GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: jackssmirkingrevenge on November 22, 2020, 02:34:59 PM
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I read through this thread (https://www.gatewaytoairguns.org/GTA/index.php?topic=158367.0) recently and it had me looking at the Huben "hammerless" valve in more detail.
This is the manufacturer's animation:
(https://i.imgur.com/ufIaLpr.gif)
I made my own simplified animation of how I understand it works:
(https://i.imgur.com/a2DDug6.gif)
A two-part piston held by a sear seals the breech.
When the sear is tripped by the trigger, the piston can move back allowing air to flow out.
If that was the end of it then the entire chamber would be dumped.
However the is a second valve that separates the de factor firing chamber from the main reservoir.
This is normally held open by a spring but the air flow forces it closed, choking the flow.
This allows the pressure to drop in the firing chamber, and the piston can re-close and be caught by the sear.
The firing chamber then pressurizes again and as the firing chamber and reservoir equalize, the flow choking valve opens again.
The cycle can then be repeated.
Another clever thing is that the drop in pressure is linked to a piston that indexes the rotating magazine.
It struck me that it is something I had been playing with more than a decade ago (https://www.spudfiles.com/viewtopic.php?f=5&t=12302&start=15):
(https://i.imgur.com/jkM1N0z.gif)
That didn't work very well in practice, the stroke of genius is the addition of the choking valve to enable the piston to cycle.
In my naivete I thought that by simply having a low flow compared to the outlet it would do the trick, but obviously a dynamic valve is needed.
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That is however just an aside, the reason I was looking at the Huben is because it can apparently achieve quite high levels of muzzle energy as a result of its unconventional valve.
It seems to me that this is largely due to the axial flow directly into the breech. If I understood correctly, there is no indexing of the pellet into the barrel, it is fired directly from the magazine.
I was therefore wondering if this would be a good way to go about maximizing power:
(https://i.imgur.com/NnQsKV1.png)
The hammer held by the sear knocks open a slightly balanced spool when released.
The pellet itself could be in a tight fitting sliding block in the same manner of the Girandoni action:
(https://i.imgur.com/LEBRPhb.jpg)(https://i.imgur.com/d7Oa6kL.jpg)
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I studied those animations for a while trying to wrap my head around it.
One thing I noticed though is how the air pressure is used to seal the chamber.
Thanks for trying to explain what you understand of it.
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Just my 2c here...don't take it too critically
These direct flow valves are nothing new, so stirring your wits up about how to design your own direct flow valve is just unnecessary if you're trying to close any large gaps between current potential power outputs in valves already accessible in quite a few mass produced pcp's, and whats not available...
The power difference between direct and indirect flow valves is in my opinion marginal and easily calculable, and requires design challenges to overcome just for the minor benefits, such as no magazine, or a magazine you cannot remove. Sure if you design the breech to accommodate both a direct flow valve and a removable magazine that would be a small step in the sense of convenience but not so much as achieving power levels that haven't yet been achieved....I believe leishy 2 comes closest in this regard but still has an intricate magazine that I am not too educated on as of right now.
That said, the largest power jump still awaits being made into a consistent and reliable piece of tech, and direct flow valves ain't it, additionally I wouldn't call this a 'better flowing valve' so much as 'designing an alternative direct flow valve'...again, don't take my words too critically but do assess them accordingly :)
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additionally I wouldn't call this a 'better flowing valve' so much as 'designing an alternative direct flow valve'
I don't disagree, it was the title of the post I linked to that started this train of thought.
The power difference between direct and indirect flow valves is in my opinion marginal and easily calculable, and requires design challenges to overcome just for the minor benefits, such as no magazine, or a magazine you cannot remove. Sure if you design the breech to accommodate both a direct flow valve and a removable magazine that would be a small step in the sense of convenience but not so much as achieving power levels that haven't yet been achieved.
There definitely isn't the sort of power gain you would see from bumping up the pressure for example, but in practice PCPs that eschew traditional geometry like the Huben and Air Force series do seem to have a significantly higher muzzle energy potential, so for the amateur tinkerer perhaps more worth looking at.
Looking at the previous design I posted, it would most likely open easily and stay open.
Perhaps reversing the movement of the valve would do the trick:
(https://i.imgur.com/jKC6TAg.png)
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As drawn .... IMO really poor flow dynamics having far too much Zig-Zag in flow direction AT and downstream of the poppet/seat.
Am liking the potential of a single shot valve tho offering similar attributes.
It is the IN-LINE architecture of having the poppet behind pellet, loading etc that I'm thinking about ???
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the " spool through a block " is a really good design i believe FX used some years ago on a royale.. But having the firing pressure in line with the pellet firing from directly behind it is slightly better.. I feel like design 1 would be easier to machine , and get it to seal.
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As drawn .... IMO really poor flow dynamics having far too much Zig-Zag in flow direction AT and downstream of the poppet/seat.
I'll grant you that the flow in option 1 looks better than the one in option 2
(https://i.imgur.com/VyAMOKX.png)
My concern would be that once open, poppet would want to stay open, it would probably need a choking valve like the Huben to reduce the flow sufficiently for the poppet to reseat.
Am liking the potential of a single shot valve tho offering similar attributes.
It is the IN-LINE architecture of having the poppet behind pellet, loading etc that I'm thinking about ???
I see two practical options, either the sliding/falling block mentioned above, or a coaxial tube like in the AirForce series:
(https://i.imgur.com/T6SrnEUl.png)
For my purposes single shot is fine, but the falling block could be replaced with a indexable linear or rotary magazine
I feel like design 1 would be easier to machine , and get it to seal.
Both designs could be made to seal easily using pressure differential depending on the diameter of the o-ring seal on the other end of the poppet. The difference is what happens after firing, in the first case the poppet is essentially a balanced valve without an equalization hole and gas pressure is going to want to prevent it from closing.
Just to frame this discussion, I basically forked out for an FX Streamline as a "boutique" .22" which means that I now have a Benjamin Maximus that can serve as the basis for something bigger in caliber, and I want to do something more radical than simply enlarge the existing valve design.
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The Crosman Pell Master 700 has an inline valve that uses a flow through hammer, it looks interesting.
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The Crosman Pell Master 700 has an inline valve that uses a flow through hammer, it looks interesting.
Interesting indeed, by most accounts it seems it was fairly powerful.
The loading issue was resolved with a "tap" style rotary breech:
(https://i.imgur.com/9tVWdU4l.png)
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(https://live.staticflickr.com/65535/50641682766_95da18e07d_c.jpg) (https://flic.kr/p/2ka2RXu)jacksdesign (https://flic.kr/p/2ka2RXu) by murphyrobert9 (https://www.flickr.com/photos/56743574@N07/), on Flickr
on this design , for the lower air res ( the main tube i assume ) Would it be beneficial to have a simplified check valve between the res and the firing chamber where as it fires, the " master check valve " closes for a split second allowing the poppet to start moving in the closing direction? For whatever reason , I can see the flow over the poppet actually keeping it open. ( unless interrupted
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on this design , for the lower air res ( the main tube i assume ) Would it be beneficial to have a simplified check valve between the res and the firing chamber where as it fires, the " master check valve " closes for a split second allowing the poppet to start moving in the closing direction? For whatever reason , I can see the flow over the poppet actually keeping it open.
That is my feeling, I am almost certain it would just jam open. The "master check valve" is basically what the Huben does, and regulating the closing of this valve is how power is tuned. A very interesting avenue of investigation.
In the interest of efficiency, the firing chamber size should be the minimum to allow for full flow, and the check valve should also be sized accordingly.
Side note, not sure you meant to link back to your flickr account with image link but freakin shredded bro, nice work!
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lol , thats embarassing .. not bad for 39.. ;D
anyway , i think uve got a pretty solid design pretty much laid out. Just need to plan out the " flow interrupter " and how it will be adjustable once the gun is assembled .
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I wonder if one couldn't put a balance chamber at the back of the poppet, vented though the stem like the balanced valves now commonly used... That would give the net closing force; the valve opens to fire; the balance chamber to the rear behind where the hammer strikes then fills from a vent drilled through the stem to the "barrel" end of the poppet, and thrusts the valve shut.....
Just throwing it out there,
Jesse
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This is all good discussion which is very interesting to me. I am following along with interest.
I have a hammer less valve that I am developing and have proven the concept of it working. I have made some design changes to the initial drawing I’m posting here. And have more to make.
When looking at this design, please keep in mind the shuttle is to the far left when valve closes. So this is not the same as a dump valve. One change I have made is the ‘regulated air’ input is quite large now and feeds from a large storage.
This design, like those mentioned here, does depend on a pressure drop within the works somewhere to function. I feel the biggest issue for efficiency is to keep that needed drop as low as possible.
So far I have been able to achieve a 1.1 efficiency.
I have made my design work with conventional trigger and solenoid fired.
Keep up the good work here.
Dave
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lol , thats embarassing .. not bad for 39.. ;D
7 out of 10 US adults over 20 being overweight is embarrassing, good on you for putting the work in.
Just need to plan out the " flow interrupter " and how it will be adjustable once the gun is assembled .
This is how I would see it, an adjustment screw alters the distance between the choking valve and seat:
(https://i.imgur.com/a09hmOq.png)
The Huben system seems to be a little more complex than this but I didn't quite get how it works exactly.
I wonder if one couldn't put a balance chamber at the back of the poppet, vented though the stem like the balanced valves now commonly used... That would give the net closing force; the valve opens to fire; the balance chamber to the rear behind where the hammer strikes then fills from a vent drilled through the stem to the "barrel" end of the poppet, and thrusts the valve shut
Something like this? It adds a level of complexity but I think it would work:
(https://i.imgur.com/HnOQLDW.png)
This design, like those mentioned here, does depend on a pressure drop within the works somewhere to function. I feel the biggest issue for efficiency is to keep that needed drop as low as possible.
Very interesting, thanks for sharing! It seems there really is some merit to this idea of shutting off the flow for the sake of efficiency.
I am reminded of the way airsoft blowback mechanisms work, air from the poppet is initially allowed to flow through the barrel to fire the BB but the barrel is eventually blocked off by a shuttle valve, allowing pressure to build up in the blowback chamber to cycle the action.
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My thread is here https://www.gatewaytoairguns.org/GTA/index.php?topic=175248.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=175248.0)
I think that balance valve type setup shows some great potential!
Dave
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i like both drawings , SBs vented idea, and the huben like adjustable check valve in the res.. Either could work.. But id prefer ( personally ) to be able to make the minor tweaks without a teardown..
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My thread is here https://www.gatewaytoairguns.org/GTA/index.php?topic=175248.0 (https://www.gatewaytoairguns.org/GTA/index.php?topic=175248.0)
Thanks, very well done! I added a little animation, let me know if it's accurate.
i like both drawings , SBs vented idea, and the huben like adjustable check valve in the res.. Either could work.
There isn't a clear "winner", but the tweakability of the choking valve is quite alluring.
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I think you would need to vent the middle to atmosphere
I think you could make the vent large and come in from the back with a tapered adjustment screw.
This is a neat idea.
Dave
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I think you would need to vent the middle to atmosphere
Doesn't it vent to atmosphere through the barrel?
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Not between the orings. Where the arrow is.
And my apologies, my wording messed things up.
I meant to say it needs a vent to atm where red arrow is. Let’s call that vent 2. That area always needs atm, and the barrel vent does not see atm while the valve is open and a pellet is still in barrel.
Your vent through the poppet, let’s call it vent 1, COULD be made large but adjustable by coming from the back (red line) with a screw adjuster. That way you could tune how fast it closes.
I hope that clears that up. Sorry for the confusion.
Dave
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I think I understand Jack's first drawing in Reply #14, with the red valve able to stop the flow once the barrel pressure drops, to prevent dumping the entire plenum/reservoir.... Having it adjustable, so that you can control the amount of pressure drop makes total sense.... My concern is that if you allow too much flow past that valve, the pellet may reach the muzzle before it closes (terrible efficiency).... and conversely, if you have the clearance too small, it will slam shut very early in the shot cycle (low power).... Once it shuts, all the FPE from that moment on must come from the air trapped above it, and the pressure in that small volume will drop very quickly (think tiny plenum)....
It would appear to be a pretty fine balancing act, trying to create a dump valve where you can adjust the volume of air being dumped.... Might be simple in concept, but difficult to achieve in practice.... and ultimately restricted in FPE unless you will accept low efficiency.... either a one or the other choice if you are off just a bit in the adjustment and function.... JMO....
Bob
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I hope that clears that up. Sorry for the confusion.
I think I understand, something like that?
(https://i.imgur.com/5goOcqE.png)
It would appear to be a pretty fine balancing act, trying to create a dump valve where you can adjust the volume of air being dumped.... Might be simple in concept, but difficult to achieve in practice.... and ultimately restricted in FPE unless you will accept low efficiency.... either a one or the other choice if you are off just a bit in the adjustment and function.... JMO....
Thanks for chiming in Bob, agree that it sounds like it would be extremely fiddly.
One thing that struck me with the Huben however is that you're not really creating a separate firing chamber/plenum that is dumped for each shot while being shut off from the main reservoir.
(https://i.imgur.com/bI6GwGr.jpg)
The area shaded in red is the actual air volume between the outlet valve and the choking valve, it's extremely small - and there is no way dumping that tiny volume is going to give you 80 ft lbs in 0.22". When you think about it, it makes sense that this volume should be as small as possible, because once the chocking valve actuates, anything past it is going to be dumped and you want to keep that to a bare minimum for the sake of efficiency.
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That’s it!
That vent is need for proper operation but also as a safety. If forward oring leaked, it would have a bias to open the valve.
I may give that valve a go sometime. I think it has potential.
Dave
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I may give that valve a go sometime. I think it has potential.
It certainly seems like it would be ideal for big bores. The spool does not need to have a lot of bias so it can be opened with a relatively weak hammer, and since the flow goes direct in line with the barrel you do not have a lot of transfer volume.
I wonder to what extent the adjustment screw would allow you to fine tune the closing speed though.
Here is the expected firing cycle animated for completeness sake:
(https://i.imgur.com/9C02CNo.gif)
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My opinion would be that it (the vent) needs to be large. This would accommodate very fast closing.
Then, the taper on the adjustment screw be long and slender. Then you would have an adjustment that would not be super sensitive and could essentially be choked to where the valve would completely dump the reservoir.
I agree that this could be made to operate with a very light hammer and delrin or maybe ptfe for the seat.
Dave
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That is definitely an interesting setup... One other potential benefit of such a design (if it could be made efficient and tuneable, which has yet to be actually done), is the now extremely short action of the gun... If you look at the average tube, how many inches are lost to valve/hammer/spring/power adjuster that could be minimized with a setup like this? Could make for a big reservoir and long barrel in a short gun, and the action would only need to cock a very light spring and advance the mag...
Intriguing to say the least,
Jesse
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Jack I agree that in the Huben the vertical valve must be staying open long enough to allow enough air through to produce 80 FPE.... This means the efficiency is going to be related to having that valve close at exactly the right time so that the bullet has absorbed much of the energy in that air, but before it exits the muzzle.... I'm sure it can be done, but a lot of experimentation would have taken place to achieve exactly the right balance, I think.... and consistency of that dwell will be critical to producing a low ES....
Achieving the power should be relatively simple, if efficiency is not an issue, simply hold the valve open until the bullet exits.... That would be even easier to achieve because the barrel pressure would drop suddenly at that point, slamming the valve shut.... Basically a dump valve, being closed immediately after the bullet has exited.... This results in extremely low ES, but in my experience, also results in about 0.5 FPE/CI, however.... Closing the valve when the bullet is only halfway to the muzzle can give you about 0.9-1.0 FPE/CI.... even shorter dwells are required to get what these days is considered acceptable efficiency.... The shorter the dwell, the more consistent it must be or the ES suffers....
The theory is fine, but building it and achieving the power, efficiency, and low ES, all at the same time, will be the challenge....
Bob
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I'm sure it can be done, but a lot of experimentation would have taken place to achieve exactly the right balance, I think.... and consistency of that dwell will be critical to producing a low ES...
No doubt that the choking valve would need to be extremely and finely adjustable.
I am still not clear on how the Huben does it exactly.
The chocking valve has its own return spring that is not adjustable:
(https://i.imgur.com/H2CTSE2.gif)
There is however a second adjustable element that is used for tuning, I haven't figured this out yet.
(https://i.imgur.com/xdLMQ6X.gif)
There is a pneumatic element to it, the bottom of the pin seems to have a seal in the housing and possibly a bleed hole at the base:
(https://i.imgur.com/WhWA4Ec.png)
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From how I understand it
The spring at the closing valve only effects it once the chambers are equalized after a shot. It just brings the closing valve back open.
The red spring is a lot stronger. It is biased to close the valve. When the valve is at full pressure, the effect that pressure has on the stem for red spring (seal at bottom) compresses red spring allowing closing valve to open. Ready to fire.
Depending on how tight red spring is adjusted vs pressure in valve, it will close closing valve when pressure drops low enough.
That’s just my take on it.
Dave
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That’s just my take on it.
Makes sense, something like that:
(https://i.imgur.com/BhsC3O9.png)
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That’s about it!
Need atm to outside for stem.
Spring tension adjustable. Will need oring added for that piece that I show threaded.
You could technically show a larger path from plenum air to spring. That would indicate a fast response to pressure change.
Man, your salty with this stuff.
Dave
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There we go:
(https://i.imgur.com/llKrbRq.png)
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Wouldn't this whole cut off valve issue be solved with a regulator? That should cause enough of a pressure drop to actuate the valve.
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That would depend on the plenum volume, which dictates how quickly the pressure drops at the valve seat....
Bob
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And how low the pressure would be.
I was thinking about this valve the other day. Looking at the rear portion of the poppet, it appears the sear must hold a substantial force. Force enough that can open poppet, overcome oring breakout friction and compress spring.
To make this where you used reg and plenum size to control closing, the pressure upon closing would either be very low or the return spring would be very large. So large that it would not open reliably.
The way designed, it can close at a higher pressure since it is dependent upon a small rod/heavy spring. This allows independent control and does not effecting poppet opening. A two poppet system, so to speak.
It does still require a pressure drop, so plenum size still contributes to overall performance in a large way.
Dave
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Since either solution requires a plenum area where the pressure drops, either solution should have roughly the same efficiency right? I had briefly thought one advantage of the valve as designed is that the exhaust always sees tank pressure. Then I remembered that the valve body is essentially a plenum and that the exhaust pressure will drop as the plenum empties.
I realize now why this design is more tunable, especially with external adjuments. The only way I can see a regulator working is if it had a telescoping plenum.
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IMO the valve body is only a plenum if the inlet is significantly smaller than the outlet.... If the inlet area is large, the pressure inside the valve will approximate reservoir pressure during the shot cycle.... This all changes once the "choking valve" starts to close.... or even if the area for the HPA to pass through it is significantly less than the smallest port downstream of it....
Bob