Valve assembly for shortest action.
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Valve assembly for shortest action.
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Topic: Valve assembly for shortest action. (Read 1061 times))
Jim Holmgren
Plinker
Posts: 155
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Real Name: Jim
Valve assembly for shortest action.
«
on:
September 13, 2020, 03:48:30 PM »
While working on another project I have been thinking about short actions.
Especially in big bores the valve/hammer assembly take up a lot of space and if one is making a bullpup or a pistol that will be a considerable amount in percent of the whole length, a pistol with a 10 inch barrel may maybe have a 6 inch valve/hammer assembly, that's almost 40% of the whole length as an example, with a shorter action on could have used a 15-16 inch barrel or a more compact air pistol.
This may explain why there are barely any big bore pistols out there?
A balanced valve will cut down the length but they can still be quite long.
So if we start to make some compromises and put shoot count and efficiency to the side to start with (A normal big bore pistol will never have any major shoot count anyway to start with).
What would be the shortest action one could come up with? dump valve or not?
I'm thinking of something that will not add more then a inch or two to the barrel length.
At the moment the only thing that I have come up with is valveless system with the projectile being held and seal the air camber, but these have their own problems with specialize ammunition and sealing the camber of the "sear/trigger" mechanism holding the bullet.
So I put forward this as a little thought experiment, anyone have any ideas about this?
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Motorhead
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Real Name: Scott
Re: Valve assembly for shortest action.
«
Reply #1 on:
September 13, 2020, 04:38:59 PM »
While I've come up with plenty of valve mods etc ... generally these have been with production guns.
Now if one looks at such guns as .. say the old UK manufactured THEOBEN PCP's ... the "length" of the valve body to end of the poppet spring IT WAS SHORT !!
This because there is No valve body, just a seat/throat/ stem guide going into a mono block receiver. Everything indexed on shoulders so no external retention screws required. ( tho a single small one to keep transfer exit clocked )
To make POWER with heavy hammers and long stroke ... Balanced valves get very attractive which lend too light hammers and short strokes ... So having a short and effective firing system is very doable.
Then you have SADLY a short barrel ( Pistol as you stated ) leaving you with very limited power potential no matter the pressure or air released to drive any big bore projectile. End result being you very quickly can get up the latter, but very quickly top out as to how far you can go
In Big Bore air guns barrel length is very very important if you want any sort of decent power, Or what the point
Just sharing thoughts as you had asked
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Rob M
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Posts: 6308
Re: Valve assembly for shortest action.
«
Reply #2 on:
September 13, 2020, 05:26:19 PM »
a daisy 880 style dump valve, the same can be said for the p17 valve. as a pcp p17 i was getting 13 fpe and thats with stock ports. Im not saying to use an actual p17 or 880 valve but to duplicate one with proper porting . Very compact , but both are dump valves.. so a big bore pistol configured like thaat would truly be a 1 shot.. I also made a large bore co2 gun where a piston sealed the air chamber from the TP , a b18 springer trigger held the piston in place , when the trigger was pulled , 180 lbs of co2 force was released, slamming the piston out the way and firing the round.. It wasnt very practical , also 1 shot per fill. another option is reply 55
https://www.gatewaytoairguns.org/GTA/index.php?topic=146903.40
a piloted qev
«
Last Edit: September 13, 2020, 05:32:03 PM by Rob M
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Louisiana
MJP
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Posts: 2136
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Real Name: Marko
Re: Valve assembly for shortest action.
«
Reply #3 on:
September 23, 2020, 03:00:23 AM »
Conventional valve works ok if you make it right, making it very flow efficient you can use slightly smaller diameter and still get good power.
Radius throat and seal and turn to TP with polished surface gets you pretty far.
I use standard Crosman hammer travel on my 9mm pistol and 10mm valve port. Opens just fine and stays open as long as the bullet is in the barrel.
Marko
«
Last Edit: September 23, 2020, 03:05:30 AM by MJP
»
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Finland
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rkr
GTA Senior Contributor
Posts: 4343
Re: Valve assembly for shortest action.
«
Reply #4 on:
September 30, 2020, 05:16:39 AM »
Rotating hammer and a gun that shoots straight from the magazine (no probe) like Evanix AR6 makes for a very compact action. Add balanced valve and the hammer + spring can be greatly reduced in size.
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CableStop
Marksman
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Real Name: Tom
Re: Valve assembly for shortest action.
«
Reply #5 on:
December 05, 2020, 12:47:01 PM »
The valve sb327 posted about recently would be a good contender because it's hammerless. Whether the whole thing can be shrunk shorter than a traditional poppet, I don't know.
However a balance valve is inherently a little longer than a normal poppet so that may make up for the reduced hammer stroke.
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JPSAXNC
Sharp Shooter
Posts: 506
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Real Name: James
Re: Valve assembly for shortest action.
«
Reply #6 on:
January 01, 2021, 01:46:52 PM »
Hi Jim, I built a pcp pistol and wanted the valves as short as possible, the fill valve is 1" long and the firing valve is 5/8" long. The gun uses the hammer and hammer stroke as a Crosman 2240.
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USA, North Carolina, Saxapahaw
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Valve assembly for shortest action.