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Forum Index > Historical Arms Talk > Documenting the dynamics of swords Reply to topic
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Bohdan Umertov




Location: New York
Joined: 15 Apr 2017

Posts: 4

PostPosted: Sat 15 Apr, 2017 5:45 pm    Post subject:         Reply with quote

I find this thread extremely interesting! I must ask, however, a question. In particular as someone very interested in picking up Mr. Johnsson's book.

Does his book have all the required information for the swords so that one could input the parameters into your calculator and compare historical examples, to each other and/or production swords?

It sounds like pivot points in particular are difficult to ascertain, yet they also seem to be required to use your software.
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T. Kew




Location: Cambridge, UK
Joined: 21 Apr 2012

Posts: 168

PostPosted: Sun 16 Apr, 2017 10:53 am    Post subject:         Reply with quote

There is a section near the start of the catalogue which includes graphs for most of the swords present. These are fully detailed, with mass curves, agility cones, and pivot points etc.
Instructor and scholar, Cambridge HEMA
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Vincent Le Chevalier




Location: Paris, France
Joined: 07 Dec 2005
Reading list: 15 books

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Posts: 843

PostPosted: Sat 22 Apr, 2017 8:18 am    Post subject:         Reply with quote

Do note however, that while the graphs are included as well as some numerical output (mass and percentage at the blade node), there is no table of input data that you could just enter into the tool. This was ommited for two reasons, the first was space constraints and the second was that at the publication time, the tool was not available yet.

However, you have the possibility of measuring on the sword drawings again. They are all to 1/12th scale. On these you have pivot points, nodes and everything you need.

Regards,

--
Vincent
Ensis Sub Caelo
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Bohdan Umertov




Location: New York
Joined: 15 Apr 2017

Posts: 4

PostPosted: Sat 22 Apr, 2017 2:03 pm    Post subject:         Reply with quote

Vincent Le Chevalier wrote:
Do note however, that while the graphs are included as well as some numerical output (mass and percentage at the blade node), there is no table of input data that you could just enter into the tool. This was ommited for two reasons, the first was space constraints and the second was that at the publication time, the tool was not available yet.

However, you have the possibility of measuring on the sword drawings again. They are all to 1/12th scale. On these you have pivot points, nodes and everything you need.

Regards,


Ah, thank you very much! That is what I needed to know.

(I am sure Peter's book is wonderful. Happy Yet it is of a large expense for someone like I, and I needed it to be certain it will provide inputs for your calculator to suit avenues I wish to explore.)
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Vincent Le Chevalier




Location: Paris, France
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PostPosted: Wed 03 May, 2017 1:02 pm    Post subject:         Reply with quote

Vincent Le Chevalier wrote:
Given the surge of interest in the matter, I'm going to share my own pendulum setup sometimes next week. I just have to build it anew Happy


Right, so it took me longer than I thought, but here it is:
Measuring swords as pendulums

This describes a simple device to make pendulum tests, and how to use this with the new version of the tool.

Regards,

--
Vincent
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Timo Nieminen




Location: Brisbane, Australia
Joined: 08 May 2009
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PostPosted: Wed 03 May, 2017 2:53 pm    Post subject:         Reply with quote

Even hand-held, the pendulum test is more accurate IME.

I use the version without a stopwatch. Just do it side-by-side with a weight on a string (a golf ball is good, because it's heavy enough so that the string is very light in comparison, small enough, and won't damage the blade). Change the length of the string until the periods are the same. Place the pendulum (weight on string) against sword, places where the sword and string were held together, and the weight is at the pivot point.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Vincent Le Chevalier




Location: Paris, France
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PostPosted: Thu 04 May, 2017 12:26 am    Post subject:         Reply with quote

Hello Timo,

I've found hand-held pendulum hard to do reliably. There is a lot of dampening and I can't get a lot of oscillations, so precision is limited.

But I've been told the same about the waggle test by others, so in the end... Let everyone pick their favourite!

Regards,

--
Vincent
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Mike F.




Location: Vancouver BC
Joined: 16 Jul 2016

Posts: 3

PostPosted: Fri 12 Jan, 2018 9:43 am    Post subject:         Reply with quote

Does anyone have a database of various well-known swords they would care to share?
I have computed the two training (long)swords I own, and they show a difference which is borne out in the feel of handling, but I'd really like to see how they compare with a variety of others...

Maybe there could be a dropbox of databases!
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Vincent Le Chevalier




Location: Paris, France
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PostPosted: Sat 13 Jan, 2018 12:59 am    Post subject:         Reply with quote

Expanding the dataset available is the next goal, now that the tool gives an easier way to exploit measurements.

My own public database is here, but this is just my collection of modern swords. I know several other persons have started to assemble databases, but the most comprehensive and trustable is in book form right now, in the catalogue.

The problem is that such data is not always free to go public (some museums are picky about this, I've heard), and if the person measuring is also a swordsmith - as is often the case, it can be seen as a sort of 'trade secret' for the conception of historical swords. These are the main reason why big, comprehensive datasets are hard to come by. The book was a big step in that regard.

As the developer of the online tool, I was fine with providing computation, but did not want to deal with the hassle of managing and maintaining a central database for everyone. Privacy and reliability concerns are primordial in this task if one wants to do it right, and this is not my area of expertise at all. It also takes more time than I have available right now... This is why the data is quite scattered right now.

I expect that the availability of data will expand in the future, however slowly. I am also analyzing the data I have access to but can't make public, and this might eventually be reflected in the tool, making it more useful even without data to compare with.

Regards,

--
Vincent
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Bohdan Umertov




Location: New York
Joined: 15 Apr 2017

Posts: 4

PostPosted: Sun 14 Jan, 2018 3:49 pm    Post subject:         Reply with quote

Vincent, if you would be so kind, can you explain what all of the abbreviations are in the data file? For example, if rather than autoloading the data I were to work backwards and input values in the calculator by hand, which are which?

I'm getting most of them. Many like "CoG" are pretty obvious, or I can infer them from the order they appear in the data file. But I'm definitely not figuring them all, and I'd like to be able to. It really helps me visualize what's going on better that way, taking time to input by hand.
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Vincent Le Chevalier




Location: Paris, France
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PostPosted: Mon 15 Jan, 2018 12:35 pm    Post subject:         Reply with quote

Bohdan Umertov wrote:
Vincent, if you would be so kind, can you explain what all of the abbreviations are in the data file? For example, if rather than autoloading the data I were to work backwards and input values in the calculator by hand, which are which?


Hello Bohdan,

The data in the file is fairly straightforward, mostly a capture of user input. Here is an explanation:

As you might have guessed "weapons" is the map from the weapon name to a weapon object containing the measurements. Inside the objects:

  • M: Mass
  • butt: Hilt Extremity
  • H: Grip Reference
  • tip: Blade Extremity
  • CoG: Center of Gravity
  • lever: Lever Reference
  • node1: Hilt Node
  • node2: Blade Node
  • m: Measurement method, "p" = pendulum tests, "w" = waggle tests
  • K: Square of the radius of gyration
  • dK: Variation of K

The last two are included purely because I wanted to be able to make further computations, including in private tools, without recomputing the values.

Then you have the waggle tests data:

  • conf: array of confidences
  • p0s: array of Action points
  • p1s: array of Pivot points

And the pendulum tests data:

  • Np: number of periods timed
  • pps: array of Axis
  • Ts: array of Time

The last integer "version" is just there to allow me to check before loading if the database format has changed, and convert as appropriate.

Out of curiosity, what is your goal when looking directly into the file? Is there something that you feel the tool does not properly display?

Regards,

--
Vincent
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Bohdan Umertov




Location: New York
Joined: 15 Apr 2017

Posts: 4

PostPosted: Tue 16 Jan, 2018 6:37 am    Post subject:         Reply with quote

Vincent Le Chevalier wrote:
[

Out of curiosity, what is your goal when looking directly into the file? Is there something that you feel the tool does not properly display?



Oh no, or at least I don't think so.

I mostly just wanted to tinker with some of the parameters slightly on the tool, to model the relative affects. For example, move the CoG a small bit, see how if affects the moment of inertia, things like that. I'm curious to compare one parameter to another and their relative effects. But based on real world examples, not just throwing in starting values for parameters blindly.
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