Radiator barrels

[Justin Hell]

After stripping a number of parts over the last few weeks, including several gas tubes...I made a bit of an epiphany regarding the finned barrels found on some Chinese SKSs.

If you have ever tried to get a gas tube into the white, you probably found yourself wondering why they made it such a pain in the neck with all those ribs under the handguard being so difficult to remove the bluing/paint, what have you. This feature of all SKSs doesn't get discussed, and is just considered the way it is I guess...but it serves a purpose.  Cooling.

By ribbing the surface, you are increasing the surface area of the part in question. The gas tube is obviously getting some pert dern volcanic activity going on in there...especially under continued fire, the handguard is actually INSULATING it on more than half of it's surface, so the ribbing helps to combat that. 

The ribbed barrels caused some to speculate that it was worn machinery putting a nick in the surface while it was being machined, but that would be more of a threading effect whereas the ribbed barrels exhibit more of an intent for them to be there...as they are circles, not spirals. They are combed into the surface after the barrel tapering has been completed. They are also not present in the locations where the RSB, stock ferrule, gas block and FSB are. Towards the front of the barrel taper, it seems like the combing for the ribs doesn't make contact, at least on some, my DB looks crummy in that area, whereas my 0226 it is perfectly machined...with intent. If the dating system is correct, and it it tough in this area to be sure, the DB should predate the 0226 by a couple of years....showing possible increased efficiency in doing it properly over time.

I think the Chinese were looking for a way to cool the barrels faster, perhaps to prolong life, perhaps to improve consistent accuracy...maybe just to reduce burnt hands?  I want to get one of those laser temperature gauges, run two SKSs one regular, and one with the radiator barrel (I am trying to coin that...ribbed sounds too much like it is for her pleasure, and we already have French Ticklers) run ten rounds apiece through them, and note barrel temps over time, and see if it is both a viable hypothesis, and if it actually works.

It is a little sloppy out here still to try this out, but if anyone else has one of those gauges, both types of barrel and the willingness to burn through a box of ammo for the experiment...I am very curious if I am correct.  Surface area, no mater tiny these fins are, is crucial for cooling...even a tiny amount on the surface is huge. Processors wouldn't need fans if they were given enough surface area on a heat sink to cool them, but computers would be much larger if that was how they did it. If you consider the valleys and peaks over the length of the barrel, with the ribs it gives the surface area of nearly two barrels.

After reading an article posted here (I forget by who and where) about the Chinese referring to 'improvements' they made during their production of the SKS, it makes me wonder if he wasn't just referring to the inverted take down lever. I think some of these improvements may have been more than just cost cutting procedures. I think the radiator barrel was one of them. Whether it worked or not is yet to be seen...and it may have been a minor enough improvement that it wasn't fully implemented on all late production guns.

It might just be a weird thing isolated factories attempted, kind of like the /906\ism of the 'dented' magazines. But, it still is a data point that would be interesting to see if we could nail down where these were done. It might even link up some of those factory numbers that may share the same factory....

Discuss.

[Greasemonkey]

So let me see if'en I got this right..

Your saying these are cooling fins. This example is an Ak...I know, but I have an SKS like this also, but I had these pics handy.




"If" those are cooling fins......there ain't, in my book much total surface area added by the ridges, I'd say no more than a few square inches at best, and thats what aids cooling, surface area, along with air flow. Which around any barrel, air flow would be low, short of heated air rising, being replaced by cooler air, and the whole thermal dynamics mess, then throw in the Thermal Boundary Layer, a principal in fluid dynamics that states that air will not even make contact with your gun's barrel.


If one wants surface area, a Thompson has way more cooling surface area with the little bit of fins on it's barrel than an Ak or SKS. Also... if the cooling benefit was actually worth the added time and machine work, why would the 1928A1 Thompson get rid of the barrel cooling fins.. as per the U.S. Ordnance Department, they deemed just the open bolt design was enough to cool the weapon. I don't see any SKS getting as hot as a ribbed or even non-ribbed Thompson in a "war time climate" given each rifles respective rate of fire, the Ak yes, it's do able.

[Power Surge]

We had a lengthy discussion about this topic not long ago, that was a little bit heated because it was started by a new member that was trying to sell a late production SKS and basically wanted this "feature" to be a selling point. (and ever after discussion, he did in fact use his own description of the fins in his GB ad).

They are lathe marks. I did very close inspections of them on several late production SKSs I had at the time. They have a start and end point and they are a spiral. They are not deep enough to be a heat sink of any effectiveness.

I then pulled all my early smooth barrel SKSs out of their stocks, and inspected them closely.... Guess what? You can see very faint leftover marks on some early guns too, where they didn't smooth the barrel 100%.

MY personal opinion, is that on the later guns, some arsenals did away with the barrel smoothing as a cost cutting measure. Remember, the Chinese were trying to cut production cost on SKSs during that time.

Just my 2 cents.

[Justin Hell]

Ah,

I must have missed the end of the discussion about that, or read it somewhere in passing and thought it was dismissed as lathe marks, which made sense to me at the time seeing how they just trailed off on my DB. I didn't pay attention to the other until recently and it entered my mind as I was scrubbing away.  The Thompson fins were what actually gave me the notion that could be what they were, but in a much less machining intense fashion...even as low as the ridges are, it would double the surface area...minus the parts they must have nulled off for the barrel components to live. My lack of knowledge about thermodynamics abounds.

Something I had considered was the influence of the air cooled motorcycles built nearby, but I hadn't seen any /26\ guns like that, so I dismissed the idea as being a failed experiment at smaller arsenals, since the idea didn't carry over to later guns. I also didn't get that up close to find start and end points, which I suppose would be there if they just skipped parts in finishing vs. adding ribs post finishing either way. To my eyes, they looked added...but my eyes do suck, and since it has been discussed...I will shut up about it.

I really wanted to use this as an excuse to get the laser thingy...any real world practical use for it would just add to the honey do list. Piss.

On another note, has anyone seen a two piece gas tube where they skipped the finishing? Neither of mine had original tubes.

[running-man]

Fun stuff to think about Justin, but in this case you're overthinking it by a large margin.  Those marks on a lathe cut part are called chatter marks.  They are very common at long L/D ratios (small diameter, long barrel length) and most guys with some machining experience know what they are immediately upon looking at them.  Experienced machinists or new technology can reduce or eliminate these marks by changing setups, feeds, speeds, depth of cuts, or cutters.  I suspect that during the SKS boom of the 70's where the minor shops were producing them, China took a bunch of guys with little machine tool experience and turned them loose producing a proven design.  These machinists didn't have the experience needed to remedy every issue that turned up so when they got a part that started to chatter like these barrels they either didn't have the resources or the knowledge to remedy the problem.  Maybe they simply didn't care as they could clean up the chatter marks from where the gas block and FSB press on and could produce them fairly quickly this way as opposed to either cleaning them up all the way down the barrel as PS says or simply turning down the feeds and taking longer to produce a nicer looking part. 

As for increased surface area on a ribbed barrel in natural convection, the structures have to have a certain profile to even be be somewhat efficient (fin root, fin height, fin spacing, etc.), otherwise they are little better than a smooth surface.  Little ridges like what you see on the SKS barrels are way too shallow to afford much usefulness when it comes to adding surface area for convective cooling.  What winds up happening is you form a boundary layer of very still (stagnant) air very close to the barrel.  This has the opposite effect of what you want as the heat flow must now convect from the barrel to the air, and then must conduct from the stagnant boundary layer to cooler free air farther out to convect away. (air is a terrible conductor of heat, this is why in most air cooled applications you need to have large surface areas and/or higher forced air rates to have a good heat exchanger.)   I honestly couldn't tell you whether a smooth barrel would run hotter than a barrel with chatter marks, but I suspect the difference would be quite negligible (or possibly the opposite of what's expected with the smooth barrel running cooler because of stagnant air issues).


These guys do great videos.  Haas machines are found in most every commodity machine shop (with some kind of NC machine) in in the United States.  (it's a long clip, but the first 3 or 4 minutes will make the light bulb turn on I think.)

[newchi]

Im sorry, you are all wrong, and you are all under - thinking it.
There are secret instructions on each of those barrels if you can find the right stylus and player.

[Greasemonkey]

Im sorry, you are all wrong, and you are all under - thinking it.
There are secret instructions on each of those barrels if you can find the right stylus and player.

Overthinking it... humm, I'll see you and raise 

It's a secret message to the ancient Chinese group "The Green and the Red Societies" on how to take over and destroy The Illuminati, Bilderberg, CFR, Skull and Bones and maybe even the Neo Cons. Certain factory rifles have the plans laid out, other factories have lists of items needed, criteria for the take over, troop movements and names of people in the other groups. Each factory has it's own custom cypher based of the serial number. It takes a reader and special ancient secret decoder ring keyed by the factory listed on the receiver divided by the first 3 digits of the serial, only the highest power at each factory has access to one. Apart, no one rifle would make any sense, get them all together in one place, and you have the plans for world domination, wrapped around a barrel..  

 

Guess anti 2As know this, this is why they want all weapons destroyed.

Cue up Tears for Fears, a blast from the past.....Everybody wants to rule the world... 

[Justin Hell]

Ok, I get it better now...that does make perfect sense. If only I had watched that video a few days ago...I may have saved myself a little grief and money. 

I got a lil' bit of experience with chatter the hard way on a little project.  Nothing catastrophic...but a little living and learning has left little recourse for a M44 bayo's future.....in regular use, it wobbles during deployment with it's flaw hidden, but...it sure looks like a 49 bayonet now. I actually combated the chatter a little too late by doing the exact same thing with the bayonet chucked into a drill I had wifey surging rpms with (after the chatter incident) while I guided against a stone grinder. Previously unable to control both speeds, the resonance began at a crucial point, and a little more metal was on the floor than intended.

I will try to do a search before posting about similar things...my short term memory has been so flaky lately that I am starting to worry. I searched and found the thread PS was referring to, and damned if I hadn't read the whole thing...and forgot all about it...except for the seeds it seems it had sewn in my head that grew into my initial post.

Neuropathy meds.   

I do and did need a new needle for the ol' Pioneer....but those posts were made after I forgot to post this....I did not try it.

[Phosphorus32]

Well, whenever I learn something new from a post then, as far as I'm concerned, it's a good post. Great video on the issue at hand 

[Justin Hell]

Well, whenever I learn something new from a post then, as far as I'm concerned, it's a good post. Great video on the issue at hand 

I agree, perhaps that video should be attached to the end of that other post to resolve it in case future searches lead to it. Or, merging the two leaving out my embarrassing parts.

Here is an interesting photo of where it trails off on my DB It looks like the taper of the barrel pulled away from the lathe, rather than the sander slipping past the portion being smoothed for the front sight. At least to me....then again, the tip of the barrel under the sight would have had to be milled down anyway...so, further confusion.  Perhaps a combo of chatter and a worn tool? It isn't a combo of chatter and smoothing. Perhaps the guy woke up and slowed down the lathe just for a sec, just for my gun.  Or they had a brownout.