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Malte S.





Joined: 07 Feb 2010

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PostPosted: Sun 07 Feb, 2010 2:55 am    Post subject: Maximum Velocity         Reply with quote

Good morning,

I'm writing a research paper about the physics of swords. And I got to the point where I need some information for examples. So maybe yall can help me. I need the maximum velocity of a one-handed sword which is held above the head and then smashed down to an opponent's head. I know that that is difficult to measure. If anyone knows anything about the velocity or the impact of swords at all, please feel free to contact me.

Thanks for helping.
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Toke Krebs Niclasen




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PostPosted: Sun 07 Feb, 2010 3:23 am    Post subject:         Reply with quote

Here is something on sword dynamics, I do not recall if there is specific velocities mentioned.
I have somewhere read of 50+ miles/hour

http://www.thearma.org/spotlight/GTA/motions_and_impacts.htm
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Thom R.




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PostPosted: Sun 07 Feb, 2010 9:11 am    Post subject:         Reply with quote

50 mph is in the right range I think. . in studies of major league baseball players 45-60 mph are typical for bat swing speeds, for cricket players less so. different motion admittedly but if you need a ballpark (pun intended Big Grin ) number there you go
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Malte S.





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PostPosted: Sun 07 Feb, 2010 12:45 pm    Post subject:         Reply with quote

Thanks. I'll go with that.
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Vincent Le Chevalier




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PostPosted: Mon 08 Feb, 2010 2:29 am    Post subject:         Reply with quote

Hello,

One thing to bear in mind is that a baseball (or cricket) bat is not balanced in the same way as a sword, and therefore that a sword might be able to achieve greater tip speed...

I think a good way to include that difference is to consider kinetic energy instead of speed, and eventually use it to deduce the speed if you need it, depending on the motion and mass distribution of the sword (which you'll need anyway if you want to make impact calculations).

This article gives a figure for the kinetic energy of a bat hitting something: 515 kg m^2/s^2. Assuming the same energy and rotation about the pommel at the moment of impact, with the dynamic properties of the Brescia Spadona, I arrive at a tip speed of 50 m/s, which is about 110mph... Quite a bit more than what a baseball bat with more weight near the tip can achieve with the same energy.

Will your article be publicly available at some point? I'd be interested Happy

Regards,

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Dan Howard




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PostPosted: Mon 08 Feb, 2010 3:20 am    Post subject:         Reply with quote

Tip speed of a sword is irrelevant unless that is the place that makes contact. Measurements should be taken at the point of impact.

Consider:
1. It takes very little to cut flesh - far less than the maximum velocity that can be achieved.
2. No human can swing a sword fast enough to reliably cut through armour.
So how is maximum sword velocity relevant?
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Vincent Le Chevalier




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PostPosted: Mon 08 Feb, 2010 4:31 am    Post subject:         Reply with quote

Dan Howard wrote:
Tip speed of a sword is irrelevant unless that is the place that makes contact. Measurements should be taken at the point of impact.

Indeed yes, but the principle holds true: if you base the computation on kinetic energy you probably get a different value for a baseball bat and for a sword, because the length and mass distribution are different.

Quote:
Consider:
1. It takes very little to cut flesh - far less than the maximum velocity that can be achieved.
2. No human can swing a sword fast enough to reliably cut through armour.
So how is maximum sword velocity relevant?

I don't know what Malte wants to do with that figure anyway, as I said I personally prefer to think in terms of energy.
That being said it seems that the necessary power of the cuts was not deemed quite that low in period. Possible reasons include:
1. It takes very little to cut flesh, but a decisive wound (i.e. one that has a significant chance of ending the fight) needs more power.
2. Cutting through metal armour might be impossible, but not all personal protection is metal and cutting through these protections can be critical for winning the fight.
3. As you put more power into the blow you increase the chances of blowing through weak defences and bad parries.
4. Of course, a faster cut is also more deceptive and more difficult to counter.

Regards,

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Vincent
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Dan Howard




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PostPosted: Mon 08 Feb, 2010 4:37 am    Post subject:         Reply with quote

His original post implies that he is interested in cutting heads. If so then my original comment stands. You don't need maximum velocity to determine whether a sword can kill someone without a helmet. If there IS a helmet then maximum velocity is still irrelevant since it is very unlikely that you could cut through it. The only interesting aspect is how much blunt trauma is imparted through the helmet.
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Vincent Le Chevalier




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PostPosted: Mon 08 Feb, 2010 6:32 am    Post subject:         Reply with quote

Dan Howard wrote:
His original post implies that he is interested in cutting heads. If so then my original comment stands. You don't need maximum velocity to determine whether a sword can kill someone without a helmet. If there IS a helmet then maximum velocity is still irrelevant since it is very unlikely that you could cut through it. The only interesting aspect is how much blunt trauma is imparted through the helmet.

Arguably the motion for hitting the head and the one for hitting the collarbone or shoulder are very similar... But the power needed for significant wound will vary.

Anyway, even for blunt trauma you'll need kinetic energy, and maybe he was asking for speed in order to compute kinetic energy. Velocity is not irrelevant since it is a manifestation of kinetic energy, which is what will be used to damage the target, whether successful or not.

It's true that maximum velocity is not necessarily sought, but it gives an interesting upper bound to what can be done.

Regards,

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Vincent
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Jean Thibodeau




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PostPosted: Mon 08 Feb, 2010 8:14 am    Post subject:         Reply with quote

Dan Howard wrote:
Tip speed of a sword is irrelevant unless that is the place that makes contact. Measurements should be taken at the point of impact.

Consider:
1. It takes very little to cut flesh - far less than the maximum velocity that can be achieved.
2. No human can swing a sword fast enough to reliably cut through armour.
So how is maximum sword velocity relevant?


Tip speed can be relevant to tip cuts against unprotected targets as they can cut better against soft armour than a shopping cut hitting mid blade: I think Michael Edelson's tests showed that some swords like the Tritonia where surprisingly ineffective against soft armour mid blade compared to a Katana but very much more effective with a tip cut.

So tactically tip speed may be relevant in some cases.

If we interpret the original question that seems to be more concerned with blunt trauma on a head protected by a helmet then kinetic energy/momentum achieved is more important than the tip speed in trying to evaluate the relative effectiveness of a sword blow compared to a pollaxe or an arrow or crossbow bolt: Actual effectiveness of sword caused blunt trauma I really am not sure about and only some real scientific testing could give us some idea

Tip sharpness, tip shape would also be relevant to cutting as opposed to blunt trauma effectiveness: A very pointy blade can do some serious damage with a tip cut but is more a ripping action due to these tips tending to be thick and less sharp than the more rounded spatuale tip of the Albion Tritonia that acts more like a draw cut using the tip rather than the edge. ( My opinion/conjecture only, not proved by scientific testing).

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Malte S.





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PostPosted: Mon 08 Feb, 2010 8:28 am    Post subject:         Reply with quote

I've read that it is possible to split a helmet and a head. It always depends on the period. When the French took over Europe the helmets were made out of brass and the soldiers had only little protection at all, because firearms would get through the heavy protection anyway. And so a cavalier could hit a soldier and maybe both would split.

My point of asking was because I wanted to calculate the kinetic energy. When a sword hits a target all the kinetic energy will perform work, which pretty much is the damage. I was just trying to get a picture of how dangerous sword cuts can be. Well after all it isn't accurate at all, because there are too many aspects that are involved in a cut. Starting with the body type, the sword itself (the balance, main purpose...), how profecional the sword can be led through the cut etc.



Quote:
Will your article be publicly available at some point? I'd be interested Happy

I can send it to you once I'm done with it, but it's going to be in German. So that might be a little problem.
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Dan Howard




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PostPosted: Mon 08 Feb, 2010 3:55 pm    Post subject:         Reply with quote

Ah. Well there definitely are eyewitness reports of swords cleaving through 19th century brass helmets. Just keep in mind that it doesn't have much relevance to medieval armour.
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Vincent Le Chevalier




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PostPosted: Tue 09 Feb, 2010 3:54 am    Post subject:         Reply with quote

Malte S. wrote:
Quote:
Will your article be publicly available at some point? I'd be interested Happy

I can send it to you once I'm done with it, but it's going to be in German. So that might be a little problem.

Ah yes, I don't read German at all... Though automated translators can sometimes help sort things out.

Regards,

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Timo Nieminen




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PostPosted: Tue 09 Feb, 2010 1:02 pm    Post subject:         Reply with quote

Malte S. wrote:
My point of asking was because I wanted to calculate the kinetic energy. When a sword hits a target all the kinetic energy will perform work, which pretty much is the damage. I was just trying to get a picture of how dangerous sword cuts can be.


There's a lot more to cutting than KE. Where KE is king is damage where the deformation is non-restorable; that is, the material will not spring back or flow back together in the reverse of the original process. So, KE matters where the material being cut/poked/shot into is rigid, or the damage is done on a short enough time scale so that it can be assumed to be rigid. KE matters when meeting armour, and when shooting things. Cutting with a sword, KE doesn't matter so much when cutting flesh, more so when you meet bone.

For the initial part of the cut, speed is the most important thing. Cutting into a target, energy (and thus speed) will be lost through energy required to push aside the target medium (narrow blades are good) and viscous drag (if the medium is effectively fluid, like flesh) or friction (if solid, like cheese). Not enough energy, or if the energy is lost too quickly, and it's hard to cut deeply.

Speed matters, because you want to exert the maximum pressure possible, or at least enough to cut into the target, to the surface of the target with the edge, before the target surface deforms, accomodating to this applied pressure. But it takes little energy to actually cut the target, so not so much energy is lost due to the cutting. One sign of a good cut on a soft target is that, as the cutter, you barely feel the target.
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Nat Lamb




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PostPosted: Tue 09 Feb, 2010 9:40 pm    Post subject:         Reply with quote

Not sure I am going to phrase this corectly, so forgive me if it comes out garbled. Presumably KE would also be a factor in situations where two parts of the body are made to move out of unison with each other. I am thinking of a hit downwards at an angle at a helmeted head where the helmet is not cut through and there isn't enouigh impact transfered to damage the skull, but where the head is "cranked" sideways in such a way as to injure the muscles of the neck. I imagine a lateral blow to the "snout" of a pigfaced bascinet could couse the head to twist in such a way as to "rattle" the dude inside. This is all uninformed theorising (or rather, talking bollocks).
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Bill Tsafa




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PostPosted: Tue 09 Feb, 2010 10:59 pm    Post subject:         Reply with quote

I had a friend of mine measure the speed of his swing with a chronograph. He was hitting between 160 and 180 mph after we converted from feet per second. I am planning on getting a chronograph soon myself. We tried to also figure out the Energy but it is difficult because you can only guess the mass. It might be around a pound near the tip of a Type X but much less for a Type XV.

The blades speed is slower near the forte... but the physics change considerably because when I strike with the forte, I punch the sword out. In essence I am putting more mass into a forte-punch to make up for the lesser velocity.


Interestingly enough, the measure that my friend took came close to a calculated computation I had made based on how fast I throw a baseball. I throw a baseball at about 30-35 mph. Adjusted for rotational acceleration it comes out to about 160 mph for a 30 inch blade. Of course this is a very rough computation but it game me a ballpark figure.

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Vincent Le Chevalier




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PostPosted: Wed 10 Feb, 2010 2:01 am    Post subject:         Reply with quote

Bill Tsafa wrote:
I had a friend of mine measure the speed of his swing with a chronograph. He was hitting between 160 and 180 mph after we converted from feet per second. I am planning on getting a chronograph soon myself. We tried to also figure out the Energy but it is difficult because you can only guess the mass. It might be around a pound near the tip of a Type X but much less for a Type XV.

Actually you don't have to guess the mass at the point of impact because it's a simple function of the mass, center of gravity and moment of inertia of the sword.
Let's call the impact point I. You can determine the center of oscillation associated to I (let's call it O) by the waggle-test or pendulum test (read about that here, I called it a pivot point pair back then), and you can easily measure the total mass M of the sword and the center of gravity G.

Then the mass at the impact point is:
m = M * GO / IO

If you hit at the center of gravity the full mass of the sword hits, if you hit at a point far from the center of gravity the proportion diminishes. Of course this neglects the inertia of the hand, but it has very little effect for impacts on the weak of the blade (which is why you don't feel much of the shock's energy in the hand). For your forte punch it would be different, because your hand (and arm, and body) also participate to the impact.

Taking the center of oscillation associated to the cross as the impact point (this is ordinarily close to what people call CoP whatever the definition chosen), I have the following impact masses on my swords:
ATrim Type XI: 339g
A&A Milanese rapier: 271g
Albion Squire: 219g
Darkwood rapier: 156g

Interestingly this mass is also a very good indicator of how heavy the sword feels on the wrist, which is actually why I gather this kind of data...

Regards,

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Timo Nieminen




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PostPosted: Wed 10 Feb, 2010 2:46 am    Post subject:         Reply with quote

Nat Lamb wrote:
Presumably KE would also be a factor in situations where two parts of the body are made to move out of unison with each other. I am thinking of a hit downwards at an angle at a helmeted head where the helmet is not cut through and there isn't enouigh impact transfered to damage the skull, but where the head is "cranked" sideways in such a way as to injure the muscles of the neck. I imagine a lateral blow to the "snout" of a pigfaced bascinet could couse the head to twist in such a way as to "rattle" the dude inside.


What is important in these cases is the acceleration (linear or rotational as relevant) of the head. Accelerate the head too quickly, and the skull crashes into the brain. The acceleration will depend on the applied force (F=ma). This also need to be kept up for long enough so that the skull will actually meet the brain. But this can be done by a force that is spread out over a large area of the helmet, or applied slowly enough so that it can't penetrate the helmet. For penetration, the concentration of force - the pressure - matters, while for this kind of damage, the total force matters.

The momentum of the blow will matter more than the KE - the momentum (mass x velocity) of the striking object will be transferred to the head (4kg x head velocity, or (4kg + helmet mass) x head velocity). A light fast object can have a lot of KE, and little momentum, and won't move the target much (but might damage it a lot!).

Heavy weapons will have an advantage here. Still need to be light enough to be fast enough to hit, and fast enough to make the target move fast enough, but generally a heavier weapon will have more momentum (and if used with the same muscular force as a lighter weapon, about the same KE).
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