Plenum shape
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All Springer/NP/PCP Air Gun Discussion General
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"Bob and Lloyds Workshop"
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Plenum shape
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Topic: Plenum shape (Read 1122 times))
wimpie swart
Shooter
Posts: 41
yes
Plenum shape
«
on:
September 03, 2020, 08:39:49 AM »
Hi all,
Does plenum shape influence the airflow?
If I have a "L" shaped plenum vs straight cylinder?
I am looking to make a bigger plenum for the Nova Vista/ Liberty .25. The rifle has a small plenum that can screw off, and a bigger one fitted, but space for bigger plenum is limited.
Thanks
«
Last Edit: September 03, 2020, 12:58:51 PM by rsterne
»
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Posts: 26958
GTA Forums Person of the Year 2017
Real Name: Bob
Re: Plenum shape
«
Reply #1 on:
September 03, 2020, 12:59:00 PM »
The purpose of the plenum is to keep the pressure up in the valve during the shot cycle.... As long as the passages on the inlet side of the valve are larger than the exhaust ports, I don't think there is much difference if the flow turns some corners (within reason).... Certainly a poorly designed plenum of adequate size is better than one that is too small.... Here is one I had on my .25 cal Disco Pumper, and it worked great....
The important thing was that the diameter of all the passages between the 16 gr. CO2 cylinder I used as the plenum and the inlet side of the valve were larger than the exhaust port of the valve....
Bob
«
Last Edit: September 03, 2020, 01:02:50 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).
wimpie swart
Shooter
Posts: 41
yes
Re: Plenum shape
«
Reply #2 on:
September 05, 2020, 01:00:57 PM »
Thank you so much, Bob
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darkcharisma
Expert
Posts: 1517
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Real Name: duy
Re: Plenum shape
«
Reply #3 on:
September 05, 2020, 03:30:36 PM »
I made a bottle conversion for the Freedom using the same oem plenum used on the Liberty. I Noticed the Linear types of plenum installed in the freedom "outperform" the liberty. I can make 55fpe on the freedom vs 53fpe on the liberty at same pressure and same plenum volume. I am convinced the linear type will give more vs the 90 degree type.
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rsterne
Member 2000+fps Club
Bob and Lloyd
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Posts: 26958
GTA Forums Person of the Year 2017
Real Name: Bob
Re: Plenum shape
«
Reply #4 on:
September 06, 2020, 12:23:24 AM »
I'm not arguing that.... However, given the choice between an under the tube plenum with two 90 deg. bends, or no plenum, I would choose the former....
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).
darkcharisma
Expert
Posts: 1517
yes
Real Name: duy
Re: Plenum shape
«
Reply #5 on:
September 06, 2020, 01:54:16 AM »
I agree a plenum is better than no plenum.
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wimpie swart
Shooter
Posts: 41
yes
Re: Plenum shape
«
Reply #6 on:
December 06, 2021, 12:34:22 PM »
Hi all,
I made this additional plenum for a Client with an Avenger in .22 cal. Original plenum was 8.7CC, I added 15.3CC plenum. One can go bigger, but then it would really look out of whack.
Awaiting his testing results.
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South Africa
subscriber
GTA Senior Contributor
Posts: 6810
yes
Re: Plenum shape
«
Reply #7 on:
December 08, 2021, 01:52:33 AM »
Dit sal werk!
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USA
wimpie swart
Shooter
Posts: 41
yes
Re: Plenum shape
«
Reply #8 on:
December 19, 2021, 08:54:45 AM »
Quote from: subscriber on December 08, 2021, 01:52:33 AM
Dit sal werk!
Dankie Broer!
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South Africa
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Plenum shape