Author Topic: Liberty plenum (Read 6277 times - 1 votes)
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Rohmpm · « **Reply #20 on:** March 29, 2019, 04:14:44 PM »

Quote from: dpittman on March 29, 2019, 08:54:15 AM

Am I wrong on this but with increased plenum size we can decrease our reg setpoints without losing power ( Maybe even gain power) and get an awesome number of shots without ridiculous (hand pump) fill pressures.

I have already demonstrated that with a gun that was already modified so the results could have been inconclusive. Exactly why I am startind anew with a bone stock gun to document each change.

USAFANG6799 · « **Reply #21 on:** March 29, 2019, 10:12:35 PM »

Looks like there will not be shortage of Liberty owners whom are willing to take their's to the next level of performance.
Sounds very promising.

smythsg · « **Reply #22 on:** March 30, 2019, 12:01:08 AM »

Count me in, looking forward to this one.

AVS Stephen · « **Reply #23 on:** March 30, 2019, 07:13:35 AM »

Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.

Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.

Does my logic sound ok?

Rohmpm · « **Reply #24 on:** March 30, 2019, 09:01:04 AM »

Quote from: thebanker4 on March 30, 2019, 07:13:35 AM

Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.

Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.

Does my logic sound ok?

Wow, impressive. It is beyond my experience to predict what kind of power a fully modified gun will produce. I've done a lot of cylinder head development for motorcycles, drag racing, top speed, road racing. At that level of performance, the farther we got, the more diminishing the return.
My initial goal was more shots at equal to factory power levels. I am certain that there are some who will seek the extremes at both shot count and power. It will be very interesting to follow.

darkcharisma · « **Reply #25 on:** March 30, 2019, 10:10:48 AM »

Quote from: thebanker4 on March 30, 2019, 07:13:35 AM

Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.

Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.

Does my logic sound ok?

the key word is larger plenum and mods. i have no doubt it will be 60-65 fpe if you go to .25 caliber. hitting 65fpe will be hard on .22 and if possible its for limited shot counts at closer to 3000psi with the current barrel length.

Rohmpm · « **Reply #26 on:** March 30, 2019, 01:17:17 PM »

Quote from: darkcharisma on March 30, 2019, 10:10:48 AM

Quote from: thebanker4 on March 30, 2019, 07:13:35 AM
Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.

Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.

Does my logic sound ok?

the key word is larger plenum and mods. i have no doubt it will be 60-65 fpe if you go to .25 caliber. hitting 65fpe will be hard on .22 and if possible its for limited shot counts at closer to 3000psi with the current barrel length.

There you are from someone who knows.
I'm busy on the dyno today but hopefully I'll get done in time to work with the plenum this afternoon.

darkcharisma · « **Reply #27 on:** March 30, 2019, 03:34:06 PM »

Oh i dont know it at all. i am just good at guessing...

not really. i just compare to the gaunlet with 25cc in 25 cal making 70fpe and in 22 cal making 50fpe...same set up and cothran valve with bigger ports on 2000psi.

cosmic · « **Reply #28 on:** March 30, 2019, 04:57:21 PM »

darn USPS misread the zip on my package to Duy and it is sitting in PA! I was tracking it and I'm in Illinois and Duy is in Texas !! They misread the first # .... Hopefully it will get there Monday or Tuesday for his magic touch..

USAFANG6799 · « **Reply #29 on:** March 30, 2019, 06:00:28 PM »

Quote from: cosmic on March 30, 2019, 04:57:21 PM

darn USPS misread the zip on my package to Duy and it is sitting in PA! I was tracking it and I'm in Illinois and Duy is in Texas !! They misread the first # .... Hopefully it will get there Monday or Tuesday for his magic touch..

They only do this when they know you are anxiously waiting for it

Wayne52 · « **Reply #30 on:** March 31, 2019, 09:15:26 AM »

The furthest I want to push my Liberty right now would be to open the barrel port, shim the hammer spring and turn the reg up but for now I'm happy with the way it is. Tomorrow I think I'll try it in woods but I'll have to be using my single shot tray because the mags haven't come yet, should be here Tuesday or Wednesday

I did fill it up to 4K after my last shot string from 250bar, it's the highest I've ever filled a pcp to. It didn't seem to phase the gauge on my SCBA too awful much in doing so but it is one of the 87cf ones.

Wayne52 · « **Reply #31 on:** March 31, 2019, 09:20:50 AM »

Quote from: thebanker4 on March 30, 2019, 07:13:35 AM

Billy, last night I was able to achieve 50.69fpe shooting a 25.39grain jsb 947.4fps. the mods include the adjustable HST and a custom TP rod drilled to a little larger than 3/16" (not adjustable). And of course increase reg pressure.

Based on your 3 fpe ncrease with no other mod I would expect you can achieve 65fpe with the larger plenum and mods. I'm thinking you will be able to shoot a 30grain slug if the barrels twist rate is good for slugs at the correct fps.

Does my logic sound ok?

Steven I haven't tried a slug in mine yet but I'm sure the Liberty would shooting them well with the non choked barrel and slow twist rate for the 30 grain BBT's They shot really great from my SPAM16 which is non choked and 1 in 20" twist barrel before I tamed it back down for the Magnum Hunter's that I dearly enjoy hunting with.

Bob Pratl · « **Reply #32 on:** March 31, 2019, 09:22:45 AM »

Quote from: Wayne52 on March 31, 2019, 09:15:26 AM

The furthest I want to push my Liberty right now would be to open the barrel port, shim the hammer spring and turn the reg up but for now I'm happy with the way it is. Tomorrow I think I'll try it in woods but I'll have to be using my single shot tray because the mags haven't come yet, should be here Tuesday or Wednesday
I did fill it up to 4K after my last shot string from 250bar, it's the highest I've ever filled a pcp to. It didn't seem to phase the gauge on my SCBA too awful much in doing so but it is one of the 87cf ones.

I did get a little nervous in filling my Liberty to 3500 PSI and for now I may leave it at that.

Wayne52 · « **Reply #33 on:** March 31, 2019, 09:36:45 AM »

Bob I'm sure that with a titanium airtube they're plenty strong, nothing is leaking at all on mine that I can notice. The next time I take the barrel off I'm going to replace the o rings on it because I noticed one had sheered just a tad. I might even have the right ones for it because quite some time ago I ordered some thin metrics in a kit from "The O Rings Store" and there's a good assortment of probably just what I need. They're 70duro which I figure should be good enough on the barrel.

FuzzyGrub · « **Reply #34 on:** March 31, 2019, 12:12:13 PM »

Back when I first got the Liberty, I thought it was being constrained by the small plenum, more than it actually is. I looked on AliExpress at those small air/water filters for PCP pumps. I assumed the plenum was a M10X1 thread, but never verified. I found one that was about the same external size, but probably less internal. Even ones that were 30mm OD X 80mm length, didn't seem to have a good size internal volume, and would be a problem with the wood stock. Just adding a gauge to the oem plenum will be right at the bottom of the wood stock.

TheSaint · « **Reply #35 on:** March 31, 2019, 01:20:34 PM »

I've always filled my Liberty's to 4300psi. Never had a problem. If the manufacturer rates the gun for that pressure, I'm filling to it. If it doesn't hold, the gun goes back.

Months of daily use, and several thousand pellets later, still no issues.

And it's obvious that the manufacturer has built in a large margin of safety. The gun has a 6000psi burst disk, telling me that the tube and components are rated to handle way more than the 4300psi max listed fill pressure.

FuzzyGrub · « **Reply #36 on:** March 31, 2019, 01:29:04 PM »

Quote from: TheSaint on March 31, 2019, 01:20:34 PM

I've always filled my Liberty's to 4300psi. Never had a problem. If the manufacturer rates the gun for that pressure, I'm filling to it. If it doesn't hold, the gun goes back.

Months of daily use, and several thousand pellets later, still no issues.

And it's obvious that the manufacturer has built in a large margin of safety. The gun has a 6000psi burst disk, telling me that the tube and components are rated to handle way more than the 4300psi max listed fill pressure.

I think the weak link is, if the reg fails and 4300psi is throughout, the poppet may fail. It will certainly valve lock.

darkcharisma · « **Reply #37 on:** March 31, 2019, 01:40:42 PM »

I am sure the manufacturers done their work before and after publishing their recommended max working pressure. What we don’t know is at what safety factor. I would love to know all that detail and the rating of the material they used. I am sure someone would know and chime in soon

If it were me I would put in a 5k burst disk instead so that the tube would not reach the “point of no return” . I am no expert but if the 4300psi was calculated on the yield strength. Which means if someone goes beyond that pressure, the material is approaching point of yield (depends on safe factor 2:5 or 3:1 or 3:5?) ...you are stepping into the yellow and soon reach the red zone. Yes it won’t burst at 6k but...how many fill cycles remain NOW? Yes it can handle more than 4300 before burst but is it compromised beyond 4300psi? That’s why they put the word “max” fill pressure on there right?

tkerrigan · « **Reply #38 on:** March 31, 2019, 02:35:41 PM »

It probably wouldn't hurt to mike the diameter of the air tube when new and check once a year or so for growth. Regards, Tom

Rohmpm · « **Reply #39 on:** April 01, 2019, 12:55:45 AM »

I post it as I see it.
I dissasembled the gun and drilled all ports to 3/16 with a new carbide drill bit.

Upon reassembly the regulator now reads about 1800 psi versus 21-2200 psi in prior test as received. Puzzling as I made no adjustments to the regulator.

So, I ran some pellets with both plenums. First number is the large plenum, second is original at 1800psi, 3/16 passages from valve to barrel.
large. original
Eunjin 666. 639
JSB 18.13. 863. 827
JSB 15.89. 896. 872

compare this to the original test, all factory at 21-2200psi, no porting.

large. original
Eunjin. 679. 637
JSB 18.13. 860. 817
JSB 15.89. 905. 860

what this really shows is what larger ports do at reduced regulator output. It shows that the plenums produce near the same results with 300 less psi when ported.

any input on why the regulator setpoint dropped upon dissasembly and reassembly.

Tomorrow I will raise the regulator output toapproximately where it was at the beginning.

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Liberty plenum

Author Topic: Liberty plenum (Read 6277 times - 1 votes) )

Author Topic: Liberty plenum (Read 6277 times - 1 votes)
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