Simplified Balanced Valve



Author Topic: Simplified Balanced Valve  (Read 9523 times))

Offline rsterne

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Re: Simplified Balanced Valve
« Reply #600 on: February 10, 2019, 12:15:45 PM »
Beautiful job on the animation, for sure.... Wish I had that talent....

Bob
  • 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), .22 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" Bench PCP, 6mm Regulated PCP and .257 Unregulated, Three BRods.

Offline jackssmirkingrevenge

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Re: Simplified Balanced Valve
« Reply #601 on: February 10, 2019, 12:40:03 PM »
Beautiful job on the animation, for sure.... Wish I had that talent....

Cheers!  I wouldn't call it a "talent", just copy-pasting on MS Paint to make each individual frame then combining them on this nifty website.

Here's a quickie with the subject of this thread made with just 3 unique frames:



edit: or if one was feeling a little silly, voila


« Last Edit: February 10, 2019, 12:52:40 PM by jackssmirkingrevenge »
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Offline Hobbyman2007

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Re: Simplified Balanced Valve
« Reply #602 on: February 10, 2019, 04:35:49 PM »
Well look at that , a Quebecois and Ontarien actually getting along . Again good work Jack . Iím up in Northern Labrador for work right now . -40c and blowing snow 30 to 40cm . Canít wait to get home to the -30c . The mine site has been on shut down for the last 18 hours , pretty nasty out . I havenít seen a winter storm like this since the early 80ís .
The Evanix is similar with blowback ,but not quite . It doesnít blow back directly on the hammer . Thereís another mechanism involved .
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Offline jackssmirkingrevenge

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Re: Simplified Balanced Valve
« Reply #603 on: February 10, 2019, 04:43:06 PM »
Well look at that , a Quebecois and Ontarien actually getting along .

Well I'm Toronto born and raised irredeemably Anglophone so that must explain it ;) 

Quote
Iím up in Northern Labrador for work right now . -40c and blowing snow 30 to 40cm . Canít wait to get home to the -30c . The mine site has been on shut down for the last 18 hours , pretty nasty out . I havenít seen a winter storm like this since the early 80ís .


Nice and warm with -12 degrees here ;) It does seem to be particularly harsh this Winter though.

Quote
The Evanix is similar with blowback ,but not quite . It doesnít blow back directly on the hammer . Thereís another mechanism involved .

Is there an exploded view online somewhere?  I'm curious as to how it works exactly.
  • Quebec, Canada
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Offline Hobbyman2007

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Re: Simplified Balanced Valve
« Reply #604 on: February 10, 2019, 07:07:39 PM »
No blown up pics available or exploded parts diagram available as of yet . You know how straws a fast food joints come with a paper cover , if you remove just one end of the paper and blow into the end of the straw the cover goes flying . Thatís how it works. Now just think of how the hammer would be the paper cover .
  • Dowling,ontario, Canada
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Offline Lob0426

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Re: Simplified Balanced Valve
« Reply #605 on: February 10, 2019, 08:56:10 PM »
Edit: Yes some paintball guns vent gas from the exhaust to the hammer near the valve stem. Some have a grub screw in the vent to adjust the flow to the hammer.

Efficiency is effected by venting to the hammer and the bolt opening while still pressure in the bore. Need a way to separate bolt movement from hammer movement. Or keep the chamber sealed longer. Like hammer hitting a spring loaded bolt farther back than sear. Separated bolt from hammer.

Might be a system to consider for higher performance semi airguns. Might work better with larger calibers, poppets and pressures.
« Last Edit: February 10, 2019, 09:08:59 PM by Lob0426 »
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Online rkr

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Re: Simplified Balanced Valve
« Reply #606 on: February 12, 2019, 11:25:49 AM »
That sure looks a lot like the Evanix air speed mechanism.

That's interesting, I've never seen the mechanism for this one.  I had an FX Monsoon which used air pushing on a piston in the shroud to recock the mechanism but wasn't aware that there are rifles on the market that use direct blowback to cycle the action.


There's Steyr, Crosman Nightstalker and now Evanix. Evanix is the only one with a probe, others fire from magazine.

Edit, that is they use air from transfer port to cock the mechanism. Caselman uses air at the probe, heavy mass and long soft spring.

Edit 2, there's also another reason why Caselman works, the probe can retract a long way before it wents out air giving it decent speed before the bullet leaves the barrel. I tried similar approach with a normal .177 airgun and while the probe shot back it gave a loud pop once it exited the barrel and stopped quickly when it hit the hammer. A much softer spring for the hammer with hammer+bolt locked together and some 1" or so retraction before venting out could have made it work. So yes, this balanced valve may help in development of simple semi/full auto airguns. 
« Last Edit: February 13, 2019, 03:22:16 AM by rkr »
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BSA Scorpion SE .177 - plinker/training gun
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+ a couple of springers

Offline Jim Holmgren

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Re: Simplified Balanced Valve
« Reply #607 on: February 15, 2019, 06:10:49 PM »
I did just skimmed thought this thread and wondering.

1. Is there any advantages of this design compared with a valve with the balancing cylinder behind the poppet, (like the one that Lloyd did make?)

2. Why do you put the bleed hole in the valve stem and not though the poppet? A smaller stem in the throat would help flow but if you have a hole in it, it must be thicker right?

3. Does it matter if the thimble have to poppet inside or the poppet is hollow going over a fixed rod. (If not would this be easier to machine)?

4. I think I read something about interchangeable bleed jets? Were would you put them in that case so it could easily be exchanged?

My idea was to machine a valve now in the weekend and consider to make one based of Lloyds design, but I will maybe reconsider and make something like this instead.
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Offline rsterne

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Re: Simplified Balanced Valve
« Reply #608 on: February 15, 2019, 07:37:27 PM »
Hey, Jim....

1. A balancing cylinder behind the poppet like Lloyd's or the one used by AAA is harder to make, because the poppet must be made in two piece so that it can be assembled.... AAA use a jig to hold the parts aligned while they are pressed together while in the valve body....

2. There isn't much room between the bottom of the O-ring groove and the stem for a vent hole.... certainly if you wanted a single straight hole.... Depending on the size of the parts, you may be able to have two holes intersecting, with the front hole on an angle.... If the front part of the poppet is large enough, and the stem small enough, you may have room for a vent hole paralled to the stem....

3. You could use a poppet with the outer portion hollow at the front, going over a (semi) fixed rod, however you would have to make sure the wall of the poppet is strong enough to not collapse from the pressure outside it and only atmospheric pressure inside it.... The Cothran valve does this but uses a metal sleeve for the front hollow section of the poppet.... I would allow the rod to move radially to allow for self-alignment with the poppet, like Cothran does....

4. The interchangeable bleed jets on the front of the valve are not used in this design.... only in the SS valve and the Cobra/Python valves.... The purpose is to control the airflow out of the front chamber which acts as an air spring (some SS valves don't use that feature, particularly in high power applications)Ö. This valve has no vent from the inside of the valve body to the balance chamber, only the rear vent through the poppet to the exhaust port....

Something else to consider.... One of the guys in this thread had some poppets pull apart at the bottom of the O-ring groove.... The main body of the poppet is held back against the seat by air pressure, and the balancing force is acting forward on the O-ring, effectively trying to stretch the poppet lengthwise.... His problem was that the cross sectional area below the O-ring groove where the vent hole is, was insufficient for the Delrin he used, and the poppet was pulling apart and failing at the bottom of the O-ring groove.... He made a PEEK one, and I understand hasn't had that occur since.... My valve has the threaded stem continue all the way to the front of the poppet, in fact it becomes the spring seat.... Therefore, the stem takes some of the tensile load.... That is the advantage to continuing the stem all the way past the O-ring groove, I kind of lucked into that feature, and it resulted in me not having any poppets pull apart.... You need to consider that tensile load in your poppet design.... If you are going to make the front of the poppet tubular, and of metal, that should not be an issue.... but of course the stem you use, fastened to the front of the valve, will end up with that tensile load at the bottom of the O-ring groove, so allow for it there....

Bob
  • 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), .22 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" Bench PCP, 6mm Regulated PCP and .257 Unregulated, Three BRods.

Offline HYspd

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Re: Simplified Balanced Valve
« Reply #609 on: February 17, 2019, 12:31:14 AM »
I'm also still learning how to do some of these things on the lathe so it's a learning experience and gives me something to tinker with 

Like using a butter knife to carve prime rib ..... yea that would be rather difficult.
Doable but not pretty.

Yea the tolerances there talking here requires good tooling and established technique .... Tho half the fun and learning comes from our mistakes & there is nothing wrong with that !


old post and off topic, BUT when  I cook a prime rib you can cut with a fork!
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Offline mackeral5

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Re: Simplified Balanced Valve
« Reply #610 on: February 17, 2019, 06:46:54 PM »
Beautiful job on the animation, for sure.... Wish I had that talent....

Cheers!  I wouldn't call it a "talent", just copy-pasting on MS Paint to make each individual frame then combining them on this nifty website.

Here's a quickie with the subject of this thread made with just 3 unique frames:



edit: or if one was feeling a little silly, voila



Very cool and very clear demonstration. 

This looks very similar to a Cothran works minus the rod.  i'd love to see a Cothran animation. 
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Offline jackssmirkingrevenge

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Re: Simplified Balanced Valve
« Reply #611 on: February 17, 2019, 09:42:41 PM »
This looks very similar to a Cothran works minus the rod.  i'd love to see a Cothran animation.

Is there a diagram for this valve?  Best I could find was this image:



Not 100% clear on how it's put together though.
  • Quebec, Canada
"You have to make many weapons, because this field is long and short life"

Offline rsterne

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Re: Simplified Balanced Valve
« Reply #612 on: February 18, 2019, 12:39:33 AM »
There is no specific diagram for the Cothran valve, this is close to how it operates, but the front of the poppet is reversed (it is hollow inside, instead of carrying the O-ring)....



In the Cothran valve, the front end of the poppet is tubular, and the rod which carries the O-ring is fastened to the front of the valve, with no axial movement but some radial movement to allow for self-alignment of the rod with the poppet.... The poppet is made in 3 pieces (4 if you count the metering rod inside it), the front tubular section, the rear stem, and the clear plastic seat, which is held in place between those two parts when they are threaded together....

The stem is hollow and the small "metering rod" fits inside that, and works like a "leaky check valve".... There is a cross hole in the stem, barely visible in that photo, you can see it in the side of the stem immediately below the O-ring.... In operation, when the valve is closed, the balance chamber is at atmospheric pressure, and provides a "lifting force" on the poppet to reduce the hammer strike required to crack it.... Once cracked, HPA from the exhaust port travels through the cross hole, along the close-fitting sides of the metering rod through the hollow stem, and raises the pressure inside the balance chamber.... This helps close the valve.... Once the valve closes, that HPA changes direction, and has to again leak around the metering rod to escape into the exhaust port and out the barrel.... This takes a small amount of time, and during that time the force holding the valve closed is greater, to resist any hammer bounce reopening the valve....

The valve "blows open" in a definite cycle.... If you don't hit it hard enough, it barely "pops" (100-300 fps)Ö. Hit it a bit harder, and it cycles normally.... You cannot tune it with hammer strike, it either works or it doesn't, a complete "cliff".... The only way you can adjust the velocity is by changing the pressure....

Bob





  • 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), .22 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" Bench PCP, 6mm Regulated PCP and .257 Unregulated, Three BRods.

Offline jackssmirkingrevenge

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Re: Simplified Balanced Valve
« Reply #613 on: February 18, 2019, 06:26:52 AM »
Thank you Bob for the explanation, I have drawn it based on your description:



Let me know if this is accurate and I will animate it.

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Offline mackeral5

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Re: Simplified Balanced Valve
« Reply #614 on: February 18, 2019, 07:07:28 AM »
Excellent description and the diagram is almost perfect.   The stem port does not pass completely through the stem.  It only penetrates one side.  The stem is bored slightly larger than the rod, with the rod also being slightly undersized/stepped on 1 end.  The rod undersize is approximately 1/4 the length of the rod.  The undersized end is towards the stem port
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Offline jackssmirkingrevenge

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Re: Simplified Balanced Valve
« Reply #615 on: February 18, 2019, 07:28:46 AM »
Thanks, just one more thing, how deep can the rod go in the stem?

edit:  Here's a more complete diagram, roughly to scale and just missing the return spring:

« Last Edit: February 18, 2019, 09:55:37 AM by jackssmirkingrevenge »
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Offline mackeral5

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Re: Simplified Balanced Valve
« Reply #616 on: February 18, 2019, 11:51:31 AM »
Thanks, just one more thing, how deep can the rod go in the stem?

edit:  Here's a more complete diagram, roughly to scale and just missing the return spring:



I dont have a valve in front of me right now but I think your diagram is correct in all aspects now.  The only uncertainty I have is the precise location where the stem port intersects the stem bore. Great job 
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Offline rsterne

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Re: Simplified Balanced Valve
« Reply #617 on: February 18, 2019, 12:48:33 PM »
Pretty much perfect diagram, IIRC the hole intersects the stem about the middle of the exhaust port when closed.... I think you can see that in the upper photo.... I believe there is a slight bevel on the ends of the rod.... At rest (as shown), the front end of the rod sits a bit below flush in the end of the hollow stem.... The exhaust port is 0.257", the stem diameter is 0.175", and the throat ID is 0.335".... The stock vent hole is 0.025" (one side only), and the valve works better (easier to tune near the cliff) IMO with that at 0.032" for most applications.... I tried sanding down the metering rod by 0.003" and got a wider adjustment range but much increased ES.... I also tried a 0.035" vent, with the same results.... Removing the metering rod destroyed the soft seat within a few shots, it hammered a huge groove into it, so the valve was slamming shut without the rod.... The stem projects 0.200", and I ran mine with a #210 O-ring against the back of the valve to limit the hammer travel.... It hits the O-ring when the lift is about 0.075, but that does little if anything to the velocity, which to me proves that the valve is "blowing open" when cycling....

Bob
« Last Edit: February 18, 2019, 12:54:40 PM by rsterne »
  • 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), .22 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" Bench PCP, 6mm Regulated PCP and .257 Unregulated, Three BRods.

Offline jackssmirkingrevenge

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Re: Simplified Balanced Valve
« Reply #618 on: February 18, 2019, 01:29:12 PM »
Thanks Bob.

Here's my interpretation:

  • Quebec, Canada
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Offline rsterne

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Re: Simplified Balanced Valve
« Reply #619 on: February 18, 2019, 05:19:32 PM »
I believe that the rest position of the metering rod is back inside the stem (the last airflow was out of the balance chamber)Ö. It accelerates forward with the stem, and momentum likely carries it on until it hits the back of the stationary rod carrying the O-ring.... and it remains there as the pressure leaks past it to increase that inside the balance chamber.... Once the poppet hits the seat, the pressure in the exhaust port drops, and the air in the balance chamber pushes the metering rod back to the rear of the hole in the stem.... The last HPA anywhere except inside the valve body would be inside the balance chamber....

That what I think is happening, anyways....  ::)

Bob
  • 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), .22 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" Bench PCP, 6mm Regulated PCP and .257 Unregulated, Three BRods.

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