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Author Topic: Designing a better flowing valve  (Read 25678 times))

Offline flaircraft

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Re: Designing a better flowing valve
« Reply #100 on: January 30, 2020, 11:37:57 PM »
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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Offline KnifeMaker

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Re: Designing a better flowing valve
« Reply #101 on: March 09, 2020, 05:21:52 PM »
I was enjoying this thread. Seems it died an early and premature death.


A shame!


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Offline bear air

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Re: Designing a better flowing valve
« Reply #102 on: March 13, 2020, 08:56:37 AM »
Hopefully it's gone quiet for R&D purposes. It would be great to have some current information on how to improve a valve.
  • Sioux City IA, USA
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Offline madeInLV

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Re: Designing a better flowing valve
« Reply #103 on: February 13, 2021, 06:42:11 PM »
 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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Offline madeInLV

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Re: Designing a better flowing valve
« Reply #104 on: February 13, 2021, 07:22:37 PM »
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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Offline billzweig

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Re: Designing a better flowing valve
« Reply #105 on: March 06, 2021, 10:02:43 PM »
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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Offline billzweig

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Re: Designing a better flowing valve
« Reply #106 on: March 06, 2021, 10:15:17 PM »
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!


Shown here is the safety interlock preventing breaking when pressurized
« Last Edit: March 06, 2021, 11:03:35 PM by billzweig »
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Offline madeInLV

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Re: Designing a better flowing valve
« Reply #107 on: March 09, 2021, 02:11:22 AM »
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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Re: Designing a better flowing valve
« Reply #108 on: March 09, 2021, 12:36:08 PM »
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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1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline madeInLV

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Re: Designing a better flowing valve
« Reply #109 on: March 10, 2021, 08:26:13 AM »
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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Re: Designing a better flowing valve
« Reply #110 on: March 10, 2021, 05:52:44 PM »
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....



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
« Last Edit: March 10, 2021, 05:57:47 PM by rsterne »
  • Coalmont, BC, Canada
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Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline billzweig

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Re: Designing a better flowing valve
« Reply #111 on: March 12, 2021, 10:05:22 PM »
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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Offline billzweig

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Re: Designing a better flowing valve
« Reply #112 on: March 12, 2021, 10:23:00 PM »
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....



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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Re: Designing a better flowing valve
« Reply #113 on: March 12, 2021, 11:11:55 PM »
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
  • Coalmont, BC, Canada
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsenal:
1750 CO2 Carbine, .177 Uber-Pumper, .22 Uber-Carbine, .25 Discovery, 2260 PCP 8-shot Carbine, 2260 HPA (37 FPE), 2560 HPA (52 FPE), XS-60c HPA in .30 cal (90 FPE), .22 cal QB79 HPA, Disco Doubles in .22, .25 & .30 cal, "Hayabusa" Custom PCP Project (Mk.I is .22 & .25 cal regulated; Mk.II is .224, .257, 7mm, .308 & .357; Mk.III is .410 shotgun and .458 cal), .257 "Monocoque" Benchrest PCP, .172/6mm Regulated PCP and .224/.257 Unregulated, Three regulated BRods in .25 cal (70 FPE), .30 cal (100 FPE) & .35 cal (145 FPE), .257 Condor (180 FPE).

Offline PelletRain

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Re: Designing a better flowing valve
« Reply #114 on: July 17, 2021, 05:31:50 AM »
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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Offline PikeP

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Re: Designing a better flowing valve
« Reply #115 on: July 18, 2021, 01:07:54 PM »
Quote
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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