Sliding weights

[Jens Nordlunde]

Sliding weights has been discussed more than once, but I don’t remember ever having seen with which effect the weight adds to the blow. Do we have one on the forum with an analytic mathematical brain, who can figure out which formula to use?

Let’s say that the sliding weight weighs 250 g, the sliding distance is 90 cm and that the impact speed without the weight is 40 km/h.

I know that 40 km/h probably is too slow, but if we have a formula it should be easy to change the speed. Besides I have chosen 40 km/h as the strength and enthusiasm shown in the start of a battle is likely to wear off during the day - like this, ‘fit for fight – fit – too tired to lift the sword’. Also the weight might not be heavy enough, but I don’t have any idea of how much the sliding weight on the Claymores weigh.

[fearn]

Hi Jens,

Just thinking about it, you might want to specify a few more things, namely the length of the blade, and the position of the slide relative to the blade (especially the center of impact).

Just out of curiosity, is a 90 cm slide reasonable? Most swords are less than 1 m long, and assuming a handle that is 20 cm long, you would need a 1-handed sword that has a 1.2 m blade simply to keep the weights inside, and to leave 10 cm at the tip for a solid hit. Then you have to assume that the weight can go from near the hilt (say 20 cm) in a vertically held blade, to 1.1 m on a horizontally held blade, as it hits, over about 0.1 second (I'm guessing, on the basis of 1 m/sec=3.6 km/hr). Does that sound reasonable? Ideally we'd want a perfectly frictionless slide, but I suspect that a bead in a slot (the weights I've seen), would also experience significant friction, especially if the sword was bloodied after a strike.

Neat problem though. I'll be interested to see what the physicists say about it.

Fearn

[Jens Nordlunde]

Hi Fearn

Thanks for the mail, and yes I did forsee that I most likely would miss some important pieces of information, so let me try again.

Weight 250 g.
Length of blade 90 cm, impact 60 cm down the blade.
Length of sliding 60 cm. Starting 15 cm from the hilt.
Speed of impact 40 km/h
We must assume, not to make it too complicated, that the blade is straight, that the weight is in one piece sliding in the middle of the blade (double edged), and that the friction at any time is close to nil, although you are right that while fighting blod would slow the slider down.
I will comment on what you write about the beads, steel balls later on this thread.

Jens

[Jeff D]

Hi Jens,

As always you ask a interesting question. The purpose of a sliding weight (if it is indeed functional not decorative) is to move your point of balance down the blade. Essentialy converting a rapier (light blade with a point of balance closer to the hilt) into an axe. As you know the cutting ability has a lot of variables such as edge geometry, draw cut etc. However the sliding weights function would be to add mass to the point of impact thus increasing the kinetic energy which then gets converted into cutting energy. KE=1/2mv2 (kinetic energy = one half mass times the velocity squarded). The amount of mass added will then depend on where your sliding weight is in relation to the point of impact which ideally will be on the point of impact.

As a disclaimer I am not a physicist
Jeff

[Jens Nordlunde]

Hi Jeff,

Thanks for the kind words.
Would the effect not be bigger when, like I have done, let the glider pass the point of impact with a few cm?
My idea with this thread is not to get an exact answer, but to get an idea of, how much extra power a gliding weight did/could add to the sword.
I will comment on you quertion, 'The purpose of a sliding weight (if it is indeed functional not decorative) is to move your point of balance down the blade.' later, as I find this very interesting.

Jens

[Jeff D]

Originally Posted by Jens Nordlunde

Would the effect not be bigger when, like I have done, let the glider pass the point of impact with a few cm?

Hi Jens

Yes, the effect should be increased as there is a rotational kinetic energy that should increase directly proportional to the distance past the point of impact squared (I=mr2).

Jeff

[Roland_M]

Originally Posted by Jens Nordlunde

Do we have one on the forum with an analytic mathematical brain

Really no mathematical brain but you can calculate either the kinetic energy (ekin= 0.5m*v^2) or the momentum (p=m*v).

In the first formula the weight of the blade is imho underrepresented.

It is a similar thing if one discuss about the effect of a bullet, not very easy to answer!


Roland

[kronckew]

we should be using angular (rotational) momentum, the blades COP and the length from the COP (varies with weight movement) to the centrum (elbow or shoulder? depends on how you are cutting). reducing the radius increases the velocity but maintains angular momentum, which doesn't change unless acted on by an outside force.
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[Ibrahiim al Balooshi]

Originally Posted by kronckew

we should be using angular (rotational) momentum, the blades COP and the length from the COP (varies with weight movement) to the centrum (elbow or shoulder? depends on how you are cutting). reducing the radius increases the velocity but maintains angular momentum, which doesn't change unless acted on by an outside force.
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That is all well and good kronckew but the trials on the sliding weight sword somewhere in the North of England in the early 19thC came to a very abrupt conclusion; The sword was hollow and half filled with Mercury. The proving ground was on a small bridge over a brisk fast flowing stream...It is said that the swordsman was the local blacksmith who on giving the test weapon a hefty swing was instantly off balanced, the great sword throwing him over the parapet of the bridge into the water below.

[Roland_M]

Originally Posted by Ibrahiim al Balooshi

That is all well and good kronckew but the trials on the sliding weight sword somewhere in the North of England in the early 19thC came to a very abrupt conclusion; The sword was hollow and half filled with Mercury. The proving ground was on a small bridge over a brisk fast flowing stream...It is said that the swordsman was the local blacksmith who on giving the test weapon a hefty swing was instantly off balanced, the great sword throwing him over the parapet of the bridge into the water below.

That is the sliding weight? A movable weight inside the blade to increase the momentum of lightweight blades? From the fighting point of view, that is ridiculous.

The strongest man in the world in the early 20th century filled his barbell with mercury. But his aim was to make the barbell unusable for other strong man's. He demonstrated this often on stage in a competition, but it was just a cheap trick.

Roland

[Ibrahiim al Balooshi]

Originally Posted by Roland_M

That is the sliding weight? A movable weight inside the blade to increase the momentum of lightweight blades? From the fighting point of view, that is ridiculous.

The strongest man in the world in the early 20th century filled his barbell with mercury. But his aim was to make the barbell unusable for other strong man's. He demonstrated this often on stage in a competition, but it was just a cheap trick.

Roland

Yes it is ridiculous, however, I bumped into a peculiar reference in the Met Museum of Art archives about hollow swords and it appears that swords were actually made by "The Hollow Sword Blade Company" with a hollow blade filled with mercury so that the weight on thrusting was transferred down the blade to the tip therefor giving extra weight to the momentum...

To source this reference simply tap into web search Swords From The Dresden Armoury from which I Quote "One learns, for example, of the Hollow Sword Blade Company which was chartered for the professed purpose of making hollow swords with running mercury inclosed to gravitate to the point when a blow was struck and so increase the weight and momentum of the stroke". Unquote. Or follow the link http://www.jstor.org/stable/3255703?...n_tab_contents

[kronckew]

there is something called the 'free surface effect' that has serious influences on stability. basically of you have a wide square shape ship, it can be very stable about it's centre of gravity. a push down on one side and the hull weight on the other side keeps it from tipping. add just a bit of water (or mercury) and the slightest movement can cause the fluid to abruptly and uncontrollably run to the lower side, overbalancing the ship and causing a permanent list. it's why ships have longitudinal as well as transverse bulkheads (partitions) to ameliorate the sloshing. and you can pump from one side to the other to balance the ship if one side has more fluid than another.

fernando, don't have anything european without re-researching, but i did have a asian drawing where chinese soldiers with overly long anti-equine swords were paired up to draw each others sabres more quickly. it did mention the individual could pull the blade out in stages by grasping the blade (carefully) part way each time he pulled out a bit. not the best way if set upon suddenly, but i guess OK for a more controlled and traditional gentlemanly duel, tho in the cases seconds (or servants) were in attendance to assist anyway. i think it's posted here somewhere. asuspect i was thinking about a shakespearian passage where one of the principals called out to his servant to hand him his rapier which was discussed on another forum.

aha! found a small version of the drawing for unscabbarding miao dao.