Valve Poppet Material
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Valve Poppet Material
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Topic: Valve Poppet Material (Read 5642 times))
JumboPellet
Shooter
Posts: 47
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Real Name: Jeremy
Valve Poppet Material
«
on:
March 08, 2017, 11:13:13 PM »
I'm looking for advice on what material folks machine their valve poppets out of. I'm setting up to machine some new poppets for a Hatsan Gladius, same valve as an AT-44. Looking through my materials, I have 303SS, 4130, and some O1 tool steel. Would any of these suffice? Is one better than the other? Any advice is greatly appreciated.
Regards,
Jeremy
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Columbus, Ohio
Motorhead
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Re: Valve Poppet Material
«
Reply #1 on:
March 09, 2017, 12:23:54 AM »
An all steel poppet wearing on an acetal / peek or nylon type material seat ... any of those mentioned IMO would work fine.
Only issue of concern I can think of is the STRIKE end of poppets stem being hit with a steel hammer is Mushrooming if too soft ... work hardening & fretting or shattering if too hard.
You should get more info on this shortly as some others see it.
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Gippeto
Sharp Shooter
Posts: 863
Re: Valve Poppet Material
«
Reply #2 on:
March 09, 2017, 12:44:29 AM »
Have used 304, 316 and O1...hardened and not.
Throw a bit of a taper where the striker hits and don't worry about it.
Al
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Alberta, Canada
QVTom
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Real Name: Tom
Re: Valve Poppet Material
«
Reply #3 on:
March 09, 2017, 01:40:02 AM »
O1 is the way to go. You can easily shop harden the striker end with a propane torch. 300 ss is very soft, it may be fine if you are not hitting it too hard.
Tom
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JumboPellet
Shooter
Posts: 47
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Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #4 on:
March 09, 2017, 10:40:19 AM »
Thanks, O1 it is. Have you ever had any hardened poppet stems fracture by chance?
Regards,
Jeremy
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Columbus, Ohio
TimmyMac1
Expert
Posts: 1793
"You've Come A Long Way BB"
Poppet Valve Materials
«
Reply #5 on:
March 09, 2017, 12:30:36 PM »
The Steroid stems and USFT stems are Reamer Blanks fitted to a Concave Delrin head. My CO2 stems are 4130 Heat treated BEFORE machining. Seal material is D scale 80 shore Urethane.
I consider the Urethane up to 1500 psi and Delrin is above that by up to 1000 psi. Concave seats up to 1500 psi. Flat seats beyond 1500.
Consider taking the stem size down by sleeving valve hole. In PCP the porting must scale without the head and stem going up for best results. It is a lot easier to get air to go around a 2MM stem than a 5MM. The Koreans went the wrong direction with the enormous stems, heads and seats with big area giving enormous challenges for the hammer to unseat softer seal material.
TimmyMac1
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QVTom
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Re: Valve Poppet Material
«
Reply #6 on:
March 09, 2017, 05:46:00 PM »
Quote from: JumboPellet on March 09, 2017, 10:40:19 AM
Thanks, O1 it is. Have you ever had any hardened poppet stems fracture by chance?
Regards,
Jeremy
Never, It's very difficult to get a max hardness in the shop. If you are concerned, just anneal by heating slowly to grey which is just past blue and let cool slowly. This way will leave you with adequate hardness and reduce the brittleness.
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JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #7 on:
March 09, 2017, 10:47:22 PM »
Thanks, I'll harden it up with some heat and oil bath for good measure.
Tim, I'll be using Peek for the seat material. Regulated pressure will be ~150bar. I'm machining a new assembly to expand the size of the throat for porting reasons (going full bore at .250) and need new poppets to match. Could you elaborate on 'sleeving the valve hole'? I'm not familiar with that. Please forgive, this is my first go at fully porting a rifle.
Thanks for the advice guys, invaluable and will help from having a broken rifle during a shoot!
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rsterne
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Re: Valve Poppet Material
«
Reply #8 on:
March 09, 2017, 11:22:46 PM »
I think Tim is referring to sleeving down the hole in the valve where the stem runs, to allow using a smaller diameter valve stem.... The smaller stem allows more airflow through a given size valve throat.... If you use a large stem, then for a lot of flow area you need a large poppet and valve seat.... and the force required to open that valve increases, requiring a heavier hammer and/or hammer spring.... The limiting factor for a slim valve stem is structural strength, of course....
Hatsan already use a pretty slim stem, and you can slim it down to about 0.090" in the throat area without structural issues (I'm talking an AT-44 here).... I'm not sure if you could do that with a 1/4" or larger throat, and the larger poppet head, however.... as that will increase the forces significantly....
In that photo is a Canadian "non-PAL" stem for under 500 fps, a stock 0.120" AT-44 stem, and one I thinned to 0.090", running in a 0.203" throat.... In a .25 cal with 3/16" porting straight through from valve to pellet, the gun limited out at about 80 FPE.... Final valve with single 3/16" exhaust port below....
Bob
«
Last Edit: March 09, 2017, 11:38:30 PM by rsterne
»
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #9 on:
March 10, 2017, 06:53:23 AM »
Thanks Bob,
I understand now what he was referring to. I think what threw me off is the Hatsan poppet stems were already pretty slim and Hatsan stems are all I have experience with.
Your valve on your AT-44 is what I was modeling off of. I think I read that entire thread over 10 times
. I'll be turning my own body out of 360 brass to get the single transfer port. This means I get to choose my own throat size and make a PEEK valve seat. I was planning on going larger than .203, but will have a regulator in front set at ~150 bar. My hope was the regulator plus PEEK seat would also function to keep the opening forces at manageable levels. The regulator is a Huma Air model that will be mated to a custom 90cc plenum, all sitting in a 30" air tube made of 2024 T3 aluminum. I'll hydro test the entire setup once it's fully built.
The ultimate goal is to generate enough power to effectively shoot 51gr FN and 47gr HP BBTs out of a ~29" TJ .25 ACP barrel (9/16 OD). If I can't get more than 90 FPE from the platform, I do have a 41gr FN mold as an option. It's been a fun and rewarding project so far, I've learned a tremendous amount in both studying the theory and being hands on with it. I just hope I can keep the effeciency above .90 FPE/CI.
Regards,
Jeremy
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Columbus, Ohio
JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #10 on:
March 10, 2017, 08:56:44 AM »
I did some calculations this morning.
.203" diameter throat = .03236 in2
~200 bar force = 417.5 N
.250 diameter throat = .0490 in2
~150 bar force = 474.2 N
The equivalent force of 417.5 N at 150 bar vs 200 bar is roughly a throat of diameter of .234". Hmm, food for thought. I don't have enough experience in the arena to know how heavy of a spring would be required to crack a poppet off a PEEK seat at 474 N.
Regards,
Jeremy
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Columbus, Ohio
JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #11 on:
March 10, 2017, 10:13:11 AM »
I think the problem may have solved itself. The tubing I have for the TP is measured .240 ID. That works out to 437 N of static force. I'll use that as a starting point as it appears much more manageable.
Regards
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Columbus, Ohio
rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
Re: Valve Poppet Material
«
Reply #12 on:
March 10, 2017, 03:06:03 PM »
The PEEK poppet MAY make up for the increased cracking force (474/417) = 14%.... it wouldn't surprise me.... I have several other .25 cal PCPs, and most of them use a 0.219" (7/32") porting system straight through.... With a 0.090" stem, that would require at least a 0.240" throat to have equivalent area, and I usually go a bit larger to allow for losses.... I would strive for that 1/4" throat if you can get it.... Making the ports 1/4" if the throat is only that size will not increase the FPE, and may in fact reduce it slightly, because the extra volume in the porting system between the valve seat and the pellet will cause a drop in pressure at the pellet.... The larger the volume, the greater the drop.... I try and keep everything the same diameter/area, with the exception of the throat, where I like to see about 10% more area (once you subtract the stem area).... Most of my .25 cal PCPs use a 1/8" valve stem, and a 0.266" throat diameter, which works out to the area of a 0.235" hole, about 15% larger than the 0.219" porting.... There is little difference in FPE if I go down to a 1/4" throat (the equivalent area to a 0.217" hole), but a bit less efficiency.... With a 0.090" stem in a 1/4" throat, your equivalent port diameter is 0.233", just about perfect for a 7/32" porting system from there to the pellet....
In terms of performance, based on what my .25 cal PCPs do at 2200 psi, with 0.219" ports you should be able to hit about 100 FPE when you max. the hammer strike to get the gun operating on the plateau (based on a 24" barrel).... If you have the AT-44 Short, that may be more like 80 FPE, however.... That will result in less than 0.5 FPE/CI, however, at that power level, so then you will have to detune it to the knee of the curve.... What I am saying is, that getting to 90 FPE at 150 bar may prove to be a challenge.... You may need to achieve bore-sized porting throughout, and even with a 0.090" stem, that means a valve throat of at least 0.266", and 0.281" (9/32") would be better.... What success you would have doing that in a Hatsan, I have no idea.... but Good Luck....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #13 on:
March 10, 2017, 09:36:55 PM »
Bob,
I owe you a few tins of the finest pellets for that post. Some wonderful information I'll be referring back to on more than one occasion! I'll try and see what I can get away with on the larger side of the throat diameter and porting. If it doesn't work out, I can always just turn another seat and stem on the lathe.
A few items I've planned in to help me hit 90FPE: I've got a 29" barrel (TJ .25 ACP) and a new machined airtube at 350cc that's rated for 250bar. If I need a little more, plan is to bump up the reg. The 150bar setpoint was taken off one of your charts you posted sometime ago. Hopefully It'll end up being a heavy bench rifle slinging some accurate BBTs! Definitely won't be taking it into the field. I'll report back in a month or so when I'm out of the shop and at the range (and the temps get more palatable)
Regards,
Ieremy
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
Re: Valve Poppet Material
«
Reply #14 on:
March 10, 2017, 10:12:30 PM »
The 29" barrel will make your job a lot easier, for sure.... In fact, with that barrel length, I would leave all the porting at 7/32", with a 1/4" throat in the valve and a 0.090" stem.... You should be fine with that setup, and as you say, you can always bump the setpoint up a bit if you need to, especially since you can fill the reservoir to 250 bar.... I'm glad to see you are using a 90 cc plenum, that will again make your quest easier to achieve.... If you can achieve bore size porting, all the better....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
AirGhN_Ike
Shooter
Posts: 16
yes
Real Name: Isaac
Re: Valve Poppet Material
«
Reply #15 on:
March 20, 2017, 06:08:30 PM »
I was just about to post and ask if anyone new of a place or person that I could order a new valve stem for an at44 from. I recently broke mine. My at44 is a .25 and I have it shooting around 46 fpe. I would really like to get something a little more durable. So if need be I can crank it up a little more without worrying about breaking another one. I don't have the tools or the skill set to make one. If u made yours and it's working I would definitely be interested in buying a couple if that's something u would be willing to do. Just let me know and we can make arrangements.
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Re: Valve Poppet Material
«
Reply #16 on:
March 21, 2017, 12:27:08 AM »
Try the CAF Store....
http://www.airgunforum.ca/store/product_info.php?cPath=25&products_id=102&osCsid=9r6p5op2hnssh7p8injs6cviu6
Note you can order the stem in <500 fps (for Canada) or Full Power....
Bob
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Coalmont, BC, Canada
🇺🇦
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since! 🇺🇦
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).
Gippeto
Sharp Shooter
Posts: 863
Re: Valve Poppet Material
«
Reply #17 on:
March 21, 2017, 09:11:24 PM »
The valve stem in the AT44 is a pretty rugged piece...how the heck did you break it?
Al
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Alberta, Canada
JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #18 on:
April 04, 2017, 05:21:13 PM »
Quick follow up, got this turned out of O1, heat treated and polished up. Stem diameter ended up being .091, close enough for my tastes. Thanks for all the help.
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Columbus, Ohio
JumboPellet
Shooter
Posts: 47
yes
Real Name: Jeremy
Re: Valve Poppet Material
«
Reply #19 on:
April 16, 2017, 10:30:47 PM »
I got out over the holiday weekend to test the new setup. Valve throat ended up being .270, TP .245, barrel .190x.300. With the regulator at 150bar it was making ~770FPS for 76FPE, BUT when the reg was dropped to 125bar it was making ~865FPS for 84FPE. Now off to source a stronger hammer spring
Regards,
Jeremy
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Columbus, Ohio
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Valve Poppet Material