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Maurizio D'Angelo




Location: Italy
Joined: 09 Feb 2009
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PostPosted: Mon 01 Jun, 2009 6:11 pm    Post subject: I hit the flat of the blade or the side of the cutting blade         Reply with quote

Hi all,
Lightly strike the pommel of the sword with the heel of your off hand causing the sword to vibrate. Observe the point near the blade tip where the blade does not vibrate (usually several inches from the point) this will be the sword's primary node. The primary node is also known as the Center of Percussion (CoP). The CoP is nothing more than the sword's "sweet spot" or the area where the sword will deliver its maximum impact to a target without energy dissipating through vibration.
The secondary node will be found, usually, below the guard within the grip where the index finger of the hand will be located. This node can be found be holding the sword, point down, with the index finger and thumb. Lightly strike the blade with the palm of your hand thereby causing the sword to vibrate. The area below the guard where no vibration is felt will be the location of the secondary node. The locating of this node is important as it will prevent undue fatigue of the sword's components and will prevent vibration from being transferred to the user's hand.

(with the heel of your hand off causing the sword to vibrate.) Where? I hit the flat of the blade? If I have translated well, it would be more just hit the side of the cutting blade? Some time ago, I said in my previous post, that I would have built a tool. It is almost ready, playing with an accelerometer, I discovered that things are very different. If striking the flat, I have a very different outcome if that affects the cut. Then the CoP? (I attribute this to the term commonly used here, but I agree with Vincent that is incorrect) explanations are appreciated.
Regards
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Colt Reeves





Joined: 09 Mar 2009

Posts: 466

PostPosted: Tue 02 Jun, 2009 12:39 am    Post subject:         Reply with quote

I usually whack the pommel myself, but I never thought of it as an exact science. I pin the COP down to within a few inches and don't worry too much about it since I seem to automatically aim for that spot without really thinking about it (did it right out of the box without checking where it was the first few times).

Also, it has been discussed a few times that tip cutting can be more effective than COP cutting. Too lazy to look up a topic with it though. Wink

Unfortunately I didn't answer a single question... I am sort of curious to know how striking different areas will affect perception of the COP though.
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Vincent Le Chevalier




Location: Paris, France
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PostPosted: Tue 02 Jun, 2009 4:52 am    Post subject: Re: I hit the flat of the blade or the side of the cutting b         Reply with quote

Maurizio D'Angelo wrote:
(with the heel of your hand off causing the sword to vibrate.) Where? I hit the flat of the blade? If I have translated well, it would be more just hit the side of the cutting blade? Some time ago, I said in my previous post, that I would have built a tool. It is almost ready, playing with an accelerometer, I discovered that things are very different. If striking the flat, I have a very different outcome if that affects the cut. Then the CoP? (I attribute this to the term commonly used here, but I agree with Vincent that is incorrect) explanations are appreciated.
Regards


It all depends on what you're after. As far as vibrations are concerned, you're after the first mode of vibration, that shows the greatest amplitude. This mode has two nodes, one on the blade near the tip and one nearer or in the handle. As long as you strike the sword somewhere else, the first mode will be excited and its vibrations will be slowly dampened, so that the nodes will be possible to measure.

About striking the edge vs. striking the flat:
Vibrations edge-to-edge have a very small amplitude because the blade flexes very little in this plane. They are dampened very quickly. Therefore they are impossible to see accurately, and that's why the test is done by striking the flat.

The energy stored in vibrations is very small anyway, relative to the total kinetic energy of the sword. There should be no concern about energy loss due to the vibrations. What happens, however, is that the impact will often provoke flat-to-flat vibrations, that can prevent the edge from cutting properly. That is why on hard targets it is better to cut near the node of flat-to-flat vibrations. The edge-to-edge vibrations can be safely neglected. On soft targets, vibrations are not a problem at all, and you can cut nearer the tip, taking advantage of the thinnest part of the blade and sharpest edge.

The nodes of the edge-to-edge and flat-to-flat vibrations are different, but not by much. I don't know exactly what you are measuring with your accelerometer or how you set it up, so I can't comment on that.

Anyway, swords are designed to be swung and cut without bending around so much. I still believe that harmonic behaviour has been vastly over-stressed... We're not exactly considering music instruments here Happy

--
Vincent
Ensis Sub Caelo
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Maurizio D'Angelo




Location: Italy
Joined: 09 Feb 2009
Likes: 3 pages
Reading list: 3 books

Posts: 649

PostPosted: Tue 02 Jun, 2009 6:10 am    Post subject: Re: I hit the flat of the blade or the side of the cutting b         Reply with quote

Vincent Le Chevalier wrote:
[

Anyway, swords are designed to be swung and cut without bending around so much. I still believe that harmonic behaviour has been vastly over-stressed... We're not exactly considering music instruments here Happy


Hello Vincent
I am satisfied with the answer.
Perhaps I have given much importance to harmony, wishing to estimate accurately.
My thought is, however, a starting point, your thinking, a point of arrival. Let me explain better. You measure the nodes after a sword was built, I want to do it before you build. I think you agree with me, it's a little more difficult.
After your post I realized that Ansy 12 (a simulation program) is not, so do not risk becoming swords as musical instruments. Razz
Now I can go back to see the sword as a means of cutting.
I think I understand what is a sword, I can now begin to study. Wink
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