ABS carbon barrel heat dissipation......

[goodgrouper]

I have been paying very much attention to my barrel on my 338 thunder as far as how fast it cools off but I got absolute concrete facts about it recently with the help of a thermal imaging camera owned by my good friend, Idaho Preacher.

Pictures will be posted here soon of the heat getting sucked right out of the barrel! For more details, check out my thunder thread here. In one word: AMAZING!

 

[Buffalobob]

A month or so ago, I took a little time and checked the thermal conductivity of barrel stainless steel versus carbon fibers. Conductivity is a measure of the speed at which heat will flow from one spot to another or from one area to another. It appears that there are so many differrent formulations of fibers that you can make it do whichever you want it to insulate or dissapate. Some types of fibers are a 100 times more conductive than barrel stainless steel and some are only two times more. Then there is the gel that is used to bind the fibers together and make it stick to the barrel (if any). I do not know what it is but it would have a major bearing on heat transfer. Even a thin film can be a major barrier or help to heat transfer. An example of this is in building tank armor. A thin layer of air will shut down a lot of heat transfer and will absorb a lot of shock transmission so air sandwiched between steel layers is better protection than solid steel for a shaped charge explosive head. So any thin film between the steel and the fibers is vitally important to know about.

My original impression on carbon fiber was the same as Kirby's that it was used as insulation and what I now believe is you really must look carefully at the metal of each application and the type of carbon fiber that is used in order to determine what the final outcome will be. Heat may be retained or transfered. A lot of science involved in order to get the right combination.

Just one note on the thermal imaging. The external surface of the barrel is obviuosly not what is at issue. It is just what can be measured. The critical area is the first few 0.01 inches of of steel inside the barrel. There will be a temperature gradient from the throat area inside the barrel to the outside. The current theory on fire cracking inside a gun barrel or even other steel seems to be linked to the inside (not outside) surface layer temperature versus the temperature just a few hundreds of an inch deeper in the steel and the coeffeicient of expansion of the steel. The difference in temperature in those few hundreds of an inch of steel casues differences in expansion and therefore stress cracks appear. The heat also causes some hardening of the steel which then not only increases the stress fractures but also creates a spalling effect. In other application besides barrels, the term heat cycles is used. In other words, a boiler is fired up and run at temperature (or a car engine) for a while and then shut down and is considered one cycle. With a bolt action rifle, it is unclear what a cycle is. I have seen demonstrations where M-60 (308) machine guns were fired until the rounds were cooking off from the chamber temperature and then continued until the barrel was actually red with heat. This one time destroys a barrel in one "cycle". The question of what actaully causes heat checking is still being debated and thusly the cure for it is still at question. And finally, I would simply say that my looking into it on the internet does not constitute any real research of a scientific nature. If you want to find bad science the internet is definitely the place to go. Lastly, this post is not to contradict anybody or anything it was just that I tried to spend some time understanding what was actaully going on and thought that I would post my understanding of carbon fiber barrels and throat life. Mostly I concluded that there is a big debate over what causes heat checking - except that it is heat.

If carbon wrapped barrel help throat life then it is going to be a big boon to people who shoot lots of rounds.

Editorial note:
It fits here a little better than over there.

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[Desert Fox]

It is my understanding that the whole purpose of machining a barrel as thin as you could possibly get and wrapped it with carbon fiber was to reduced barrel weight without sacrificing rigidity. As an added bonus, the carbon fiber can act as an insulator. As far as heat dissipation is concerned though, I don't see any contributing characteristic a carbon fiber have to make me believed that it will help to facilitate barrel cooling. The rapid cooling I believed can be attributed to the barrel being thin and therefore has less mass. On the opposite extreme, it is my belief that you could easily cooked these barrel if you aren't carefull. Don't get me wrong though, I like to own one of these barrel. As a matter of fact now that I got an okay from the wifey, I'll be ordering one of Dave's 338 SnipeTac rifle with one of these pole. Just my 1 cent. /ubbthreads/images/graemlins/confused.gif

 

[Buffalobob]

Desert fox

As I said before, one needs to be careful with internet "science" but here is some that illustrates what I was trying to say. There are different types of "carbon" fibers. A barrel wrapper has to choose the right one or else he will be making an oven to cook the barrel.

Science?

[ QUOTE ]
Currently, high thermal conductivity fibers are being evaluated as a reinforcement for metal matrix composites. The objective is to produce a less dense material with an even higher conductivity than that of the metal matrix. A carbon fiber/copper composite with a 39 percent volume fraction of fibers has a density of 6.24 g/cc, as compared to 8.96 g/cc for pure copper. However, the density of carbon/carbon composites, approximately 1.5 -1.9 g/cc, is considerably lower. Thus, from the viewpoint of weight reduction, the use of carbon/carbon would still appear to be preferable.

Surprisingly, studies have shown that the thermal conductivity of a composite often depends more on the matrix than on the fibers. One possible reason is that often some of the fibers are broken and are thus discontinuous down the length of the composite, reducing thermal transport. Therefore, when a high thermal conductivity matrix such as graphitic carbon is used, not only do the fibers contribute to high thermal conductivity, but the matrix does as well. Since the thermal conductivity of graphite is higher than that of any metal, carbon/carbon would appear ideal for high thermal conductivity composites. Furthermore, at temperatures exceeding 1100°F, carbon/carbon composites exhibit higher strengths and moduli than metal matrix composites (see Figure 1). Thus, this combination of higher strength, lower density, and higher thermal conductivity makes carbon/carbon preferable to metal matrix composites in numerous applications.








[/ QUOTE ]

 

[Buffalobob]

P.S. Desert Fox

You are a lucky dog to be getting a Snipe Tac. /ubbthreads/images/graemlins/grin.gif

 

[royinidaho]

gg,

I'm looking forward to those images. ID Preacher's camera is a real boon to the project.

I also appreicate the 'round table' discussion that is going on here.

My feable attempts at documenting barrel temp across the length of the barrel have been more than a little confusing. For an all metal barrel heat seems to flow out from the bore and along the barrel from hotter to colder areas.

I'll have my test barrel back maybe today and will continue the attempts to measure temperature and heat flow patterns.

My Nukalure training left me with two heat xfer eqn's:

Q = MCdeltaT Q=Heat transfer. M = mass flow rate and delta C = constant for the type of material T = temperature difference.

This eq'n doesn't apply to our subject.

Q = uAdeltaT, the other eq'n, seems to be more appropriate for the subject.

Q = heat transfer
u = a constant for the type of material
delta T = temperature difference

However this eq'n is usually applied where there is a constant temperature along the pipe, so to speak.

It seems to be generally understood that the hottest barrel temperature would be at the throat and the lowest somewhere towards the muzzle.

My attempts at altering this heat pattern is to concentrate the higher temperature more towards the case head than the throat.

However, if the carbon fiber not only enhances heat flow away from the bore but also along the barrel at a rapid rate it wouldn't be long until every high intensity cartridge would have a properly carbon wrapped barrel. And all of this because gg is pushing the envelope a bit. Good goin!

So much for that. I'm off to Rexburg to see if that idiot has the RUM barrel fitted yet. The first estimated delivery date back in January /ubbthreads/images/graemlins/frown.gif

 

[7mmRHB]

Desert Fox

maybe you and Buffalo Bob should just go to Rock Creek Barrels web site and hit the links to ABS inc.
It explains how and why Carbonmans fiber works as a heat dissapater.

The independent testing was done by the University of Nebraska School of Enginering.

Mike Degerness (Carbonman) receive a patent on this technology because it works!! It will cool a barrel 3.72 times faster than a steel bbl.

I was there when GG and Idaho P were doing the test and it is very obviouse how good the carbon wrap works at cooling the barrel.

It seems like it would be more productive to read about Mikes technical data and patent data(he includes the patent number so you can check it out)instead of typing speculation as to why something couldn't-shouldn't-wouldn't work even though you have no personal experiance with an A.B.S.Inc. barreled gun.----RHB

 

[goodgrouper]

Buffalo Bob is correct. There are many different forms of carbon fiber and adhesives. Christensen uses an altogether different formula than ABS. ABS's is engineered to transfer heat and do it quicker than anyone else's and I have seen it to be a real deal. It is however slightly heavier than Magnum Research and Christensen's wraps.

 

[Buffalobob]

7mmRHB

If my discussion lead you to believe that I said it wouldn't or couldn't work I am sorry about that.

My discussion was about carbon fibers, gels and heat transfer in general. It is possible to build a light barrel that retains heat or a light barrel that sheds heat. One would a have to know a lot of detailed coeffecients and thickness of materials such as Roy's post says before one could calculate what will happen. There is also the alignment of the fibers, which affect heat transfer.

Some people are may not be very interested in the science behind a carbon wrapped barrel and some people may. Some people will just want to know if it works and could care less why it works.

My preference in looking at sceince is not the commercial vendor but independent research that supports the claimed application. The article I posted a link to was from Penn State and was discussing areonautical applications and comparing carbon to other heat transfer materials. Research scientist are people just like anybody else and their results are often influenced by who funded the research and follow up promises of additional funding. About a month ago when I looked into this, I actually collected the thermal conductivity coeffiecients of barrel stainless steel and about 10-15 diffeerent types of fibers. This information alone was enough to convince me that the heat transfer was theoretically feasible.


Sometimes I just draw up little cartoons of sharks and stuff and sometimes I don't. There was and is no intent to debate or argue with anyone. It was just background information.

 

[Black Diamond 408]

Guys:

The testing i did on the Carbon ABS bbl on the 338 Snipe-Tac was like this. During the bbl break in, i used the Mike Rock method, i kept checking the bbl temp and could feel the temp of the carbon rising fast, after 5 shots it was rather warm on the outside. The steel shank was almost cool to the touch. The carbon fiber was pulling the heat away from the steel bbl. I didn't have a thermometer to do any actual tests. The bbl dia on this rifle was 1.400 at the breech, 1" at the muzzel 33" long. I did a very scientific test between the two rifles, after 5 shots i would let the cleaning rod sit in the bbl for a min, the carbon bbl the cleaning rod was just warm. The non-carbon bbl the cleaning rod came out hot.

My personal 338 snipe-tac has a std stainless bbl, same length. after 5 shots the bbl is so hot you cant touch it. It takes quite a while for it to cool down. The carbon bbls really do the job! At least ABS bbls do.`

I read articles on other carbon bbl makers, ones the problems occured with, they seem to insulate the bbl liners.

Mike is a great guy to deal with!!!

Go Huskers!

 

[Black Diamond 408]

Desert Fox:

I will be getting some new action blanks in soon. I have a re-designed Rem 700 type action made special for the 408 case. These are in stainless steel, wire EDM cut. My Ti actions are only in the full bolt style, they need a special hardened insert for the high pressure case.

I am thinking of using an ABS carbon bbl on my 10,3mm project. It will have a 1.650 breech tappered to 1.250 at the muzzel. Mike says that if and when the bbl is shot out he can rebore it to 50cal. You get double life out of the bbls. Same with the 338 snipe-tac, he says you can have it bored to 408 or 375 cal.

Dave

 

[Guest]

[ QUOTE ]
Research scientist are people just like anybody else and their results are often influenced by who funded the research and follow up promises of additional funding.

[/ QUOTE ]

You might want to reconsider that outrageously condemning myth. A researcher is only as good as her work and credibility. Having participated in funded research for the last two decades I can tell you I've never read a paper or met an investigator who skewed results for short term funding. I suppose when the VP is calling the best research junk (then admitting he was wrong a few years latter) it's easy for the public to believe that myth.

Other than the disparaging comment, your post was stellar.

[ QUOTE ]
Desert Fox: ...The rapid cooling I believed can be attributed to the barrel being thin and therefore has less mass...

[/ QUOTE ]
For a homogeneous/isotropic material (gun barrel steel, carbon fiber is not isotropic) you have the correlation exactly opposite. For a given conductive material, heat transfer is increased with mass and surface area. A thinner barrel cooling faster must be MUCH more conductive.

Roy in ID.
Temp can be calculated on a pipe via solving the product form of the wave equation. See any elementary book on numerical solution of partial differential equations.

I plan on using 5 of omega's Thermocouples connected to my A/D (going to my laptop). At the same time I'll have an RSI strain gauge recording pressure. I was hoping to correlate the timestamps, pressure, temp change and get good reading for the barrel surface. I think buffalobob is right, what counts is the temp inside the barrel. To solve the heat equation for every position on the pipe you need the boundary conditions (ie, the temp in the throat)

 

[Guest]

Click this for GG's IR report

Here's the images.

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http://img.photobucket.com/albums/v358/goodgrouper/thermal3.jpg
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[goodgrouper]

Thanks for your kind words and for the link B1g B0re. I really appreciate it.