Balanced valves

[Pale_Rider]

I recently just purchased some parts from Don Cothran(https://cothranmachine.com/). One of those parts being his balanced valve. When talking with Don he advised that his valve runs best without a regulator. This made me think about the JSAR Raptor which also has a balanced valve but is regulated. What’s your guys’ experience with balanced valves (unregulated and regulated)?

 

[DanielL]

I recently just purchased some parts from Don Cothran(https://cothranmachine.com/). One of those parts being his balanced valve. When talking with Don he advised that his valve runs best without a regulator. This made me think about the JSAR Raptor which also has a balanced valve but is regulated. What’s your guys’ experience with balanced valves (unregulated and regulated)?

There should be no correlation unless you don't have enough plenum. If you don't have the plenum, then a balanced valve will give you more power and shot count than the OEM valve and adding a regulator will only cause you to lose power and shot count.

Many unregulated airguns do not have sufficient plenum volume for anything but the lowest power settings when used with a regulator.

 

[Pale_Rider]

Why would a plenum allow you to run a reg with the balanced valve?

 

[FuzzyGrub]

I don't have personnel experience with them, but have heard the same thing about the Cothran valve. The JSAR Gen2 can be used in both regulated and unregulated. My understanding is the Cothran valve is that it will open easier than a standard valve, but take same to close. Getting the right hammer energy (spring/weight) can be challenging. More geared toward high-powered non-regulated guns. The JSAR is more tunable and can close more quickly for a tight dwell. Obtaining a JSAR valve at this time will be a challange. I think they are in process of turning that over to someone else, be it sales, or both mfg and sales. But, in general, the main advantage of a balanced valve is the agility to open with much less energy than equivalent standard poppet valve.

 

[Pale_Rider]

I don't have personnel experience with them, but have heard the same thing about the Cothran valve. The JSAR Gen2 can be used in both regulated and unregulated. My understanding is the Cothran valve is that it will open easier than a standard valve, but take same to close. Getting the right hammer energy (spring/weight) can be challenging. More geared toward high-powered non-regulated guns. The JSAR is more tunable and can close more quickly for a tight dwell. Obtaining a JSAR valve at this time will be a challange. I think they are in process of turning that over to someone else, be it sales, or both mfg and sales. But, in general, the main advantage of a balanced valve is the agility to open with much less energy than equivalent standard poppet valve.

Thanks for the insight. I understand the advantages of a balanced valve. I was just perplexed as to why the JSAR balances valve works with a reg. Now I’m being told it’s because it has a plenum. I’d like to know why a plenum allows you to run a reg with a balanced valve. I’m thinking the plenum gives the reg enough time to catch up to the abruptness of the balanced valve?

 

[FuzzyGrub]

I am not sure about the plenum Maybe it is in relation to a specific gun??? Maybe Scott (Motorhead) will have some comments. He has much, more experience with just about all these valves in both regulated and non-regulated formats. He has worked with, tested, and helped refine the designs. Built his own, etc.

I will make a correction to a prior statement. I did work with a prototype balance valve for the Prod. It was non-regulated. I was not able to control it well with the oem hammer, regardless of hammer spring. I didn't have a light weight hammer to try, so used an O-ring buffer to limit excessive dwell. That was much better. Again, this was the prototype to the 1st gen balance valve. The 1st generation had a stiction problem, such that if the gun sat for a period of time, it would take a few shots to get back to the tune. Not the best for a hunting gun. My understanding is the gen 2 are much better in this aspect.

 

[Pale_Rider]

Are you talking about the jsar prod valve? I have a jsar bulldog valve that I never installed after hearing feedback on the stiction issues, too bad I didn’t hear about it before I bought it lol. Looks like they fixed those issues with the valve they use on the raptor

 

[Motorhead]

Bit late getting with this threads subject.

Balanced valves or as a more appropriate name ( Opening force reduced valves ) the ratio in what a balanced valve opens in required force to a conventional poppet varies quite a bit. The proportions of throat diameter / poppet to balance chamber diameter dictates how quickly the valve opens and gets to max flow.

The Cothrin valves are Ratio'ed pretty much towards the side of dang near operating like a spool valve Being MAX FLOW light switch On/Off sort of operation.

Because of this they operate best having the entirety of the HP air tank to draw from. There design is for POWER and don't respond well to being throttled down.



The JSAR Gen2 valve as well the current RAPTOR balanced valves are Ratio'ed more conservative and while they open easier than a conventional poppet valve, there no where near as let's say RADICAL as the Cothrin. Due to this they respond better to being throddled down in power, operate within a broader pressure range therefor can operate in regulated applications.





There is quite a lot going on with these valve even tho they sound easy enough to work with .... In reality they operate very differently than a conventional PCP valve. hammer weight, spring energy & stroke become different too. TOO MUCH hammer weight and spring energy is Very very easy to do !

 

[Pale_Rider]

Bit late getting with this threads subject.

Balanced valves or as a more appropriate name ( Opening force reduced valves ) the ratio in what a balanced valve opens in required force to a conventional poppet varies quite a bit. The proportions of throat diameter / poppet to balance chamber diameter dictates how quickly the valve opens and gets to max flow.

The Cothrin valves are Ratio'ed pretty much towards the side of dang near operating like a spool valve Being MAX FLOW light switch On/Off sort of operation.

Because of this they operate best having the entirety of the HP air tank to draw from. There design is for POWER and don't respond well to being throttled down.



The JSAR Gen2 valve as well the current RAPTOR balanced valves are Ratio'ed more conservative and while they open easier than a conventional poppet valve, there no where near as let's say RADICAL as the Cothrin. Due to this they respond better to being throddled down in power, operate within a broader pressure range therefor can operate in regulated applications.





There is quite a lot going on with these valve even tho they sound easy enough to work with .... In reality they operate very differently than a conventional PCP valve. hammer weight, spring energy & stroke become different too. TOO MUCH hammer weight and spring energy is Very very easy to do !

Thank you for chiming in! How do you adjust ratio on a balanced valve to make it suitable for a reg?

 

[DanielL]

Why would a plenum allow you to run a reg with the balanced valve?

I was talking about the general case of having enough volume of pressurized air. With a regulator and a small plenum volume the pressure drops considerably during the shot cycle...which is over before the regulator has time to compensate with more air. 

If you have an unregulated gun with a limited shot count due to the velocity/pressure curve a balanced valve can help improve the situation. A regulator added to that equation will severely limit power if there isn't enough plenum volume to provide the volume of pressurized air necessary during the shot. As you increase the volume of the plenum the pressure drop during the shot becomes less and less. 

 

[Motorhead]

Bit late getting with this threads subject.

Balanced valves or as a more appropriate name ( Opening force reduced valves ) the ratio in what a balanced valve opens in required force to a conventional poppet varies quite a bit. The proportions of throat diameter / poppet to balance chamber diameter dictates how quickly the valve opens and gets to max flow.

The Cothrin valves are Ratio'ed pretty much towards the side of dang near operating like a spool valve Being MAX FLOW light switch On/Off sort of operation.

Because of this they operate best having the entirety of the HP air tank to draw from. There design is for POWER and don't respond well to being throttled down.



The JSAR Gen2 valve as well the current RAPTOR balanced valves are Ratio'ed more conservative and while they open easier than a conventional poppet valve, there no where near as let's say RADICAL as the Cothrin. Due to this they respond better to being throddled down in power, operate within a broader pressure range therefor can operate in regulated applications.





There is quite a lot going on with these valve even tho they sound easy enough to work with .... In reality they operate very differently than a conventional PCP valve. hammer weight, spring energy & stroke become different too. TOO MUCH hammer weight and spring energy is Very very easy to do !

Thank you for chiming in! How do you adjust ratio on a balanced valve to make it suitable for a reg?

The ratio is NOT adjustable and is BUILT IN per-say as a design trait when the parts are manufactured. Only if one has a LATHE and knows how to use it could you REBUILD the parts specs ( Poppet & Thimble ) to a different balance ratio.



This is where my own R&D has led .... Radically changing ratios, chamber volume and bleed hole specs. Doing so I've self educated myself to the cause & effect of doing so.





Scott S



here a few photos of differing designs that operate similar, but tune far differently.

I've even gone as far too flip the design around with the thimble becoming part of the poppet head, even having it adjustable for chamber volume by having the chamber plug able to go shallower or deeper within chamber.

LOTS of ways to configure .. only constant being the parts quality and surface finish must be kept at a very high standard or they won't seal up properly. 

* Also done Hard poppet against soft seat and Soft poppet against hard seat. Each change has results to take note of and my current in use design is a blend of many trial & error prototypes. That design I keep to myself using in my personal rifles.



* I Do Not manufacture these for sale ... but happy to share the R&D with those who can.

 

[Roachcreek]

I had one in my Bulldog fed by a 4500 psi ti tube,



It displayed stellar performance, but it had a slow leak and needed refilled every few days back up to hi psi to keep it ready. It is fine for range work or hunting, but I removed it for the non leaking oem tube and valve that gives me 865FPS with NOE 357-152 hp.



Regards,





Roachcreek

 

[ackuric]

balanced valve = extra dynamic seal that needs cared for...if you don't mind tearing down and performing required maintenance, and an INEVITABLE stiction regardless single / dual o-ring / sealing methods (this is due to lack of DYNAMIC lubrication in the current models, a dynamic o-ring lubricating system during the shot cycle could remedy this, think of the piston rings in your cars engine, are they just set it and forget it? No they lubricate each cycle thanks to oil left behind on the cylinder wall...)



I find it absurd to balance a valve using current methods in anything other than single/dual shot large bores . Side levers work wonders for larger ported systems that have a lot of force holding the valve closed, no need to create this complex mechanism / valve system that is inherently problematic, and inadequate in my honest opinion. You want a dynamic seal, you better get dynamic lubrication onto that bad boy, or you're being dismissive of the needs for dynamic seals. The seal WILL run dry, the seal WILL stick after non-use over time due to opposing force of air pressure while closed and fluctuating air pressure while open.



Most enthusiasts treat their rifles as good as their cars, if not better. Would you run your car with a few drops of oil and just set it and forget it, and then go into competition feeling confident it will perform flawlessly every time? I don't think so.

 

[mackeral5]

I've used Don's valves in many different applications. They really shine in some applications, dont work so well in others. I've also configured them in ways that Don did not intend, with mixed results, mostly not so good.

One key thing to understand is Don's valves are tuned with pressure. You will be hard pressed to achieve a bell curve in an unregulated application. You will also find that there is very little tuneability by varying hammer spring tension. It is largely an on-off valve.

They are a VERY consistent valve.

In the sub 75fpe range, a properly sized valve isn't that hard to open--for the most part---not much need for a balanced valve. Much of the time we go too large on the valve throat, making a valve harder to open than it needs to be.

If you are looking for max power and greater than say 75 or so fpe, they shine. Just know that the greater the pressure drop between shots, the greater the ES. Simply put, smaller reservoirs will have greater velocity drop between shots. They make for an easy to open valve capable of max fpe for an given pressure/porting.

I tend to disagree with the majority here in the topic of regulation.. Don's valves really shine in regulated applications, again when seeking say greater than 75fpe. An example is I have a bottled, regulated .30 that with a very mild tune produces 90fpe. It does this with an ultralight all peek hammer weighing 14grams and a relatively easy to cock hammer spring. The shot cycle is a muted "click" with virtually no vibration nor recoil due to the hammer strike. You literally see the pellet impact cut a hole in the target with every shot. Don's valve made this easy to accomplish, even at 90fpe.

They are not the answer for every application, but they are a very effective tool in many applications. Yes, there is 1 more oring to maintain, but that is a small price to pay, IMO.

 

[Motorhead]

Matt would be incorrect on many aspects and if not mistaken has never made a successful balanced valve. * please correct me if wrong ?

An o-ring in dynamic use sure it wears just like those in a Regulators spool or the o-ring sealing the loading Probe. There are certainly lubricants that maintain very high adhesion on the surfaces of the balanced valves thimble and along with that we're generally using 90 duro rings that are super tough ! ... Still think they will run dry ... no problem run a QUAD ring ( X-ring ) like this where lubrication is trapped between sealing segments.

Will agree that for most applications there best left to high power applications .. Not necessarily big bore, BUT ... High power relative to caliber.



Scott S

 

[mackeral5]

Scott---your comments are 100% in line with my experience with a single balanced valve, the Cothran. I've spent a bunch of lead and a few cylinders of nitrogen in running the Cothran with larger throats, with the rod, without the rod with peek and delrin seals, larger stem vents, adapting Cothrans into platforms other than Marauder or 7/8 tubed guns, and even running them exactly as Don designed them. Many of these experiments were dismal failures. However I do have 2 very good shooting guns that are running a not so traditionally setup Cothran valve. Both are easy to cock and have fast, snappy shot cycles. But both are relatively high FPE (90fpe .30 cal and a conservatively tuned 260fpe .357) . Honestly in all this time I have yet to find a gun that leaked down due to balance chamber oring failure. I previously lubed the thimbles/balanced chambers with Superlube, but have recently switched to Ultimox. Guns torn down after several hundred rounds still retain Ultimox in the thimble.

 

[Airgun-hobbyist]

... I did work with a prototype balance valve for the Prod. It was non-regulated. I was not able to control it well with the oem hammer, regardless of hammer spring. I didn't have a light weight hammer to try, so used an O-ring buffer to limit excessive dwell. That was much better. Again, this was the prototype to the 1st gen balance valve. The 1st generation had a stiction problem, such that if the gun sat for a period of time, it would take a few shots to get back to the tune. Not the best for a hunting gun. My understanding is the gen 2 are much better in this aspect.

Did you guys figure out what actually caused the stiction problem in these valves after sitting and requiring multiple shots to work correctly again?

 

[Motorhead]

... I did work with a prototype balance valve for the Prod. It was non-regulated. I was not able to control it well with the oem hammer, regardless of hammer spring. I didn't have a light weight hammer to try, so used an O-ring buffer to limit excessive dwell. That was much better. Again, this was the prototype to the 1st gen balance valve. The 1st generation had a stiction problem, such that if the gun sat for a period of time, it would take a few shots to get back to the tune. Not the best for a hunting gun. My understanding is the gen 2 are much better in this aspect.

Did you guys figure out what actually caused the stiction problem in these valves after sitting and requiring multiple shots to work correctly again?

Indeed we did ... Looking at how a ROUND o-ring behaves in its SQUARE containment groove when pressure is being exerted on it. We find the o-ring no longer remains round and it gets extruded in a shape of near square. ( Just like when you service a PCP after years of use ) The o-ring come out looking nothing like a round ring !!

This pressure and subsequent shape shift of the o-ring increases not only the surface area in contact but the compression forces has the 0-ring also "Traction if you will" wanting to really hold onto the surfaces it is in contact with. In a STATIC application this a normal and poses no issue being thats what an o-ring is designed to do !



Now go DYNAMIC with this and motion of one part now required to SKID along over or threw the o-ring you can understand that as the part sits motionless the extrusion of the o-ring hangs on tight !! and when first moved will resist motion, tho once broken free will reluctantly slide easier until such time as it sits a spell and grabs on again.



First off it became aspirant HARDER the o-ring ( Higher Duro rating ) less shape shift / extrusion the o-ring has. but with increased hardness comes less elasticity and o-ring has a harder time creating a seal. So .... o-ring cross section / cord diameter needed to be increased. ( The Gen 1 SS valve used very thin cross section o-rings and 2 of them at that ) When the Gen 2 was designed it omitted 1 o-ring and beefed up the second to being cross section larger and harder. 

My personal R&D with the inverted design allowed use of QUAD / X-ring that is already square and does not suffer the shape shift, while also exerting less contact friction because of the narrow sealing bands of the X-ring design.

*Sad, Bad part of using X-rings is that there cord diameter / groove size required and the size we generally use in PCP valves has the ROOT DIAMETER of the o-ring groove very small. Used in a conventional opposing stem poppet where we have a vent hole passing threw the center of the o-ring groove it makes it too weak and it will break away under high pressure. On an inverted design as shown 2 posts above, there is no vent hole and the x ring / o-ring groove becomes much stronger.



Long winded .. hopefully educational.



Scott S

 

[Pale_Rider]

... I did work with a prototype balance valve for the Prod. It was non-regulated. I was not able to control it well with the oem hammer, regardless of hammer spring. I didn't have a light weight hammer to try, so used an O-ring buffer to limit excessive dwell. That was much better. Again, this was the prototype to the 1st gen balance valve. The 1st generation had a stiction problem, such that if the gun sat for a period of time, it would take a few shots to get back to the tune. Not the best for a hunting gun. My understanding is the gen 2 are much better in this aspect.

Did you guys figure out what actually caused the stiction problem in these valves after sitting and requiring multiple shots to work correctly again?

Indeed we did ... Looking at how a ROUND o-ring behaves in its SQUARE containment groove when pressure is being exerted on it. We find the o-ring no longer remains round and it gets extruded in a shape of near square. ( Just like when you service a PCP after years of use ) The o-ring come out looking nothing like a round ring !!

This pressure and subsequent shape shift of the o-ring increases not only the surface area in contact but the compression forces has the 0-ring also "Traction if you will" wanting to really hold onto the surfaces it is in contact with. In a STATIC application this a normal and poses no issue being thats what an o-ring is designed to do !



Now go DYNAMIC with this and motion of one part now required to SKID along over or threw the o-ring you can understand that as the part sits motionless the extrusion of the o-ring hangs on tight !! and when first moved will resist motion, tho once broken free will reluctantly slide easier until such time as it sits a spell and grabs on again.



First off it became aspirant HARDER the o-ring ( Higher Duro rating ) less shape shift / extrusion the o-ring has. but with increased hardness comes less elasticity and o-ring has a harder time creating a seal. So .... o-ring cross section / cord diameter needed to be increased. ( The Gen 1 SS valve used very thin cross section o-rings and 2 of them at that ) When the Gen 2 was designed it omitted 1 o-ring and beefed up the second to being cross section larger and harder. 

My personal R&D with the inverted design allowed use of QUAD / X-ring that is already square and does not suffer the shape shift, while also exerting less contact friction because of the narrow sealing bands of the X-ring design.

*Sad, Bad part of using X-rings is that there cord diameter / groove size required and the size we generally use in PCP valves has the ROOT DIAMETER of the o-ring groove very small. Used in a conventional opposing stem poppet where we have a vent hole passing threw the center of the o-ring groove it makes it too weak and it will break away under high pressure. On an inverted design as shown 2 posts above, there is no vent hole and the x ring / o-ring groove becomes much stronger.



Long winded .. hopefully educational.



Scott S

Very educational, thanks for sharing the knowledge. 

Will changing the O rings to Quad rings on the JSAR bulldog valve solve the stiction issue? Or is it not inverted?

 

[Airgun-hobbyist]

@motorhead that was very educational, and much appreciated. Thanks for your insight.