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Dieseling

March 6 2006 at 8:32 AM

bill  (Login mfgwwh)
YC

Ok this may sound stupid but what exactly is dieseling? What I mean what are the symptoms. I have done a search on here and all I find is my gun is dieseling...... I have shot approximately 1000 rounds through my Springer and I still get smoke coming out of the breech when I load the next pellet. Is this dieseling? I am using cpl's and I did try the Lube one thing. I ran a bore snake through with a patch threaded on so I could see what exactly I was getting out and it was black. I may have over lubed the pellets I suppose. To lube them I took an old sock sprayed it down with some Lube One and put the pellets down in it and just roll it around a bit.

thanks

 
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Steve in NC
(Login pneuguy)
GM

The "bad" kind of dieseling is detonation - when your springer sounds like a .303.

March 6 2006, 10:34 AM 

A little smoke and smell is okay. If the gun is accurate, ignore it. Springers depend on diesel combustion of lubricant for about half their muzzle energy.

Steve

 
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Phil Schmidt
(Login PhilSchmidt)
YC

"Springers depend on diesel combustion of lubricant for about half their muzzle energy."

March 6 2006, 10:46 AM 

I don't think so.

"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve. "

 
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Steve in NC
(Login pneuguy)
GM

Then kindly explain this.

March 6 2006, 10:49 AM 



http://www.germanft.com/SECRETSE.html

This obviously did also father and son Cardew and contemplated about a way to proof the combustion phase. The result was the so-called "Nitrogen Experiment". To perform this they took a Weihrauch HW 35 air rifle in caliber .22, took it down totally, degreased all parts thoroughly, assembled it again lubricating carefully and correctly all necessary parts and spots. After that it was "worn in" until a chronograph showed constantly a muzzle velocity of 636 Fps with a 14.4 grain pellet. This corresponds to a muzzle energy of 12.9 Ftp. Thereafter the stock was removed and the air rifle was packed in a plastic bag together with a sufficient amount of pellets which was attached for 30 minutes to a vacuum pump to remove all air. Then the bag was sealed gas-tight and filled with nitrogen which is an inert gas not allowing combustion. The barrel was outside the bag but the hole in the latter was air-tight sealed around the barrel the muzzle of which was closed by a rubber bang. Then a series of shots was performed in that way the the rubber bang was removed shortly before firing and then immediately inserted again. The result was impressive: the muzzle velocity was only about 426 Fps which corresponds to a muzzle energy of approx. 5.8 Ftp. Removed from the nitrogen bag and operated in the fresh air the good HW 35 easily developed again its original power. Convinced now?

 
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Phil Schmidt
(Login PhilSchmidt)
YC

It's an interesting experiment

March 6 2006, 11:05 AM 

But they need to remove other variables. Like they would have to remove the action from the bag and place the gun back in the stock when testing. All variables (atmospheric pressure of the nitrogen within the bag, etc, etc) except for the gas in the chamber must be identical for the results to be accurate.

Though probably inaccurate as hell, I'll admit, the experiment they did does tend to lend validly to your claim.

"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve. "

 
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Steve in NC
(Login pneuguy)
GM

Re: "the experiment they did does tend to lend validly to your claim"

March 6 2006, 11:08 AM 

LOL! No offense, Phil, but that line reads as if you typed it through clenched teeth.

Steve

 
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Phil Schmidt
(Login PhilSchmidt)
YC

Clenched teeth?

March 6 2006, 11:17 AM 

Not at all. I think they had some fundamental flaws with their testing methods which would cause inaccuracies in the results but that it still did seem to show that at least a goodly percentage of springer FPE comes from combustion. Whether it is as much as they say would require better testing procedures.

"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve. "

 
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Steve in NC
(Login pneuguy)
GM

Yup. The classic Cardew "Nitrogen Experiment" showed 122% more muzzle energy...

March 6 2006, 11:36 AM 

...is produced when O2 is present in the compression chamber than when it isn't, and yet you're quibbling over speculative experimental "inaccuracies" that might (?) caused by how the action is or isn't mounted.

Unless you really mean to suggest that such "inaccuracies" could account for more than a factor of two difference in muzzle energy, to me it sounds more than a little grudging - hence agreement "through clenched teeth."

Steve

 
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Phil Schmidt
(Login PhilSchmidt)
YC

"caused by how the action is or isn't mounted."

March 6 2006, 11:52 AM 

I DID mention other things. LOL! I just don't accept "results" from questionable testing as gospel truth. I always look at things people say are "THE TRUTH" with a bit of skepticism. It's the Lutheran in me. I try to glean the kernel of truth from their statements. The KERNEL of truth is, "a significant percentage of airgun power appears to come from combustion".

"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve. "

 
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Ken Fawcett
(Login kenatthefarm)
YFOT

Steve is correct and you don't need an experiment...

March 6 2006, 12:27 PM 

to prove it. See above post. Another mathematical way to prove this is to compute the maximum amount of energy that can be derived from the mainspring of your rifle. You will find that it is always about half the FPE at muzzle. Which as you know is exactly the opposite of what we would expect if no chemical reaction were taking place.

 
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Phil Schmidt
(Login PhilSchmidt)
YC

"A significant percentage of airgun power appears to come from combustion"

March 6 2006, 12:42 PM 

FPE at muzzle is determined by the velocity of the pellet and the weight of the pellet. We all know that different pellets of the same weight will give you different FPE at muzzle due to many factors (like blow by, loose fit in breech, etc, etc). So though you can calculate the maximum amount of energy that can be derived from the mainspring (minus lose from transfer of energy), the pellet factors would skew the exact percentage of energy that is created by the combustion. It STILL would totally prove that "a significant percentage of airgun power appears to come from combustion"

I'd say the experiment that Steve quoted was a better measure of exactly how much of the energy is by combustion. B^)

Was suppose to be a smily face below . . .
*** ***
o o
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*****


"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve. "


    
This message has been edited by PhilSchmidt on Mar 6, 2006 12:44 PM


 
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Scot
(Login ishoottrap)

Interesting point

March 6 2006, 12:58 PM 

and something which I'd always assumed was the other way round! Due you have an example you've measured/calculated? I've actually got a sufficiently accurate scale that I use to measure force/draw curves for bows, I could probably do this but am certainly interested in your data!

-Scot

 
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Steve in NC
(Login pneuguy)
GM

Actually, Scot, it IS the other way 'round. The energy released by the mainspring...

March 6 2006, 1:03 PM 

...is typically about three times the kinetic energy imparted to the pellet.

Note the last line in the table on page 10 of this interesing article by Gerald Cardew.

http://www.jonger.dabsol.co.uk/GC%20square%20section.html

Steve

 
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Scot
(Login ishoottrap)

Thanks Steve, that's what I'd always assumed but never calculated... -nt-

March 6 2006, 1:56 PM 

.

 
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Scot
(Login ishoottrap)

I dunno Phil, sounds pretty convincing to me.

March 6 2006, 12:55 PM 

Your objections include "same pressure" and "action in the stock". If they bag the gun is in is inflated at all, it's at least the same pressure as atmospheric and could be a bit more (although, not any significant amount more). As for in or out of the stock, if shot all my guns through the chrono in and out of the stock, I see no discernable difference in velocity and am hard pressed to think of a reason why there would be.

The difference in energy cited in the article is huge, especially compared to the tiny deviations possible from the effects you cite in your objections. Couple that with the observed (albeit, far from controlled) effects of increased energy due to the presence of excess fuel and I think the conclusion is irrefutable.

-Scot

 
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scot laughlin
(Login clasicalgas)
YFOT

Scot- I remember some tests posted here that DID show

March 6 2006, 5:37 PM 

a very small,but repeatable, velocity variation in a springer,depending on whether the gun was held loose or tight.Evidently,when the sping is moving the gun backwards without resistance,less power(by a small amount) is available to the pellet.Makes sense,when you think about it.So in the "no stock" configuration,you'd see a little less power,maybe? Not 50%,or anywhere near...


    
This message has been edited by clasicalgas on Mar 6, 2006 11:05 PM


 
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Scot
(Login ishoottrap)

I'm in Missouri on this one...

March 6 2006, 7:06 PM 

show me. The velocity of the rifle to the rear as the pellet exits the barrel, even if the rifle is completly free to move, has to be so small that it will get lost in the noise of measurement/other factors. It's after the initial piston bounce so most of the rearward motion due to piston acceleration is gone and only the momentum of the pellet/gun system is significant and that's almost nothin' (an 8 grain pellet at 800 fps has .9lbft/sec of momentum so an 8 lb. gun firing said pellet will have .1ft/sec of velocity rearward).

-Scot

 
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Steve in NC
(Login pneuguy)
GM

It's not the recoil of the pellet, Scot, it's the piston and mainspring reaction.

March 6 2006, 7:49 PM 

By the time the pellet leaves the breech, the mainspring has been pushing the gun backward for several milliseconds with an average force of a couple hundred pounds. So the net impulse is actually more than a lb-sec, which will give a gun with a mass of 8lb/32.2lbs/slug = ~0.25slug a backward velocity of ~4fps.

Since the pellet comes unstuck from the breech prior to piston bounce, it's reasonable to assume that it will carry that negative 4fps all the way to the muzzle, and 4fps is easily enough to pick up in an averaged series of chrono readings.

Steve

PS: Did you forget that the English unit of mass is the slug and 1 slug = 32.2 pounds?

 
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scot laughlin
(Login clasicalgas)
YFOT

Thanks,Steve,you explained that lots better than I did...

March 6 2006, 11:06 PM 

as usual....sigh....

 
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Scot
(Login ishoottrap)

But the pellet then regains the velocity

March 7 2006, 9:39 AM 

as the gun comes to rest due to the piston bouncing.

What am I missing? I agree that initially the pellet relative to the ground is 4fps slower but only in the bore, by the time it's out, the gun is no longer moving backward.

No, I didn't forget, I just used lbm and 7000gr/lb.

-Scot

 
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