a work around to the issue of initial sticktion ???
Certainly o-ring material type come into play, but with such SMALL 1mm cross section o-rings this is a very tall order indeed !
Just thinking and sharing thoughts on whats going on.
Scott
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In the case of my Bulldog, I tuned around it. The loss of first shot FPS is very repeatable, and shows up after the rifle sits for just a short time. The FPS loss doesn't appear to increase very much after that. So I increased my spring load a bit and found a place where my first shot, and then even a follow up shot are within 10 fps of each other. This is my hunting tune. If I am target shooting, I just tether at the pressure equal to that second shot, a few hundred psi less in the case of my Bulldog. Since I will always have a delay between making the rifle ready, and arriving at a hunting spot, this works well for me so far. This is how I deal with it now, but it will be nice if we find a way to improve the design.
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What about adding PTFE to the list of things to try?
Industry figures say you don’t want to stretch it more than 5% - 10% so the thimble would need to be a 2-piece construction. That makes it more expensive to manufacture but if the properties of PTFE solve the issue, it would be worth it. FWIW, the final stage of a Chinese high pressure pump I worked on has a brass “hat” that unthreads from the end of the shaft. This feature wasn’t necessary to replace the O-ring but it gave access to replace the rigid backer ring that accompanied it. Same idea.
Regarding the question of whether PTFE’s properties are good for this role, frankly I don’t know but it just might. It’s slick as snot so it has that going for it. And it’s a plastic, not rubber (elastomer). It cold flows to match the shape of the parts. So if we think about what is happening whenever the thimble is being knocked free, a traditional O-ring wants to stick because it is soft and compliant. Contrast that with a relatively hard, dense PTFE. It doesn’t change shape instantaneously the way an elastomer does so I’m thinking it would break free more consistently.
If that alone does not sufficiently reduce/stabilize the stiction, perhaps the wall could be given a slight taper. That way the instant the thimble breaks free, the PTFE loses contact with the walls so there’s no drag. Seems like that would further improve consistency.
I haven’t investigated what the geometry would need to be to ensure normal operation pressures don’t cause the material to extrude to the point of failure so that might be the challenge. A backer ring is one possible answer but apparently there are also filler options like bronze that reduce cold flow.
https://www.alliedmetrics.com/seals/o-rings/ptfe-o-rings.php (https://www.alliedmetrics.com/seals/o-rings/ptfe-o-rings.php)
Notice also molybdenum disulfide for better sliding properties.
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What about adding PTFE to the list of things to try?
Industry figures say you don’t want to stretch it more than 5% - 10% so the thimble would need to be a 2-piece construction. That makes it more expensive to manufacture but if the properties of PTFE solve the issue, it would be worth it. FWIW, the final stage of a Chinese high pressure pump I worked on has a brass “hat” that unthreads from the end of the shaft. This feature wasn’t necessary to replace the O-ring but it gave access to replace the rigid backer ring that accompanied it. Same idea.
Regarding the question of whether PTFE’s properties are good for this role, frankly I don’t know but it just might. It’s slick as snot so it has that going for it. And it’s a plastic, not rubber (elastomer). It cold flows to match the shape of the parts. So if we think about what is happening whenever the thimble is being knocked free, a traditional O-ring wants to stick because it is soft and compliant. Contrast that with a relatively hard, dense PTFE. It doesn’t change shape instantaneously the way an elastomer does so I’m thinking it would break free more consistently.
If that alone does not sufficiently reduce/stabilize the stiction, perhaps the wall could be given a slight taper. That way the instant the thimble breaks free, the PTFE loses contact with the walls so there’s no drag. Seems like that would further improve consistency.
I haven’t investigated what the geometry would need to be to ensure normal operation pressures don’t cause the material to extrude to the point of failure so that might be the challenge. A backer ring is one possible answer but apparently there are also filler options like bronze that reduce cold flow.
https://www.alliedmetrics.com/seals/o-rings/ptfe-o-rings.php (https://www.alliedmetrics.com/seals/o-rings/ptfe-o-rings.php)
Notice also molybdenum disulfide for better sliding properties.
Because PTFE is such a dense material, it cannot be “melt-processed”. It must be compressed and sintered to form useful shapes (like o-rings).
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Travis, are you saying that statement precludes it from being used in this application? I took that statement as dealing with how PTFE seals are made rather than how they are used.
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Travis, I have been pondering this stiction situation since it was mentioned in this thread. An observation, since the o-rings really don't seal the hpa, (after all, after just a few seconds, the pressure equalizes on both sides of the orifice) it acts more like the piston in a springer pushing air through the orifice to control the speed of the poppet, does the o-ring need as much squish as a true sealing o-ring? Instead of a .010" squish, would a .005" work just as well with less stiction? Just a suggestion.
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I've been shooting with the SS valve for about a month now. No matter which way I try it, it likes to be hit hard. Today I shot a 51 Shot string. Regulator set to 2000psi. First shot 831 and last shot 830.ES was 16 and SD was 3. Maybe I could have extended it more, but I ran out of the 34 gr. jsbs.
Before shooting the gun it sat all day in a cold house since I forgot to turn on the heater. I have a TSS installed with the springs it came with and the MDS super hammer. The striker has been cut and screwed flush with the hammer face. There is nearly no gap between the hammer face and valve pin. So I feel like it is hitting the valve pretty hard and I'm getting good consistency from the beginning till the end of the shot string. Whenever I gave it more gap(less fps in attempt to get more shots) my ES went to 30+. This is just my experience with the SS valve. Its max power for the given regulated pressure or you get less consistent strings. Maybe my less consistent strings had something to do with stiction, I'm ok with running highest power only since I'm getting 50+ shots per fill.
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I picked up a viton oring kit might be able to use a couple out of the kit and try it if some fit
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I've been shooting with the SS valve for about a month now. No matter which way I try it, it likes to be hit hard. Today I shot a 51 Shot string. Regulator set to 2000psi. First shot 831 and last shot 830.ES was 16 and SD was 3. Maybe I could have extended it more, but I ran out of the 34 gr. jsbs.
Before shooting the gun it sat all day in a cold house since I forgot to turn on the heater. I have a TSS installed with the springs it came with and the MDS super hammer. The striker has been cut and screwed flush with the hammer face. There is nearly no gap between the hammer face and valve pin. So I feel like it is hitting the valve pretty hard and I'm getting good consistency from the beginning till the end of the shot string. Whenever I gave it more gap(less fps in attempt to get more shots) my ES went to 30+. This is just my experience with the SS valve. Its max power for the given regulated pressure or you get less consistent strings. Maybe my less consistent strings had something to do with stiction, I'm ok with running highest power only since I'm getting 50+ shots per fill.
I'm surprised you only got 51 shots with that Brod you got with a 350cc tank filled to 4400-4500psi.
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I could have kept going but I ran out of pellets. I currently have 2500psi of air left. I’m pretty confident I can get 2 more mags out of it before coming off the regulator. I will finish up the shot string tomorrow.
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I picked up a viton oring kit might be able to use a couple out of the kit and try it if some fit
Viton swells under pressure it will make stiction way worse.
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What about adding PTFE to the list of things to try?
Industry figures say you don’t want to stretch it more than 5% - 10% so the thimble would need to be a 2-piece construction. That makes it more expensive to manufacture but if the properties of PTFE solve the issue, it would be worth it. FWIW, the final stage of a Chinese high pressure pump I worked on has a brass “hat” that unthreads from the end of the shaft. This feature wasn’t necessary to replace the O-ring but it gave access to replace the rigid backer ring that accompanied it. Same idea.
Regarding the question of whether PTFE’s properties are good for this role, frankly I don’t know but it just might. It’s slick as snot so it has that going for it. And it’s a plastic, not rubber (elastomer). It cold flows to match the shape of the parts. So if we think about what is happening whenever the thimble is being knocked free, a traditional O-ring wants to stick because it is soft and compliant. Contrast that with a relatively hard, dense PTFE. It doesn’t change shape instantaneously the way an elastomer does so I’m thinking it would break free more consistently.
If that alone does not sufficiently reduce/stabilize the stiction, perhaps the wall could be given a slight taper. That way the instant the thimble breaks free, the PTFE loses contact with the walls so there’s no drag. Seems like that would further improve consistency.
I haven’t investigated what the geometry would need to be to ensure normal operation pressures don’t cause the material to extrude to the point of failure so that might be the challenge. A backer ring is one possible answer but apparently there are also filler options like bronze that reduce cold flow.
https://www.alliedmetrics.com/seals/o-rings/ptfe-o-rings.php (https://www.alliedmetrics.com/seals/o-rings/ptfe-o-rings.php)
Notice also molybdenum disulfide for better sliding properties.
The poppet would actually need to be 3 pieces as it has two O-rings, and with how small it is that isn't going to happen. I think we'd also run into sealing issues.
Travis, I have been pondering this stiction situation since it was mentioned in this thread. An observation, since the o-rings really don't seal the hpa, (after all, after just a few seconds, the pressure equalizes on both sides of the orifice) it acts more like the piston in a springer pushing air through the orifice to control the speed of the poppet, does the o-ring need as much squish as a true sealing o-ring? Instead of a .010" squish, would a .005" work just as well with less stiction? Just a suggestion.
The O-rings keep HPA from leaking into the vent in the stem.
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Hi Matt, okay thanks for commenting on the difficulties of making the part accommodate a semi-rigid seal.
I have a question that relates to Mobilehomer’s comment and your answer. If I’m understanding you correctly, there is indeed a differential pressure across the O-rings when the poppet is at rest. Is that right? That makes more sense to me because otherwise there would be no pressure squeezing the O-ring against the wall to make it want to stick…none other than that which is dictated by how tightly the parts are fitted in which case it would be as he said, something you could address by simply modifying the part dimensions.
That also suggest a Viton O-ring’s tendency to swell won’t necessarily cause it to exert a substantially higher force on the surrounding wall because it represents a tiny fraction compared to the high pressure air that is squeezing it, pressing it against the wall. That’s not to say I’m asserting some confidence Viton’s lubricity will substantially improve things compared to, say, Buna-N but I’m a bit skeptical that it’s likely to make things substantially worse.
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Continuing to research and brainstorm…
I ran across this article https://www.parker.com/literature/O-Ring%20Division%20Literature/Static%20Files/frictionestimation.pdf (https://www.parker.com/literature/O-Ring%20Division%20Literature/Static%20Files/frictionestimation.pdf) which ranks O-ring friction (whether break-out or running friction) factors in order of importance:
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TABLE A6-1 FRICTION FACTORS (IN ORDER OF IMPORTANCE)
TO INCREASE FRICTION FACTOR [b]TO DECREASE FRICTION[/b]
Increase Unit Load (squeeze) Decrease
Increase RMS Surface Finish (metal) Decrease RMS
Increase Durometer Decrease
Decrease Speed of Motion Increase
Increase Cross Section of O-Ring Decrease
Increase Pressure Decrease
Omit Lubrication Use
Decrease Temperature Increase
Decrease Groove Width Increase
Increase Diameter of Bore or Rod Decrease
Decrease Surface Finish (O-Ring) Increase
Stretch O-ring Joule Effect* Compress O-Ring
Lower Durometer of O-Ring Coefficient of Friction# Increase Durometer
* Refer to rotary seals.
# A minor factor and should be ignored in design work other than for ultra high speeds
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Of particular interest is the coefficient of friction being at the bottom of the list so I guess we can shelve that idea. However I see a few things in the top half of the list that are feasible to try:
1. Polish the walls
2. Reduce the durometer (may require backup ring or tighter tolerances to prevent extrusion failure)
3. Use an O-ring with smaller cross section (obviously that means fabricating new parts, or perhaps some industrious person could fill the groove with J-B Weld and grind a shallower groove).
4. Use lubricant. Parker has a product called Super O-lube that is touted to alleviate stiction. The MSDS says it’s dimethyl siloxane based so it’s some sort of silicone lubricant. Is there a secret ingredient in the sauce, I don’t know. I would use Super Lube (the oil #51004, not the grease) because it’s slick and I have a bottle :)
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Very interesting Jason. We are dealing with 1mm O-rings now so not much to work with on surface tension to begin with. I'm still in favor of the correct lube and a hard hammer strike.
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Very interesting Jason. We are dealing with 1mm O-rings now so not much to work with on surface tension to begin with. I'm still in favor of the correct lube and a hard hammer strike.
No so much HARD But FAST ... being the valve opens easy enough, it just seems to prefer a fast slap than a more gentle nudge.
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Keith Im sending you the heavier(40G) Buffer Hammer it will almost eliminate the Stiction.
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Yeah regarding a smaller cross section, I agree. Not desirable to leave the realm of common off-the-shelf sizes but that design element ranks high on the list so I didn’t want to dismiss it.
http://www.applerubber.com/products/microrings/ (http://www.applerubber.com/products/microrings/)
What is a MicrOring® Seal?
As a general definition, a MicrOring® seal is any O-ring that measures less than 1 mm in either inside diameter or cross section. Apple Rubber offers MicrOring® seals in more than 2,000 sizes…
http://www.applerubber.com/src/pdf/microrings.pdf (http://www.applerubber.com/src/pdf/microrings.pdf)
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Keith Im sending you the heavier(40G) Buffer Hammer it will almost eliminate the Stiction.
Thanks Travis, you did remember. Looking forward to that.
I wonder how FP-10 would work. It's not affected by temps and doesn't require being shaken before use. I know it is slick stuff. I'll probably clean the poppet and try this once the hammer arrives.
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I'll throw this out there. I have been working on some really neat thin film coatings. This morning I coated some of my concept valve parts.
The coating trial was to see if I could coat the ID of a part. It works ;D ;D ;D
The idea would be to have a smoother surface and lower COF between brass to o ring.
These pic's of the parts are under high magnification. The ID of the sleeve id .25" and on the piston is .08". What a beautiful coating.
and another good article on dynamic o orings situations.
https://www.physics.harvard.edu/uploads/files/machineshop/epm_oring_handbook.pdf (https://www.physics.harvard.edu/uploads/files/machineshop/epm_oring_handbook.pdf)
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Brass can be grabby anyway, so I like the idea of the friction surface being something slicker.
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What about HBNR are they harder or softer and do we want harder orings or softer the chart has me confused
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I'll throw this out there. I have been working on some really neat thin film coatings. This morning I coated some of my concept valve parts.
The coating trial was to see if I could coat the ID of a part. It works ;D ;D ;D
The idea would be to have a smoother surface and lower COF between brass to o ring.
These pic's of the parts are under high magnification. The ID of the sleeve id .25" and on the piston is .08". What a beautiful coating.
and another good article on dynamic o orings situations.
https://www.physics.harvard.edu/uploads/files/machineshop/epm_oring_handbook.pdf (https://www.physics.harvard.edu/uploads/files/machineshop/epm_oring_handbook.pdf)
Tim you have the correct approach the issue has to be addressed at the thimble not the poppet. I have tried a variety of orings and lubes and the only way around it is to just waste the first shot or use our buffer hammer and hit it fast. I was told that a thin film Teflon coating would wear out quickly under those pressures and have looked at parleen and Diamond coating also.
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The coatings I have been working with is a nano ceramic suspended in a polyurethane. Today I also added a sub micron PTFE dispersion to it. ;D
Although,
I do have a PTFE coating made for aluminum and stainless that uses a chromic/phosphoric accelerator to maximize adhesion and hardness of the PTFE. Problem is, it is extremely hard to deposit on an ID as a very thin conformal coating. Super slick and great adhesion though.
It's not your ordinary PTFE coating.
It was just a thought.
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So my mds hammer with peek striker that I can run recessed weighs about 35 grams and hit it hard and fast . Should I polish the thimble up too
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So my mds hammer with peek striker that I can run recessed weighs about 35 grams and hit it hard and fast . Should I polish the thimble up too
Only if your not taking material away from thimble
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I'll use a q tip and real fine metal polish that I have it doesn't seem to remove any material as long as I don't use a Dremel
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When it comes to breaking "Surface Tension" a microscopically rough surface such a crosshatch has less drag than a polished one.
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When it comes to breaking "Surface Tension" a microscopically rough surface such a crosshatch has less drag than a polished one.
That's true. The reason dimples are on golf balls sorta thing.
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When it comes to breaking "Surface Tension" a microscopically rough surface such a crosshatch has less drag than a polished one.
Yep, it is the same principle with racing slicks, vs treaded tires. The smooth slicks put more material in contact with the pavement. I guess the goal here would be the reverse of the tire thing. You want minimum surface contact required to seal. I think in this case, the solution will come with finding contact surfaces that can seal, but are in minimal surface contact on a microscopic level. That along with tuning for a fast strike. That's my pseudo scientific interpretation :D
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I sure am looking forward to the all new gen 2 SS valve. Shouldn't be too much longer now, I hope.
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Is it going to be a retro fit to the old valve or completely new
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Is it going to be a retro fit to the old valve or completely new
Completely new SSV2. They made an all steel poppet, and are using peak or something for the seat. A little different, but should be a good one that won't leak or break. It's coming in the new Raptor. Travis said there would be a deep discount for previous SSV1 owners.
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That is good news on replacement poppets are going to be discounted pricing for SSV1 owners, I have 4 of them.
Two of them are having issues in my Prods.
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That is good news on replacement poppets are going to be discounted pricing for SSV1 owners, I have 4 of them.
Two of them are having issues in my Prods.
We didn’t redesign the Prod valves we haven’t had any issues with them. We’re also not making replacement poppets it’s s Whole new valve design
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Looking forward to it
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Heck, I was plenty impressed with the first edition in my Bulldog. Regards, Tom
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Hi guys. What do you think about FFKM orings? Can they reduce the stiction? I am asking because they are called rubber versions of PTFE.
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Hi guys. What do you think about FFKM orings? Can they reduce the stiction? I am asking because they are called rubber versions of PTFE.
No clue here ??? Generally finding a replacement in correct size is really tough with a lot of the more exotic O-ring materials.