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All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: tjensen on January 15, 2017, 10:39:01 AM
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Hi all.
I have a Crosman 1377 valve.
Wondering how much pressure it holds?
For reasons I cant go into I threw away the pistol and only kept the valve and want to make a pcp rifle ( I am a gunsmith).
Will this valve hold 230bars?
Will it work with CO2?
Power doesnīt matter, only accuracy.
Thanks.
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I haven't done the math on the strength of the valve itself, but 3300 psi might be a stretch.... The tube you mount it in would have to be strong enough to contain any failure, of course.... Anchoring it into the tube will likely be your biggest challenge.... You would want to check to make sure that the burst strength and anchoring system (indeed, all failure points) exceeds the loads at 11,600 psi (800 bar) to have the recommended 3.5:1 safety margin to burst.... The mounting system must be capable of withstanding 3500 lbs. of end force before failure.... You would have to eliminate the check valve in the front, or you would be limited to the tiny volume inside the valve itself, which even at that pressure will severely limit your FPE.... Of course you will have to have a much heavier hammer and spring to open the valve against that HPA pressure as well.... It should work OK on CO2, but you may find the O-rings swell, making it hard to disassemble, when using that gas.... so may have to use a different material for those.... What caliber and barrel length are you considering?.... Are you thinking of a dump shot (like a pumper), or a conventional PCP that only releases a small portion of the air in the reservoir?....
Bob
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Was thinking ,177 and about 14" barrel.
I could make a more suitable valve but need the dims, or a plan.
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Dump valve or timed?.... ie is it your plan to only have air in the valve and dump it all, or have a large reservoir and have the valve "sip" air from it?....
Bob
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Dump valve or timed?
I donīt even know the difference :P
Was also thinking maybe using a Sodastream CO2 bottle.
Wich has a valve....
What do you think about that rsterne?
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A dump valve, when fired, dumps all the air available to it.... In a pumper (like a 1377), that air is inside the valve only, and is about 1.6 cc.... Most PCPs have a large reservoir, and the valve is similar to a 1377 valve in operation, but it does not have the check valve on the inlet side, just a hole to feed through air from the large reservoir, which may be several hundred cc's.... By carefully controlling how hard you hit the valve, you can control how far and for how long it opens, before the air pressure in the reservoir slams it closed again.... It the typical unregulated PCP, we adjust the hammer strike so that the velocity at maximum fill pressure is a bit below the peak.... As the pressure drops, the valve opens longer, and the velocity increases slightly with each shot as the pressure drops.... At some point, the valve can't open any more, so the pressure dropping reverses the trend, and the velocity drops as well.... This produces the typical "bell-curve" of velocity we see in a properly tuned PCP.... A valve operating in this manner is said to be "self-regulating"....
CO2 is stored as a liquid, and boils to become a gas.... The higher the temperature, the higher the pressure that occurs at.... so the velocity on a CO2 gun depends on the temperature.... At room temperature, the pressure is about 850 psi....
Bob
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So, I could use a Soda stream bottle and regulate the hammers weight and springforce to strike the valve in the bottle sufficiently to open the correct amount of time?
Thereby not needing any other valve?
Would be using it indoors.
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850 psi, is that about 60 bar?