AEA Varmint mods

[Firewalker]

I’ll try to draw something up that is close to scale. It won’t be exact but it’ll give a good idea. I’m heading to work shortly and it’ll be a couple weeks before I can do any more measurements and such.

Dave

I greatly appreciate any help you can offer! 

[customcutter]

Thanks Dave.  I'm confused again as usual!  Maybe a short video of the valve from all angles also and how it installs in the gun.  It looks like it screws into the Varmint receiver where the other knock open valve goes, but not sure how it works.  I guess the lack of a spring may be what's confusing me.  Also I don't see how the hammer can contact the valve stem.  There isn't a stem small enough to go through the small hole in the Varmint receiver.

[sb327]

Ok, some more pictures to show how it assembles. Top in first picture is a factory poppet and spring, with a couple of test poppets and my factory modified plug (it has an internal snap ring to hold the balance piston, and finally my current valve assembly.

The stem is the same diameter as factory stem.

 It closes fine without a spring once it’s aired up. If it doesn’t take air from empty, I screw my adjustment in until it forces the poppet closed then reset it.

I’m still going to draw it up, just don’t have time today.

Dave

[sb327]

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[customcutter]

Thanks Dave, I think I've finally got it.  Unless there are vent holes somewhere in the valve that I'm not seeing.  I thought this valve replaced the poppet.   You're still using a poppet, it's just not being closed by the spring and HP air from the tank/cyl.

[MJP]

Nice design David!
Really like the simplicity.
Something similar I have been thinking that could fix the stupid fx bobcat atmosphere balancing system. It's always leaking, but there's very little room in the housing.

Marko

[sb327]

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[customcutter]

Thanks for the detailed drawing Dave!  The small external stem on the right hand side, looks like it is missing half of the o-ring.  Also I see that it is threaded.  Is it threaded for assembly or for adjustment, or both?

[sb327]

Yep, missed part of the oring, lol

Yeah, it’s for adjustment. It turns the cage that holds the balance piston. If screwed in, it lets the piston reside deeper in the balance cylinder. This minimizes the blow open effect and allows more hammer strike dependent lift.

If screwed out, it increases the blow open effect.

I’ll try to mark up the drawing a bit when I get some more time.

Dave

[sb327]

With some marks

Dave

[customcutter]

Thanks Dave.  I'm thinking the cage serves two purposes, adjustment of the balance piston, and also it supports/aligns the rear of the balance piston.  Just a few thousandths clearance so that air can pass around it.

[sb327]

That’s a good question. In my balanced valves, I like to have a generous amount of freedom. I see no reason to attempt to restrain the piston in any direction besides how far it sits into the balance cylinder.

If you notice in the photo above how the piston stem can move quite freely within the cage. The stem of the balance piston could literally be held with a chain and still create the desired effect.

Dave

[Firewalker]

That’s a good question. In my balanced valves, I like to have a generous amount of freedom. I see no reason to attempt to restrain the piston in any direction besides how far it sits into the balance cylinder.

If you notice in the photo above how the piston stem can move quite freely within the cage. The stem of the balance piston could literally be held with a chain and still create the desired effect.

Dave

I am not very smart, I cannot figure out how it works but I WANT ONE!! 

[customcutter]

Dave a few more questions. 

I have a carbine, just doing the balanced valve shouldn't affect the semi-auto function should it?  I know you changed trigger function as well for your Varmint model.

Approximately how much did you reduce your cocking force using the balanced valve and music wire spring?  10%, 25%, 50%?

I've never attempted making a spring.  Did you anneal and the re-temper the music wire?  Or is just winding the music wire acceptable?

Thanks again for sharing and drawing this out for us.  Ken

[sb327]

I would not suggest putting one in a semi. The hammer spring helps hold the bolt in battery during the shot cycle.

You can always turn your semi into a bolt though. And test the valve/lighter spring. Then switch back to semi and test. I would do so without a magazine though.

I’m sure it decreased my cocking effort by 50% at least. But I didn’t tune for a bunch of power and I didn’t measure the pull before and after.

Fwiw, the semi really doesn’t need a lower cocking force because you only cock it once per mag. That’s only my opinion though, I have a carbine and mag changes are not the easiest thing in the world, so I also understand.

Dave

[sb327]

Just wind the spring to desired dimensions then put in the oven at 450 for an hour.

Dave

[Mr.P]

That’s a good question. In my balanced valves, I like to have a generous amount of freedom. I see no reason to attempt to restrain the piston in any direction besides how far it sits into the balance cylinder.

If you notice in the photo above how the piston stem can move quite freely within the cage. The stem of the balance piston could literally be held with a chain and still create the desired effect.

Dave

I am not very smart, I cannot figure out how it works but I WANT ONE!! 

I’ve been staring at that diagram trying to figure it out myself…

I would love to know why and how that mechanism operates and how it is an improvement over the basic return spring, I guess it’s time to search for threads on balanced valves if anyone has a link I’d appreciate it.

[customcutter]

I would not suggest putting one in a semi. The hammer spring helps hold the bolt in battery during the shot cycle.

You can always turn your semi into a bolt though. And test the valve/lighter spring. Then switch back to semi and test. I would do so without a magazine though.

I’m sure it decreased my cocking effort by 50% at least. But I didn’t tune for a bunch of power and I didn’t measure the pull before and after.

Fwiw, the semi really doesn’t need a lower cocking force because you only cock it once per mag. That’s only my opinion though, I have a carbine and mag changes are not the easiest thing in the world, so I also understand.

Dave

Thanks Dave, I noticed that your HS allows for free travel of the hammer.  Didn't think about it holding the bolt in battery.  I have thought about converting to a bolt action .17 slug shooter.

Like you said simple as making another "plug" and drilling the hole for the adjuster bolt.  Just have to figure out if the plug is metric thread (my guess is yes) and finding out how to change the gears to convert my lathe to metric threading.

Yeah, only problem is the magazine changes and they are a PITA sometimes. 

This mod is definitely on my to do list.

[Rob M]

Nice work Dave , is there a reason the balance piston is floated as opposed to fixed in place?

[customcutter]

That’s a good question. In my balanced valves, I like to have a generous amount of freedom. I see no reason to attempt to restrain the piston in any direction besides how far it sits into the balance cylinder.

If you notice in the photo above how the piston stem can move quite freely within the cage. The stem of the balance piston could literally be held with a chain and still create the desired effect.

Dave

I am not very smart, I cannot figure out how it works but I WANT ONE!! 

I’ve been staring at that diagram trying to figure it out myself…

I would love to know why and how that mechanism operates and how it is an improvement over the basic return spring, I guess it’s time to search for threads on balanced valves if anyone has a link I’d appreciate it.

Marko, here you go.  I've been reading/studying them for some time and still trying to figure parts of them out.  Here is a link to a search.  I clicked on the search function then below the search box is an advanced search, click on it.  I put in "balanced valve".  Also lots of YT videos on balanced valves.

https://www.gatewaytoairguns.org/GTA/index.php?action=search2