GTA
All Springer/NP/PCP Air Gun Discussion General => "Bob and Lloyds Workshop" => Topic started by: Hobbyman2007 on May 18, 2019, 08:03:22 AM
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We all know that an inline valve will make more power than a conventional setup whether it’s a ballanced design or not . Let’s say all other factors are the same , ports, barrel length hammer weight etc . The inline will come out on top for power . What I was thinking was making a valve with no hard 90* corners redirecting the air flow to the back of a projectile . We’ve all rounded off corners in the air path and in my experience has given me some substantial gains both in power and efficiency . Can it or has it been done where the redirection of air from the valve to the projectile was more gradual ( for the lack of better terms ) ?
Here’s an example , of what I mean . I have a Cothran powered gun and the absolute most power it will make in .257 is 162 fpe at 3200 psi . An inline valved gun with the same barrel length will make 180+ fpe . Maybe I’m missing something here , but I’m pretty sure the restriction in flow from our “conventional “ setups are holding back some serious power.
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Like an Air Force valve ?
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I've always wanted to make a AF type rifle, in the overall shape of a flintlock musket... But that's way too ambitious of a project, even for me. Agreed though- the AF setup does lend itself well to making power more easily. The main issues being ergonomics and frame flex. I wish AF would sell a "custom shop" version of the Texan...
What have you got in mind Hobbyman?
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In theory an inline valve should deliver greater FPE from the same barrel length, port size, and pressure as changing the direction of the airflow by 180 deg.... What most people forget is that what we call inline valves still (at least in production form) are nowhere near straight flow.... The would better be called "axial flow" valves, because the air still has to pass the seat of a conventional poppet (two approximately 90 deg. turns in opposite directions), and then has to perform another "slalom" through the passages around the stem before reaching the pellet.... In a stock AirForce valve, that slalom consists of two more 90 deg. turns through drilled ports....
The high flow valve made by dyotat100 uses much larger holes, on a much shallower angle (45 deg. or possibly less) for the second direction change, and there is no question that is at least somewhat better than even the best porting system where the airflow has to turn through 180 deg.... However, BOTH valves still have the flow problem around the poppet, where the air turns twice (at the minimum performing another slalom) to get past the poppet....
But is that really true, for a well designed conventional valve?.... Certainly it is for the inline valve, as the air ends up flowing in the same direction as it started (forward, away from the tank)…. However, just like in a well designed automotive port, if the exhaust port of a conventional valve is angled towards the seat, and the corners suitably rounded, the air escaping through the throat of the valve flows on that angle, and in fact flows past the head of the poppet on an angle, instead of making two 90 deg. turns....
Does a well designed axial flow valve outperform a well designed conventional layout, however, is the key.... The answer is yes, but by a smaller margin than you might think.... Denis stated that the most you can get from a conventional .257 at 3200 psi is 162 FPE.... I have done that at 3000 psi, with a gun that still had a loading probe on the bolt.... At 3800 psi, I have achieved 216 FPE with a 113 gr. bullet at 928 fps with full bore-area porting and a retractable bolt nose.... Yes, both these guns have to be detuned to a more reasonable FPE level to have decent efficiency.... but I'll bet the same applies to any of the high FPE claims you see on ANY gun.... I mean why would anyone brag about lower results, that is just not human nature.... ;)
If I were totally convinced that an axial flow valve had huge advantages over conventional valves, without significant problems to overcome in other areas of the design, I would be using them.... I'm not saying they can't be made to produce more power than a conventional layout, they can.... The guns that utilize them, however, can also suffer from things like tank dumps, which can be pretty exciting when they occur.... Just today, Doug Noble posted this....
The one thing that is a issue with the inline valve is getting it to close after a shot. Especially with larger valves.
I'm not against new developments, but kind of like electric cars, I'm not personally convinced they are right "for me"....
YET.... ;)
Bob
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I'm with Hobbyman in this. We know that a smooth turn from valve tunnel to transfer port gives some 30-40 fps extra speed, now why don't we do the similar thing at the barrel end? An oblong barrel port can be radiused at the front to provide smooth turn to the barrel. In similar manner we could shape the front of the probe at roughly 45 degree angle (assuming needle nose probe) to aid the airflow to turn in to the barrel. Add a touch of a dremel to round things up and we could look at another 30-40 fps increase?
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For an experiment , I’m going to use a disco valve and with some two part epoxy fill the entire valve and carve it out to a progressive curve . This should eliminate all corners . As RKR suggested modify a probe with a rounded tip rather than the typical pin or hollow design . Last but not least the poppet , I’m going to try to get it as close to teardrop shaped as I can . If this does improve the performance . I’ll have to find a different solution as I’m not sure how long epoxy will last.
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Yep.
But not a issue on 25 or 257. It's when you get up to 308 and bigger.
The only obstruction is the poppit in my valve. That's the only place air has to make a real turn.
There are a few other factors that come into play and effect how a AF valve works also.
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rkr, I already use an angled exhaust port in all my valves, similar to the porting in a car cylinder head.... That allows the easiest flow through the seat and into the port, instead of having it flow straight back and then turn 90 deg.... The change in direction of the flow occurs right at the seat, in fact I think the flow through the seat is assymetric (angled), something you can't get with an air force style axial flow valve, it has to flow straight past the poppet....
I already angle the front of the barrel port to smooth the flow into the bore.... You are correct that angling the nose of the bolt, ideally on a smooth curve, but even just a 45 deg. face, tilted forward at the top, should help.... The problem is that shape cannot load a bullet square in the bore.... and any loading probe, however thin, reduces the flow area in the chamber.... The best solution I have so far is a square nose on the bolt face (for loading) that is retracted flush with the back of the barrel port for firing.... It is interesting that having the bolt face slightly forward of the back of the barrel port actually gains a few fps, instead of having it flush.... I don't know it that is improving the flow, or if the slight reduction in port (chamber) volume is raising the pressure at the base of the bullet enough to produce that gain.... but it is pretty consistent, gun to gun.... Occluding the back of the barrel port by about 1 mm or so does boost the velocity a fraction (not even 1% though)….
Doug, have you tried using a steel poppet with a 45 deg. angle, shaped like an automotive valve.... running in a Delrin or PEEK seat in the valve body?.... With a round, parabolic or teardrop shaped head upstream of the seat, that should give the best flow, also in a conventional valve, of course.... Something like this might work.... both in air force and conventional valves....
(https://i378.photobucket.com/albums/oo221/rsterne/Parts%20for%20Sale/Poppet3_zps72w5rhis.jpg) (http://s378.photobucket.com/user/rsterne/media/Parts%20for%20Sale/Poppet3_zps72w5rhis.jpg.html)
Bob
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On the Texan valve it has 60 degrees.
I will be switching the 257 to a angled port and poppit. The biggest problem is it has to be the same everytime. The valve has to stick out a certain amount out of the body for the breech lock. Everything has been drawn and will be made here soon.
Right now I'm spending what little free time I have getting ready for RMC. I have only shot 3 times since last RMC. Have new gun but not sure if I will shoot it. Need to test it on paper.
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I haven’t seen any valve design yet that can out perform the Huben K1 it’s basically the best design out there today bar none. It’s very efficient and extremely powerful. After having owned a K1 for awhile now my future efforts will be in this direction of hammerless technology. I have my own take on it that should yield even more power If you haven’t seen one work check it out on YouTube
https://youtu.be/v8qJ5-p_YkM
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One thing no one talks about is the efficiency of the Huben . From what I gather , still trying to wrap my head around that one is it’s pretty much a dump valve . They aren’t known to be efficient . I must be missing a key point .
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Spent some time reworking a BT65 valve that at one time was able to produce 140fpe. Although this valve was able to make power it took a huge amount of hammer force and I’m thinking the dwell was way longer than needed . I had already remover the return spring and put it on the front of the valve , the seat was replaced with a 1/2” peek with a .290” port. The first pic you can see the huge step between the valve and tube diameter , I removed the step by cutting a taper to 30* . Next was to rework the port job , this is now cut to 45* right through to the seat . Last but not least was the design of the valve stem itself . Because in stock form the return spring resides inside the valve the stem has a built in “sail” . I used a piece of plastic tubing and slid it over the end of the stem and turned it so it has close to the same shape as a boat tail bullet , which should improve flow . Next up is the porting on the rifle and the pellet probe .
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It would be interesting to see the power before and after you port the pellet probe.
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One thing no one talks about is the efficiency of the Huben . From what I gather , still trying to wrap my head around that one is it’s pretty much a dump valve . They aren’t known to be efficient . I must be missing a key point .
I had a Huben 25 that was making 85fpe for 35 shots. It was filled to 4000psi and shot down to 2600psi. I thought that was pretty good for the fpe.
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This project will be on hold for the next couple weeks . I will definitely get results before and after . I have a second tube and valve that performed alsmost identically and once I figure what to do with the probe I’ll get them tested side by side .
Now ,, although this was not a redesign of the valve it is much more streamlined in comparison . If I were to look at ALL of the PCP rifles and pistols in my collection . Not one of them has an efficient way of getting the air to the back of the projectile . I would assume this is mainly due to manufacturing costs . There must be a simple solution , maybe a resin cast valve ?
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I was thinking like this, make the probe long enough to cover barrel port. The drill it for the needle. Then shape it like in picture (although smoother of course) and finally attach the needle. If possible smooth out the barrel port edge even more as that's the biggest obstacle for airflow.
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The thin probe would be problematic, IMO.... For pellets it has to be longer to allow for the hollow skirt, and of course you do lose cross sectional area in the chamber because of the area of the probe.... The probe diameter becomes critical, not only because if too thin it would be prone to damage, but it will cause a dent in the back of the projectile.... While not really a problem for pellets, which are easy to load, they don't really need full bore area porting anyways, we can drive them too fast without resorting to that....
Where we really need maximum flow is for PCPs shooting bullets.... They need to be pushed into the leade, and unless you only use one specific bullet, since all bullets are not the same length, they load differently.... Also, we play around with the sizing diameter, and larger bullets are definitely too hard to load for a skinny probe, they put a huge dent in the back.... In fact, if the bullet is just 0.001" over the groove diameter, and long enough to need pushing pretty much past the taper of the leade, you will need a probe of about 1/2 the caliber to not dent the back of the bullet.... and God help you if you try and load a bullet that is just a little to large, you will either damage the probe, or won't be able to close the bolt, and end up having to drive the bullet out backwards through the breech.... Yes, I have had BOTH experiences....
A probe that is 1/2 the caliber produces a chamber that is only 86.6% the bore diameter, minus the turbulence to the flow to get around to the top side of the probe.... This isn't a problem with a drilled barrel port of 80% of the caliber, but as soon as you go to an oblong port to gain more area, you need a slimmer probe, and that can be a problem when loading bullets if you go too skinny.... I currently make my probes no less than 40% of the caliber.... Using 40% of the caliber increases the flow area to the equivalent of 91.7% of the caliber, which is still only 84% of the bore area.... I have tried thinner, and it dents the back of any snug fitting bullets....
Air Force style guns, where you load by pushing the bullet into the chamber with your thumb aren't immune to this problem, the Texan won't allow you to load many bullet more than 1/4-1/2 way into the chamber, because it is too shallow.... We had a thread in this Gate last fall to design some bullets for the Texan, where the front of the bullet is semi-bore riding, because of this.... NOE has the designs.... Yes, you can machine the chamber deeper, but using a longer bullet than the chamber was made for will leave it sticking out of the breech....
Lloyd made a bolt nose like you drew, without the probe, where the bottom of a flow-through bolt was cut away, and the inside radiused and smoothed to aid flow.... It had about 3/4 of the flat face remaining (sides and top) for loading, and worked for pellets and flat-based bullets.... but could not be used with boattail bullets, as the smaller base would jam inside the bolt nose.... Tom at AAA uses a retractable bolt PROBE in the Slayer, so there is no reason that the nose of the bolt could not be streamlined, and he may already do that.... At the extra complication involved, that is probably the best solution....
The only way to test any improvement in bolt nose design is to start with a gun with a retractable, squared off bolt nose, such as I use with my "J-slots" receivers.... Tune the gun for a specific bullet, at a specific pressure, and then adjust the bolt retraction for the highest velocity (usually just proud of the back of the barrel port)…. Then without changing ANYTHING else, try the new fancy bolt nose, and measure the increase in velocity you get.... Assess if that is worth any loading problems, and the difficulty in making it, and then decide if it is worth it....
Bob
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Bob, those are good practical limitations but I believe that probe mod would be for people who are shooting bullets and looking for that last bit of oomph from their guns. In such scenario the ammo is usually matched to barrel twist rate (i.e. max bullet length is more or less set) and chamber is fit for ammo which is sized so a thin needle in the probe should not be an issue. I use 1.5mm needles in my guns fitting the above criteria and there's no deformation of bullet bases. The problem with that hollow nose half moon probe approach (I actually use it in my .25 BSA) is that it reduces the available volume/cross sectional area much more than a thin needle nose.
One thing that was mentioned in another thread and that I've been wondering about is if there's an optimal distance from barrel port to the bullet base? I've had mixed results about this on my guns.
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In theory, the smaller that distance, and consequently the smaller the total port volume, the higher the pressure at the base of the bullet before it moves.... I actually wonder if that is the reason that not retracting the nose of my bolt quite clear of the back of the barrel port gives a slight increase in velocity.... The nose of the bolt is restricting the flow area, but the initial pressure is higher.... resulting in more power....
I seat my bullets just ahead of the forward radius of the barrel port....
Bob
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In theory, the smaller that distance, and consequently the smaller the total port volume, the higher the pressure at the base of the bullet before it moves.... I actually wonder if that is the reason that not retracting the nose of my bolt quite clear of the back of the barrel port gives a slight increase in velocity.... The nose of the bolt is restricting the flow area, but the initial pressure is higher.... resulting in more power....
I seat my bullets just ahead of the forward radius of the barrel port....
Bob
Or it could direct the flow/pressure pulse towards the bullet base instead of the barrel roof ...
My .224 has the bullet base about 2mm (haven't measured actually) in front of the barrel port and it still manages a respectable 100+ fpe. In my Evanix I have also noticed that a small velocity increase can be had if the rear of the barrel port ever so slightly (half a mill or fraction of mills) covers the rear of the transfer port. In this case it is a 9mm transfer port that is reduced to .257 but I did notice the same phenomenon even when using .357 barrel. In this case the actual volume in the barrel is not changed as the probe and thus bullet stay in the same position while barrel is mover frontwards a bit. I think there's something going on with bullet position and probe nose shape/position that we do not understand yet.
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To be truthful, I have seen very little difference in performance with port shape.... Port diameter, barrel length and pressure are the primary factors.... Is it possible to come up with a very BAD design, of course.... Once you pay reasonable attention to obtaining the shortest, smoothest path possible, the possible gains are much harder to come by.... at least that has been my experience....
That doesn't mean somebody might come up with a better mousetrap, of course.... and it is worthwhile pursuit for those so inclined....
Bob
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In my Evanix I've seen up to 30-40 fps difference when the barrel was further in or out.
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Sorry, I have no idea what moving the barrel "further in or out" does on an Evanix….
Bob
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Sorry, I have no idea what moving the barrel "further in or out" does on an Evanix….
Bob
As it is locked in place with grub screws and there's an adjustable screw in collar in front of the breech, you can have the barrel go further in the breech to a point where mgazine no longer fits in. We are talking a millimeter difference here.
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What ever happened to the edit button? I was about to add that by screwing the "collar" out I can then move the barrel towards the muzzle in the breech causing the barrel port partially block the transfer port. For some reason a very slight blocking/overlapping at the rear of the transfer port seems to increase power. Of course that also means that the bullet is closer to the transfer port.
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Ahhhhhhh, I get it.... so the barrel port is slightly forward of the transfer port.... slightly blocked at the back, but creating a tapered inner corner at the front....
Bob
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One thing no one talks about is the efficiency of the Huben . From what I gather , still trying to wrap my head around that one is it’s pretty much a dump valve . They aren’t known to be efficient . I must be missing a key point .
I would refer to it as more of a controlled or isolated plenum. I have to assume that the tuning is done by pressure change only. I'd like to get my hands on one.
Bill
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After reading all the post here, I'm curious to know if a poppet valve COULD BE PLACED 90* vertically trough piping would perform better by eliminating one turn???
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Providing the plenum feeding the valve did so inline with the poppet, it might help a bit.... However if the plenum was under the barrel, and the air had to turn 90 deg. to get to the poppet, I don't think you would notice any gain....
Bob
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I just read on automotive injection valve and would it be any good for an airgun?????
In diesel injector, they can reach 2400 psi.. Put right behind a hollow bolt is attractive solution for negating the flowing air.
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I just read on automotive injection valve and would it be any good for an airgun?????
In diesel injector, they can reach 2400 psi.. Put right behind a hollow bolt is attractive solution for negating the flowing air.
A Diesel engine injector doesn’t have the internal volume needed . In actuality the injector is in fact a small pump , way to complex for Airgun use and would need a complete redesign .
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I just read on automotive injection valve and would it be any good for an airgun?????
In diesel injector, they can reach 2400 psi.. Put right behind a hollow bolt is attractive solution for negating the flowing air.
A Diesel engine injector doesn’t have the internal volume needed . In actuality the injector is in fact a small pump , way to complex for Airgun use and would need a complete redesign .
I might read something different!!
I read about jetta diesel injection and the pump sit by itself and not A PART of the injector..
The needle can be changed or removed and since the pressure can be as high of 2400 psi in this type of injection, the volume of air injected can be accomplish with 2 injector.. ….. RIGHT!
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Time to put some of these ideas to the test, Alain.... and start making parts.... 8)
Bob
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Alain,
The injector you have pictured is a combination of electronic and mechanical . Like I said , it would need a complete redesign . There is no where near enough volume in that injector . Maybe have a look at a locomotive injector , it might have enough volume but then you have nozzle cracking pressure and the passages that the fuel actually flows through . An injector is designed to atomize fuel , not to flow fuel in a stream like what we want in Airgun use .
Trust me , I’ve looked at this . It is my background and have an extensive amount of experience working on Diesel engines . The only part of an injector that would be of any use would be the coil and even then that would be a long shot and would need some substantial electronics to control the pulse width .
This thread is about a better flowing valve , I don’t think this is a solution for that .
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It dose make me wonder if having a electric poppet valve and plenum inline with the barrel could be something? Of course now you need a complicated bolt and probe. I only wonder if it would work but really dont think it is feasible to do efficiently. It is about the closests I can envision a "injector" style poppet and plenum could work.
The other version would need to be a needle and seat or would it really be called something and a pental I don't recall the proper terms for them. Use a solenoid to open the valve but not have a stem to pass by if that makes sense. I get that you still have a wall to push past but not restricted but the valve stem.
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I'm wondering if it is the valve we should concentrate on. If you think about it the most restrictive parts are the rather sharp turns air needs to make when it goes from valve tunnel to transfer port and again from TP to barrel through the barrel port. As an example I and Tom got 30-40 fps increase (about 4.5%) in speed when we made a smooth large radius turn from valve tunnel to the transfer port while tuning our Evanixes. Making a smooth large radius turn from TP to barrel could easily net the same amount getting us close to the efficiency of inline valves.
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To be truthful, I have never seen a huge increase in efficiency with inline valve designs.... Yes, they can produce a bit more power from a given pressure and barrel length, in guns that are already maxed out for port size.... Generally, however, they use a lot of air to do that....
Really efficient PCPs get their efficiency from closing the valve early in the travel of the pellet/slug down the bore.... Therefore, the amount of air a valve "flows" makes little difference, because you are using the expansion of a relatively small amount of air to produce the FPE....
Once you start trying to extract the maximum FPE from a given pressure and barrel length, then having large ports that are as straight as possible allow more air to flow.... At the limit, that can allow a gun to develop more power.... Still, it isn't a huge difference.... With equal barrel length, pressure and bullet weight, you might be talking a 10% increase in FPE between a really good axial flow valve, and a good conventional PCP with a 180 deg. turn to the air path.... Back the power down 20% to get a decent shot count, and you would be hard pressed to see any difference, from the numbers I have seen....
Bob
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But not everyone is after the efficiency but all out power from the valve, there is the challenge there, how much can there be?
As long as we here can't hunt with air the consumption is meaningless to me.
Air is the cheapest commodity in this sport. And there is still plenty around. ;D
Marko
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Air may be free (until you compress it)…. but the downside of using maximum power is that the air you are wasting shows up at the muzzle as additional recoil and report.... Back the velocity down just a bit, and you can cut the report in half, to go along with the 50% of air you save.... for a loss in power of maybe 5%.... Still, I get the satisfaction of building the most powerful PCP you can, and the bragging rights that go with that.... I do that with every one I build....
before I dial it back a small amount to double the shot count and get half the report at reduced recoil and the increased accuracy that comes with that.... 8)
Bob
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Ric;
Seems that would be inducing a bit of a curve ,even though a rough one, in the rear of the port. Causing it to act an an elbow toward the projectile rather than simply straight up toward the roof of the chamber.
Knife
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Seriously I keep saying this but look at the K1 Huben valve system I own one its well ahead of its time and no need for any electronics.
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I threw the injector idea at Lloyd years ago. David
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A cutaway or drawing of the Huben valve would help us understand it.... or at least some disassembled photos.... I understand the need to protect proprietary devices, but without understanding how it works, there is little point in talking about it.... JMO....
Bob
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Bob, Huben has a very good 3d view of how it works on youtube. you can slow it down
and here is a link to the drawings one of the dudes on AGN. sorry if linking it here violates anything
https://www.airgunnation.com/topic/reverse-engineered-huben-k1/ (https://www.airgunnation.com/topic/reverse-engineered-huben-k1/)
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Sorry Bob here’s a video I found there’s some lengthy tear down videos as well.
https://youtu.be/v8qJ5-p_YkM
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OK, so I see that there is a valve that seats against the breech, held forward by the sleeve controlled by the trigger.... I'm not quite following the purpose of the vertical valve underneath that, or what controls it.... ???
Bob
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Bob, the chamber underneath is called the "velocity adjuster" in the Huben manual. i guess it can increase or decrease volume when the wheel under that chamber is turned externally.
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Valve dumps the chamber and vertical valve is opened, regulator under that to control the pressure.
Marko
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Vertical valve is spring loaded.
When is pressure in chamber, vertical valve is open becouse valve steam is atmosferic.
When you push the trigger orizontal valve will open and pressure in chamber will lower so the spring from vertical valve will push the valve to close the transfer port.
Vertical valve stem is atmosferic and sealed with oring .
You can adjust spring tension from the whell under the chamber so you can control how fast vertical valve will close.
But this valve will not seal perfectly. It has a dent on it to leave a little pressure to help orizontal valve to seal.
In that type of valve , dwell is beetwen orizontal valve opening and vertical valve closing.
It is a dump valve with a separate controlled closing valve .
Sorry for my english.
Hope you understood me
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https://youtu.be/p7MLR_RPaYs
Hope this video will enlighten you.
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gabi.nechita…. that is a very clear and concise explanation....
In that type of valve, dwell is between horizontal valve opening and vertical valve closing....
You can adjust spring tension from the wheel under the chamber so you can control how fast vertical valve will close.
I understand perfectly now.... Many thanks.... 8)
While I certainly understand how the dwell of this type of valve is more precisely adjustable.... I don't see how the design fits into a discussion of a "better flowing valve"?.... There are still two 90 degree turns to the airflow, and a poppet (the vertical one) that the air must pass.... Perhaps the passages can be made larger without being hard to open, because the main (horizontal) valve blows open, so that would be an advantage for sure.... as it can be bore-sized.... In addition, the "wasted" transfer port volume is nearly non-existent, so there should be nearly full pressure available at the pellet.... It certainly is an innovative design, although hard to make for the amateur....
Bob
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You must try to made one sometime.
I bet you will find it interesting. I am working at one but still in project faze.
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I have yet had a chance to revisit the BT65 with the improved version of the valve . For whatever reason I just can’t get the valve to seal. I’m neck deep in projects right now and plan on getting back to it shortly . As mentioned the Huben valve is real neat and all but I don’t see how there’s any improvement to the flow when compared to a traditional valve .
There’s got to be a better mousetrap .
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If someone can fit a bigger vertical valve chamber that would be an improvement for power. its already pushing 100fpe in 25 cal. semi auto to boot.
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If someone can fit a bigger vertical valve chamber that would be an improvement for power. its already pushing 100fpe in 25 cal. semi auto to boot.
We have .224s that make 100+ fpe with traditional valves. Inline valves in .257s going around 200 fpe and traditional valves in that caliber around 170 fpe. 100 fpe .25 does not sound very exciting.
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its true that 100fpe is not all that but "semi auto", my friend. 100fpe is enough to kill anything medium sized up to 100 yards in the right hands. super quiet too.
i am okay with 100fpe semi auto. i am even okay with 80fpe as long as its accurate like the NSA in the impacts reaching out to 250 yards by Utah airguns on utube.
not to start an argument, but he inline airforce valves in .257 probably yields 10 shots at the most. the Huben valve is also efficient, i got 3 mags worth of shots at 80fpe.
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its true that 100fpe is not all that but "semi auto", my friend. 100fpe is enough to kill anything medium sized up to 100 yards in the right hands. super quiet too.
i am okay with 100fpe semi auto. i am even okay with 80fpe as long as its accurate like the NSA in the impacts reaching out to 250 yards by Utah airguns on utube.
not to start an argument, but he inline airforce valves in .257 probably yields 10 shots at the most. the Huben valve is also efficient, i got 3 mags worth of shots at 80fpe.
Semi auto is good but we have working semi-autos with traditional valve designs. With balanced valves you could even use a blowback design due to low cocking force needed. Making 100 fpe quiet is quite easy as well, use one of the existing LDC designs and up the volume. I agree that Huben valve is very innovative but it is also quite complex when compared to traditional poppet design. The topic was about better flowing valve and that is closely associated with maximum power output where the flow is needed. Efficiency is then another thing and that may be where Huben design shines. It would actually be rather interesting if Huben made a .224 version that could shoot long 50ish grain bullets at 100+ fpe, that would almost make me buy one.
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I’ve been looking at the internals of the Evanix air speed real close over the last few days after breaking the probe off after shooting at too low of a pressure .It would appear that a balanced chamber would fit with a bit of work . Again , I’m neck deep in projects and won’t have time to dive into it any time soon but you can bet I’ll be digging in ASAP . The sound of 80 fpe semi auto is very interesting .
Not a better flowing valve but interesting none the less.
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Once again, and this is only my opinion.... inline valves have the ability to deliver more FPE from the same pressure and barrel length, when used AT THE LIMIT.... ie when tuned for maximum power and a declining shot string (or used on a tether)…. As soon as you back the power down to close the valve when the bullet is only half way down the bore, or less.... they don't show stellar efficiency, but act very much like any other valve arrangement.... Remember, closing the valve when the bullet is at 50% of the barrel length only drops the velocity about 3%, but uses half the air....
Want maximum power?.... go inline.... For anything else, most any valve will work just fine, IMO... Larger ports allow the use of less pressure (and/or shorter dwell) for the same FPE, of course.... When somebody builds a gun with an inline valve and shows me a shot string with an efficiency of over 2.0 FPE/CI.... then maybe I'll change my mind.... ::)
Bob
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LOL Bob, i want an 80fpe gun that can do 2.0fpe/ci, i am sure the airforce guns with Co2 adapter can hit that magic number but its not usable.
Rkr, i was shooting 55 grains in huben 25 cal around 845fps. but that pellet can only group at 25 yards, it was spiraling and printed 3 feet at 100 yards. LOL
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I have a few ideas to improve flow. The oblong transfer port is not as good as a round hole for flow. Shifting the shape from round to oval then back to round can’t be good . Also the oblong is inline with the stem and probe lengthwise. I think a .025 wire positioned flush in the center of barrel transfer air hole to support the pellet as it is chambered would be better. A bore size round transfer hole could be used then. How to machine provisions to add this ?
Shouldn’t be too hard. Has it been tried already?
Edit: wouldn’t be a wire exactly but a thin insert installed from underneath.
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LOL Bob, i want an 80fpe gun that can do 2.0fpe/ci, i am sure the airforce guns with Co2 adapter can hit that magic number but its not usable.
Rkr, i was shooting 55 grains in huben 25 cal around 845fps. but that pellet can only group at 25 yards, it was spiraling and printed 3 feet at 100 yards. LOL
Yes, it has the power (or almost has, probably could be sorted by tuning) but you'd need a barrel with suitable twist rate and magazine that can hold those long bullets. As the frame is in two pieces it wouldn't be impossible to make a longer magazine and some spacers. What I'd really like to see is a .257 version putting out about 150 fpe.
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I have a few ideas to improve flow. The oblong transfer port is not as good as a round hole for flow. Shifting the shape from round to oval then back to round can’t be good . Also the oblong is inline with the stem and probe lengthwise. I think a .025 wire positioned flush in the center of barrel transfer air hole to support the pellet as it is chambered would be better. A bore size round transfer hole could be used then. How to machine provisions to add this ?
Shouldn’t be too hard. Has it been tried already?
Edit: wouldn’t be a wire exactly but a thin insert installed from underneath.
JB used somewhat similar approach in one of his prototypes, a two "channel" barrel port where air comes in from the sides of the barrel. Basically splitting the flow in two at the bottom of the barrel as it comes from the transfer port and then filing/grinding/drilling two channels at an angle so that they go inside the bore. Many ways to do it in practice but such arrangement would easily allow over bore size porting making the barrel itself the bottle neck. I would even assume that such arrangement would allow traditional valve system to reach the power levels of inline valve system.
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Oblong port, makes more power than round one, you can use much over bore size porting making the barrel the restrictive part.
Marko
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Even with a round full size barrel port most bullets will slide past it just fine unless the drive band length is very short.
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I think the multiple transfer hole would be the easiest to machine as long as the barrel OD is big enough. That might just be the ticket for the Winchester . I’ll have to take the barrel out for a look . Maybe not a better flowing but definitely able to flow more air . Seen that done with the FX Impact where the probe is drilled from both sides ( top and bottom )
Now what about drilling a series of holes similar to how the Hatsan valves are made . I’m sure that playing with the size and angles on the “ports “ would increase flow like a venturi effect.
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Well I used four ports on the Lucky Shot 223. Worked very well.
Marko
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Well I used four ports on the Lucky Shot 223. Worked very well.
Marko
Marko do you have a post with pictures of the lucky shot 223? i would love to see and hear how it works for you
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Somewhere innthe machining gate.
If the pictures still show, its over a year old thread.
Marko
Edit: its in the Show and Tell section. Another 223...
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I had an 850 which used multiple barrel ports around the barrel, fed by an annular chamber in the receiver.... Drilling a single, larger port on the bottom, in line with the transfer port, increased the power.... On the Hatsans, replacing the six ports around the valve outlet with a single, larger port aligned with the transfer port, also increases the power and efficiency.... It is my opinion that the extra volume of the feed channel around the barrel, and the inefficient feeding of the additional ports on the top and sides.... is less efficient than a properly sized single port....
I agree that the oblong barrel port, fed by a larger transfer port.... with the two blended together properly.... is the best solution I have seen so far for a conventionally placed valve (under the barrel)…. While you may be able to use a bore-sized round barrel port on a bullet shooter, providing the bullets have a long enough bearing area to span the port on loading.... it won't work for pellets without damaging them.... unless you hold the gun upside down.... ::)
There is so little power difference between my guns with a J-slot, flat faced bolt, and oblong barrel port.... I have quit looking for something better.... This is particularly true because I never run my guns "wide open", even the big bores.... because they waste so much air if the valve is still open when the bullet reaches the muzzle.... I would sooner give up 3% on the velocity and get 2 much quieter shots (and less recoil) for the same amount of air used....
Bob
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My idea would be more geared towards pellets than bullets. I made an example sketch. The example dimensions would fit a .250 wall barrel. A razor blade could be adapted for maximum effect.
On some applications I think it could be used.
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My idea would be more geared towards pellets than bullets. I made an example sketch. The example dimensions would fit a .250 wall barrel. A razor blade could be adapted for maximum effect.
On some applications I think it could be used.
It's a nice idea. Unfortunately oblong barrel port is easier to make and has more flow potential. Still, good thinking.
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The valve, and the whole air flow geometry in most air guns, is a weak point. The convoluted path through small orifices, direction changes and the radial injection to the barrel are creating vortexes and a loss of energy. Here are simplified air flow trajectories in a typical air-gun at the moment the pallet starts moving and the valve still open.
(http://)
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I am now building a very different type of air-gun (in 45 calibre) with improved geometry that hopefully will give me a much better performance by eliminating the traditional valve and introducing an axial injection. Those the flow trajectories at the moment the pallet starts to move.
(http://)
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You do realize that at the instant the pellet starts to move, the column of air behind it has little velocity, beyond just filling the chamber and ports with air to the pressure of the reservoir, right?.... In fact, just as the valve opens, what is happening is that the random vibrations of the air molecules just becomes organized in the direction of the pellet, as it increases the pressure in the ports and chamber behind it....
Once the pellet is halfway down the barrel, and travelling perhaps 800 fps, then the airflow velocity is a similar value, and you can use CFD to model the flow.... but I don't see how you can do that before the pellet moves.... Perhaps I just don't have a good enough understanding of CFD....
Regardless of the details of CFD modelling, I look forward to your results when you get a working prototype of your "axial flow" design....
Bob
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You do realize that at the instant the pellet starts to move, the column of air behind it has little velocity, beyond just filling the chamber and ports with air to the pressure of the reservoir, right?.... In fact, just as the valve opens, what is happening is that the random vibrations of the air molecules just becomes organized in the direction of the pellet, as it increases the pressure in the ports and chamber behind it....
Once the pellet is halfway down the barrel, and travelling perhaps 800 fps, then the airflow velocity is a similar value, and you can use CFD to model the flow.... but I don't see how you can do that before the pellet moves.... Perhaps I just don't have a good enough understanding of CFD....
Regardless of the details of CFD modelling, I look forward to your results when you get a working prototype of your "axial flow" design....
Bob
You are quite right that the modelling is difficult. I've tried a time dependent modelling but there seem to be too many variables, though I am still investigating this.
What I've presented here is more for the demonstration of the difference between the two systems. I assumed an arbitrary (or imaginary...) moment after the pellet is some distance down the barrel, but the valve still open. My initial tests (only a few days ago and on a test setup that hardy resembles an airgun) with the axial injection (and no valve in a conventional sense) are promising.
Thank you for the comments.
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Got any pictures on your new design Bill? Even a napkin drawing . I’m havin a hard time seeing it .
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Very interesting. Way to go thinking outside of the box. This type of forward thinking is what keeps technology moving forward. I cant wait to see how it all plays out.
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I shall certainly share the design details once I do little more development. While the concept seems to work it is still a lot of work to make a working product. My aim is to either achieve higher velocities (i.e. energies) than current designs under same conditions and with the same air consumption, or same energies with smaller air consumption. I am experimenting with 45 and 9mm calibres and some test with custom made copper and copper-lead pellets - or rather bullets.
(http://)
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That basic concept drawing (the lower one, the upper one is just an "x") seems to show a regulated tank feeding the valve from the back.... If that is the case, where is the plenum?.... You need a significant amount of air available to the valve to provide the energy for the shot without a large pressure drop.... For high powered regulated PCPs, about 1 cc per FPE you are hoping to achieve is the recommended plenum volume.... A .45 cal, or even a 9mm/.357 uses a lot of air....
Bob
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I’m impressed with the drawing , not what I was expecting . What program are you using ?
Reminds me of an Airforce gun but different . Keep us posted on any progress .
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i would also like to know where the hammer and valve is. what type they are.
nice drawing. move the scope forward though...
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That basic concept drawing (the lower one, the upper one is just an "x") seems to show a regulated tank feeding the valve from the back.... If that is the case, where is the plenum?.... You need a significant amount of air available to the valve to provide the energy for the shot without a large pressure drop.... For high powered regulated PCPs, about 1 cc per FPE you are hoping to achieve is the recommended plenum volume.... A .45 cal, or even a 9mm/.357 uses a lot of air....
Bob
Bob, it is a very different approach, there is no conventional valve. I shall show all the details very soon and will be looking forward to your much appreciated comments. Please forgive me if I am a bit secretive now but I want to get the details worked out. And about a week to recover from a medical procedure....
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Looking forward to your recovery and some details at the appropriate time.... I'm also in the hospital next week for day surgery.... I get a new ICD, the batteries on this one are toast.... ::)
Bob
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Looking forward to your recovery and some details at the appropriate time.... I'm also in the hospital next week for day surgery.... I get a new ICD, the batteries on this one are toast.... ::)
Bob
Ah...the joys of aging...
Best wishes for a fast recovery!
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Looks like valve is behind the barrel, most likely air actuated with pilot valve.
If you want to surpass the existing power levels, you need to ditch the regulator from the bottle.
Not the only one who has been thinking it like so if that is the case.
Marko
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Exactly why I asked about plenum volume, Marko....
Bob
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Looks like valve is behind the barrel, most likely air actuated with pilot valve.
If you want to surpass the existing power levels, you need to ditch the regulator from the bottle.
Not the only one who has been thinking it like so if that is the case.
Marko
Marko, I am still working on this and the design looks now a little different. It is really no conventional valve. I will be away now for - hopefully - no more than one week and should be able to get the details on my return. Thank you for the comments.
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Have had a long recovery and still not that well, but hopefully able to go back to the projects next week. Sorry for keeping you waiting....
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No need to be sorry for taking care ones health.
All other things can wait.
Wishing for speedy recovery for you, but don't get to working too soon. Healing is more important.
Marko
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I did manage to make the first test. Results are encouraging and I am still at the development stage (and progressing slowly as still working only a couple of hours in a day). I will show the design details soon. Here is the video:
youtu.be/3bh1qDong58
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Bill,
Glad you are moving in the right direction, both with your health and your new design. Getting a prototype to work well is a serious, and admirable, accomplishment. Waiting for the next installment!
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Bill,
Glad you are moving in the right direction, both with your health and your new design. Getting a prototype to work well is a serious, and admirable, accomplishment. Waiting for the next installment!
Thanks!
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Glad to see your back up and moving around and tinkering again. Anxious to see how this unfolds.
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Thank you.
I am putting together a full "disclosure" :D. Will have it soon.
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That is a really small plenum volume for that power, how much volume is there for air?
Nice looking work!
Marko
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I'm wondering the same thing, Marko....
Bob
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You guys are not alone...
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i am waiting the for full disclosures as he has promised.
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Uploaded a new video:
https://www.youtube.com/watch?v=hnmhKNyoKlQ (https://www.youtube.com/watch?v=hnmhKNyoKlQ)
This one includes a link to full details.
I am sorry if I was a bit secretive and did not show all the information initially. Maybe now, that it is all disclosed, it does not look that interesting anymore. I doubt very much if this has any commercial value, but I did apply for a US patent (provisional) . I am afraid this will be the worst investment of USD70.00
At this stage of development I am looking at reducing the consumption of the air and some easy way of ejecting the spent disk.
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Speaking as a fellow person who thinks "outside the box", I really appreciate the creativity that went into this design. Best wishes on your development journey!
I could envision this being a break-barrel design, with the spent disc being ejected by a mechanism similar to the ejector used on a break-barrel shotgun/rifle...
$70 for a provisional patent application is peanuts compared to the typical cost of a patent :)
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I was enjoying this thread. Seems it died an early and premature death.
A shame!
Knife
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Hopefully it's gone quiet for R&D purposes. It would be great to have some current information on how to improve a valve.
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I must admit i had lost interest in airguns for quite some time. I myself have also devoted MANY hors of my life cracking the puzzle of the elusive practical inline valve for an air gun. This concept is new. The burst disc idea in itself is not new, but the electrical rtigering of it...that's good thinking outside of the box. Ith all that being said i must add however: my research showed that efficiency lies in the ability to close the valve while the bullet is still in the barrel. A broken burst disc will not "heal" itself magically. From a power perspective...money!!! No twists or turns=max possible useful work practically achievable. Great work. Keep it up. Honestly i would buy a goodlooking working 9mm hunting gun using this technology but applied in a cartridge formfactor. Loading my 15(cm3) titanium "cartridges" with say...600 bar of compressed air via a dedicated compresor ( one that further compresses what your tank/pump gives you) slyding any kind of projectile i want...having say a stock of 10 000 burst discs...wow. i like the idea. Ultimate hunting kit. And you'd really need like 10 cartridges at most. Make something like that. Make sure the device is light as possible a d sexy as *(&^....you'll get my money:) Good luck. Keep us posted.
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Ok...just realized something! Your test bed is actually ideal ( almost) for a test that i failed to do. It's actually haunting me to this day and has been brought up in this thread multiple times. Underlying assumption of an inline design is the superiour efficiency and consequently more power when compared to a traditional configuration. How much? NOBODY....I REPEAT NOBODY!!! at this stage can give you a concrete emperical number. Just educated guesses and figures that get washed out in the noise when comparing two complete platforms that have different dynamics during a fireing cycle. Now...if you can take your rig and simply modify it by adding a "link" between your barrel and fireing chamber. That link would efectively mimic a traditional transfer port with 2x90 deg turns. Keep the barrel length, plenum volume and the projectile mass constant. Fire multiple shots at different prrssures say...300/250/200/150 (bar). Do like 10 shots at each pressure setting. Repeat the same procedure with the " transfer" port installed. Your yardstick will be the muzzle velocity which will varry with each pressure setting. Remember: efficiency of work conversion in this adiabatic system depends on the velocity of the moving layers of gas. In other words the closer you are to the local speed of sound the harder it is to transfer energy to the projectile you are trying to accelerate. Plot both graphs side by side and....voila! A comprehensive/undisputable empirical comparison between a straight vs 2x90 ductwork in air gun design. I haven't been this excited in a long time!!!:)
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Thank you all for the interest and the comments. I am still around - the reports of my death have been greatly exaggerated (with apologies to Mark Twain)...
However I have not been active for some time. Various health issues, mostly resolved, and now catching up with more important (as far as earning money) work. I did a few more test with the gun, this time with slightly different calibre and larger (re-bored) plenum. As observed, stability at high velocities is a problem and I returned to heavier bullets and lower velocities. In all those tests I did not use any ignition, just increased the pressure until the disk bursts. Tried different disc thicknesses to burst in the range of 3000-4000 psi. Results encouraging but I think I can go back to it all only in late spring 2021.
I am trying to find a .5, .45 and/or .357 air-gun rifled barrel (without spending a fortune). Any suggestions appreciated.
Alex, can you elaborate on your statement efficiency lies in the ability to close the valve while the bullet is still in the barrel. I would think that having a higher pressure behind the projectile all the way is always better and allows - especially in my design - to take a full advantage of the air in the plenum. And there is no question here of efficiency (if you mean air consumption) as all the air volume in the plenum is always released.
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Speaking as a fellow person who thinks "outside the box", I really appreciate the creativity that went into this design. Best wishes on your development journey!
I could envision this being a break-barrel design, with the spent disc being ejected by a mechanism similar to the ejector used on a break-barrel shotgun/rifle...
$70 for a provisional patent application is peanuts compared to the typical cost of a patent :)
My first design was a break action version!
(http://air-gun.ca/Break-Action.jpg)
Shown here is the safety interlock preventing breaking when pressurized
(http://air-gun.ca/Assembly.jpg)
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Bill,
Glad to hear you are continuing the project.
As for the efficiency, it's quite simple really. You want your plenum as large as practically possible to have the least pressure drop in the barrel as the bullet travels down the barrel. W=(F)x(D)=(PxA)×(Barrel length). So theoretically once the bullet is at the muzzle you want the valve to close and trap the remaining air in the plenum. The air in the barrel is unfortunately lost. You will then require less air from the tank to get the plenum back to the required pressure ( regulated system). In practise however my experiments indicated that closing the valve somewhere midway the barrel had a slight decrease in muzzle velocity ( we are talking around 300m/s velocities here...so close to the speed of sound) but a significant impact on the shot count and the sound of the shot. You could hear the difference between an efficient shot vs a wastefull one.
Hope this helps.
What did you think of my idea with the 2x90 degree link to emperically measure the loses of the traditional vs inline design?
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In simple terms, closing the valve with the pellet halfway down the barrel results in about a 45% reduction in the volume of HPA used, compared to closing it at the muzzle.... but only about a 5% loss in velocity and 10% loss in FPE.... This means roughly a 60% increase in efficiency, less recoil, and way less report.... Having the valve still open after the pellet leaves the muzzle gains nothing, except more wasted air and way more muzzle blast....
Bob
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Bob,
Sounds about right.
Unfortunately the proposed design with a burst disc cannot close since the closing body ( the disc) is no longer intact. I still love the concept in terms of standalone cartridges.
However, i believe the rig can be beautifully used to test/compare the traditional vs inline designs allowing to exclude all the other variables. Thoughts?
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With a burst disc you are, of course, working with a dump valve.... The larger the valve, in proportion to the barrel volume, the more potential FPE, but the less efficient the gun will be.... I never exceed 50% of the barrel volume with a dump valve, and 25-33% is a lot more common.... Going larger than 50% is chasing diminishing returns.... Here are a couple of examples....
(https://hosting.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/.highres/DumpValves_zps8ff30e30.jpg) (https://app.photobucket.com/u/rsterne/a/2b6b9a8f-bf4c-41f4-8426-985eaf5ed6aa/p/a0fd3d9a-96c7-4f4f-bfc0-9e346f70e1db)
My last post was to show why I seldom use a dump valve, the efficiency is low, unless you are going for relatively low FPE....
Bob
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Bill,
Glad to hear you are continuing the project.
As for the efficiency, it's quite simple really. You want your plenum as large as practically possible to have the least pressure drop in the barrel as the bullet travels down the barrel. W=(F)x(D)=(PxA)×(Barrel length). So theoretically once the bullet is at the muzzle you want the valve to close and trap the remaining air in the plenum. The air in the barrel is unfortunately lost. You will then require less air from the tank to get the plenum back to the required pressure ( regulated system). In practise however my experiments indicated that closing the valve somewhere midway the barrel had a slight decrease in muzzle velocity ( we are talking around 300m/s velocities here...so close to the speed of sound) but a significant impact on the shot count and the sound of the shot. You could hear the difference between an efficient shot vs a wastefull one.
Hope this helps.
What did you think of my idea with the 2x90 degree link to emperically measure the loses of the traditional vs inline design?
Thank you for elucidating this. Yes, the advantage of higher air pressures once the projectile is approaching the end of its travel in the barrel is is declining rapidly. In a conventional design you would want to close the valve before to increase the air consumption efficiency. The process is somehow different in this, fixed volume discharged. If, for example, we assume equal volume of barrel and plenum, the pressure at the end of projectile travel will be 0.5 of the starting pressure and 0.5 volume of the air will be "wasted". So rather tan "healing" the burst disc to close, I can get a similar effect by controlling the ration of the plenum/barrel volumes.
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With a burst disc you are, of course, working with a dump valve.... The larger the valve, in proportion to the barrel volume, the more potential FPE, but the less efficient the gun will be.... I never exceed 50% of the barrel volume with a dump valve, and 25-33% is a lot more common.... Going larger than 50% is chasing diminishing returns.... Here are a couple of examples....
(https://hosting.photobucket.com/albums/oo221/rsterne/Millenium%20Pumper/.highres/DumpValves_zps8ff30e30.jpg) (https://app.photobucket.com/u/rsterne/a/2b6b9a8f-bf4c-41f4-8426-985eaf5ed6aa/p/a0fd3d9a-96c7-4f4f-bfc0-9e346f70e1db)
My last post was to show why I seldom use a dump valve, the efficiency is low, unless you are going for relatively low FPE....
Bob
Thank you, Bob. Interesting graph. In my tests the plenum is 80cc for about 100 cc barrel (0.45" x~40" long. But I am still a long way to fine tuning the performance. I am now building a new test receiver with an adjustable volume - a threaded piston in the back. This will allow me a wide range of pressure/volume ratios. I am using now steel foils and experimenting with a magnetic bolt face to extract the spent disk.
madeInLV, you suggestion of comparing in-line vs two right turn design is interesting, but maybe something to do at a more advanced stage.
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For an 80% valve volume, your residual muzzle pressure would be [ 80 / (100 + 80) ] time the starting pressure.... ie 44.4% of the starting pressure.... and that is the amount of air "wasted".... The average pressure would be 72% of the starting pressure.... If you could close the valve the instant the bullet exited the muzzle, you would trap that 44% of your initial plenum charge, instead of it leaving the barrel without doing any good.... Using my "lofty goal" formula, a 100 cc barrel at 100 bar might be able to produce (100 / 16.4 ) x ( 100 x 14.5 ) / 24 = 368 FPE.... Let's use 300 FPE to keep it simple, and let's start with 100 bar in your 80 cc plenum (double the pressure, double the FPE).... Starting with those numbers, it is easy to compare a dump valve with a conventional PCP....
Dump Valve.... Air used is 80 cc at 100 bar = 8000 bar.cc.... (8000 / 300) = 26.7 bar.cc/FPE = 0.61 FPE/CI
Closing Valve at Muzzle.... Air used is (100 - 44.44) bar x 80 cc = 4444 bar.cc.... (4444 / 300) = 14.8 bar.cc/FPE = 1.11 FPE/CI....
Closing Valve at 50% of Barrel Length (drop the FPE 10%).... Residual pressure is [ 80 / (80 + 50) ] = 61.5%.... (100 - 61.5) bar x 80 cc = 3080 bar.cc.... (3080 / 270) = 11.4 bar.cc/FPE = 1.44 FPE/CI....
You may not care about the efficiency, I just wanted to give you a comparison to ponder.... If you had a larger reservoir in a PCP, with the same valve timing, the pressure drop would be less, and the power and efficiency would increase further....
Bob
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In theory, the smaller that distance, and consequently the smaller the total port volume, the higher the pressure at the base of the bullet before it moves.... I actually wonder if that is the reason that not retracting the nose of my bolt quite clear of the back of the barrel port gives a slight increase in velocity.... The nose of the bolt is restricting the flow area, but the initial pressure is higher.... resulting in more power....
I seat my bullets just ahead of the forward radius of the barrel port....
Bob
After reading most of this thread, I have one idea that could well be dumb, but... If you put a tiny rubber o-ring on a slug or a pellet, so it delays the burst and allows pressure to build up behind the pellet, wouldn't it increase power? if you put it close to the end of the pellet, it could roll out of it and fly out of the barrel after the pellet. :-\
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After reading most of this thread, I have one idea that could well be dumb, but... If you put a tiny rubber o-ring on a slug or a pellet, so it delays the burst and allows pressure to build up behind the pellet, wouldn't it increase power? if you put it close to the end of the pellet, it could roll out of it and fly out of the barrel after the pellet. :-\
The only practical way to increase the pressure at the base of the pellet is by increasing the pressure at the base of the pellet...
What I am saying is, larger plenum = more pressure. Higher set point / fill point = more pressure. Larger pathway from valve seat to pellet up to bore size = more pressure, less turns, obstruction and distance between valve seat and pellet = more pressure.
Our valves flow plenty good. Want more flow? Go with bigger bore...or raise pressure. Flow is not the issue as much as is the energy potential in compressed air, versus say helium.
There are no large gains to be had, even going from a valve 180 degrees out from its bore to one in line...its marginal when compared to most of the other factors mentioned above.
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Looks like Ed has figured this one out . https://youtu.be/WTeMJC4nRw0
Talk about redesigning the wheel. All I can say is WOW. I’m putting mine through is paces and it’s well worth the price of admission.
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After reading most of this thread, I have one idea that could well be dumb, but... If you put a tiny rubber o-ring on a slug or a pellet, so it delays the burst and allows pressure to build up behind the pellet, wouldn't it increase power? if you put it close to the end of the pellet, it could roll out of it and fly out of the barrel after the pellet. :-\
The only practical way to increase the pressure at the base of the pellet is by increasing the pressure at the base of the pellet...
What I am saying is, larger plenum = more pressure. Higher set point / fill point = more pressure. Larger pathway from valve seat to pellet up to bore size = more pressure, less turns, obstruction and distance between valve seat and pellet = more pressure.
Our valves flow plenty good. Want more flow? Go with bigger bore...or raise pressure. Flow is not the issue as much as is the energy potential in compressed air, versus say helium.
There are no large gains to be had, even going from a valve 180 degrees out from its bore to one in line...its marginal when compared to most of the other factors mentioned above.
Not entirely Correct Matt there are many ways to aid in the bullet velocity beyond these normal methods. I've been working on a choked flow yielding very good results as well as another method that so far has trumped all other methods Ive ever tested and as soon as the patent is In place Ill share the method but for now the Choked flow method is working very well in our 50 cal test rifle.
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Looks like Ed has figured this one out . https://youtu.be/WTeMJC4nRw0
Talk about redesigning the wheel. All I can say is WOW. I’m putting mine through is paces and it’s well worth the price of admission.
This works very closely in design as the Umarex Hammer valve.
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Yeah both are pilot valve operated main valves. Pressure difference opens and closes the main valve.
Interesting design on the Leshiy 2
Testing rocket nozzles for more power, the problem with chocked flow is the chocked part.
Marko
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While a properly designed C-D nozzle can accelerate the gas itself past Mach 1, the problem is that when the flow chokes, the pressure is reduced by 47%.... This leaves less force to accelerate the projectile....
Bob
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I tested De Laval nozzles in the past, with very light projectiles you would gain some speed but anything heavier than plastic pellet would loose velocity.
Like Bob said you loose too much pressure and the flow is not fast enough over the nozzle to gain anything.
On open nozzle the thrust is bigger but then you have flow velocity gained from the nozzle.
Marko