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Michael Pearce
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PostPosted: Tue 04 Oct, 2005 9:00 am    Post subject: Harmonic Balance- Myth? Hype? No...         Reply with quote

In a previous post on the ARMA forums Randall Pleasant expressed the belief that so-called 'Harmonic Balance' is nothing more than 'Marketing Hype' and should be included in the 'Greatest Myths' article. I would like to take this opportunity to present a rebutal to this assertion. Please note that I am not attempting to drag the argument here- I have revised some of my beliefs concerning this phenomonen and thought it would be of value to bring those revised beliefs to this forum for discussion.

I must respectfully disagree with the assessment that so-called 'Harmonic Balance' is nothing more than marketing hype. A brief explanation may be in order as to why I disagree- please bear with me if my terminology isn't spot-on. I am a researcher and sword-maker, not a physicist and am somewhat handicapped by the technical language that has evolved in the sword-making industry.

The theory of Harmonic Balance is very simple- when a sword strikes an object the sword vibrates in a wave. Every wave expressed by a solid object has Rotational Nodes where the wave reverses at either end of the object. On swords the rotational node on the blade is what is commonly referred to as the Center of Percussion. This was first recognized and described in modern times in Richard Burton's 'Book of the Sword.' Examination of antique swords has shown that overwhelmingly that the Node at the opposite end of the sword tends to be located where the sword is gripped by the strong-hand of the user. In practical terms this means that shock is not transmitted to the hand when striking with the sword. This location of the rotational nodes creates the effect that we now refer to as 'Harmonic Balance.' This has been observed in actual antiques by not merely myself but by researchers such as Peter Johnson, a well known and respected European researcher and recreator and Craig Johnson of Arms and Armor- also curator of the Oakeshott Collection. Other respected researchers/recreators such as Vince Evans have also noted this phenomonen. Harmonic Balance is independantly confirmed, demonstrable, repeatable and fully meets the standards of scientific proof.

This can be tested for quite simply- Grip the sword firmly with the unsheathed blade pointed straight up, then use your off-hand to strike the pommel firmly. You will observe a spot on the blade that vibrates markedly less than the rest of the blade- this is the 'Center of Percussion' or 'Sweet Spot.' If you feel a corresponding 'dead spot' of minimal vibration under your hand gripping the hilt then the sword is what we call 'Harmonically Balanced.'

I will agree with Mr.Pleasant on this score however- I no longer believe that swords that are 'Harmonically Balanced' cut better due to reduced loss of energy through vibration. He is quite correct that energy loss through vibration will generally be minimal and have little effect on observable cutting power in most cases. After continued study and observation I have come to believe that swords that cut better tend to be Harmonically Balanced (as defined here) rather than swords that are Harmonically Balanced tending to cut better. Generally speaking swords that are closely modelled on medieval swords tend to be Harmonically Balanced. Makers such as myself, Albion Armory, Peter Johnson, Vince Evans and others produce swords based on our observations about the design characteristics of antique swords and as a consequence we make swords that exhibit the characteristic we call Harmonic Balance- just as the antiques do.

The use of the term Harmonic Balance in marketing describes a real and important characteristic found in good quality reproductions and antiques alike. In the past it has been claimed that these swords cut better due to reduced energy loss from vibration- this was not 'hype' in the sense of deliberately misleading the customer but rather a mistake that proceeds from a false assumption. I am sure that with our continually evolving understanding of this phenomonen this will be corrected by makers- at least reputable makers of good character.

A final Note- the term Harmonic Balance is part of the lexicology of the sword-making and sword using culture- it has become a technical term widely used in the community via the internet. It is not the best term for this phenomonen but has become so widely distributed that attempts to employ more technically accurate terminology have been overwhelmed by inertia- however much I wish it otherwise we seem to be stuck with this imperfect terminology. I will say however that I didn't invent this terminology- it was already in use in the sword-making community when I became a sword-maker. It was passsed on to me in the early '90s by sword-maker Chuck Sweet, whom I believe had it from Ike Roe. Mr.Roe had observed these qualities in antiques but I cannot say with any certainty whether the terminology is one that he invented to describe an observed phenomonen or whether it was passed to him by some unknown person and subsequently verified by observation.

It will likely be evening before I am able to respond to any posts on this thread- please be patient!

Michael 'Tinker' Pearce
-------------
Then one night, as my car was going backwards through a cornfield at 90mph, I had an epiphany...
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Josh Brown




Location: Mukilteo, WA
Joined: 08 Sep 2005

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PostPosted: Tue 04 Oct, 2005 8:41 pm    Post subject:         Reply with quote

You know what harmonic balance reminds me of? The archer's paradox.

Sorry, that was a bit of a segue. Anyway, I can certainly see at least one good reason for harmonic balance improving cutting potential - it's less of a scientific thing than an ergonomic thing. A lot easier to focus on following through with a proper cut when your hand is a stable node then when the sword is tyring to vibrate itself free of your grasp. Anyone who's played baseball can tell the difference between a "sweet spot" hit and one that's decidedly not - that slow smooth pressure of a nice line drive vs. that jarring shock like you just tried to barehand a rotating crankshaft...

From a mechanical standpoint, though, the effect on the cut will probably vary in direct proportion to the hardness/toughness of the material struck. After all, all that collision has to go somewhere... and what isn't taken up by drag of the blade pushing through (relatively) soft material is going to be transferred to vibration and elastic collision... neither of which is any too easy on the old sword arm. At the very least, striking while gripping a node is a lot easier on the swordsman, but I could well see striking with a large node/"sweet spot" giving a bit more solid of an impact, as well as tracking far more truly as the cut is completed.
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Mikko Kuusirati




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PostPosted: Tue 04 Oct, 2005 10:11 pm    Post subject:         Reply with quote

While it may not greatly increase cutting power, it seems fairly obvious to me that proper harmonics are vital to a sword meant for striking things. Don't believe that? Take a crowbar, swing it at something solid.

Hurts, doesn't it? Happy

The subtle tongue, the sophist guile, they fail when the broadswords sing;
Rush in and die, dogs -- I was a man before I was a king.
-- R. E. Howard, The Road of Kings
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Risto Rautiainen




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PostPosted: Wed 05 Oct, 2005 4:41 am    Post subject:         Reply with quote

IIRC there was a military saber in use at one time (can't remember where and when) that didn't have good harmonic balance. The troops called it "The Wrist Breaker". So yes, very much an ergonomic thing.
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Joe Yurgil





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PostPosted: Wed 05 Oct, 2005 5:32 am    Post subject:         Reply with quote

Very enlightening post Michael. It seems to me that the reson for wanting a harmonically ballanced sword isn't to perform a better cut, just more of them. Mikko is exactly right. That would hurt. On a smaller scale (a sword) it wouldn't nessesarily hurt right away but in a battle the constant vibrations form striking or even being struck would wear on a person's hand, thus making it more difficult to fight.

Two things came to mind in this post: fencing and baseball. Fencing blades are pretty well harmonically ballanced, the second node (I'm thinking foil here) is usually right in my index finger and thumb. Baseball bats are not really harmonically ballanced. That's why people wear batting gloves. The big difference is with fencing (and sword fighting in general) you are more likely to make several strikes whereas in baseball you just hit the ball once and you don't really need to worry about your hand tiring out.

Sjá, þar sé ek föður minn.
Sjá, þar sé ek móður mina ok systur mina ok bróður minn.
Sjá, þar sé ek allan minn frændgarð.
Sjá, kalla þeim tíl min.
Biðja mér at taka minn stað hjá þeim í sölum Valhallar, þar drengiligr menn munu lifa allan aldr.
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Glen A Cleeton




Location: Nipmuc USA
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PostPosted: Wed 05 Oct, 2005 2:01 pm    Post subject:         Reply with quote

Risto Rautiainen wrote:
IIRC there was a military saber in use at one time (can't remember where and when) that didn't have good harmonic balance. The troops called it "The Wrist Breaker". So yes, very much an ergonomic thing.


This was a nickname that the first American version of the French 1822 picked up from folk who had been using somewhat shorter (and lighter) sabers for several decades. This was the M1840, here in the states and was not replaced by the M1860 (another 1822 derivative) until the American Civil War was well under way.

If someone has some information that the 1822 was widely unpopular with the French and other European countries that used it, I'd be most interested.

Also of note is that a large quantity of the M1840s were imported (mostly from Germany).

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Cheers

GC
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Sean Flynt
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PostPosted: Thu 06 Oct, 2005 11:23 am    Post subject:         Reply with quote

I was under the impression that the 1840 was called the "Wrist Breaker" due to it sheer weight and awkward balance. The 1860 was smaller and lighter specifically in response to those shortcomings. In any case, by the time of the Civil War, cavalry sabers, despite their design, were most effective (lethal) as thrusting weapons. They were also rapidly being abandoned in favor of pistols and carbines, if I remember my American arms history. I'm not particularly interested in how all this relates to the issue of HB, but it's worth pointing out the many potential problems of applying HB theory to later (1700 forward), mass-produced arms. Consider, for example Neumann's description of how hangers typically were manufactured:

Contemporary manufacture normally began with a cast steel bar which was cut into two lengths, each of which would make two blades. After being fed through waterpowered rolling mills which pressed them to the desired shape and size, they were ground by large stone wheels, tempered by warm oil or water, and struck by hardwood blocks for testing. Before being finished by a polisher, the blade had a soft iron tang welded to its upper end. For assembly of the hilt, the components had hollow centers and were simply compiled one above the other on the thin tang. When complete, the tang's end was hammered down like a rivet head, or threaded for a screw-on cap (52).

Apart from the testing of appropriate temper, that process doesn't seem to leave much room for great consideration of nodes and harmonies and such. Perhaps mass-produced weapons might exhibit the desired characteristics simply by virtue of their standard design rather than by individual attention by a smith or cutler. Anyway, starting in the mid-to-late 17th century the western military sword didn't really have much practical combat application for the average soldier (officers, cavalry and Scots excepted as always, of course).

-Sean

"Everywhere I have searched for peace and nowhere found it, except in a corner with a book"- Thomas a Kempis (d. 1471)
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Greg Griggs




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PostPosted: Thu 06 Oct, 2005 12:48 pm    Post subject:         Reply with quote

Thank you michael for the treatise. I don't think anyone who has done cutting or even swinging practice to any extent would argue that even though a harmonically balanced blade may not help in the cut, it definitely is much more pleasurable in the hand to use. Having gone through carpel tunnel and ulnar nerve surgeries in both hands and elbows(not caused by this), I can honestly say that there is a difference in the feel and fatigue factor. My two cents worth.
Not one shred of evidence supports the notion that life is serious.
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Glen A Cleeton




Location: Nipmuc USA
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PostPosted: Thu 06 Oct, 2005 3:34 pm    Post subject:         Reply with quote

Hi Sean,

I found the description of hanger manufacture very interesting but I think it would be short sighted to apply that to sword manufacture (worldwide) that evolved right through to the 20th century. Most countries did favor a thrusting cavalry sword, in the end.

All nations were following this trend.

I believe the 1840 was not decommisioned until 1864. twenty odd years of service that probably saw a strong parallel on the continent (that was my question/thought)

Cheers

GC
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Josh Brown




Location: Mukilteo, WA
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PostPosted: Fri 07 Oct, 2005 8:07 pm    Post subject:         Reply with quote

Sean Flynt wrote:

Contemporary manufacture normally began with a cast steel bar which was cut into two lengths, each of which would make two blades. After being fed through waterpowered rolling mills which pressed them to the desired shape and size, they were ground by large stone wheels, tempered by warm oil or water, and struck by hardwood blocks for testing. Before being finished by a polisher, the blade had a soft iron tang welded to its upper end. For assembly of the hilt, the components had hollow centers and were simply compiled one above the other on the thin tang. When complete, the tang's end was hammered down like a rivet head, or threaded for a screw-on cap (52).


Eek!

So... cast steel bars, cold worked, "tempered", welded to a soft iron tang? The heat treatment wouldhave to be pretty good... and maybe the warm oil bath allowed for some aging to take out some blade stresses? Otherwise... I'd see it as a race between the tang weld fatiguing out and the blade shattering like the stainless katana on QVC...

Excalibur it would surely not be, and I can't imagine the balance, physical or harmonic, being all that great given the processes involved.
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Jared Smith




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PostPosted: Fri 07 Oct, 2005 11:39 pm    Post subject:         Reply with quote

I am not aware of any universally accepted engineering definition of “Harmonically balanced”. Within the specialized field of acoustics there would probably be some pretty good consensus of what it could mean. I consider it fair game for this forum and “martial arts” to define it as it sees fit regarding sword design. I expect that to be pretty challenging though.

A better system for conveying how swords handle would probably describe each model as being equivalent to a certain length and weight pendulum, with some added mass at the handle. (Mass in the handle not really affecting how rapidly it can be accelerated in rotation.)

The couple of people I have seen who expertly demonstrate cutting state that they primarily focus on speed and blade alignment. Vibrations along the flat of the blade are not of much interest. If cutting technique is good, vibration oriented with the flat of a blade will be a small part (couple %) of the result on the wielder’s hand. If thrusting or “spanking with the flat of the blade” is done, the stiffness of the blade and vibration along the flat will be more significant.


This article discusses sword motion with regard to rotational (most applicable to cutting) motion. http://www.thearma.org/spotlight/GTA/motions_and_impacts.htm.

Absence of evidence is not necessarily evidence of absence!
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Mike Luke




Location: Nevada
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PostPosted: Sat 08 Oct, 2005 7:26 am    Post subject:         Reply with quote

Jared Smith wrote:

The couple of people I have seen who expertly demonstrate cutting state that they primarily focus on speed and blade alignment. Vibrations along the flat of the blade are not of much interest. If cutting technique is good, vibration oriented with the flat of a blade will be a small part (couple %) of the result on the wielder’s hand. If thrusting or “spanking with the flat of the blade” is done, the stiffness of the blade and vibration along the flat will be more significant.


This article discusses sword motion with regard to rotational (most applicable to cutting) motion.
http://www.thearma.org/spotlight/GTA/motions_and_impacts.htm.




Your quite correct, personally I think that Harmonics plays little or no role in cutting. However, it's very important to how a sword reacts and recovers after impact. In this case impact is defined as actual fighting. When a sword is struck on the flat, say in a ward a harmonic resonance pattern (standing wave) will result. High anti node amplitudes result in violent behavior and difficulty in controlling the sword. Poor quality swords tend to exhibit this behavior. However the amplitude can be controlled with attention to mass distribution, geometry and temper. Actually "Harmonic Dampening" rather than "Harmonic Ballancing" is probably more accurate.

There is no man worth a leke,
Be he sturdy, be he meke,
But he bear a basilard.
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Mikko Kuusirati




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PostPosted: Sat 08 Oct, 2005 8:50 am    Post subject:         Reply with quote

Mike Luke wrote:
Your quite correct, personally I think that Harmonics plays little or no role in cutting. However, it's very important to how a sword reacts and recovers after impact. In this case impact is defined as actual fighting. When a sword is struck on the flat, say in a ward a harmonic resonance pattern (standing wave) will result. High anti node amplitudes result in violent behavior and difficulty in controlling the sword. Poor quality swords tend to exhibit this behavior. However the amplitude can be controlled with attention to mass distribution, geometry and temper. Actually "Harmonic Dampening" rather than "Harmonic Ballancing" is probably more accurate.

Actually, I find "balancing" to be quite a fitting term. You can't just dampen the vibrations outright - the sword needs to vibrate in order to absorb the shocks it receives fom impacts, and to avoid transferring them directly to your hand. You have to fine tune its vibrational harmonics so that the spot you're holding onto won't shake itself loose from your grip or bruise your hand. If the vibrational balance is off by too much, in either direction, holding onto the sword becomes a feat - and a painful one - in itself; it'd be like trying to hold onto the swinging end of a pendulum clapper as it crashes against the walls of the bell, as opposed to grabbing the stationary pivot.

(This can actually be observed in tools such as hammers and axes, too - if you grip a wrong part of the haft, stiff as they be, it will hurt. You know those ubiquitous cheap hammers with steel tube hafts and rubber grips? The grips usually have a swelling where you're supposed to wrap your meathooks around it. If the tube gets bent, as it often does, the vibrational harmonics of the hammer change, and you'll have to hold onto a different part of the grip to keep your hand from getting unduely stressed. Been there, done that, had the blisters and bruises to prove it.)

Like everything in sword design, it's an act of balancing on the fine line between "too little" and "too much".

The subtle tongue, the sophist guile, they fail when the broadswords sing;
Rush in and die, dogs -- I was a man before I was a king.
-- R. E. Howard, The Road of Kings
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Mike Luke




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PostPosted: Sat 08 Oct, 2005 2:16 pm    Post subject:         Reply with quote

Actually I beleive you are dampening the vibrations or “tuning” them if you will.
All objects when forced will vibrate at a natural frequency or set of natural frequencies the lowest of which is the fundamental frequency. These frequencies are associated with a standing wave pattern. A standing wave pattern is described as reflected waves from one end of the medium that interferes with the incident wave and establishes specific points (nodes) along the medium that appear to be standing still. These patterns are only created at specific frequencies and are known as “Harmonic Frequencies” or simply harmonics. Frequencies other than these will result in irregular and non-repeating wave patterns.
The number of ways in which an object can vibrate is countless; each object favors only a few specific patterns. The favored patterns result in the highest amplitude with the least amount of input of energy. In swords, these favored frequencies tend to be low which is what you want. If not dampened (tuned) the result will be high amplitudes and a very spirited blade hard to control.
The shock (jolt) you feel from impact is a function of leverage and not harmonics (with swords). Hammers, crowbars and baseball bats all have one thing in common that is they are short, ridged, and round for the most part. They all tend to favor high frequency vibrations. What you feel and what causes a great deal of pain is a high frequency high amplitude wave traveling through the crowbar/hammer/bat. You can buy hammers with wave canceling/tuning technology built into the handle.

There is no man worth a leke,
Be he sturdy, be he meke,
But he bear a basilard.
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Mikko Kuusirati




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PostPosted: Sat 08 Oct, 2005 2:53 pm    Post subject:         Reply with quote

All true.
The subtle tongue, the sophist guile, they fail when the broadswords sing;
Rush in and die, dogs -- I was a man before I was a king.
-- R. E. Howard, The Road of Kings
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