Improved "dump valve" for max power

[subscriber]

"Max Power" valve stays open until projectile leaves muzzle.  So, not an actual "dump valve" because it closes at the end of the shot cycle.  Not the recipe for efficiency, but that does not seem to be the goal. 

Section of interest starts 1:30 into video.

Note the supersonic velocities on the data tables displayed.  Is this specsmanship, or smart science?

[rsterne]

WOW, I'm impressed.... although somewhat confused at the same time.... 

Here is a screenshot of the claims in .22 cal....



The FPE claims are high, but since no barrel length is stated, they cannot be disputed.... although the 1624 fps claim on air for a 9.8 gr. pellet seems extremely high.... The 103 FPE with a 37 gr. bullet on 3000 psi air is not terribly unreasonable (depending on barrel length), I did 106 FPE on 3000 psi with a 41 gr. bullet in a 28" barrel in my Hayabusa….

Here is a screenshot of the claims for the Seneca Dragon .50 cal....



The claim of 483 FPE on 3000 psi air is not unreasonable, as it represents 91% of my "lofty goal" calculation for the Seneca Dragon with it's 21.65" barrel (0.50 x 0.50 x PI/4) x 3000 x 21.65 / 24 = 531 FPE....

They claim that the pressure stays constant during the shot, which of course is only possible with an infinite reservoir.... They also claim 6-8 shots at "full power" with air and 4-5 shots with the lighter gas on a fill.... I wonder how they keep the pressure constant, to keep the velocity constant, while using that much air per shot?.... Some things to consider....

The Seneca Dragon has a 500 cc reservoir in the .50 cal model.... It has a 21.65" barrel.... That means that the barrel volume is 70 cc.... They state that the valve stays open for a "preset time", until after the bullet has left the muzzle.... Let's assume that they can close the valve instantly, at exactly that instant....

The pressure at the muzzle on the first shot is (500 / (500+70)) x 3000 = 0.877 x 3000 = 2632 psi.... On the second shot it is 0.877 x 2632 = 2309 psi.... On the third shot it is 0.877 x 2309 = 2025 psi.... On the fourth shot it is 0.877 x 2025 = 1776 psi.... On the fifth shot is it 0.877 x 1776 = 1557 psi.... On the sixth shot it is 0.877 x 1557 = 1366 psi.... On the seventh shot it is 0.877 x 1366 = 1198 psi.... After the eighth shot the air remaining in the reservoir is down to 0.877 x 1198 = 1050 psi.... and that is assuming the valve can close instantly and completely the instant the bullet leaves the muzzle.... It has to be open at least that long, to meet their claim that the "pressure is constant until the bullet leaves the muzzle".... If it's open longer (very likely, particularly as the pressure drops), the pressure each shot will drop even more.... My guess is that the 6-8 shots they claim on a fill (4-5 with the light gas) is to empty.... not at all "full power" shots....

I see a couple of obvious conclusions.... With a valve that stays open until the bullet leaves the muzzle, the velocity must drop as the pressure drops.... The FPE of any PCP is roughly proportional to the average pressure inside the barrel during the shot.... This means that the gun cannot deliver 6-8 "full power shots" on a single fill.... If they can prove otherwise, I will gladly apologize.... 

Bob

[anti-squirrel]

Only way I can follow claims like that is an outrageously large plenum and some trick timing on the springs/closure rates.

Still fun stuff, though

[subscriber]

Thanks for the careful analysis, Bob. 

To add to the massive air reservoir pressure drop between shots; if the valve stays open until the projectile leaves the barrel on the "first shot", the pressure would not "stay constant" during the shot, because the barrel becomes a long skinny pipe (especially in .22) with significant flow losses.

Above the data tables is CAP's website:  https://www.cap-guns.com/

Perhaps capguns is an appropriate name, or this is an early April 1 announcement of sorts   Or, the "light gas blend" is a stoichiometric hydrogen air mix, with an undisclosed spark plug somewhere...

Their tagline, "Pneumatic Guns using C.A.P. technology can now equal or exceed conventional firearms in energy and velocity performance." has me scratching my head.  A claim of exceeding a .22 rimfire with its diminutive powder capacity hardly seems justification for such a broad statement.  Then, in the back of my head there is "why?"  Perhaps like black powder muzzle loader season and bow season, "air rifle season" could fit in somewhere.  Else, if you need PB ballistics, use a PB.  Certainly, such broad claims may get noticed by those who are looking to frown on airguns in general, and used in a campaign against them.

[subscriber]

Only way I can follow claims like that is an outrageously large plenum and some trick timing on the springs/closure rates.

Still fun stuff, though

Operative words are "outrageously large claims"

[Insanity]

Ok so I am not the only one who caught the hydrogen mix and think detonation of some sort. If that is the case it is not longer a air gun but a firearm.

[Rob M]

well , im not even sure why they posted " light gas " numbers, unless everyone that owns an airgun happens to have said light gas compressed to 3000psi. ..( which is not the case_

would be nice if we could buy 12 gram helium carts though , filled to 3000 psi (-;

[grand-galop]

One thing worth to mentionned...
Since Bob does calculate the claims and come close to them, shout out to this company to do close to what Bob perform daily for us airgunners..
Some will be ticked off with the claims, but, they are a step up from the original version and will push other brands to catch up..

[Doug Wall]

The "light gas blend" is pretty much a gimmick. I've never heard of a helium/hydrogen gas mix being used for anything else, and I expect it would be hard to get. Also, most welding type cylinders that you would get from a gas supplier are only 2200 psi. That would mean running the gas through a compressor to get it into a 4500psi tank so that you could fill the gun. - I suppose that you could run the gas (regulated to 100 psi) into certain types of hand pumps to fill a gun.

[Ribbonstone]

Just one guy's opinion.
Velocity/energy claims seem possible....have reservations about the shot count claims.

Folks have experimented/posted with dump valves. The energy levels produced on the vid don't seem out of line with what is possible.

So far as projectile speed/energy is concerned, closing the gas off right at pellet exit wouldn't be any different than never closing the valve at all....it happens after the shot is on it's way.

Even at face value,would be using at best about Bob's estimate of 70cc'sper shot...only if they actually achieve the pertfect valve shut off....which cast some confusion/doubts about the shot count claim.

Maybe they did create a magic valve that would be able to shut off at just the right moment....and be able to tell self-adjust for difference in timing needed between a light slug and a heavy one...am just not buying the "fullpower" shot count from a non-teathered rifle.

[moorepower]

The "light gas blend" is pretty much a gimmick. I've never heard of a helium/hydrogen gas mix being used for anything else, and I expect it would be hard to get. Also, most welding type cylinders that you would get from a gas supplier are only 2200 psi. That would mean running the gas through a compressor to get it into a 4500psi tank so that you could fill the gun. - I suppose that you could run the gas (regulated to 100 psi) into certain types of hand pumps to fill a gun.

I thought the tanks were 4500 psi.? I might go out to my garage and look, after my coffee!

[Insanity]

The "light gas blend" is pretty much a gimmick. I've never heard of a helium/hydrogen gas mix being used for anything else, and I expect it would be hard to get. Also, most welding type cylinders that you would get from a gas supplier are only 2200 psi. That would mean running the gas through a compressor to get it into a 4500psi tank so that you could fill the gun. - I suppose that you could run the gas (regulated to 100 psi) into certain types of hand pumps to fill a gun.

I thought the tanks were 4500 psi.? I might go out to my garage and look, after my coffee!

You can get tanks that go above the 2200PSI it really is dependant on your supplier. I could get a 6k PSI bottle if I wanted but its very costly.

[Doug Wall]

The "light gas blend" is pretty much a gimmick. I've never heard of a helium/hydrogen gas mix being used for anything else, and I expect it would be hard to get. Also, most welding type cylinders that you would get from a gas supplier are only 2200 psi. That would mean running the gas through a compressor to get it into a 4500psi tank so that you could fill the gun. - I suppose that you could run the gas (regulated to 100 psi) into certain types of hand pumps to fill a gun.

I thought the tanks were 4500 psi.? I might go out to my garage and look, after my coffee!

You can get tanks that go above the 2200PSI it really is dependant on your supplier. I could get a 6k PSI bottle if I wanted but its very costly.

Are you sure? I know that 6k psi AIR is available, but I've not heard of 6K psi specialty gasses.

[Insanity]

It was nitrogen in my case.

[rsterne]

The only Helium I can get here is 2200 psi.... I plan to boost it using a ShoeBox, feeding that through a regulator on the He tank set at 125 psi.... Just based on the much lower density of the Helium, which is 1/7th that of air, you can expect about a 50% increase in FPE with relatively heavy bullets.... and that would increase with light ones, because their mass is a smaller percentage of the total.... meaning that reducing the mass of the gas is even more important.... I don't have any experience using Helium (or an even lighter H / He mix), so I can't comment on the numbers claimed....

I still have serious doubts about that 1624 fps claim with a 9.8 gr. pellet on 3000 psi air, though.... 

Bob

[subscriber]

Hi pressure helium and hydrogen are hard to keep in a tank.  Those small molecules tend to diffuse through materials; never mind small flaws.  Hence their usefulness for leak detection.

Hardened steel may be damaged by high pressure hydrogen, although it may need to me in mono-atomic or ion form to cause rapid hydrogen embrittlement: www.imetllc.com/training-article/hydrogen-embrittlement-steel/

Now, you might want to consider helium only, due to its inert nature, so hydrogen's problems may be moot.

[rsterne]

Personally not interested in Hydrogen due to its combustibility....

Bob

[Rob M]

Personally not interested in Hydrogen due to its combustibility....

Bob

just make the entire gun telfon coated (-'

[Ribbonstone]

OK...at least we agree that keeping things up to 3K would be a good idea for any kind of  testing/practice.

So lets say the "elvish-magic-valve mod" turns out to live up to expectations.

Which makes considering the filling of one the step AFTER they have proved to do what they are claimed to do.


Believe 92-99% of  us would just have to deal with the air/nitrogen side of the spec. sheet.

Do know how easy it would be for me,living in an urban/industrial area, to find/buy/ret 4.5K tanks of air.....or 6K tanks of Nitrogen.. .or other industrial gas that wouldn't be useful (too heavy) for airgun uses......but don't have a clue how easy it would be to buy/rent really high pressure (lets say between 4 and 6K) tanks of "mixed gas"....or even if I could.

[MJP]

Oh why oh why does every freaking company boast with the most powerful airgun bs when they are not even close.
On air they are not doing magical numbers, and with special elf farts they are just being ignorant of the danger. Hydrogen has a very broad ratio where it becomes flammable with air. And it is very easy to ignite.

Its just critically balanced valve that closes when pressure drops as the cork leaves the barrel.
How else would you drop it in a claw?
And 500fpe with 3000psi on .50, very easy with .457 so should be child's play with fifty.

Marko