Built a Operational balanced valve using a Gen 1 M-rod valve body

[Motorhead]

First off credit is due to a few GTA members here for there vast sharing of design ideas, drawings and some mighty exhausting threads on the subject of Balanced valves.
You know who you are ... Thank you !

This was for me an exercise of prototyping a design idea based on what i had to work with for a valve body. All the parts to make this work were fabricated via machine shop tools or by hand etc ... Some not pretty, but remain functional for the task of testing etc ...

Started out with a bare Gen-1 M-rod valve body with the internal sleeve removed.  Next fabricated a dished / concave poppet seat being o-ring sealed to I.D. bore and slightly self centering having a bit of radial motion possible.   Picture #1

Next was fabricating the poppet which was done using a .052" drilled stem having cross holes @ mid throat position.  Poppet head made from PEEK having the stem be a TIGHT press fit w/adhesive.  The .052" hole threw stem continues out the balance chamber end.  Because we have the very real possibility the pressure within the valve ripping the o-ring & tip of poppet right off decided to scale down the 0-ring size and groove depth required leaving more thickness at the chamber end of poppet.  O-ring a very small 1mm x 3mm 70 duro buna/n.

Up next came the balance chamber & did much pondering on what material was actually required ? ... this based upon knowing the balance chamber is at atmosphere and the pressure within valve is trying to CRUSH IN INWARD.  Steel, brass etc likely best ... BUT having dug around in my Misc plastics found a stick of 3/4" glass reinforced acetal polymer, Huh perhaps that would not crush being this material is super stiff and really tough.  So thats the route went ... fabricating a screw in balance chamber where the poppet and o-ring end would reside at minimal radial clearance ( running @ .004" )  Chamber depth JUST ENOUGH to allow poppet to lift @ .100" and become flush with valve body if bottomed out.  Small shallow secondary bore to get in the small stiffl return spring and just going to coil bind same at same previous distance specs.

Poppet down in throat you see the balance end and vent hole.  Assembled with balance chamber screwed in and tightened the 3 Radial intake slots line up and valve can actually take in air.
The last picture looking THREW a hogged out m-rod gauge manifold at the air path as seen from the plenum side of the system.




    Now you likely wondering, Did it work ?  How well did it work ... Whats the reduction in cocking force, Reduction in energy to actually crack the valve open etc 
With the sizes chosen in Poppet head diameter at sealing margin and the balance chamber diameter we're at a 41/59 area ratio.  The opening force required has dropped to 64% ( Thanks Bob S for the math work )

Am able to get my previous 940 fps with a .177 JSB 10.3 using a 14 gram hammer and a much shorter spring which as eased cocking effort and sped up the shot cycle ( lower lock time )
Dang it if it don't work, seals up just fine and appears to have no sticksion issues.  Came out this AM after gun sitting all night ... 940 first shot 

Now @ 150 shots done, head of the peek poppet stem has not sheared off, o-ring is not leaking ... now we let TIME and shooting tell the tale if balance tubes going to crush and seize poppet or any other catastrophic failures.

Fun stuff !!

Scott

[tnt76]

Nice, tidy execution.
Does the cross hole in stem pass through or one sided?
And have you tried preload on the stem? I know preload is not needed, however I found with mine, any preload at low pressure gets a dump shot of several hundred psi under 2000psi. Just an indication of how stable it will be at various pressures.
I am considering trying mine regulated soon with pellets rather than bullets. Just for testing.
Have you recorded es% figures with the shots taken?

[Machinist]

It looks nice.  Really amazing that all the volumes worked out on the first try.

Steve

[Motorhead]

Nice, tidy execution.
Does the cross hole in stem pass through or one sided?
And have you tried preload on the stem? I know preload is not needed, however I found with mine, any preload at low pressure gets a dump shot of several hundred psi under 2000psi. Just an indication of how stable it will be at various pressures.
I am considering trying mine regulated soon with pellets rather than bullets. Just for testing.
Have you recorded es% figures with the shots taken?

Cross hole is @ .040" and threw both sides, so 2 holes.
No preload, it don't like it and you can hear dwell go way up if you do.
While not crunching the number while over the chrony ... ES figures were running +/- 3 fps shot after shot.

It looks nice.  Really amazing that all the volumes worked out on the first try.

Steve

I do have the knowledge of working with PCP valves a lot, and recently got an SS2 and had it apart.  being a visual sort of guy ... got it ! leaving just the execution & design work to make this one off version.

[Hobbyman2007]

Good work Scott. Very creative on how you went about the valve inlet . So it appears that between 50 and 65 % reduction in opening force seem to work best .

[oldpro]

 Well done my man! Not the easiest mod to make is it?

[tnt76]

Good work Scott. Very creative on how you went about the valve inlet . So it appears that between 50 and 65 % reduction in opening force seem to work best .

"Works best" is probably a premature term. There are only a few ratios documented so far and all have worked to a degree.  Start pushing the limits of force reduction via ratios and we'll find what doesn't work.

[oldpro]

Good work Scott. Very creative on how you went about the valve inlet . So it appears that between 50 and 65 % reduction in opening force seem to work best .

"Works best" is probably a premature term. There are only a few ratios documented so far and all have worked to a degree.  Start pushing the limits of force reduction via ratios and we'll find what doesn't work.

I’ve tried many many ratios and he’s right it’s between 50 and 65% based on power requirements

[tnt76]

Good work Scott. Very creative on how you went about the valve inlet . So it appears that between 50 and 65 % reduction in opening force seem to work best .

"Works best" is probably a premature term. There are only a few ratios documented so far and all have worked to a degree.  Start pushing the limits of force reduction via ratios and we'll find what doesn't work.

I’ve tried many many ratios and he’s right it’s between 50 and 65% based on power requirements

With all due respect, I understand how much r&d you must do behind the scenes, however I don't see a lot of publicly documented dimensions, specific data or internal pics from your testing with the rsterne simplified balance valve (SBV) version of the SS valve. So from a DIY perspective, it is good to see specific specs and results in this thread and in Bob's of what works and equally important what does not. 
I also understand there are commercial restraints your end too. But once again, in a DIY thread it should shown. 

[Motorhead]

GTA members ... this thread is simply DOING what many have talked about within numerous threads using the base information contained within such threads.
While commercial balanced valves do exist and can be purchased, this was not about whats out there commercially, but what one can build using ones creative & mechanical skills without breaking the bank.

Come end of the day ... Does a 22 ft lb .177 M-rod NEED a balanced valve ?  Heck No !!!!! .....  Will the gun operate more efficiently ?  Not likely !!!!!  .....  Will it cock easier, make equal power with less mechanical effort to purge the pneumatic power of the compressed air ?  Well actually YES !!!!! ..... Is it fun to build stuff, think outside the box and actually apply ideas into reality ?  Yes it is !!!!!   And that's the point, No less no more.

Scott

[oldpro]

Good work Scott. Very creative on how you went about the valve inlet . So it appears that between 50 and 65 % reduction in opening force seem to work best .

"Works best" is probably a premature term. There are only a few ratios documented so far and all have worked to a degree.  Start pushing the limits of force reduction via ratios and we'll find what doesn't work.

I’ve tried many many ratios and he’s right it’s between 50 and 65% based on power requirements

With all due respect, I understand how much r&d you must do behind the scenes, however I don't see a lot of publicly documented dimensions, specific data or internal pics from your testing with the rsterne simplified balance valve (SBV) version of the SS valve. So from a DIY perspective, it is good to see specific specs and results in this thread and in Bob's of what works and equally important what does not. 
I also understand there are commercial restraints your end too. But once again, in a DIY thread it should shown.

Trent go read threw Bobs thread youll see its 50-65% theres hard facts why i just dont go into great detail why but its apparent if you read bobs whole thread and by the way I had and operational simplified version long before he started the thread but I agree theres plenty to learn and if all goes well even the balanced valve will be a thing of the past soon more on that later. Scott excellent adaptation using whats at hand thats real world engineering. If you want to see a marvel of engineering look at the huben k1 or if you have had the privilege  lloyds diaphragm valve is quite amazing as well , So much to learn so little time.

[Blutroop]

Were do y’all get your peek from? Does this make the best poppet material, or just easiest to work with or something? Was recently studying the Lewis and Clark rifle and its leather poppet valve of course it’s only operating at around 800 psi though.

[Rocker1]

Bravo Scott Good job my friend. David

[Hobbyman2007]

Were do y’all get your peek from? Does this make the best poppet material, or just easiest to work with or something? Was recently studying the Lewis and Clark rifle and its leather poppet valve of course it’s only operating at around 800 psi though.

PEEK can be bought in rid form on Amazon , quite pricey . It’s great material for pipers but there’s a catch . It’s difficult to get it to seal when compared to Delrin or similar products .

TNT, I have also made quite a few and can assure you I didn’t just pick a couple numbers out of a hat. Anything over 65% and the valve blows open with very little hammer strike . Anything less than 50 and the dwell just isn’t long enough to make power efficiently. The problem with the ones I’ve made all had valve inlet issues I couldn’t figure out . Scott ‘s design looks to have solved that part .


Travis , by the sounds of it . I would say you’re working on a hammerless drop in valve . This should be very interesting .

[KnifeMaker]

I reserve PEEk fo puppets being used in high pressure applications. Delrin is better for low pressures as it deforms and seals much easier.  However, peek is much less prone to deformation and extending into the valve face, and is perfect for higher pressures.


Now If i only had the intelligence to understand the balanced valve builds. Or at least a lathe to build it. 

[FuzzyGrub]

Always impressed by the work and knowledge shared here on GTA.   Great work, Scott. 

[USAFANG6799]

Scott....you and the folks who contributed to this build are some pretty amazing hobbyist!
Amazing the talent that the GTA members have......very humbling to me as a spectator.

[oldpro]

I reserve PEEk fo puppets being used in high pressure applications. Delrin is better for low pressures as it deforms and seals much easier.  However, peek is much less prone to deformation and extending into the valve face, and is perfect for higher pressures.



 Michael is quite right peek is great in high pressure vessels to help get the poppet off the seat but will likely be problematic in a balanced valve where your cutting the clamping pressure down more than 50%. Delrin is a much better choice in my opinion and can be easily purchased from Amazon or EBay


Now If i only had the intelligence to understand the balanced valve builds. Or at least a lathe to build it. 

[Motorhead]

I reserve PEEk fo puppets being used in high pressure applications. Delrin is better for low pressures as it deforms and seals much easier.  However, peek is much less prone to deformation and extending into the valve face, and is perfect for higher pressures.



 Michael is quite right peek is great in high pressure vessels to help get the poppet off the seat but will likely be problematic in a balanced valve where your cutting the clamping pressure down more than 50%. Delrin is a much better choice in my opinion and can be easily purchased from Amazon or EBay


Now If i only had the intelligence to understand the balanced valve builds. Or at least a lathe to build it. 

Not sure what Travis was wanting to say or add here ?  But did want it known ... in a balance valve having the entirety of poppet head made from delrin WILL NOT WORK.  If you read my OP getting into the dynamics of where the pressure is and its effect on the parts as configured.  As stated I'm not sure PEEK is up to the task either

Ideally and how JSAR is doing the SS2 valves, poppet is 100% metal/s and comes to rest against a soft seat material which creates the required seal.  having the poppet head made of metal there is no chance for the internal pressure shearing off the 0-ring & tip within balance chamber.

[KnifeMaker]

Well now that makes perfect sense!