Simplified Balanced Valve

[PikeP]

I think I may have a way to measure the actual valve lift.... If it works, I will give you a table of lifts at various SSG Gaps and two tethered pressures....

Bob

Bob that is fantastic..I'll eagerly await your results and cant wait for you to share the method. Any and all data is useful!

A 1,000,000 fps camera is all we truly need to get the perfect dwell and lift model that'll give us micro second resolution

[PakProtector]

I'd still use high quality metal rated for HPA as itll allow thinner walls that reduce volume taken away in the valve.

What steel's are 'rated for HPA'? Or for that matter, any metal? Are you serious?
cheers,
Douglas

Are you serious? Do your own research...rating for hpa would be based on Tensile strength and wall thickness and can be nearly any metal, provided you size it right...I was vague  because I'm not going to go through a list of every element in earth comparing tensile strengths and thicnkess... thats not what I signed up for...if you're building this valve or anything to do with HPA then that is YOUR responsibility..

Everything I build is made from rated materials then...thanks.

No need for 1,000,000 fps...what you do is interleave. Or with one, you just adjust the start, and repeat.
cheers,
Douglas

[PikeP]

Bob, does Lloyd's sheet have a coefficient of diffusion factor? If not I highly recommend integrating one for low lift conditions and probably all around. If he already has it then that's awesome. Ficks law explains why I argued  the pellet moves at a later time then you think. At the time it was a concept in my head till I researched it..

[rsterne]

Mike, Lloyd's spreadsheet, as I said, works on Newtonian physics, good ol' F=ma (or rather a = m/F)….

Well, guys, I Rube Goldberged together a method to make direct measurement of the lift on my Hayabusa…. I couldn't do it through the back because the SSG was in the way.... and then in the middle of the night I woke up and smacked myself in the head.... This gun has an EXTERNAL COCKING HANDLE mounted directly on the hammer....  …. All I had to do was make an indicator that showed how far ahead of the rest position (against the valve stem) the handle moves during firing.... Here it is....



The brass tube is sitting against the breech band so it can't slide forward, and held in place by two cable ties and a couple drops of glue.... The aluminum tube slides inside it, and an O-ring slides on that inner tube.... You slide the O-ring forward before you cock the gun, so it rests against the end of the brass tube when the end of the aluminum tube is against the cocking handle, while the hammer sits against the end of the valve stem.... You cock the gun, load a bullet and take aim through the Chrony, fire it, the cocking handle slides the aluminum tube forward, and the O-ring slides back to create a gap (as shown in the photo above) between itself and the end of the brass tube.... You push the aluminum tube back against the cocking handle, which you force to sit tight against the end of the valve stem my putting a turn of preload on the SSG.... Measure the gap between it and the end of the brass tube, and you know the valve lift.... I checked to see if firing a second time slid the O-ring back further and found that it didn't, within my ability to measure the gap.... I was using the 77.2 gr. bullet in the .257 version for this testing.... I was able to measure the lift to the nearest 0.005".... Here are the results....



The lift at 3000 psi went from 0.125" at zero gap down to 0.040" at 6 turns out, and then dropped to zero lift at 8 turns because the gun would not fire at that gap.... The velocities were quite close to my previous data, so the lift indicator device I am using is not slowing the hammer enough to worry about.... Trying a second shot after the O-ring had already moved on the aluminum tube made no consistent difference to velocity or O-ring position.... I then tethered the gun to my other regulator, which is set at 1850 psi, and repeated the tests....

This series was quite interesting.... I expected to measure greater lift, because with only 62% of the pressure, you only have 62% of the opening and closing forces for the hammer to overcome.... That was indeed the case, the lift was 0.190" at zero gap, decreasing to 0.110" at 6 turns of gap, during which time the velocity sat solidly on the plateau at just over 800 fps.... The velocity dropped off over 100 fps to 689, and the lift decreased to only 0.035", during the next 2 turns on the SSG.... This means that the spring I am using for 3000 psi is way too strong at 1850 psi.... I suspect if I used a much lighter hammer spring I would be able to get a decent adjustment range at the lower pressure.... 

If you look at the lift where the velocity started to drop at 1850 psi, it looks like it was about 0.125".... That is the same as the starting lift at 3000 psi.... This means that if the lift exceeds that amount, you are basically up on the plateau, you get no further velocity increase at either pressure.... That happens to be 1/3 of the throat diameter.... This leads me to conclude that if I allow a maximum poppet travel of 0.150", that should be sufficient.... I currently have 0.250" of balance chamber height in the thimble, so I can put in a spacer to make the volume smaller.... It should make quite a difference in the tuning range of the valve, I would think.... It would also be a good idea if I do that to make sure that the hammer can't drive the poppet into that spacer, as it could break things.... I am going to ponder removing the valve and changing these thing before I fit the .308 cal barrel, which is now ready for testing.... I'll ponder that overnight.... It's nice to know how much lift I have to allow for, and 0.150" should be plenty....

Bob

[PikeP]

I have told enough for those that can listen and understand basics that can build similar valves that I have made, I just don't make pictures and diameters available in open forum.

It's ticking me off that some of the manufacturers use forums as R&D and then make profit out of it, patenting someone's ideas!

Marko

You weren't wrong by having these feelings or beliefs and I whole heartedly understand why now. Hindsight is 20/20

[rsterne]

From the very first post of this thread, the intention was to bring balanced valves into the limelight, and to develop them openly.... Little did I know that it was first tried over 17 year ago, and the guy that did it, Brian, shared what he did in this thread!!!!…. 

Anyways, there is the idea for a simple balanced valve, with minimum parts, that is relatively easy to machine.... By putting this out in the public domain, I hope to encourage others with the skills and equipment to jump on the train and let's get these balanced valves out of the station, and roaring down the track, into the mainstream of PCP airgunning….

If that results in some companies making a buck off them, so be it, we all benefit in the long run.... I am very proud of what all of us have accomplished in this thread, and I thank each and every one of you for your input.... We still have a lot more to learn, but we are well on the way.... Congratulations, all.... 

Bob

[oldpro]

From the very first post of this thread, the intention was to bring balanced valves into the limelight, and to develop them openly.... Little did I know that it was first tried over 17 year ago, and the guy that did it, Brian, shared what he did in this thread!!!!…. 

Anyways, there is the idea for a simple balanced valve, with minimum parts, that is relatively easy to machine.... By putting this out in the public domain, I hope to encourage others with the skills and equipment to jump on the train and let's get these balanced valves out of the station, and roaring down the track, into the mainstream of PCP airgunning….

If that results in some companies making a buck off them, so be it, we all benefit in the long run.... I am very proud of what all of us have accomplished in this thread, and I thank each and every one of you for your input.... We still have a lot more to learn, but we are well on the way.... Congratulations, all.... 

Bob

I agree sharing is how we all learn. When Brian said he built his 17 years ago for me it was like saying they found computers in the pyramids  thousands of years old  😀

[MJP]

Now we just wait for the Hammer to come out, now they have a working solution at hand.
Its down to the most basic things of human nature that makes me mad, greed.
I do respect your decision to do it openly for progress, let's just hope it won't come back to bite us in the end.

There are people just for this type of forums, scavenging information and patenting everything just that everyone else needs to pay to them to use "their" inventions.
People too stupid to make anything without directions or blueprints but sly enough to profit from others work when handed out in a silver platter.
Yes I have seen it, from too close.

Marko

[oldpro]

Now we just wait for the Hammer to come out, now they have a working solution at hand.
Its down to the most basic things of human nature that makes me mad, greed.
I do respect your decision to do it openly for progress, let's just hope it won't come back to bite us in the end.

There are people just for this type of forums, scavenging information and patenting everything just that everyone else needs to pay to them to use "their" inventions.
People too stupid to make anything without directions or blueprints but sly enough to profit from others work when handed out in a silver platter.
Yes I have seen it, from too close.

Marko

I’d like to see if their patients are infringements on my older balanced valve patent and maybe this is why they haven’t released it? Hhhmmmm

[Motorhead]

Why is it when a TEAM does much good ... there are those in said team that feel slighted

Great job guys !!  take a bow and be proud of your contributions .... take a chill pill or have a beer with a buddy and smile .... PLEASE !

[MJP]

Well I wasn't born yesterday, so I view my world the way I see fit.
Think back a decade or two, and I would have seen it your way, now its all about the big eating the small that has the ideas.

Tell me Scott that the world hasn't changed in that time and for the worst.

The team might have this one, but it's the corporate bosses who'll have the last laugh on this one also.

More money and better lawyers is the name of the game these days.

I'm just a bystander, my contributions don't really matter much at least to me.
I gave my all one time and there's a company logo on it somewhere.
Its called business you see, that's what they tell you.
Sorry for the ot.

Marko

[MJP]

Bob how large port did you try for the balancer?
When you have two or three bigger ports to fill the chamber immediately after valve opening you'll endup with hammer driven dwell like regular non balanced poppet.
I found that not good for my application as I don't care for bellcurve, but for you it'll work.

Marko

[PikeP]

All data approximate. 2 small bore revisions, cannot comment as to any potential end results or towards the practicality of either models. Good luck building old friends..I have a few different approaches to this valve but I think itll all figure itself out in time. 

[rsterne]

Marco, I currently have a single 0.052" (1.32mm) vent.... I am going to try reducing the volume in front of the poppet by installing a spacer in the balance chamber, since I have determined I allowed for more lift than I need....

The valve is perfectly usable for my needs the way it is now.... Ideally what I would like is a balanced valve on opening that reverts to a conventional valve on closing.... That would be the best of both worlds, IMO.... and the hammer strike would still be reasonable....

Bob

[rsterne]

Mike.... Those look good.... I find the colours quite difficult, in particular the grey background makes the red hard to read on the screen for my colourblind eyes.... 

There is a LOT of data there, I would have to print them out to try and absorb it all....

Bob

[Motorhead]

Well I wasn't born yesterday, so I view my world the way I see fit.
Think back a decade or two, and I would have seen it your way, now its all about the big eating the small that has the ideas.

Tell me Scott that the world hasn't changed in that time and for the worst.

The team might have this one, but it's the corporate bosses who'll have the last laugh on this one also.

More money and better lawyers is the name of the game these days.

I'm just a bystander, my contributions don't really matter much at least to me.
I gave my all one time and there's a company logo on it somewhere.
Its called business you see, that's what they tell you.
Sorry for the ot.

Marko

I'm 60 and been around long enough to see exactly what you state ... But then again YOU DO HAVE A CHOICE to fall into feeling the victim or empower yourself to continue in doing what you love to do in spite what others may do with your contributions what ever they may be.  I'm sour enough in my age to have some hard feelings too .. but have made the choice in my life to share what i can to the benefit of those who know less and be humble enough to listen & learn from those who know more.  This Life trip we're all on is a one way journey and getting caught up on what's just and fair is a waste of ones energy & talent. 

JMO ...
Scott

[triggertreat]

Mike.... Those look good.... I find the colours quite difficult, in particular the grey background makes the red hard to read on the screen for my colourblind eyes.... 

There is a LOT of data there, I would have to print them out to try and absorb it all....

Bob

I agree...Separate out the sections with different colors for easier reading.  Kinda something along these line, but make it your own.  Great graph!  A little over my head, but Looking forward to it to learn from.

[oldpro]

Pastels work great for this sort of thing. Looks real good and data flow looks good. Excellent work

[rsterne]

 I took the gun apart and made a spacer for inside the thimble to fill the volume I don't require.... Here it is sitting on the valve spring....



The front part reduces the diameter of the spring chamber from 1/4" to 13/64".... and the flange portion takes up 0.090" of length, to reduce the maximum poppet movement from 0.240" to 0.150".... I determined yesterday that I don't need more than about 1/8" of lift.... This spacer will reduce the volume of the balance plus spring chamber (when the volume of the spring and seat are deducted) from 0.52 cc to just 0.29 cc.... When the poppet is open 0.090", like it is when I have 2 T of SSG Gap, the volume is further reduced by 0.11 cc, which means the balance chamber volume that needs to be filled through the vent drops from 0.41 cc to just 0.18 cc.... nearly a 56% reduction.... This should make a big difference in the tunability of the valve....

I still have to shorten the poppet stem so that the hammer can't drive the poppet into the space and break something.... and I plan to add another O-ring to the flange on the large end as a thicker bumper for added protection....

Bob

[Brian W Cook]

My inspiration was back when LD built his piston assist valve . Other than thinking he put a piston between the valve and the hammer i had no idea how it was configured.    I think i started to build a valve going that direction but decided to try and simplify it a bit and i started drawing up stuff .   I think the patent idea crossed my mine once but i was working night shift and it seemed like a lot of trouble.   
I love all the nice compact versions you guys have came up with .