Cothran valve stem question
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Topic: Cothran valve stem question (Read 778 times))
oneshot61
Sharp Shooter
Posts: 998
Real Name: Daniel
Cothran valve stem question
«
on:
July 20, 2017, 12:42:49 AM »
Does anyone know what happens if the small vent hole in the cothran balanced valve stem gets plugged?? Does it revert back to acting like a regular valve and will it cause any damage to the valve??
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Eufaula Alabama
A man with experience is never at the mercy of a man with an opinion.
rsterne
Member 2000+fps Club
Bob and Lloyd
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Real Name: Bob
Re: Cothran valve stem question
«
Reply #1 on:
July 20, 2017, 12:56:42 AM »
If the hole is plugged, I would assume the valve would either dump all the air, or at least be very reluctant to close.... because enlarging the hole causes it to have less dwell (close faster)....
Bob
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Coalmont, BC, Canada
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oneshot61
Sharp Shooter
Posts: 998
Real Name: Daniel
Re: Cothran valve stem question
«
Reply #2 on:
July 20, 2017, 09:12:57 AM »
That makes sense, as when I opened it up I got a bit flatter string. I think you removed the stem pin in testing, did you ever block it completely... canceling out the balance effect?
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Eufaula Alabama
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rsterne
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Bob and Lloyd
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Real Name: Bob
Re: Cothran valve stem question
«
Reply #3 on:
July 20, 2017, 01:35:03 PM »
No, I did not.... Removing the pin inside the stem can cause you problems by making the valve close so quickly it may destroy the soft seat material.... Enlarging the hole can do the same thing.... The best setup I found was with a 1/32" hole and the stock pin in place, but that was at 2000 psi, not at 3000.... I have never managed to achieve a bell-curve with a Cothran valve, the velocity drops along with the pressure....
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).
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GTA
»
All Springer/NP/PCP Air Gun Discussion General
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Cothran valve stem question