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Angus Trim




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PostPosted: Mon 28 Jan, 2008 3:12 pm    Post subject: What If? {harmonic question/thoughts}         Reply with quote

Several years ago, I was asked if the harmonics of an antique sword, with an iron core and steel edges would be the same as a modern sword of homogenous steel. Excellent question, I certainly didn't have an answer, nor do I now......

In machine tools, cast iron is used as the base, and hardenable cast iron as the ways {surfaces that bear the weight of the moving table, or turret depending on machine type].

Cast iron deadens vibration. When carbide tools meet some of the more exotic or harder steels {and other metals} quite often a vibration starts. And if the machine's ways or base is steel instead of iron, vibration can be a bear. But its usually manageable when its iron. Enough iron, placed properly will deaden the vibration of most machining operations.......

So, how will this work with a sword blade?

I used to think the answers, today though, more questions than answers.........

swords are fun
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Kjell Magnusson




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PostPosted: Mon 28 Jan, 2008 5:54 pm    Post subject:         Reply with quote

Maybe that could depend on the type of iron used? Checking an old textbook about such things, it says that grey cast iron has very good vibration dampening properties due to the graphite it contains, and that this is put to use in machine fundaments and the like. Accordingly, other forms of iron without the graphite (white cast iron and wrought/pure iron) should be lacking the extraordinary dampening capacity. And I might be quite wrong indeed here, but wouldn't iron cores in antique swords be wrought iron? On the other hand, perhaps the harmonics of these materials still differ enough from steel to make a noticeable difference?
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Jared Smith




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PostPosted: Mon 28 Jan, 2008 5:57 pm    Post subject:         Reply with quote

I like your post's topic and general line of reasoning a lot. You may want to tighten up on time frame a bit. When I think of soft iron cored weapons, I consider it to be an item that is not readily available in good condition.

Swords made by Germanic tribes near 0 A.D. were characterized as bending pretty easily. I think these would be good to compare with your cast iron analogy. Swords made near 600 A.D. and later started to exhibit much better mechanical qualities, although still not consistent any where near the degree of quality of modern reproductions. Around 12th century, water propelled fargues were used to drive rapid forging hammers to produce better steel. By 13th - 14th century, steel production was rapidly converted to fairly modern methods (Catalan forges and such.) I would GUESS that most available antiques are from later eras and have more similarity to modern steels than to the earlier iron cored weapons that bent easily.

Absence of evidence is not necessarily evidence of absence!
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Chad Arnow
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PostPosted: Mon 28 Jan, 2008 6:01 pm    Post subject:         Reply with quote

Actually, iron cores are more recent than most people think. As late as the 18th century or so, the smiths in Toledo were wrapping steel around an iron core for their swords.

As far as bending easily, there is written evidence from 800-900 AD of swords that could be flexed to the extreme and still return to true. There were also many mentions of swords that didn't live up to that.

Happy

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Angus Trim




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PostPosted: Mon 28 Jan, 2008 6:10 pm    Post subject:         Reply with quote

Jared Smith wrote:
I like your post's topic and general line of reasoning a lot. You may want to tighten up on time frame a bit. When I think of soft iron cored weapons, I consider it to be an item that is not readily available in good condition.

Swords made by Germanic tribes near 0 A.D. were characterized as bending pretty easily. I think these would be good to compare with your cast iron analogy. Swords made near 600 A.D. and later started to exhibit much better mechanical qualities, although still not consistent any where near the degree of quality of modern reproductions. Around 12th century, water propelled fargues were used to drive rapid forging hammers to produce better steel. By 13th - 14th century, steel production was rapidly converted to fairly modern methods (Catalan forges and such.) I would GUESS that most available antiques are from later eras and have more similarity to modern steels than to the earlier iron cored weapons that bent easily.


Hi Jared

This article:

http://www.myArmoury.com/feature_bladehardness.html

Gives kind of a hint to the construction of medieval sword blades. In that there was no uniformity. Talking to Craig before this article was published, he mentioned that there were a few blades he was aware of that were iron core, with steel outers. I have no idea from that conversation whether we're talking just the edges, or the surface too......

What I'm getting at here, is different construction methods may play a factor in harmonics. What we actually "know" of harmonics in sword blades has to do with the modern repros, which of course, we use modern steels.

So, this is likely a question that will never have a really, firm, verifiable answer. I suspect though, that different blade constructions may very well affect the way blades vibrate. Which would then affect performance......

For me, questions..... and no answers yet.........

swords are fun
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Jared Smith




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PostPosted: Mon 28 Jan, 2008 7:38 pm    Post subject:         Reply with quote

As I peruse it, the article reads;
"The included swords ranged from the 9th to the 16th century. While recognizing that this is not a large enough group to be statistically significant, I separated them into groups by their period, as it is difficult to compare industrial technology from such a wide span of time. Two additional swords were tested, from the 17th and 18th centuries respectively; these were not included in my considerations, though it maybe interesting to note that their average hardness (the only number given for them) were 441VPH (~45Rc) and 472VPH (~47Rc)"

Many of these sampled and graphed in Craig's article would pass as having an average of 50 points carbon content, enough to pass a present day Master knifemaker's test if one knows what they actually have and how to heat treat it. I have not got my forge fired up yet ( am still working out some kinks on the regulator that came with stripped threads and propane tank gas capacity issues..) However, as I understand it, many current day artisans choose a 1050 steel roughly similar in composition to historical blade steel of the last 1000 years just because it is easy to predictably heat treat and produce hardness and temper that begins to approximate optimally modern steel.

I wonder a great deal about the softer cores, and wonder if some of this is not explainable by quench methods, coal and charcoal forging processes of the era. It is not difficult to replicate with modern moderately mild carbon steel materials using "traditional methods." If I ever get to the point of making my own heat treat oven, I hopefully anticipate that blades annealed in a charcoal filled box will exhibit enhanced surface and edge hardness.

Absence of evidence is not necessarily evidence of absence!
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Vincent Le Chevalier




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PostPosted: Tue 29 Jan, 2008 2:29 am    Post subject:         Reply with quote

I guess it depends on what you call "harmonics" exactly...

I don't think the position of vibration nodes would be perceptibly different, as they seem to be mostly a result of the sword's shape and not of its material.

Dampening of the vibration could happen indeed. But I wonder if it is possible to make a blade that flexes, does not bend, and yet dampens the vibrations? One that flexes and dampens but bends I can figure. One that does not flex, does not bend, and dampens would have to be thicker, but it's possible (maybe katanas are in this category?). One that flexes, does not bend, does not dampen much is what we have with modern steels. But all three qualitites together?

And bottom line, does all this change the instant performance of the sword, or mainly its durability?

--
Vincent
Ensis Sub Caelo
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Jared Smith




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PostPosted: Tue 29 Jan, 2008 2:20 pm    Post subject:         Reply with quote

Just for interest, was there such an actual antique sword that you got to see? Sharing some of the details (era, style, provenance, etc.) of it, even if you don't have a photo, would be very interesting to me.
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