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Chad Arnow
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PostPosted: Fri 03 Aug, 2007 4:11 pm    Post subject:         Reply with quote

Jared,
From a practical standpoint, if you want a CoP measurement, you need a reference point from which to measure it. Measuring it from the tip won't work as a reference point since the tip will be varying distances from your hand, depending on the sword. Same with measuring from the pommel. If we use your method of the middle of your grip, that assumes that everyone holds every sword the same way, which isn't true. Some people choke up on one-handed swords. For longer grip, some people place their hands together, some space them farther apart/

Practically speaking, you need some place every sword has. The first people to talk about this concept on internet forums measured it from the intersection between the blade and the hilt and it's stuck for several years now. It makes sense.

After all, twenty inches from the guard is twenty inches from the guard regardless of whether you're talking about a 24 inch blade or a 36 inch blade; a sword with a 5 inch grip or 10 inch grip; or a sword where you want to choke up on the grip or don't want to, etc. Happy

Also, it places it shows you where the CoP is in relation to your hand(s) very easily: CoP distance from the guard juncture + distance to center of how you want to grip it.

On this site, we include grip lengths too, so you should be able to calculate roughly where the CoP is in relation to your hand if you know your hand width, where you want to grip a sword, and can guesstimate how thick the guard is.

Happy

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Vincent Le Chevalier




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PostPosted: Fri 03 Aug, 2007 4:30 pm    Post subject:         Reply with quote

Jared Smith wrote:
My "nit pick" here is that CoP is relative to where you define it.


I would like to underline this good point of Jared here.

We really have a problem of terminology accross disciplines. CoP could be three things for impact:
-the point where the most energy is used to damage the target
-the point which does not start great vibrations in the blade
-the point which does not transmit the forces of impact to the hand

All three are different. The first is linked to the center of rotation of the weapon (which is not even in the handle in many case), and to the nodes in the case of a hard heavy target. The second one is the blade node. The third one is the pivot point associated to some reference point in the hand (as Jared said which reference point is chosen is not all that clear either). It just so happen that on many swords, perhaps most good swords, that the last two are closely related, because of the link that made me start this thread. This fact has obscured the issue a bit, possibly lending to the blade node more importance than it should have had.

Jared Smith wrote:
My point, in such a case, is that the guard is probably not very close to the location where the wielder's perception of handling traits are likely to be derived. I suspect the relevant location is nearer to the center of the two handed grip.


I think the thing is that there is no single location for the wielder's perception of handling. We shift focus permanently... For example when I cut, I'm first throwing the point forward to start the motion as fast as possible (here leverage matters, focus on both hands), then I let the weapon accelerate naturally around my back hand (here it's tracking, so aft pivot point, back hand), then after the cut I try to stop the weapon and recover point on (here again leverage + tip control, lead hand). In general I found that I rely on the most forward portion of my grip for things like control and feeling, and on the rear portion for power and speed. I don't have any real perception of the middle...

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Angus Trim




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PostPosted: Fri 03 Aug, 2007 4:35 pm    Post subject:         Reply with quote

Jared Smith wrote:
I consider the Munich to be very docile. I can execute my poor zwerchau technique as fast (actually faster) with it as I can with any other sword I have been lucky enough to use and test cut with. The leverage afforded by the long grip undoubtedly influences my impression of the sword.

My point, in such a case, is that the guard is probably not very close to the location where the wielder's perception of handling traits are likely to be derived. I suspect the relevant location is nearer to the center of the two handed grip.

This line of reasoning could be all wrong, but similarly for one handed grip I would expect the most relevant location would be closer to the center of the one handed grip (roughly 2" down along the grip from the guard, rather than right at the guard.) As far as harmonics go, I think Vincent has already stated that they do not vary as greatly within a well designed tang and grip. Balance and inertia are still fully relevant relative to where one holds the sword though, rather than at the centerline of the guard.

My "nit pick" here is that CoP is relative to where you define it. In any practical engineering calculation, CoP is defined relative to some location where a motor, gear, or possibly a wrist muscle (such as center of hand grip area on a baseball bat..actually dictated by an ASME standard for giving CoP of bats) applies a torque to make something rotate. There are an infinite number of them for any object. If you hold a blade for a "murder stroke", there is a completely new CoP for that application located down somewhere near the guard, and it depends upon where you grasped the blade. Vibrational nodes are not the whole story here either. They do matter, but you can probably relate to the concept of a baseball bat being gripped in the "wrong location" with resulting hand shock, even though it was an o.k. bat. Everything is relative to where you hold or pivot a rotating object when discussing CoP.

I consider most forum participants here to be quite sharp mentally, and capable of estimating rough rotational characteristics of swords with greatly similar geometries and grips (using only CoB/CoP and weight) regardless of where CoP has been defined. However, if you want to compare two swords where the grips are drastically different, blades similar, now the true perception in actual handling might be much harder to predict using the guard as a reference point for CoP.


Hi Jared

This is one of those times where subjective terms, and the different way we handle the same language doesn't come thru on this text medium. Part of this is the word docile..... from my perspective, maybe I'd use the term subtle, but since I've never handled a Munich, I don't know. And in a subject like this, answering when you aren't sure precisely what the other is refering to, can create more misunderstanding than anything else.......

I suspect though, that my answer would be I wouldn't change a thing. If you want the long handle for leverage, either "in the cut" or for winding, then changing that for one reason would defeat the first purpose {leverage in handling}....

Everything works together. If you aim for six different features, like five, and dislike the sixth, then you have to decide to live with it, or compromise something else. By the time you get the sixth where you want it, likely the 2nd and fourth are off.....

If your asking about where to place the nodes....... its not really a decision based on where one would like them. Its a decision based on the best place for the sword....... ie, if you pull the handle node to the center of the handle, you're likely going to screw up the "harmonics", and possibly wind up with a sharp tuning fork, instead of a sword. Some of these things are rather limited to the blade geometry, tang geometry, etc. There are nominal positions for these things, and they might not always make sense from a controlling perspective, but from a "natural", or "nominal" perspective they do.

You can "pull" nodes, and likely pivot points, by adding weight to the pommel....... I wouldn't do it, but that's just one swordmaker's opinion....... and I've become a bit of a contrarian these days...........

I make swords from a performance standpoint...... and my interpretation of how to get there isn't always the same as those leading the "discussion" these days.......You might ask Peter the same question........

{minor exageration {sp}, "sharp tuning fork"}

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Bram Verbeek





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PostPosted: Fri 03 Aug, 2007 4:50 pm    Post subject:         Reply with quote

I think I can add some problems to my own calculation; While the speed of sound in a bar of steel and a shaped sword stays the same, the frequency of a generated tone does not, and thereby the cop changes, in order to calculate a cop you will need a complete audiographic fingerprint of the sword (a tapering bar could be calculated, but a bar tapering in two directions with a fuller is beyond me). I have no idea how to calculate this from a shape and material, thus I have no idea how to precalculate the cop. This would have been the idea of my part in the discussion, if you know how vibrations work, you can make them work for you, and if you know the shape of an original, you could calculate the cop (it can not be correctly measured after considerable corrosion). It might be possible to make a weighted average, and thereby provide an area with decreasing harmonic disturbance with in its lowest the cop (I think it will be in the bottom 1/3 of the unweighted average)

There are other things to the cop. Harmonic oscillation will go the length of the blade and tang, but is hindered by the abrubt change in material and weight on the guard, it will move on a little, but the added hindering of a fixed point (the hand) will further minimise it. Therefore, the shape and width of the tang and its close surroundings will affect the first node, but also will the hand that grips it. I dare argue that the COP can not be calculated exactly, but only estimated.

I hate to bring it up again, but I think the moment of inertia would be of interest here, since this, in corellation with cog and total weight might be able to ease the mathematics around harmonics, as tapering has a very similar effect on both harmonics and rotational inertia. I fear I will not get to the books and computer programs that might give an answer until after school holiday, but a harmonic model of a steel sword in an advanced computer might shed some light in the relation.

These are all post-midnight thoughts after a birthdayparty with friends, and I am not entirely sober, so please point out all the mistakes you like
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PostPosted: Fri 03 Aug, 2007 5:28 pm    Post subject:         Reply with quote

I have mentioned this previously, but think it is worth revisiting again.

CoP in most engineering and physics texts relates to the point where maximum impact energy will be imparted assuming a torque applied to a pivot point (motor shaft attachment point, gear location, or human wrist grip location.) It is judged this way in U.S. courts of law regarding disputes over performance of any kind of athletic equipment (tennis racket, golf club, ball bat, etc..) Academically it is strictly a function of mass distribution in the plane or rotation. Nothing else. Local golf club and softball bat manufacturers here in my own home town have lost over $10 million in a single year as a result of failing to recognize this. At least in my college era text books, there is no discussion of vibrational harmonics what so over in terms of defining CoP. It is strictly a function of mass distribution in relation to an assumed pivot point.. The pivot point assumed in courts (where allegations against tournament sporting equipment manufacturers came into play) was always based upon grip geometry. The CoP has been also manipulated as a demonstration prank in such a way as to correspond to the worst possible hand shock at grip location, maximum probability of structural failure upon impact, etc. It is still the CoP based upon maximum energy. I admit this is preposterously rigid, but in terms of physics and governing law regarding swinging motion to impart destructive energy, thats what CoP is.

Personally, I depend upon the in person reviews (at this site) of knowledgeable collectors using phrases such as "heavy blade presence/ shield cracker", or "deceptively agile despite weight" to reveal more about how consistently manufactured swords handle than the published statistics.

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Charlee Garvin




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PostPosted: Fri 03 Aug, 2007 9:08 pm    Post subject: Nodes         Reply with quote

Hi gents,

Did a blacksmith in a hut in England really know about nodes in the 1200s? If he did, I'm impressed.

Regards,

Charlee
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Angus Trim




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PostPosted: Sat 04 Aug, 2007 7:17 am    Post subject: Re: Nodes         Reply with quote

Charlee Garvin wrote:
Hi gents,

Did a blacksmith in a hut in England really know about nodes in the 1200s? If he did, I'm impressed.

Regards,

Charlee


Maybe not a blacksmith in England, but I'd bet professional sword bladesmiths, and cutlers did..........Don't see why someone shoeing horses would need to know, but a cutler probably would........

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Robin Smith




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PostPosted: Sat 04 Aug, 2007 9:27 am    Post subject: Re: Nodes         Reply with quote

Angus Trim wrote:
Charlee Garvin wrote:
Hi gents,

Did a blacksmith in a hut in England really know about nodes in the 1200s? If he did, I'm impressed.

Regards,

Charlee


Maybe not a blacksmith in England, but I'd bet professional sword bladesmiths, and cutlers did..........Don't see why someone shoeing horses would need to know, but a cutler probably would........

Personally I doubt they did. I believe all of these concepts are ideas modern sword enthusiasts / makers / collectors have created to quantify dynamics which old sword smiths would have understood on an intuitive level. Though I am sure they would have known where the sword is balanced (CoG), and perhaps the best area with which to strike (CoP), I doubt they would have any understanding of the propagation of harmonic waves and the nodes associated with them. No doubt they had an intuitive understanding of what was going on, but I can't see a medieval sword maker trying to quantify such a thing. Surely he could pick a blade up and tell you if it was a good blade (i.e. good dynamics), but I don't think he would have any way to try to measure such a thing. It was probably something he would just know, through years of experience.
Quote:
Personally, I depend upon the in person reviews (at this site) of knowledgeable collectors using phrases such as "heavy blade presence/ shield cracker", or "deceptively agile despite weight" to reveal more about how consistently manufactured swords handle than the published statistics.

I have to agree here. Trying to pin numbers on all these traits I believe says more about the person using the numbers than it says about the sword. To me, and I'm not faulting anyone here, but it seems to be a case of missing the forest for the trees.

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PostPosted: Sat 04 Aug, 2007 10:07 am    Post subject: Re: Nodes         Reply with quote

Robin Smith wrote:
created to quantify dynamics which old sword smiths would have understood on an intuitive level. Though I am sure they would have known where the sword is balanced (CoG), and perhaps the best area with which to strike (CoP), I doubt they would have any understanding of the propagation of harmonic waves and the nodes associated with them. No doubt they had an intuitive understanding of what was going on, but I can't see a medieval sword maker trying to quantify such a thing. Surely he could pick a blade up and tell you if it was a good blade (i.e. good dynamics), but I don't think he would have any way to try to measure such a thing. It was probably something he would just know, through years of experience.


Hi Robin

They may not have done the modern thing of trying to make everything into a math model, can't disagree with you there. But whether you want to consider it, "intuitive" knowledge, or however you want to consider it, I'm pretty sure that it was well known that the nodes were important, and that this and dynamic balance were closely tied.

Type XI and type XIX blades are extremely sensitive to harmonic problems. Done properly, these can be very effective cutters...... They can seem fine handling, but may not cut well if the harmonics are subtly off. Type XIs were fairly popular around 1200AD....... And that's about all of the evidence I need that the folks making swords knew what they were doing, and weren't just some hulking hammer jockies slamming things together......

One of the greatest lessons I learned on swords, was handling a type X that Craig Johnson brought to WMAW 5 years ago. Part of the Oakeshott collection, that sword "opened up my box" as far as both harmonic and dynamic balance. It wasn't guess work that put that together. It was knowledge and experience. No, may not have been done using fancy geometric calculations {but swordmakers today don't use that either}, but the individuals that were responsible for that sword knew what they were doing......... and yes, I'm sure that they knew the relationship between nodes and dynamic balance, no matter that they would express it differently than today.............

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PostPosted: Sat 04 Aug, 2007 10:15 am    Post subject: Re: Nodes         Reply with quote

Robin Smith wrote:
Angus Trim wrote:
Charlee Garvin wrote:
Did a blacksmith in a hut in England really know about nodes in the 1200s? If he did, I'm impressed.

Maybe not a blacksmith in England, but I'd bet professional sword bladesmiths, and cutlers did.

Personally I doubt they did. I believe all of these concepts are ideas modern sword enthusiasts / makers / collectors have created to quantify dynamics which old sword smiths would have understood on an intuitive level.


Well observing the two nodes on a vibrating blade is not difficult at all. I'd expect someone spending his life doing blades to observe it, even if no one was there to tell him... And Jean Thibodeau described in this post some feelings clearly related to pivot points, so...

Did they have the scientific knowledge on how to define them exactly and relate them to motion? probably not. But for the practical effects, if they are in the historical weapons, then it's important that we understand them.

Quote:
Trying to pin numbers on all these traits I believe says more about the person using the numbers than it says about the sword. To me, and I'm not faulting anyone here, but it seems to be a case of missing the forest for the trees.


I cannot really see how numbers could somehow be more subjective than a personal impression by someone else...

I think the problem is that the current stats used have left the feeling that all stats were somehow not relevant. The problem is that the stats we use now do not even reflect the behaviour of the simplest model one could make of a sword... That does not mean that it's impossible, it's just not done now.

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Jared Smith




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PostPosted: Sat 04 Aug, 2007 3:19 pm    Post subject:         Reply with quote

In addition to suspecting that someone would have caught on to the importance of vibrational modes within swords, we know that some craft guilds were producing exquisite bells ( Auchtermuchty Parish Church still has some from early 13th century, could go on and on...here). In the same time frame (11th-13th centuries), the modern musical scale of C major was invented and popularized. Understanding of vibration and mastery of utilizing it within forgings/castings and instruments was taking place in medieval times. I find it puzzling to think that something undergoing such mastery in other areas would not have carried over as a consideration by at least some bladesmiths.
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PostPosted: Sat 04 Aug, 2007 4:17 pm    Post subject: Jared, very interesting         Reply with quote

Jared

The C note comparison to bells makes a lot of sense to me. I'm not really a math person, but the music or vibration element to sword crafting seems to really fit. All in all though, since we are smarter now, we may as well use current technology to make superior swords.

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Jared Smith




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PostPosted: Sat 04 Aug, 2007 4:28 pm    Post subject:         Reply with quote

I have reservations about "us being a lot smarter now." I think we have vast amounts of common knowledge, useful for trivia, etc., but may have fewer "masters" (allowing for craftsmanship taken to extreme competence) as a percent of our population. I honestly don't know. I just don't automatically assume we work towards perfection to the same degree as many did back then.

Another interesting example that is related, the tower of the Cathedral of San Miniato, Pisa, was constructed in such a way that the entire thing resonates with the bells, right down to the foundations. This has been studied, and is believed not to have been an accident at least by some. When I consider the number of crafts involved, and the level of mastery required in integrating all of that into a major construction project....it blows my mind!
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PostPosted: Sat 04 Aug, 2007 6:42 pm    Post subject:         Reply with quote

Jared Smith wrote:
In addition to suspecting that someone would have caught on to the importance of vibrational modes within swords, we know that some craft guilds were producing exquisite bells ( Auchtermuchty Parish Church still has some from early 13th century, could go on and on...here). In the same time frame (11th-13th centuries), the modern musical scale of C major was invented and popularized. Understanding of vibration and mastery of utilizing it within forgings/castings and instruments was taking place in medieval times. I find it puzzling to think that something undergoing such mastery in other areas would not have carried over as a consideration by at least some bladesmiths.

This hints at something to me. From what you have said so far, I would be very surprised if you ARE NOT involved in music somehow, or atleast highly interested in the subject. By the same token, I assume Vincent is an engineer, or something similar that deals with things through mathematics. This is what I meant when I said the numbers a person use say more about the person than it actually does about the sword. It seems a modern conceit to me to think that just because masters of old were able to achieve amazing results that they thought about them in a way familiar to a modern engineer or mathematician.

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PostPosted: Sat 04 Aug, 2007 7:28 pm    Post subject:         Reply with quote

I agree exactly Robin.
I like to try to play classical guitar (very slowly, stumbling as I go. My wife has the ability to play and sing anything she has ever heard by ear.) I actually possess a masters degree in engineering, but am still amazed at how often others prove my opinions to be wrong or simply a case of mincing words. One thing I have learned, the generations of engineers before me (3 in my family) were extremely ingenious when it came to innovation. Puzzles such as the pyramids in Egypt show us that at least someone was pretty sharp and experimenting with very challenging feats at almost any point in the era of recorded history.

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PostPosted: Sun 05 Aug, 2007 3:28 am    Post subject:         Reply with quote

Robin Smith wrote:
By the same token, I assume Vincent is an engineer, or something similar that deals with things through mathematics.


Good guess, Robin Happy In fact I graduated from an engineering school, and I'm currently doing a PhD in applied mathematics, so yes, thinking with maths is quite natural to me now... I cannot really turn that off Big Grin

Combined with the fact that I've been fascinated by swords from an early age... That's two of my passions that merge, in a way.

Robin Smith wrote:
It seems a modern conceit to me to think that just because masters of old were able to achieve amazing results that they thought about them in a way familiar to a modern engineer or mathematician.


It's not exactly what I'm thinking, but I have a hard time explaining... If a swordsmith of old and myself were looking at the same sword, we would see the same object, with the same properties. He would describe it using his own concepts and words (we don't know exactly how), and I would perhaps try to describe the behaviour in terms of pivot points, and surely Gus would pay attention to harmonic balance... It's just different filters that allow us to analyze what we see and talk about it. If the filters manage to catch roughly the same amount of information, whether it was historically used or not does not really matter. We are still paying attention to the same important things, but describing them differently. If there is some quality in much of the originals, that Gus describes as harmonics, and me as pivot points, it does not really matter to know if they described it like that back then. The important thing is that it's here.

There would be an analogy with architecture, maybe. The builders of the cathedrals were probably not describing what they were doing in terms familiar to modern construction engineers. It does not mean that we cannot describe their work in our own ways... And that if we wanted to build cathedrals again, we wouldn't be able to do so with our engineering point of view.

Of course things like aesthetics, subjective feelings (for example, doing something with a sharp sword is different, and I suspect that is partly because of the extra risk and associated concentration we have when handling dangerous objects), will escape the "math filter".

The advantage of what comes out from the "math filter" is that it does not depend on the person doing the math. So to compare two objects, you don't have to have them side by side, handled by the same person at the same time. They do not depend on the time of the day (I sure know that my swords feel different depending on my own condition at the moment, it does not mean that they have changed). There are things they won't tell, but to know how much there is, we have to try.

Best,

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