Continuing the "Twist vs Damascus" thread

Posted by: Clunkermeister

Continuing the "Twist vs Damascus" thread - 03/03/03 10:44 PM

It's getting too long to load so it needs to be restarted.
Here's my thoughts on the strength subject for what they're worth. We have a modern gun with a "composite" barrel, a Winchester M59. They have a steel liner with a glass thread wound over it and "welded" to it with epoxy resin. This type of winding of a wire or thread would be by far the strongest way to resist a hoop tension load. (wound like thread on a spool) That being the case one would think that the straighter the ribbands were in a damascus barrel the stronger it would be and the excessive twisting and braiding would serve to weaken it if anything. I think this is why the Laminated barrels came out on top in the 1888 tests. Also, the simple twist barrels are weaker mostly due to the poorer materials and lower skilled workers involved rather than the way they were wound. Comments?
Posted by: Oscar Gaddy

Re: Continuing the "Twist vs Damascus" thread - 03/03/03 11:38 PM


With all due respect, I believe that you are again confusing Belgian barrels that were labeled “laminated steel” with the higher quality British barrels that also had the same name. Belgian laminated steel barrels were nothing more than plain twist barrels and should not be compared or likened to the British laminated steel. British barrels that were labeled laminated steel were, by law, required to have a minimum of 60 % steel in the composite. High quality British laminated steel barrels did NOT look like twist barrels or have a twist pattern.. If you read Greener carefully, you will find that the barrels that came out on top in the 1888 trials were three blade (or iron) laminated steel----not twist. If you further read Greener on this subject, he describes the three blade laminated steel barrels as similar to three blade Damascus but assembled in a slightly different manner such that a herringbone pattern was produced on the barrels. They were probably assembled with the twisted ropes forming the ribands all having the same twist direction whereas normal crolle Damascus is made with the ropes having alternating twist directions. John Brindle's multi-part article on Damascus barrels in early issues of the DGJ also addresses the increased strength of Damascus compared to plain twist for welded pattern barrels

Posted by: 2-piper

Re: Continuing the "Twist vs Damascus" thread - 03/03/03 11:40 PM

Russ; I think you may be on to something there though I do not personally feel qualified to answer the question as you state it. Looking forward to seeing others answers. I will add that I feel like there is a definate difference in twist bbls from the better makers, even though on there lower grades, such as H Lefevers, P Parkers, B Bakers etc than the ones found on JABC's. Another aspect I gather from Greener was that he felt they were more apt to break if receiving a sideways hit on a sharp object than a damascus bbl. This of course has nothing to do with strength in shooting.
Posted by: fox16

Re: Continuing the "Twist vs Damascus" thread - 03/04/03 12:10 AM

Also not qualified to pass judgement but I have noticed a fine twist vs. a course twist. The H Lefever I have has a finer twist than the Baker 1897 hammergun twist. The Lefever barrels are much lighter (1905 vintage) and since the gun has seen much use but not abuse (finish gone but barrels perfect) I'll guess it has seen a lot of smokeless in it's life. Just a comment.

happy shooting,
Posted by: TexasGerd

Re: Continuing the "Twist vs Damascus" thread - 03/04/03 07:04 AM

The thing that is not being considered in this is the adhesion or weld strength in the different materials. This is the reason that the M59 failed as a gun because the fiberglass disbonded from the steel causing a matrix much weaker then initially designed.

W/ the Damascus, the key is that the different steel structures were effectively bonded (within each ribbon and even ribbon to ribbon) Shear stress, causing failure of the inter-layer boundary layer, would be the primary method of failure. By angling the welds slightly, you would place a degree of lesser stress across the layers welds allowing them to shed loads into the bands. The overall matrix becomes stronger then it’s individual parts.

In theory Russ is correct in that perfect hoop stress is best mitigated by perfect hoops. Hence, Winchester made their ultra light composite bbls. Problem with a gun is that the dynamic loading/unloading is not best answered by a strict hoop stress analysis.

I’m going to dig some wording up from my old strength of materials and matrix books to get the exact wording, but that’s as close as the old brain bucket can remember.

Posted by: Clunkermeister

Re: Continuing the "Twist vs Damascus" thread - 03/04/03 10:52 AM

Oscar, Yes I know the JABC laminated was not the same as Brit laminated. I was attacking this from strictly a strength standpoint. Do you deny that simple wraping of wires like thread on a spool is stronger than braiding it? We could make a pretty strong barrel by taking a Briley tube and wrapping it with music wire and covering it with duct tape! For damascus we would substitute a small wound cable for the music wire. Tests like the 1888 Brit tests would seem to be an exercise in futility anyway. A barrel thicker of flawless would always beat out a higher order barrel that was thin or flawed and they didn't have ways to test for that in those days.

As for patterns, I find very little difference in the looks of laminated and twist patterns though I admit some laminated are quite beautiful. Some JABCs aren't that bad if redone. Isn't it true that the main difference between the two is in the quality of the material? :rolleyes:
Posted by: Oscar Gaddy

Re: Continuing the "Twist vs Damascus" thread - 03/04/03 03:31 PM


I cannot argue with your model under the simplifying assumptions that you have made. However, if one adds some reality to the assumptions, your model breaks down. These assumptions as I see it are: 1) no flaws exist in the iron and steel strips welded together to make the twist tube, 2) the welds holding the strips together are perfect and cannot be broken and 3) the pressure is always uniform in the tube and does not vary with position. In reality, the welds are not perfect and the pressure indeed varies in the tube in reality. The pressure in front of the shot column is essentially atmospheric and the pressure behind the base wad is whatever pressure is created by the powder burn. At the moment of peak pressure, there is a tremendous pressure gradient in the direction of the bore axis and this gradient exists over a very short distance. This pressure gradient can create a large force in the barrel wall in a short distance and can tend to pull the welds apart. This effect also exists with Damascus barrels but because of the twisting, individual welds in the piled bar are not under stress and there is much less probability of damaging a weld with the twisted construction of Damascus barrels. The most compelling argument is, however, made by John Brindle in Part I of his series in Vol. IV, Issue 2 of the Double Gun Journal. His argument is that the iron and steel strips used to make these barrels inherently have longitudinal and transverse flaws that can result in rupture under pressure. The twisting of the welded bar of iron and steel strips confines any one flaw (no matter how long or wide) to a very small area and in doing so allows the adjacent strips to compensate and take up the slack in holding the barrel tube together under pressure. He also argues that the same cannot be said for twist barrels. I highly recommend reading this article for anyone interested in this subject.

With regard to British Laminated steel, Greener also points out that there were two varieties of British Laminated barrels. The older type did not necessarily have a high percentage of steel and could be either twist or Damascus. The modern “Laminated “ barrels as he called them were the kind that fared best in the 1898 Birmingham tests. These barrels, with up to 75% steel content could look exactly like Damascus (three iron for example) or could have the herringbone pattern because of a variation in construction..

Posted by: Clunkermeister

Re: Continuing the "Twist vs Damascus" thread - 03/04/03 04:10 PM

My "simplified" model was intended to help us neophytes to better understand the basics of how they were made and how the stresses flowed as any stress engineer would do. Of course we won't be making any by those methods.
As for the flaws, I once turned down in the lathe a thick twist barrel to make something and uncovered large areas of crud, probably nonmetalic inclusions or slag that were an inch long and THAT turned me into a non damascus rouletteer! I feel the flaws and imperfect welds are the big difference in a good barrel and a bad one and not the amount or type of pattern/twist/braid they were subjected to. That means good material and best workmanship equals the best barrels. Period.
I must add that the only way to tell if a barrel is cool and flaws are held to a minimum since no two are exactly alike is to proof it and that being the case twist barrels that pass a tough proof are probably as good as any other kind.
Posted by: Oscar Gaddy

Re: Continuing the "Twist vs Damascus" thread - 03/04/03 05:01 PM


I agree that the proof of the pudding with welded barrels is the proof test. However, I think that we are just going to have to agree to disagree re Twist and Damascus. If I was going to play Damascus roulette, I would do so with a three iron Damascus barrel with thick walls with the highest possible steel content like the one that fared best in the Birmingham test or with a gun like my 2 frame Parker GH grade gun with three iron Damascus that Tom Armburst blew up by finally taking the pressure to over 30,000 psi. I definitely would not play roulette with a gun with twist barrels.