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Old 07-23-2013, 01:47 PM   #1 (permalink)
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Smart engineering types.... can you reverse flow a cocker valve.

Have a project I'm working on and I may need to do something like that.

Assuming a build in the air volume needed think I can run a cocker valve in reverse?

PS... also assume the front of the valve stem will be sealed as well
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Old 07-23-2013, 01:52 PM   #2 (permalink)
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Sure. There will be as much, if not more turbulence in it depending on how you feed it.

But yes, it will work... and should work well. The kicker will be capturing the valve seal itself where ever you are going to put it.... either in the bolt if this is inline, or somewhere else. In line would be the hardest but I'm sure you could figure out a way.... and I have a feeling that may be the route your are going, because flowing a Sheridan valve backwards in a stacked tube isn't that big a deal (conceptually)

Be interested to see how this pans out.

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Old 07-23-2013, 01:58 PM   #3 (permalink)
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I am up to no good....

Perhaps a shelson or a neridan.... not sure what conceptually it will work out to. But I need a valve design for a first strike rifle I am working on. But want to use cocker hammers ad I have several hundred.
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Old 07-23-2013, 02:59 PM   #4 (permalink)
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I think you'll get some dynamics similar to a sprinkler valve on a nerf launcher. The flow does a little to hold the valve open, instead of helping a lot to close it. It seems like it would need some heavy springing. Controlling the filling of the dump chamber might be useful in adjusting the pressure profile of the shot (i.e. not letting the gas flow fight the closing of the valve).

I think the hammer is about the same, but should go lighter for the same dwell compared to the usual arrangement.
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Old 07-23-2013, 03:04 PM   #5 (permalink)
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Likely it will be low pressure operation.
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Old 07-23-2013, 03:22 PM   #6 (permalink)
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Quote:
Originally Posted by BigOldSkool View Post
Likely it will be low pressure operation.
Yeah, flipping it for high pressure operation would be a big change. At 300 psig you're flipping about a 20 lb force on a .3125 valve face. At 800, it's about 40 lbs on a .25 valve face. That just being the static pressure.

***

If you are going to seal the stem anyway, you might as well enlarge that seal to balance the seat. That way the extra tension from a valve spring won't be sitting on the seal when there is no gas pressure.
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Old 07-23-2013, 04:53 PM   #7 (permalink)
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I have an idea for the valve actually.. more like a mini ion bolt than a poppet. I have to find some time to tinker with this.
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Old 07-23-2013, 06:58 PM   #8 (permalink)
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Quote:
Originally Posted by BigOldSkool View Post
Assuming a build in the air volume needed think I can run a cocker valve in reverse?
-Basically the same orientation and setup, except the air would come from the bolt passage, and out through the valve into what was originally the valve chamber?

Yes and no. Yes, up to a certain pressure, but above a surprisingly lowish pressure (depending on the valve) you wind up needing truly massive valve springs, else you get a low, constant 'weeping' leak.

The dwell time is also a factor- in a conventional setup, the air pressure in the chamber, and the air flow, both help close the valve. In your setup, the air pressure and flow act against the valve closing.

If you need something where the air comes in from the side and goes out in line with the valve, try an old Crosman or old Brass Eagle Nightmare valve.

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Old 07-23-2013, 07:16 PM   #9 (permalink)
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Thats what I'm going for..

I want to make an inline "sheridan" valve but out of pre-existing parts.

I was "blessed" to end up with several hundred stock valves and hammers from a friends proshop. I am working on a mag fed bolt action rifle design of my own and I would prefer to use alot of "off the shelf" items because well it will keep my over all R and D down and keep down machining costs......

That and well... the end result would be a "cocker" basically so it would be easy for me to tune.
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Old 07-23-2013, 07:32 PM   #10 (permalink)
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Quote:
Originally Posted by DocsMachine View Post
-Basically the same orientation and setup, except the air would come from the bolt passage, and out through the valve into what was originally the valve chamber?

Yes and no. Yes, up to a certain pressure, but above a surprisingly lowish pressure (depending on the valve) you wind up needing truly massive valve springs, else you get a low, constant 'weeping' leak.

The dwell time is also a factor- in a conventional setup, the air pressure in the chamber, and the air flow, both help close the valve. In your setup, the air pressure and flow act against the valve closing.

If you need something where the air comes in from the side and goes out in line with the valve, try an old Crosman or old Brass Eagle Nightmare valve.

Doc.
Yup there is the correct answer.
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