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Maurizio D'Angelo




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PostPosted: Thu 09 Apr, 2009 7:05 pm    Post subject: Vibrations and harmony         Reply with quote

Dear readers,
I hope that you don't laugh at my English, I assure you that in Italian I write better. Humor apart, I want to make to climb you on a mountain, making to believe you to climb on a waterslide.
Questions: is it possible to measure the vibrations of a sword? is it useful to know this?
If it is not useful whether to give so much importance to the point of impact? Center of Percussion (CoP).
If it is true that a sword is the harmony of so many things, also the vibrations reenter in this.
You help me to build an utensil that verifies the vibrations.

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Chad Arnow
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PostPosted: Thu 09 Apr, 2009 7:14 pm    Post subject:         Reply with quote

Maurizio,
Vibrational properties of swords have been discussed many times. In our spotlight topics you can find several threads in the "Dynamics, Properties, and Performance" section that deal with this.

Happy

ChadA

http://chadarnow.com/
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Maurizio D'Angelo




Location: Italy
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PostPosted: Thu 09 Apr, 2009 7:21 pm    Post subject:         Reply with quote

I think I have read.
measurements but I do find very empirical. I want to measure them accurately. There are tools to do this.
But if I make a pendulum, which simulates the impact of a sword, when it must be his weight?



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Vincent Le Chevalier




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PostPosted: Fri 10 Apr, 2009 2:35 am    Post subject: Re: Vibrations and harmony         Reply with quote

Hi Maurizio!

Maurizio D'Angelo wrote:
Questions: is it possible to measure the vibrations of a sword?

It is possible, as described in the feature article. It's true that the precision is not great, but it's plenty enough for our needs.
Quote:
is it useful to know this?

Not that much in my opinion, and that's why the measurement is already accurate enough Happy

Quote:
If it is not useful whether to give so much importance to the point of impact? Center of Percussion (CoP).

The significance of the "CoP" (meaning, node of the primary mode of vibration on the blade), is less than was once thought. There is a good discussion of that aspect here:
http://forums.swordforum.com/showthread.php?t=87258
You'll learn also that the term CoP is inaccurate and should not be used with that meaning at all.

If you're interested in the mechanical properties of swords I'd urge you to try and look into the properties of the mass distribution first: mass, center of gravity, moment of inertia. These are some of the most important properties related to the sword's function. Vibrations are visually entertaining but are secondary in my opinion, especially if you wish to take the scientific approach with accurate measurements and objective assessment.

Perhaps you could be interested by this thread as well, it is not a spotlight and maybe harder to find:
http://www.myArmoury.com/talk/viewtopic.php?t=10929

Quote:
You help me to build an utensil that verifies the vibrations.


If you really want to do that, I think one of the most promising method would be to play with resonance.
If you manage to fix a vibrating device to the pommel and vary the frequency of the vibrations, at the proper frequencies of the sword the amplitude of the vibration should get bigger. Once you have the vibrating sword it should be easy enough to take another tool to the blade to detect the nodes. With this method you should be able to measure even higher harmonic modes and not just the first.

But as I said this more accurate measure will not help you much understanding how a sword works Wink

Regards,

--
Vincent
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Maurizio D'Angelo




Location: Italy
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PostPosted: Fri 10 Apr, 2009 4:31 am    Post subject:         Reply with quote

Dear Vincent,
I have seen is very much appreciated your superb work.
But I want to set a point.
A sword is appreciated having it in hand and seeing how it behaves.
Example: I do not care if the sword is a set of guard and pommel, or if it is built from one large piece with no parts added. What is important is to see how it behaves in combat.
I do not want to do a mathematical model for the problem.
There are too many things that work together. A large team of scientists we would like. Even you say.
Then if you do not feel a need to establish, why you have done so much good work? I ask this without wanting to seem polemical.
If only 1 mm difference for the entire length of the blade changes things a lot, you know this.
If we use mathematical calculations, the average reader is bored, only few would follow the speech, I am not one of those select few.

Data of a real sword, dismounted
Blade length: 900 mm
Width 1 = 50
Width 2 = 20.5VOLUME = 1.0288769e+05 MM^3
SURFACE AREA = 6.7130269e+04 MM^2
DENSITY = 7.8500000e-03 GRAM / MM^3
MASS = 8.0766834e+02 GRAM
CENTER OF GRAVITY with respect to coordinate frame:
X Y Z 0.0000000e+00 5.3507451e+02 0.0000000e+00 MM
INERTIA with respect to _LAMA coordinate frame: (GRAM * MM^2)
INERTIA TENSOR:
Ixx Ixy Ixz 3.0299476e+08 -3.9867953e-01 0.0000000e+00
Iyx Iyy Iyz -3.9867953e-01 5.2483844e+04 0.0000000e+00
Izx Izy Izz 0.0000000e+00 0.0000000e+00 3.0304526e+08
INERTIA at CENTER OF GRAVITY with respect to coordinate frame: (GRAM * MM^2)
INERTIA TENSOR:
Ixx Ixy Ixz 7.1755494e+07 1.0746666e-01 0.0000000e+00
Iyx Iyy Iyz 1.0746666e-01 5.2483844e+04 0.0000000e+00
Izx Izy Izz 0.0000000e+00 0.0000000e+00 7.1805997e+07
PRINCIPAL MOMENTS OF INERTIA: (GRAM * MM^2)
I1 I2 I3 5.2483844e+04 7.1755494e+07 7.1805997e+07
RADII OF GYRATION with respect to PRINCIPAL AXES:
R1 R2 R3 8.0611367e+00 2.9806505e+02 2.9816992e+02 MM

All these data do not tell me nothing, or rather, can be calculated before cutting steel, while mathematically correct but missed a sword over.
What I want is a unique way to measure the vibration, with a shot that simulates a sword. You can help in this.
This might be a different swords comparison of different measures. The resonance can destroy the system by the excessive accumulation of energy, only a matter of time.
With great humility, I greet you
ps.
courtesy: Write a simple and direct, I have difficulty with your language, Italian is better for me
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Vincent Le Chevalier




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PostPosted: Fri 10 Apr, 2009 5:13 am    Post subject:         Reply with quote

Hello again Maurizio,

Sadly I do not speak Italian Sad If you speak French we continue in private messages, else we will have to discuss in English... I try to write as clearly as possible, I hope you understand...

Maurizio D'Angelo wrote:
There are too many things that work together. A large team of scientists we would like. Even you say.
Then if you do not feel a need to establish, why you have done so much good work? I ask this without wanting to seem polemical.


My point of view is this:
1) There are important properties that we need to measure
2) The measure needs to be as accurate as your hands and eyes can be, not more, because it is your hands and eyes that will evaluate the sword in use
3) The vibrations are not really important properties

That is why I think that for vibrations the usual method is sufficient.
The computations I have made about vibrations were more a game. Something I did because I wanted to learn simulation techniques, not to gain a practical useful knowledge of swords. The real useful (I hope Wink ) computations that I have done are without vibrations at all.

The sword data that you gave, where does it come from? CAD software? The results are some of the things I try to measure on swords. They can be used to compare swords...

You are right, excessive vibrations might destroy the sword. But without significant vibrations the node of vibration is impossible to measure... I think a real sword would be solid enough and survive a short measurement, but I have never tried...

--
Vincent
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Maurizio D'Angelo




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PostPosted: Fri 10 Apr, 2009 7:43 pm    Post subject:         Reply with quote

It is all those figures come from a CAD.
If you want to help me create a list of the data they serve.
I do not understand one thing.
Download a high-impact vibration in the hand.
My hand leaves the outlet. The vibrations have caused me pain. The secondary nodes are not important, it is important moment of inertia, and center of gravity.
This is correct? Better explains the concept. Tell me why I feel strong vibration on hand.
I believe that it is able to give you all the data.
This also means that it does not serve to measure the vibration resonance it.
I have some tools that measure these things.
What I did not have microphones, amplifiers to prevent contact blade. Strobe light with adjustable frequency is normally used by me.
I read all your posts, I agree to 90%.
If our work will lead to an outcome, then for my part will be a joy to share with you all.
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Maurizio D'Angelo




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PostPosted: Fri 10 Apr, 2009 8:26 pm    Post subject:         Reply with quote

Dear Vincent,
I forgot something important.
If I put as well as the properties of mass, the modulus of the material and all other characteristics of the materials assembled, I can simulate the behavior of the sword. If I change the point of impact, change many things of course. I used a force of about 300 Kg
It remains a fact however, the system calculates everything, but it is not so in reality. Heat treatment, hardness, watch assembly, assembly bone, ect. ect. approximated make the math. Certainly a good result from this directive, but it is not perfection.
Now I go to sleep, here is deep night.

Regard, Vincent
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Jared Smith




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PostPosted: Sat 11 Apr, 2009 10:45 am    Post subject:         Reply with quote

Maurizio D'Angelo wrote:

I forgot something important. ..... I used a force of about 300 Kg


I envy your strength!

Seriously, you seem to have enough knowledge to simulate the properties and motions without much help from others. A difficult aspect of these analyses is making assumptions about the sword motion. Most strikes are a combination of rotation with the wrist(s) as well as an arc of the arm(s). As such, any model of the physics is very specific to one particular type of striking motion while there are many motions to chose from. CoP tends to be a measure of pure rotation, assumed to occur at the guard. This is typically not where the center of rotation at the wrist(s) will be even if the sword is in a pure rotation (Zornhau or similar).

If truly concerned about hand shock, some other forms of tests and measurements may be useful. I would suggest suspending the sword at a location neutral to impact in cases of uniform cross section geometry (CoG) and striking the blade at several different locations both against the edge and the flat. With an accelerometer or similar vibration measuring device you could determine points of maximum and minimum reactions to the impacts. This may be more meaningful in terms of perceived reaction forces through the grip, and resulting vibrations that could result from variable motions and impacts.

Absence of evidence is not necessarily evidence of absence!
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Maurizio D'Angelo




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PostPosted: Sat 11 Apr, 2009 10:25 pm    Post subject:         Reply with quote

Dear Jared,
your ideas will be much help. I completely agree.
I am not agree to do alone, we are more than 16,000 people
I will now begin to establish some concepts.
At what speed will move the pendulum? For now suppose that the impact at 90 ° with the target.
Proper execution of a slash.
[/img]
A and B: points of departure and arrival of the blade
ABL: space path from the blade
RI: initial radius
RL: radius trajectory
a°:angle
time: 0.35 seconds
Speed = space / time
The space from the trajectory path (arc) is calculated as
following:
Arco = p * R * a ° / 180 °
ABL = 3.14 * 1.50 * 150 ° / 180 ° = 3.92 m
We can now calculate the average speed of the blade: = 3.92 / 0.35 = 11.2 meters / second at 40.32 Km / h
The speed you need to break a bone against a rigid barrier is 10 km / h.
Now we know that this speed must move the pendulum.
Each reflection is important.



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James R.Fox




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PostPosted: Mon 13 Apr, 2009 12:15 am    Post subject:         Reply with quote

Sirs-I would talk to an old cutler who has been fitting swords for 40-50 yearsm have him fit a blade to my hand, and forget it,There are more inportant things ti do, like rescuing the theoretically vergin heroine
Ja68ms
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Maurizio D'Angelo




Location: Italy
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PostPosted: Mon 13 Apr, 2009 9:43 pm    Post subject:         Reply with quote

That there are persons of mistaken ideas in almost every Art or Science,
is what few will deny. Yet I am inclined to believe there are more
erroneous opinions entertained with regard to the
Art of using the Sword than on most other subjects."
- Joseph Roland -
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Maurizio D'Angelo




Location: Italy
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PostPosted: Tue 14 Apr, 2009 12:15 am    Post subject:         Reply with quote

In the Middle Ages the technique and strength meant life or death.
Different forces are used if you use a sword: by collection, by study or by reenactors. If you want to break a sword to see if it resists then use more strength. If you use a great force, the pommel must be argued more often. The resonance can destroy the system by the excessive accumulation of energy, only a matter of time. Is always possible to limit the resonance, in a sword I do not know, but maybe it may be possibile
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Jared Smith




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PostPosted: Tue 14 Apr, 2009 3:21 pm    Post subject:         Reply with quote

As James.Fox suggested, an experienced cutler often can "empirically" tweak furniture and blade length/profiles to eliminate obvious singing (like a bell) while achieving compromises to maintain stiffness, and make handling suit a customer's preference and style. Despite the use of computer aided design and milling machines, years of study, and careful evaluation of possible "golden sections" and proportions of actual historical swords perceived to be good, some of our preferred reproduction companies still mention refinement of production models based upon experimentation with prototypes, and tuning experiments with furniture.

Maurizio, in your case is it accurate that your assumptions for the problem sword statistics give your sword mass as around 800 grams (~1.8 lbs) with a blade length of 900 mm (a little over 35")? If so, I would question with caution the idea of heavy target cutting strikes made with massive strength. I don't know if this would be a saber, rapier or smallsword. But, instinctively the numbers sound more appropriate for a cut and thrust blade that was not meant for combat in mail armour, or for tree chopping. Is there any possibility that your test cutting is a mismatched application for the blade's style?

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




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PostPosted: Tue 14 Apr, 2009 3:58 pm    Post subject:         Reply with quote

The key question to answer, if you wish to simulate something, is why do this simulation?

Often it is done in order to optimize the object. But in my opinion our goal should be to first make swords that are close to originals. Originals are not necessarily optimal for anything...

Truth to be told, there are so many factors at play during sword cuts, not related to the sword, that I doubt you could meaningfully optimize one property of the sword (for example get the optimal moment of inertia or node of vibration).

Jared Smith wrote:
Maurizio, in your case is it accurate that your assumptions for the problem sword statistics give your sword mass as around 800 grams (~1.8 lbs) with a blade length of 900 mm (a little over 35")? If so, I would question with caution the idea of heavy target cutting strikes made with massive strength. I don't know if this would be a saber, rapier or smallsword. But, instinctively the numbers sound more appropriate for a cut and thrust blade that was not meant for combat in mail armour, or for tree chopping.

I think Maurizio gave stats for the blade alone. I do not really have numbers for bare blades of various types, but I don't think it's that light... Look at the CoG as well.

--
Vincent
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Maurizio D'Angelo




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PostPosted: Tue 14 Apr, 2009 8:51 pm    Post subject:         Reply with quote

Dear Mr. Jared
Perhaps there is some “confusion”. The “blade” weighs 800 grams. (1,76 pound)
The sword weighs 1600 grams. (3.52 pound)
In Italian lama = blade not sword
The sword in question is:
Weight: 1600 gr. (3.52 pound)
Overall length: 1150 mm. (45.27 ")
Blade length: 900 mm.
Blade width: 50 mm
PoB: 110 mm
Fuller: 2 / 3 of the blade
Oakeshott typology: type XIIa
As for the force, I said before I want to stress conditions of the sword to find the weaknesses.
Best Regards

Hello, Vincent
My friend turned to me to fix his sword.
He says that the pommel must be repeated often.
The cost of this sword is $ 500 second hand.
The sword is an experienced cutler.
I have to build an equal.
I want to build a better sword, if this is possible.
Its vibrations might release the handle and pommell.
His first sound was typical, now no more. I think that ring might
also be indicative of tension in the hilt.
This is the motive for my interest for the vibrations and the resonance.
I forgot: CoB blade 535 mm. if the sword mounts CoB 110 mm. (4,33 inch)
How is my English?
See you soon, we will become good friends.
Wink

Ciao
Maurizio
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