Simplified Balanced Valve

[rsterne]

Thanks for the additional dimensions, Brian, I am trying to figure out what the sealing diameter of the poppet is.... Do you think it seals near the OD, the ID, or pretty much all the way across the seat (which would by deduction be 0.025" across)….

That shot string, other than the first shot, is continuously falling.... Did you attempt to tune for a bell curve by reducing the hammer strike, or is that basically tuned for maximum velocity on the first shot?....

One other thing.... looking at the first photo you posted, the vent hole appears to be about 1/3 the diameter of the 3/16" stem, ie about a 1/16" hole.... Does that sound right, and is that the diameter all the way through, or did you have a smaller "metering" section anywhere?....

Bob

[Brian W Cook]

Yep that was a .062 hole .  Was a bugger drilling that far in the O1 stem .   Using some measurements of the hammer i figured it weighed 175 grams and i was using a .625 od by .062 wire spring with maybe 1-1/4 of stoke.
The main reason i never shot it anymore was its reservoir is made out of 1.25 x 1” id 6061 tube.   
Measuring the valve it’s close to .530 seat diameter.   

[rsterne]

Again, thanks for the information.... It turns out that your 0.375" balance chamber is exactly half the area of the 0.530" valve seat.... Time for me to head to the shop and finish off my new valve, which has exactly the same proportions....

Bob

[oldpro]

I dug my one and only shot string out of my tool box .   
This started out at 3000 psi using close to 21 ci of air . I think the 746 FPS first shot can be blamed on sticktion

I hope its not stiction thats what were trying to work around. Brian you are ahead of your time were just catching up!

[Brian W Cook]

I guess the most obvious thing would have been the lack of hammer bounce . Those last 15 shots would be impossible for a conventional poppet valve .   
I wish all of this internet connectivity was available back in 1986 when i was taking machine shop classes at night with full intentions of building a airgun to kill a deer with .   

[oldpro]

I guess the most obvious thing would have been the lack of hammer bounce . Those last 15 shots would be impossible for a conventional poppet valve .   
I wish all of this internet connectivity was available back in 1986 when i was taking machine shop classes at night with full intentions of building a airgun to kill a deer with .

No doubt!!! The things we could have done.

[PakProtector]

No doubt!!! The things we could have done.

Like buying Ford stock at $1.25/share. Then I could just retire, build my machine shop and learn how to make the most of it...
cheers,
Douglas

[rsterne]

I finally got back into the shop today and finished the new valve.... Here is the front end, showing the perforated mounting wheel for the thimble....



The thimble is free to move radially about 0.020" where it fastens to the center of the wheel, so that it can self-align with the poppet.... The back end has a much larger port than the previous valve.... You can see the vent in the stem down inside the exhaust port....



The throat is 3/8", and the stem is 1/8", so the area is the equivalent of a hole measuring 0.354", or almost bore area for the .357 cal and larger than all the other calibers that can fit on my Hayabusa Mk.II…. The exhaust port is 0.328", and the transfer port for the .357 will be the same size.... For the smaller calibers I will match the transfer port to the caliber.... The OD of the transfer port has increased to 7/16", so I had to drill the hole in the main tube out to match that....

On first assembly I had a small leak, so I took the valve apart, ran a 1/2" end mill (by hand) up against the seat, undercut the PEEK poppet by 3 deg. so that it only touches around the outer edge, and then lapped it with Solvol Autosol, cleaned everything and then burnished the poppet against the seat.... It sealed up just fine.... I started at 500 psi, there were no issues getting it to seal, and I dropped the hammer down the tube a few times to get it to burp.... It still wasn't leaking, so I filled it to 1000 psi, then 1500, 2000, 2500 and finally 3000 psi, which is the MSWP of this PCP.... Each time I dropped the hammer down the tube to fire the valve, and as expected as the pressure increased it took more hammer strike to get the valve to "pop".... There was no tendency for the valve to burp at pressures over 1000 psi, just a nice clean pop, and if I launched the hammer a bit harder, a very loud "BANG".... I am delighted that the valve seals up fine, and look forward to getting the gun built up so that I can test further....

I will be building a new SSG for this gun, it never had one.... Once that is done I will be able to find out how tuneable the valve is.... I have my fingers crossed....

Bob

[mann]

Nice work Bob looking forward to hear about some testing

[oldpro]

 Fingers crossed I hope hope hope it works and has no stiction or tendency to blow open. I really want it to work big time.

[Hobbyman2007]

Now you’re getting somewhere Bob. Can’t wait to see the results . I’m still trying to figure out how to make the thimble stationary in an Evanix valve housing . I’ll be sticking to close to 70% ratio to start and work my way from there , using Delrin until I prove it works .

[triggertreat]

Fingers crossed I hope hope hope it works and has no stiction or tendency to blow open. I really want it to work big time.

Best of luck my friend!  Many including myself are hoping you have major success here.

[rsterne]

No tendency to dump with a wide variety of "flung" hammer strikes.... more force = louder bark, and only one of them.... I actually have quite a few things to do before I can test, I have to mill out the receivers for the larger TP, make that new TP plus an SSG, and hope I guess right on the hammer weight and stroke....

Bob

[oldpro]

No tendency to dump with a wide variety of "flung" hammer strikes.... more force = louder bark, and only one of them.... I actually have quite a few things to do before I can test, I have to mill out the receivers for the larger TP, make that new TP plus an SSG, and hope I guess right on the hammer weight and stroke....

Bob

any chance you could test with a loaded hammer?

[rsterne]

I may be able to.... but my question would be why?.... An SSG or SSS with the hammer in free-flight is so much better for not bouncing, preloaded hammers have pretty much gone the way of the dodo, at least for me.... The exception is big bores where I couldn't get enough hammer strike and had to have preload.... Hopefully, the balanced valve will make that a thing of the past....

Bob

[oldpro]

I may be able to.... but my question would be why?.... An SSG or SSS with the hammer in free-flight is so much better for not bouncing, preloaded hammers have pretty much gone the way of the dodo, at least for me.... The exception is big bores where I couldn't get enough hammer strike and had to have preload.... Hopefully, the balanced valve will make that a thing of the past....

Bob

To see if a loaded hammer will cause Ill effects as this is what most people will do.

[rsterne]

If I can find a tune that is below the plateau and a spring that will allow some preload, I will try that.... Just preloading if you are already on the plateau will tell you nothing.... as that is exactly how you tune for hammer bounce with any valve.... First of all I want to see if I can get it to shoot properly, before trying to intentionally make it act up....

Bob

[MJP]

You guys have been busy. 
Not that I have been idle, just coming to a way different approach to this airgun deal but that is going to be another topic on a some other day. 

The most problems in this type balanced valves is the machining all the parts consistent and on same rotational axis, so that no binding occures.
After that it's just finding the right proportions for balancing.
The more balanced it is the less bellcurve there will be.

I personally can't figure the use of a bellcurve other than hunting off tethered.
But why not just use a bottle gun and reg?
And for a bench gun why bother to make a valve with other characteristics than consistency and power?
Velocity can be tuned with a regulator.
Just my 2C

Marko

[oldpro]

You guys have been busy. 
Not that I have been idle, just coming to a way different approach to this airgun deal but that is going to be another topic on a some other day. 

The most problems in this type balanced valves is the machining all the parts consistent and on same rotational axis, so that no binding occures.
After that it's just finding the right proportions for balancing.
The more balanced it is the less bellcurve there will be.

I personally can't figure the use of a bellcurve other than hunting off tethered.
But why not just use a bottle gun and reg?
And for a bench gun why bother to make a valve with other characteristics than consistency and power?
Velocity can be tuned with a regulator.
Just my 2C

Marko

Your correct Marco I’ve made 5 versions of this valve with different ratios and the further from non balanced it got the less stable and lower ability it got to tune it and I expected that the biggest issues are these. Is stiction going to happen and if it does the further from non balanced it gets the worse the effect will be the other problem is adjustablness unregulated as this will be where most people building big bores will need some type of adjustability and third and most important and a thing that happened to me when the ratio was over 70% I could bang the buttstock on the ground (not hard) and make the gun go off so if this works and doesn’t have these issues then I think it’s a good change. I suspect though threw my own testing to get any adjustment the ratio can’t be higher than 60% and to keep enough force to keep it closed safely well that’s also the same ratio. We will see I’m building my version today using those parameters

[rsterne]

An SSG should prevent you from being able to bang the gun around and make it go off, because you would have to hit it unbelievably hard to overcome the preload on the spring.... Having some preload on the spring, and the closer the valve is to balanced, the worse that would be, I would think.... A 60% ratio of diameters on this valve produces exactly the same amount of balancing (36% less hammer strike) as an 80% ratio of diameters on an SS Valve, so I can understand you being happy with that.... I'm just greedy because of the high powered guns, that are so hard to cock, that I am currently converting.... hence why I am looking toward that 50% reduction (70% diameter) on both types of valves....

Even with a Big Bore I like to have a small bell-curve, because I want to have 2-3 shots within a very narrow ES.... and it usually isn't possible to tether one while hunting.... If you only shoot at paper, then tethering is a no-brainer, regardless of caliber.... High power for a give caliber and regulation without a tether is generally not possible because you need to run high pressure (4500 psi bottles help there), and need a large plenum.... Again, you need a bell-curve when you run unregulated.... Most of my varmint rifles are tuned for a shallow bell-curve to give a few shots within a 1-2% ES off tether, which has the added advantage of putting your tethered tune just on the high pressure side of the peak velocity.... That makes the gun more efficient so you use less air.... Having said that, the rifles I shoot the most are regulated, but I still have a few unregulated PCPs that get a lot of use because they are so small and light by comparison to a bottle gun….

Bob