Pilot valve??

[sb327]

I had this idea awhile back and thought I’d throw one together to check function. I have heard mention of a ‘pilot valve’ and this is kinda what pops in my mind.

I made the test valve to fit my 7/8” tube on my sidelever breech. I know, I know, this type of valve is more for easy opening, power situations but I wanted to test it.

I’ve shot it several times. It resets perfectly in spite of no springs. Matter of fact, when I put it together, I had to make sure I held tube upright to keep the poppet assembly from falling into tube until I aired it up.

It has a declining shot string (of course).

What is surprising is I have it set to blow open just a smidge and it kicks out 50fpe avg for 10 shots with 45grainers. 3100psi down to 2400. Not the best efficiency but not just a pig. 24ish inch barrel, I’d have to measure for sure.

Cocking effort…..verrry little. Especially with the side lever. My arthritis fingers love it.

Anyway, just sharing an experiment here. I don’t think it’s some great revelation. Just a different valve to tinker with for me.

Dave

The last photo is just to show function, I kinda messed up on some ‘it doesn’t matter’ aspects. It’s NTS

[MJP]

Nice work David,
I have used pilot valve on first 20mm experiment. Works but I had some issues on hydro testing it and it exploded around 500 bar. So I went woth a different design.
Have something very similar designs somewhere but never got to make and test so thanks for beating me to it!
My version was inverted and pull type hammer and rear opening valve. But concept is the same.

Edit: oh yeah, put some sort of a buffer inside the main valve very stiff spring or rubber to stop it from cracking at the corner. POM is not as shock resistant as needed on opening. At least on bigger power it shatters. Don't as how I know.
Marko

[sb327]

It worked surprisingly well first time out. Thanks for checking it out and commenting.

I was looking last night at the Leishy 2 patent and it appears he does pretty much the same thing but vents to atmosphere. I think. I have a hard time understanding patent lingo sometimes.

I’ll be testing more on this in a couple weeks. I’ve decided to bottle/reg feed my test (ugly) sidelever mule.

Dave

[Rob M]

very cool.. whats the total travel on the shuttle  part thats slams open ??

[sb327]

Right now I have it set about a 1/16”. But…what inertia it has on full open MAY carry the adjustable cylinder forward some and allow for more than 1/16” full open. Like I do with my bv’s, I don’t leave a solid surface to hit, it can float.

I only adjust hammer to crack the pilot and start the cycle. I also left a pocket in front of the pilot poppet to keep it from hitting anything.

Dave

[sb327]

Marko,

This is glass filled pei, not very shock resistant either.

Dave

[MJP]

Thats nice thinking to let the chamber reverse to reduce the impact.
I would like to see the Leshiy 2 patent info.

Marko

[sb327]

This is what I found last night

https://uspto.report/patent/app/20200248826

It really only addresses the concept and discusses a hammer as a triggering mechanism. In the actual L2, it uses hammer less design and your finger actually vents the chamber.

Dave

[MJP]

Thanks,
Took a look about the exploded view of L2 parts and it's clear there is no hammer.
It makes the trigger pull feel some what  mushy when actually firing the gun.
Had the privilege to test the new L2 at one occasion.

And if you have the habit of pulling the trigger and not letting go as the shot is taken the valve will leak. You need to pull and release.
Other than that it was really a fun thing to test.
So small hammer is a slightly better approach if wanting a really good trigger.

Marko
Edit: parts pic


Very laborious valve frame to make and many things to go wrong.

[sb327]

In this valve, the main closing force is determined by stem diameter. To a less extent, sail effect.

The single dynamic o-ring should not suffer as much from stiction due to being pressurized equally from both sides while sitting.

I am using a standard hammer at present. I believe I will make a light hammer to start the shot but can ‘get out of the way’ quickly. I do not want hammer mass or strike determining the shot cycle. Then I can tune via pressure, chamber size and vent.

Just kinda thinking on paper here.

Some nominal dimensions

Main throat   .250”
Main poppet  .312”  x  .375”
Pilot stem    .125”  thinned in flow areas
Pilot poppet  .160”
Vent             .018”

I started with the small vent because I didn’t know how fast the chamber would fill from the throat area. It has to be small so it doesn’t outrun the dumping effect of the pilot.

I wonder how much movement the pilot poppet needs to effectively dump the chamber?  I’ll need to test that.

Dave

[MJP]

Just a mm or two, the surface are of your port determines the lift of the valve head.

Marko

[sb327]

I’m still messing with this as time permits. The valve overall has not changed, but I have made a couple of tweaks.

I will say, I’m VERY EXCITED with the results so far. It is working far better than I had hoped.

My main focus though has been getting an ls motor in a 1954 bel air. That’s been pretty fun too.

Slow going but progress is being made on both projects.

Dave

[tronickero]

Hello david

Amazing design and good machined, frankly I have looked at your valve for several minutes and I can not understand how it works, could you explain how is the operating cycle? , please

Greetings from Chile 

[sb327]

Hopefully I can explain.

So look at the oring in my sketch. When valve is ‘ready to fire’, the pressure on both sides is equal. The small chamber to the right of oring receives that pressure from the tiny vent hole in the drawing. It is held from escaping through the main poppet by the small head (I will call this the pilot poppet) on the stem. The stem is free to move inside main poppet.

When stem is struck, it releases the hpa from the chamber to the right of the oring. This creates the pressure differential that blows the main poppet open. The pressure rises in the throat, causing a closing force on the stem and drags the pilot poppet back left. This creates the closing force on main poppet with some delay due to the hpa needing to travel through the vent to fill chamber again.

Hope that helps. Let me know if not. I’m not the best explainer sometimes. And even I am not 100% on all the dynamics at play here. I just know it works well in my build.

Dave

[tronickero]

Hopefully I can explain.

So look at the oring in my sketch. When valve is ‘ready to fire’, the pressure on both sides is equal. The small chamber to the right of oring receives that pressure from the tiny vent hole in the drawing. It is held from escaping through the main poppet by the small head (I will call this the pilot poppet) on the stem. The stem is free to move inside main poppet.

When stem is struck, it releases the hpa from the chamber to the right of the oring. This creates the pressure differential that blows the main poppet open. The pressure rises in the throat, causing a closing force on the stem and drags the pilot poppet back left. This creates the closing force on main poppet with some delay due to the hpa needing to travel through the vent to fill chamber again.

Hope that helps. Let me know if not. I’m not the best explainer sometimes. And even I am not 100% on all the dynamics at play here. I just know it works well in my build.

Dave

Thank u Dave, i understad perfect the idea 

[customcutter]

Dave, I'm looking at your pilot valve again.  The allen head screw on the right hand side, does it only adjust the amount of travel, and therefore the amount of air used?  Also, the approx. .250" hole at the top, is that the exit hole for the air to go to the transfer port?  Where does the HPA enter the valve?  Thanks, Ken

[sb327]

Yes, Allen head adjusts the position of the balance chamber and therefore the amount of ‘blow open’ effect.

Yes, the large hole is the exhaust (transfer port).

The air enters from the cutout area to right of large oring. It’s hard to tell from the picture but the smaller od (where the Allen screw is) continues into cutout area.

Hope that helps. I need to get back messing with this one. My second pilot valve build has my hobby attention (what little I’ve been getting) right now.

Dave

[customcutter]

Yes, Allen head adjusts the position of the balance chamber and therefore the amount of ‘blow open’ effect.

Yes, the large hole is the exhaust (transfer port).

The air enters from the cutout area to right of large oring. It’s hard to tell from the picture but the smaller od (where the Allen screw is) continues into cutout area.

Hope that helps. I need to get back messing with this one. My second pilot valve build has my hobby attention (what little I’ve been getting) right now.

Dave

Thanks Dave, I'd like to try building one (eventually).  I think I finally understand it now.  In the first picture the piece on the right hand side has a small hole drilled in it.  Are there more than one? As you said if that is where the air enters it is definitely NTS.   Does the small hole align in the cut out area as well?  From the pic it looks like it would but didn't see it in the assembled pic. 

I was researching building a .22 slug gun for 100yds plus and ran across this thread.  Then later found another that said that .22LR barrels are not the correct size for air guns.     Apparently they are closer to .223 than .218.  Any recommendations on a cheap barrel?  Thanks again, Ken

[sb327]

That tiny hole is subject at all times to plenum air (cutout). It is an .018” vent to allow chamber to fill on closing.

As for barrels, about the best for airgun caliber slugs is a lothar. Cheap, not real sure. About any without a choke.

Dave