Harmonic Balance- Introduction...

[Michael Tinker Pearce]

Here's a diagram that I hope will illustrate the basic principle of 'Harmonic Balance.

[Patrick Williams]

Okay, next newbie question in the series:

The distal node of rotation-will that always be the CoP?

[Michael Tinker Pearce]

The Center of Percussion located on the blade is the rotational node. They are the same thing for purposes of this conversation.

In general- nearly every antique from prior to the 19th century that I have personally examined is 'harmonically balanced.' This includes blades from the middle east, the Indian sub-continent, Europe and China. The principle seems to have been well understood wherever people used swords prior to the 19th century- excepting antiques that were assembled from parts well after the period of their use. The knowledge seems to have largely been but not completely lost after the begining of the wide-spread use of reliable repeating hand guns.

What Harmonic Balance does for a sword- prevent's shock from being transmitted to the users hand when striking with the sword. This conserves energy- the sword doesn't 'waste' energy shaking the user even when the strike lands off of the COP. It also prevents the user from losing control of the sword because of vibration transmitted to the user's hand. It also minimises the sword's tendency to damage it's hilt assembly through vibration. All good things!

A sword that is not 'harmonically Balanced' is not, in my opinion, a 'good' sword.

'Harmonic Balance' is to the best of my knowledge a term that originated in the Pacific Northwest of the United States by sword-maker Ike Roe to describe correct location of the Rotational Nodes in the sword, possibly as early as the 1980's. This knowledge was passed on to Chuck Sweet (aka 'Steelwolf') and then to myself by Chuck around 1993. I spread the information at ren faires and SCA events. The information of this concept reached the Internet about 6 years ago after Angus Trim, then a Swordforum Sword Reveiwer, became aware of my work and reveiwed one of my swords. Gus invited me to post the information on Swordforum.com, and I did so. Peter Johnson researched this phenomonen independantly and confirmed it's presence in antique swords that he examined in Europe, and included the information in his book on the reconstruction of the Svante Nilsson Sword (sic?) Angus Trim eventuallty went into production of his own swords, and the interplay of our research since that time has produced a much deeper understanding of this phenomonen. Angus and myself have been the greatest proponents of the importance of this phenomonen in sword design.

There has been much argument and controversy over this simple principle. It has been called 'New-Age Mumbo-Jumbo,' 'Marketing Hype' and 'Magic.' It is none of these things- it is an observable, demonstrable and repeatable physical phenomonen that is now widely documented in both the historical record and by modern observation and study- including (unofficial) study by physists working at JPL. Even the greatest detractor of this theory was eventually won over by the weight of evidence after an enormous and ridiculous hate campaign directed mainly against Angus Trim (and anyone else that disagreed with him.) It is now an accepted theory in the on-line sword community.

[Jerry Bennett]

My kind of science for 3 reasons;

Modern engineering/testing proves it.

It wasn’t accepted(at first) by the "it's not in the universal book of specs and standards asmansimillsaesme………" people. You know what kind of people I mean.

The ancients knew it, and used it all along. I love using new-old technology.


So tell us Tinker, if you have to have nodes, were is the best place(s) for them on the sword? Jerry

[Angus Trim]

Originally posted by Jerry Bennett
My kind of science for 3 reasons;

Modern engineering/testing proves it.

It wasn’t accepted(at first) by the "it's not in the universal book of specs and standards asmansimillsaesme………" people. You know what kind of people I mean.

The ancients knew it, and used it all along. I love using new-old technology.


So tell us Tinker, if you have to have nodes, were is the best place(s) for them on the sword? Jerry

The simple answer is as close to the "native" position on the finished blade as is possible. But its not quite that simple.

On a typical double edged blade of 32 inch blade length and over....

A finished naked blade {double edged} has the nodes ussually about 2/3 the way from the shoulder to the tip, and just on the blade side of the shoulder. Once mounted up, the one nearest the shoulder ussually finds its way onto the tang. In a single hand sword, the best place for this is right under the guard, or under the first finger.....

But wait...... sometimes observably there is another node on the handle, a couple of inches further down towards the pommel.......

What we have here is a phenomon of the deminodes on the handle becoming more prominent once mounted, and having more to do with how a sword handles and responds to cutting forces.......

But Tink and I will explore these deminodes more in the future. Right now Tink intends to introduce Harmonic Balance in its more simple explanation at first.......

We'll get to the more arcane stuff where high performance actually starts a bit later.......

Auld Dawg

[Jerry Bennett]

I await with much anticipation. This stuff is cool!

[Michael Tinker Pearce]

Since questions about Harmonic Balance are so common I decided to make this sticky, but feel free to continue posting under it!

[Patrick Williams]

Originally posted by Jerry Bennett
I await with much anticipation. This stuff is cool!

Way cool! Can't wait for the next installment!

[Tony Guarnera]

O.K. So we know about the points of harmonic balance. One about 2/3 the way to the tip, and another just under the gaurd. Now, what contributes to where these node are? How does one move them around when making a sword?

[S. Henning]

The main cause of the nodes is the change in material shape from the blade to the tange. As I recall from my physics classes on waves, in this case the wave travels down the blade and will take on speed and shape based on the material it is traveling through, since blades tend to have symmetry and relative constant shape down the blade, the harmonic wave remains constant until it encounters the forte, in which the material thickens and then reduces greatly as it reaches the tange. The change in material causes the wave to partially reflect back up the blade while the rest of the wave changes speed, similar to water going into a smaller pipe. The change in speed is really a change in frequency of the wave it will continue as before until it encounters a new change in material or the end of the metal tange, at which it then reflects back up the blade. The change in shape or material is the cause of the nodes in the blade. Without pulling out my physics books, that is the best description I can recall.
Cheers,
Conal MacLaren

[Jerry Bennett]

My question;
Do we, (as sword makers), want to use harmonics, and harness it to our advantage, or do we want to suppress it when possible? Jerry

P.S. S. Henning, Thanks for the interesting physics, and brining the subject back up. Is that Kent Wasington, or Kent England?

[K. Melchior]

Angus Trim wrote:

In a single hand sword, the best place for this is right under the guard, or under the first finger.....

Which calls up the question:
What is the best place for the "lower node" in a hand-and-half sword? Say one with 8" handle plus pommel?

Recently I handled a Sempach type bastard sword which apparently has the "lower node" about mid-way of the 9" handle (=where the handle thickens just before it starts to taper). What's to be thought of that? btw the blade quality and overall workmanship of that sword was very good.

And, I thought I read it before, but I couldn't find the info anymore: how does pommel mass influence the position of the nodes?

Looking forward to your info.

[Angus Trim]

Originally posted by K. Melchior
Angus Trim wrote:


Which calls up the question:
What is the best place for the "lower node" in a hand-and-half sword? Say one with 8" handle plus pommel?

Recently I handled a Sempach type bastard sword which apparently has the "lower node" about mid-way of the 9" handle (=where the handle thickens just before it starts to taper). What's to be thought of that? btw the blade quality and overall workmanship of that sword was very good.

And, I thought I read it before, but I couldn't find the info anymore: how does pommel mass influence the position of the nodes?

Looking forward to your info.

That's a good question, and I think this question takes us beyond the simple harmonics of which this post is intended.

The simple answer would be its fine, but the more correct answer is we're getting into complex harmonics now.

Typically, I look for the prime handle node to be closer to the hilt than that. But I also would expect to find one of the deminodes where you found the node.

However, sometimes it becomes fuzzy which is which. Which is the stronger node?

Caveat this to say I haven't seen the sword you mention, or even one of that model. But the photos of that sword shows a lot of taper, and I suspect that what is happening here has to do with harmonic proportions, and the distribution of mass....*g*

In other words, I'm guessing, I don't know. Peter Johnsson designed the sword, so I suspect its very well done. I also don't want to try and analize something that I've not seen myself........

[K. Melchior]

Hey Angus,

thanks for your reply.
Actually what I'm talking about is not a Johnsson sword (what made you think it was?), but one of a German smith. And, it's a stage sword at that, i.e. reinforced blade and blunt edges.
Basically it's a blunt Sempach type H&H with 4 lbs total weight. (A cutter version would be considerably lighter) Here's a pitcher:

[Angus Trim]

Originally posted by K. Melchior
Hey Angus,

thanks for your reply.
Actually what I'm talking about is not a Johnsson sword (what made you think it was?), but one of a German smith. And, it's a stage sword at that, i.e. reinforced blade and blunt edges.
Basically it's a blunt Sempach type H&H with 4 lbs total weight. (A cutter version would be considerably lighter) Here's a pitcher:

Hi Mr. Melchior

Sorry about that, I thought that it was an Albion, because of the term Sempach. It so happens that Albion has a model named that, and I think the sword looks a lot like the one you have in the photo.

The caveats would still be the same. I'd really want to see the sword before commenting except in a very general way.

[K. Melchior]

Hi again,

oh I see - well I know that Albion Sempach, but I don't know how many sword makers out there have their own replica of an historic Sempach sword.

I reckon that the theoretical optimum for node and deminode in a H&H would be:
- at the guard, or under the first fingers;
- way at the end, where the pommel meets the hilt

to the effect that the critical joints suffer no or just little vibrations; and because that's about where you grip a H&H, your hands don't get the vibrations either.
However, I also hazard that it would be very difficult, if not impossible, to place the nodes exactly there without compromising on other features.

What do you think?

Take care,
Melchior

[Michael Tinker Pearce]

Originally posted by K. Melchior

However, I also hazard that it would be very difficult, if not impossible, to place the nodes exactly there without compromising on other features.

What do you think?

Actually it's not too difficult- however a more complete answer gets into the 'Complex Harmonics' that Gus alluded to that are beyond the scope of this post.

Regards to shape affecting the nodes- yes and no. In practice the shape affects the nodes only as it affeccts the distribution of mass.

[Michael Stora]

Originally posted by Michael Tinker Pearce
Even the greatest detractor of this theory was eventually won over by the weight of evidence . . .

Do you have a link to either this or the JPL work? I'm very interesed.

Thanks,

Mike

[Thomas Brogan]

When designing a sword or, in my case, a long knife, is there anyway to predetermine the harmonic balance so the blade may ground or hammered to shape without too many post-grinding readjustments?

Many thanks in advance.

[bill tsafa]

Let me ask a reverse question. What gives a sword BAD harmonics?I would think that various diffrent changes in weight and ballance would change how you use the sword. If the COP closser to the tip, you cut. If the COP is closer to the hilt,you thurst.

[Michael Tinker Pearce]

Originally posted by Michael Stora
Do you have a link to either this or the JPL work? I'm very interesed.

Thanks,

Mike

Actually I don't- but I bet Gus does...?

[Michael Tinker Pearce]

Originally posted by Thomas Brogan
When designing a sword or, in my case, a long knife, is there anyway to predetermine the harmonic balance so the blade may ground or hammered to shape without too many post-grinding readjustments?

Many thanks in advance.

There may be- but after so many years I 'just do it,' without really thinking about it. Hard to explain- with swords look at antiques- Or Angus Trim swords... or mine... etc. Sorry I can't be more helpfull- I'm afraid you will have to experiment.

[Michael Tinker Pearce]

Originally posted by bill tsafa
Let me ask a reverse question. What gives a sword BAD harmonics?I would think that various diffrent changes in weight and ballance would change how you use the sword. If the COP closser to the tip, you cut. If the COP is closer to the hilt,you thurst.

To some degree this is true- What gives a sword bad harmonics is improperly distributed mass. Urk, how can I explain this better? Gus, any thoughts?

[Bill Butler]

I'm happy to see that some of you guys managed to do something other than simply sleep through your physics classes and then demand an A for attendence.

I haven't found the thread on "complex harmonics" but in answer to a question earlier in this thread as to how to determine the node locations prior to construction it should be possible to estimate with some data and some simple calculations. Different thicknesses of the same metal will have different wave propagation speeds and thus different resonant frequencies (note that different materials of the same thickness will also differ in frequency so beware that complication). So if you know the resonant frequency of the section then you know the wavelength, then note that the boundary conditions will correspond either to nodes or anti-nodes and the distance between any node and the next (or anti-node and the next) will correspond to half the resonant wavelength.

Further complications can likely be taken into account by perturbations on this simple principle. But in the end experimental evidence takes precidence over theory and there's something to be said for a good deal of practice.

[George T.]

I hope this thread is still being looked at because I have had some experence with swords both in the making and the breaking of many swords. Though some of the swords were and are concidered junk blades or wall hangers because we fought with them on a regular basis. We also found ways to make those junk blades stand up for years. I was a sonar technician in the navy so I understand a lot about sound and vibration. With the knowledge of sound and vibration and studing the different ways a sword broke we added or changed a number of different things in the construction of a standard sword. Some of the changes are similar to the fittings on a katana and help reduce vibration in the hilt. If anyone is interested I will post them with pictures of blades which I still teach with some which are over 20 years old.