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]

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

[Jens Nordlunde]

Hi Jeff,

I don't understand the formula, but I am relieved to say that I do understand what you write, and I find this interesting.
Now, if the blade was twice as long, and the glider could glide twice as long, but the point of impact would be the same - what then?

Jens

[fearn]

This is definitely a neat problem.

Just thinking about it, I'd break the contribution of the weights into two categories.

1) changing the centers of gravity and percussion. The best way to think of this is as a sliding weight that can be fixed in place. Fix it at the bottom of the slide, and the sword acts more as a back-weighted stabbing weapon. Fix the weight forward, and the sword acts better as a forward-weighted chopping weapon.

2) the sliding weight acts to increase the impact force by some amount. This gets weird. For instance, the weights could add a second impact to a stab. You use the blade to stab forward, and once the blade slams to a halt, the weights slide forward and add a second thump.

Conversely, when sliding, the weights move in an arc (potentially a straight line) out, from resting near the hilt to the outer end of the slide as the blade moves. Again, they add some force at the end of the slide, but it is at an angle to the cut. This might or might not be a good thing.

In both cases, there's a notable jerk or twitch when the sliding weight hits hits either end of the slide. This might or might not be a good thing.

The nice thing is that this would be relatively easy to dummy up. Put ball bearings (or whatever) in a closed pipe of the length of the slide, and attach this pipe to a practice blade (perhaps with duct tape? :D). Some empirical experimentation would be informative, I think.

Fearn

[Jens Nordlunde]

Hi Fearn,

Your observations are very good. When I thought of the problem, before I started the thread, I wondered what the maximum weight of the glider might have been, if you did not want to loose your sword - torne from you hand by the force of the glider.
You write, 'In both cases, there's a notable jerk or twitch when the sliding weight hits hits either end of the slide. This might or might not be a good thing.' Yes there would have been, and if this jerk is too hard I don't think it is any good for the user, nor for the sword - therfor the slider must not be too heavy - but heavy enough to give the wanted effect. How heavy it that?

Jens

[Rick]

Wouldn't that be measured by a formula of the distance traveled by the weight , the mass of the weight and the speed of the swing ?
The important variable being the speed of the swing ?

[Jens Nordlunde]

Yes Rick, some can to day, but how could they do iot centuries ago?

Jens

[fearn]

Hi Rick,

With a perfectly frictionless slide and a perfectly rigid blade, you're right.

The problem is, it won't be frictionless, and since we're talking about steel, there's also the possibility of the weight rebounding off the end of the slide, plus some other weirdness with the sword flexing as it hits that we haven't even mentioned.

I'm wondering, at the moment, which is more important, the basic physics of a sliding weight on a frictionless surface and a rigid blade, or all the ugly complexities. Murphy's Law suggests that the ugly complexities might, be more important. But I'm a pessimist: either I'm right, or I'm pleasantly surprised. :D

Still, we need some physicists to speak up and point is to the right calculations.

Fearn

[fearn]

A side thought:

I keep thinking about an exotic Chinese weapon I've read about: the "seven stars" rod. Basically, it's a bamboo rod of seven segments. This is a "special species" of bamboo, which I take to mean that the bamboo has pretty thick walls.

The reason it's relevant here is that each of the seven segments is half-filled with mercury and sealed. Basically, it's got sliding weights all throughout the rod.

If someone knows how to make one of these suckers, please speak up. I'm too transfixed by the vision of the rod splintering and spraying mercury everywhere to want to make one of these things.

However, a simple version of it could be made with PVC and marbles (put small, closed sections of PVC pipe inside a bigger one, and secure them with glue or whatever.

Just a side thought, but it's a possible design for any one who wants to experiment with sliding weights.

Fearn

[Rick]

Yes Rick, some can to day, but how could they do iot centuries ago?

Jens

Hi Jens , since you brought this subject up are we discussing a sword that actually exists ; or are we just brainstorming over the possibility of making a sliding weight cutter ?
In your initial post you refer to "sliding weight claymores" , does such a beast actually exist ?

If we are talking about a sword with metal balls i.e. 'tears of the afflicted' in my opinion that feature is entirely for show .

[Jim McDougall]

Wow! I had no idea that the clearly established knowledge of the members here included such command of physics!! I'm afraid I'm pretty much lost in this dynamic discussion, but its fascinating to see the potential and plausibility of such an interesting feature as the sliding weights on sword blades.

Actually this topic was discussed several years ago in a query about a much storied Scottish hero of the 17th century, whose claymore was said to have a 'ten pound weight on the back of the blade to add force to the cut'. While the hyperbole here is obvious, further research found no examples of such a feature on the back of sword blades. It seemed a bit useless to add any weight to the already heavy enough claymore let alone trying to control such a sword with moving weight changing the balance.
It seems that another tale similar describes a medieval falchion with a weight termed in literary fashion 'the apple' or 'pear' on a shaft at the back of the blade for the same express purpose of adding force to the cut.

Clearly the 'tears of the wounded' feature on Chinese and Persian edged weapons aesthetically correspond to this moving feature, but are generally considered to be ceremonial or parade weapons. There have been some accounts of blades containing mercury enclosed in a channel for the purpose of movement of force in the use of the blade, but again these tales appear to have literary origin rather than practical.

What I would like to know is if anyone has ever seen or heard of an actual weapon with a shaft and sliding weight, again without reference to the 'tears of the wounded' pearls or bearings.

Having asked that, I hope the discussion on the actual dynamics of this feature continues! Its fascinating to see how this feature would have been applied and helps in understanding possibilities. Excellent observations!!

Best regards,
Jim

[Ian]

It is some years since I addressed problems in physics, but the mechanics of this problem seem both simple and complex. We are dealing with a rigid bar traveling through an arc, which approximates the segment of a circle having the shoulder at the center of that circle. The radius of that circle is the length of the arm plus the length of the blade (or, more precisely, the distance to the point of impact along the blade).

The energy from the blow will depend on the angular momentum at the point of impact. So far, so good.

If this were a problem with a ball at the end of a weightless string it would be easy to solve (think of a yo-yo or a ball flail). But we have a bar with mass along its length, and we want to add a variable mass distribution to that situation. One way to address this variation in weight distribution is to consider several scenarios, with the two extreme cases being the variable weight at each end of its travel. I'm not sure how to address the question of mass distribution along a bar. Perhaps this requires an analysis of the moments around a fulcrum (which is the point of impact), although the "fulcrum" in this case is not an immovable object but yields with the blow.

I'm sure all of these issues have been worked out previously but it is a matter of finding a reference to the solution. Presently I'm traveling but will be back in the office next week and will talk with some engineering colleagues who have far more skills in mechanics than I do. The final solution may well include calculus, so be warned. :)

Ian.

[Jens Nordlunde]

Hi Rick,
It was actually Jim who got me started on this, as he mentioned a Claymore with a sliding weight, and this made me wonder how heavy such a weight would have to be, to be of any help. I did not know that the sword did not exist, and I have not seen such swords myself, although they may exist/have existed as experimental weapons.

Hi Fearn,
When it comes to friction, I think we should close an eye, or we will end up with too many ‘if’s’, but you are right, there are quite a few things which would/could have an influence on the weight, like blood as you mentioned, or maybe a hard blow on the blade, bending it just a little bit, would most likely stop the weight. Interesting what you write about the Seven Stars rod.

Hi Jim,
You are right, it is an interesting subject, and I hope someone will be able to show us a picture of such a sword. A sword with a sliding weight, weighing ten pounds would be impossible to handle, and more dangerous to the user than to his enemy. If the user of such a sword really held on to the hilt, he might end up with the hilt alone while the blade would be catapulted away. I don’t know, but I have a feeling that a weight of one pound probably would be too much.
We must not forget, that every time the user has used the sword, the weight is in its outer position, and he will have to get it back in order to strike again - this will make him vulnerable. The best would be if a spring could catapult the weight back into the start position, but this may be too far fetched.
I think ‘the tears of the wounded’ have a meaning, other than boasting, maybe to make the user remember the suffering of the wounded laying on the battlefield, but I agree with you that the balls, whichever material they are made of, are not sliding weights.

Hi Ian,
You are right, the problem seems more complex than I had expected from the start. It will be interesting to hear about the answers you will get next week.

Jens

[fearn]

Hi Jens,

While I like the topic of sliding weights, I can think of a couple of really good reasons why someone would "have a weight" on the back of a claymore. If the weight were _fixed in place_, it could be extremely useful either to tune the center of gravity and center of percussion, or alternately, perhaps to dampen shocks from the blade hitting a target.

While I've never seen such a weight on a sword, I wouldn't be surprised if some enterprising soul didn't try it at some point. Fixing a lead slug (or similar) to a blade would certainly be simpler than remanufacturing the blade to have better performance characteristics.

Anyway, back onto the topic: one suggestion I would make is that a shorter slide would be more useful than a longer one, because the weight could move more quickly. Imagine, for instance, a weight that was on the hilt side of the center of gravity when the sword was upright, but which could be propelled across the center by some wrist action to make the sword tip heavy. Such a sword would be easy to accelerate and would hit hard, although it would be hard to recover after a blow.

Fearn

[Jens Nordlunde]

Hi Fearn,

We may, or we may not find swords with sliding weights, but I have a strange feeling, that I have seen one many years ago in a museum, maybe in Istanbul, or somewhere else – I am not sure.

What do you mean by writing that the weight should/could be ‘fixed in place’? How would it dampen he chock?

You write, ‘Fixing a lead slug (or similar) to a blade would certainly be simpler than remanufacturing the blade to have better performance characteristics.’ Yes you are right, that was what the headmen did, if you can believe, that the tree wholes at the blunt tip of their swords were for leaden weights, but they only had to hit once, so why would they need extra weight?

I agree with you, that a short glide would solve quite a lot of possible problems, although the shorter glide, the lesser power. I think I understand what you write next, but I am not quite sure – remember that I’m not brilliant in English. Is it possible for you to explain it in another way? Do I understand you right, when I think that you are saying, that the glider should travel from the back of the blade to the front? If yes, I think this would give the whole thing more force, but I can prove why I think so.

Jens

[Montino Bourbon]

actually the weight moving forward would make a longer pendulum, thus slowing it down, I think.

Besides, for the weight to have a real effect it would have to be big enough that it would add too much weight to make the sword useable.

[fearn]

Hi Montino,

You're right, but as I recall, the time of the pendulum works in part on the distance to the center of the pendulum's mass, not just its total length.

With a weight that slides for a long distance down the blade, you're right. The blade gets progressively more tip heavy, meaning that it will take more energy to move the tip and that it will hit harder (transferring more energy).

If the slide is short, around the blade's normal center of mass, what would happen is that the sword would go from back-weighted to front-weighted. Basically, this would mean that the sword accelerated a bit faster from rest (starting out back-weighted, as in a small sword), hit a bit harder (shifting to front-weighted), and was a bit harder to withdraw (still front-weighted). This type of design makes a lot of sense when you're only planning a single blow, as in an executioner's sword. In a battle, I'm not so sure that it's advantageous, but I don't know. We'll have to see what the engineers say.

One thing to remember is that a blade with a slot down the middle is probably more fragile than a solid blade of the same weight. Jens has proposed an interesting question, and it will be interesting to see some numbers around it.

Fearn

[Rivkin]

I truly believe that any sliding weight would be totally cool, fancy, and useless. I see no reasonable advantage over permanent placement of some weight at the sword's end, etc.

[Ian]

This topic is closely akin to the physics of hitting a baseball.

BTW, I notice that the on deck hitter often puts a ring weight around the bat barrel to take some practice swings, but does not try to emulate that weight in the bat itself. It slows down the bat speed and if the bat is overly heavy too much power would be lost -- kinetic energy is proportional to the square of velocity, but only linearly related to mass.

Ian

[ariel]

I remember years ago seeing a Chinese throwing knife that always hit the target with a point and got imbedded quite deeply. Apparantly the secret was a hole drilled within the entire blade along the whole length and filled with mercury. It moved freely in this channel and changed the center of gravity. Was very impressive.
I guess, the same principle as discussed here.

[Jens Nordlunde]

Montino, you may be right, we will hopefully know later, but I agree with you that a heavy weight getting stuck at the tip could be fatal.

Ariel, an interesting mail about the use of mercury in the blade, I can imagine that the result have been impressive.

Jens

[Mare Rosu]

Jens
You are at it again, from magnetic blades to now sliding weights.
Are you sure you moved to Switzerland and was not run off, to hide/escape? :D
Anyway the idea of sliding weights is a good one, while I have little to add to this subject I do think a distance related subject might be of interest to you and others and that is; Atlatls and banner stones used with them. I have found these banner stones in years past and this is just two web sites on their use. http://donsmaps.com/atlatl.html and http://www.primitive.org/atlstealth.htm.
To me a very interesting subject you have started Mr. Jens

[Jens Nordlunde]

Interesting subject you raise Gene. You are right, this is about giving the weapons more dynamic power, and the links you give, show that this has been very important for thousands of years. This shows, that people in ancient times did know a lot about dynamics, although they did not know the formulas. When throwing a javelin or a light spear, it is important that you ‘arm’ is long, and here the Atlatl helped a lot, as the longer the ‘arm’ the more power you could put behind the throw. Interesting also to see that they adapted the length of the Atlatl to the surroundings, but what I find really intriguing is the use of Banner Stones, as I did not know such stones were used. I wonder how they figured out that the use of Banner Stones would make the use of the Atlatl more silent.

[fearn]

Hi Jens,

This is getting a bit off subject, but I was partially thinking of atlatls when I was talking about weights absorbing shock in a sword.

The other source of inspiration was a dha-style sword I made out of a machete. I very quickly learned that there were only two good handholds on the long handle: at the end, and about 1/4 of the length from pommel to tip. This was because the sword flexed on impact, and holding it at other points was a recipe for getting a very sore hand (the best handholds were at the nodes: end, 1/4, 1/2). Personally, I think that there are a lot of hidden shock-minimizers in well-designed dhas and other long-handled blades. Otherwise, they wouldn't be worth swinging.

There's no reason that a moving weight on a blade couldn't serve a similar shock-absorbing function, but that's another design question entirely.

Personally, I'm surprised that the atlatl people weren't talking about tuning their dart and thrower systems to make the things accurate. After all, if the dart flexes the wrong way, it's not going to hit whatever the person was aiming at.

Fearn

[Jim McDougall]

Outstanding discussion everybody!!!! It is extremely fascinating to read the well explained and supported observations here concerning the feasability of these weapons features. While edged weapons were in themselves primarily simple in thier dynamics, it is amazing how very complex their actual use and construction became. While the sliding weight feature discussed here remains purely conjecture found in literature thus far, many other interesting features are well established in developed examples, such as the thumb rings brought up on a concurrent thread and both hilt and blade shapes and construction.

It would appear that the sliding weight feature remains a figment of literary imagination as no existing examples have been seen, and such features are not mentioned in contemporary narratives or material describing edged weapons.

The mercury filled channel blades, while early examples seem to remain somewhat in question, the concept seems to have been applied in some latter examples of weapons, with this likely to be in response to the earlier tales of such weapons. An illustration of this occurs in at least one 'Bowie' knife produced in the 1860's with a hollow channelled blade containing mercury. Whether it was ever used is not described, however by its appearance (published in "The Bowie Knife", Norm Flayderman) it seems an extremely clumsy weapon.

As this excellent discussion continues, I remain hopeful that in some hidden corner of some archives or museum we will find evidence of the sliding weight on some long forgotten sword. I'm confident that if such a sword can be found it will be by the members and readers here!!:)

Meanwhile, the comprehension of physics and dynamics has always eluded me, but you guys make it understandable!!! Thank you so much!! :)

All the best,
Jim

[Jens Nordlunde]

Hi Fearn,

I don’t think you are off subject, or if you are, it is only a fraction, as the whole subject is about dynamic power/shock-minimizing and stuff like that, so the way I see it, you are on track. I find, what you write about your dha-style sword most interesting. I have always been wondering about the long hilt, but I was wondering about it – you did something about it and tried it out, so now you have a knowledge, which I fail to have. Thank you for sharing.
In the start I did not think about the shock-absorption made by the weights, but I guess you are right, this could be an extra plus to such a construction. The hand would not have to take the whole of the blow – it would be divided – but with how much to the weight and how much to the hand?
I am sure, that those using an atlatl centuries ago, had everything tuned in, so that they were sure to hit the target – they could not afford otherwise.


Hi Jim,

You are right; the discussion gets more and more interesting, as we get more and more implements into the discussion. What I think we can agree on is, that sword smiths in the old times must have had a very good idea about dynamics and shock-absorption – more than we normally think of, when we buy a sword for our collection.


Jens

[Jeff D]

Hi All,

While it isn't a sliding weight, the sliding hilt does change the point of balance. This is from the Landesmuseum.

Jeff

[Jens Nordlunde]

Jeff, don't hold us waiting too long - which Landesmuseum?
There are several in the German speaking countries - so where is it?
BTW thanks very much for being the first to show a sword with a gliding weight:)

Jens

[Jeff D]

Jeff, don't hold us waiting too long - which Landesmuseum?
There are several in the German speaking countries - so where is it?
BTW thanks very much for being the first to show a sword with a gliding weight:)

Jens

Oops Sorry Jens, this is the one in Zurich!

Jeff

[fearn]

Hi Jeff,

Neat sword! I think it's a solution to a different problem, though. There's a book out there (forgot the title) that's a translation of a late-medieval German swordmanship manual.

In that manual, they show the proper way to use a long sword (i.e. hand-and-a-half sword) against a foe in plate armor. Basically, you have to have gloves, on, because you grab the sword half-way up the blade and use the tip as a bayonet/pry-bar to attack the cracks in the armor at extreme close range. I say bayonet rather than short spear, because the the stance reminds me of the way one holds a rifle with for bayonet practice, as do the moves (short stabs and swings, using the pommel and guard in place of the rifle butt).

My suspicion is that this sword was designed with this half-sword grip in mind: Normally, one's finger holds the guard at the base, but at close quarters, you grab the pommel with the other hand, push the guard forward with the lead hand, and use it in a half-sword grip, without sacrificing the guard on the forward hand.

As far as swords with sliding weights, doesn't Stone's Glossary have a picture? I don't have my copy with me, but I have a memory that it does.

Fearn

[Rivkin]

In all honesty - I can imagine (barely) how one can use a movable weight in a throwing weapon, hoping to create some complex gyroscopic motion that would create a restoring force and stabilizing the trajectory as a result.

I can imagine using an adjustable grip or pommel to manage the balance and so on. I can imagine using an axe, the weapon with a high angular momentum.

I can't imagine any reasonable use for a moving mercury or anything in a sword. Suppresion of oscillations is most reasonably done by putting a tuned pitchfork into pommel. If this pitchfork is surrounded by an extremely viscous material, i.e. overdamped, you can have a very efficient transform of oscillations into heat (that's what they do in modern "professional" tools, like hammers). Another way is to design a sword in the way that all it's oscillations somehow negatively interfere with each other, so it basically damps itself (this method is way more complex, but that's what used in modern cameras to suppress the vibrations from shutter/mirror release).

Using a bottle of mercury for this purpose is rather strange.

[Jens Nordlunde]

Jeff, thanks a lot, I will try to have a look at it if possible.
Fearn, interesting what you write, but let us wait and see what I can come up with.
Rivkin, hold your horses till I - maybe can come up with something else.

:)Gentlemen it has been a pleasure:)

Jens

[Jim McDougall]

OK Fearn, I spent the better part of an evening thumbing through Stones, and didn't find any evidence of sliding weights or anything similar....but must say it was still enjoyable as always.I really love that book!!:) No matter how many times guys like to hammer away at Stone for the occasional errors, it's still fun to read so much very early data.He really set the stage for weapons research, and encouraged future researchers, such as us, to correct the inevitable errors with new evidence and revised data.
One thing I did find, and at the risk of mentioning something which applies only indirectly and is most probably irrelevant, I found:

"...Cestus: Heavy leather things, often weighted with lead or iron, wound around the hands and arms of Roman boxers to give additional weight to thier blows"
-Stone, p.168

Once again, leave it to the legacy of the ancients. Obviously, this note is purely speculative correlating the concept in dynamics and influences of many aspects of earlier cultures in application in later times. Clearly one would not need to seek such simplistic dynamics for the increase of force in a sword in ancient boxing, but the coincidence seemed worthy of note.

The search for the elusive sword with the slide continues :)

Best regards,
Jim

[Rick]

OK Fearn, I spent the better part of an evening thumbing through Stones, and didn't find any evidence of sliding weights or anything similar....but must say it was still enjoyable as always.I really love that book!!:) No matter how many times guys like to hammer away at Stone for the occasional errors, it's still fun to read so much very early data.He really set the stage for weapons research, and encouraged future researchers, such as us, to correct the inevitable errors with new evidence and revised data.
One thing I did find, and certain unnamed parties will go berserk ranting about unrelated or irrelevant data or free association etc. by my mentioning it.....

<snipped>

Best regards,
Jim

:D :D :D :D

[Jim McDougall]

Man you're fast Rick!!!!:)

[Andrew]

There is a tool used in orthopedic surgery for driving and extracting nails in bone. The concept is simple, but effective: the tool's head is placed on the nail head, and a sliding weight is forceably impacted in the desired direction. Forward to drive the nail, back to extract.

As with Jim's observation, this is not directly relevant, but may be edifying. ;)

[fearn]

Jim, thanks for checking Stone's glossary for me. Now I'll have to figure out what stray memory I was thinking of. Possibly it was a sliding sleeve on a spear (for the forward hand, so you don't sand your palm off jabbing with the spear). Otherwise, I agree with you about the value of that book. I discovered my parents' original copy as an impressionable pre-teen. Now I'm here. Go figure.

Fearn

[Rick]

Man you're fast Rick!!!!:)

Eight years of memories Jim . ;)

[ariel]

The only such weapon I can imagine being workable is an ax. It necessarily goes only up and down. Anything staying for some time in a horizontal position and /or requiring lateral movements would be unworkable.

[fearn]

The only such weapon I can imagine being workable is an ax. It necessarily goes only up and down. Anything staying for some time in a horizontal position and /or requiring lateral movements would be unworkable.

You don't like the idea of a pile-driver rapier, Ariel? :D :D :D :D

F

[Ian]

I have two engineers working on this problem.

To get them involved, I needed to rephrase the problem in terms of a baseball bat hitting a ball. :D :D :D They are baseball nuts, so this got their attention. While there is a book on the physics of baseball, as far as we know nobody has considered a bat with a sliding mass (probably not legal anyway :(), so they want to work on this in case they come up with a "super bat" they can use in their Sunday softball league. :eek:

Engineers are like that -- give 'em a question they don't know the answer to, and they will worry away at it for hours. BTW, summer is a quiet time in our office. :rolleyes:

Will be back in touch when, and if, they can find an answer.

Ian.

[Tim Simmons]

The sliding hilt is quite a good idea, how it worked in actual combat is another matter, but in theory it transforms a long thrusting weapon into something more general for close contact in the melee. Tim

[Jens Nordlunde]

Excelent Ian, but I think I on Google saw a training baseball bat with a sliding weight – only for training it said. It had some kind of sliding weight inside, but I am not sure what kind.

Imagine you had an arrow with a sliding weight on the haft. Before you took a shot, you pulled the weight back and when the arrow hit the target, the weight would make sure the impact was bigger than normal – would that work?

I hope to see the sword with the sliding hilt to morrow.

[Jens Nordlunde]

To day I went to Landesmuseum in Zurich, and found only very few weapons, and not the one Jeff show. When I asked where they were, I was told that they had packed them down, and no one knew when they would be on exhibition again, but to morrow a special exhibition would open with some weapons. I then went to the museums shop to ask after a book/catalogue showing weapons from the museums collection - no book, they had once had one, but it was sold out, and they did not plan another one:mad:.
Jens

[Ian]

Imagine you had an arrow with a sliding weight on the haft. Before you took a shot, you pulled the weight back and when the arrow hit the target, the weight would make sure the impact was bigger than normal – would that work? Jens:

I don't think this would have any effect, but perhaps it might if the weight shifted from the fletch to the head at the time of impact. Because we are talking about a piercing shaft, all energy would be concentrated at the point of impact, and the mass of the arrow lines up directly behind that point -- so however mass is distributed behind the point of contact would be immaterial, unless possibly if part of that mass is moving along the shaft at the moment of impact. Even then, I think the effect would be small and would need to be weighed against the effects of a rear-weighted arrow on its flight and accuracy. The small potential gain in penetrating power could well be offset by impaired accuracy.

Ian.

[Ian]

Here is what my engineering colleagues had to say about the question before us. I have translated from engineering-speak as well as I could.

The problem of a weight (mass) moving along a rod that in turn strikes another object is really quite complicated and we do not have enough information to answer your question. Here is a somewhat lay interpretation of the problem, which we have modified from The Physics of Baseball by Robert K. Adair.

Basically, the properties of a rod (sword, bat) relevant to striking another object squarely are defined by three weight distributions, or three moments.

1. The sum of the weight of each part of the sword, which is just its total mass (the zero moment)

2. The sum of the weight times distance, measured from the handle, of each piece of the sword (the first moment)

3. The sum of the weight times the square of the distance for each piece of the sword (the second moment or the moment of inertia)

There are three key positions along the sword that follow from these three moments.

a. The center of gravity
b. The center of inertia
c. The center of percussion

There are three additional factors that need to be considered.

d. The elasticity of the sword
e. The resonant frequency of the blade
f. The position of the vibrational node

Although the center of percussion and the vibrational node will be close to each other, they are not the same.

For a sword of fixed mass distribution, we can determine fairly simply the various points that correspond to the three moments.

The center of gravity is just the balance point. The center of percussion can be found by holding the sword lightly by the end of the hilt and striking the blade gently with a hammer; when the blade is struck at the center of percussion there is no detectable movement at the hilt. In most cases the center of percussion is very close to the vibrational node -- when the blade is struck at the vibrational node no vibrations are felt at the hilt.

The center of inertia can be determined by placing the sword on a frictionless surface (such as an ice rink) and pushed away. When the push is placed at the center of inertia the sword will move away without any appreciable rotation.

Each of the moments are manifest in obvious ways. The weight is felt by holding the sword vertically. The force required to hold the sword straight out in front of you at arm's length is proportional to the first moment. The force required to wave it back and forth vigorously when it is vertical is proprtional to the second moment. This second moment contributes most to the "feel" of the sword and is the factor most important to the user.

The elasticity is determined by the blade's resilience near the point of impact; a resilient blade may store energy upon impact and return that energy to the target.

The resonant frequency is a measure of the energy loss when a target is struck at a point along the blade away from the vibrational node. A higher frequency indicates a larger (i.e., longer) "sweet spot." Swords with longer blades and thicker handles will display higher vibrational frequencies and long sweet spots.

This is what we know about items that have a fixed mass distribution. When you add a varying mass distribution, the problem becomes more complex. When the weight distribution shifts, all of the moments change.

A sliding mass would create a tip-heavy sword, moving the centers of gravity, inertia and percussion away from the hilt. Depending on the fraction of the total mass that is moving and its final resting place along the blade, the respective moments may well be centered quite close to the tip, and essentially one would have a club. Such a shift in mass would likely make a clumsy and slow weapon.

We will think some more about this problem but it seems that any substantial shift in mass would produce a sword that could be difficult to control and would probably slow its action. How much of an effect would depend on the fraction of total mass that was shifting and the distance it traveled away from the hilt.

[Rivkin]

This list seems popular among the sword community - it's not the first time I've seen similar ideas expressed concerning the waves for example.

My problem is that for example it's hard for me to understand why the center of gravity is going to be a node for all waves (it should not be for at least for the waves with an odd number of halfwavelengths). Concerning the hilt, it seems more like a boundary condition to me, rather than a center of gravity. Concerning longer swords having higher frequencies and wider diaposon, it seems counter-intuitive to me - I would expect smaller swords to have larger frequencies and bigger separation in between of individual modes, but that's just my guess.

I'll be honest, I don't understand some of the ideas expressed above. Concerning the sliding mass question, again, what are the possible benefits of this construction vs. simply high momentum fixed mass weapon - nothing simple comes to mind.

[Ian]

... My problem is that for example it's hard for me to understand why the center of gravity is going to be a node for all waves (it should not be for at least for the waves with an odd number of halfwavelengths). The center of gravity is a balance point and the centers of inertia and percussion are located at different points along the blade. The respective centers are features of the weight distribution and mechanical properties of the sword (which mostly comprises the blade and the tang).

Waves do not originate from any of these centers. Waves are set up at the point of impact and spread out from that point. The further away the point of impact is from the vibrational node, then the more vibration will be transmitted along the blade and will be felt in the handle.

... Concerning the hilt, it seems more like a boundary condition to me, rather than a center of gravity. Concerning longer swords having higher frequencies and wider diaposon, it seems counter-intuitive to me - I would expect smaller swords to have larger frequencies and bigger separation in between of individual modes, but that's just my guess. The tang is continuous with the blade and would not be a boundary condition. Depending on the properties of the handle covering materials there may be some dampening of the vibration transmitted from the tang to the hand. My colleagues assure me that physics dictates that the longer the blade, the longer the sweet spot and the higher the frequency of vibrations.

... Concerning the sliding mass question, again, what are the possible benefits of this construction vs. simply high momentum fixed mass weapon - nothing simple comes to mind. I cannot see any real benefits to a sliding mass. That was the conclusion of my esteemed colleagues also -- they are skeptical that any greater force could be achieved, and the sliding mass would introduce unpredictable and inconsistent properties of the sword depending on how it was wielded.

Ian.

[fearn]

Hi Ian,

I think your overall conclusion is probably right--that a sliding mass is not beneficial, although it might be less troublesome in an executioner's sword.

I won't pretend to be a physics expert, but I do know a few things about swords and rods.

One thing that confused me was the difference between center of inertia and center of gravity. These are different because....?

So far as the vibrational nodes go, my limited observations are that straight swords are quite a bit like rods: the vibrational nodes are at the geometric center and the quarters. HOWEVER, the center of gravity doesn't have to be at any of these points. To give a crude example: imagine a rod two- thirds metal. It should be obvious to most people that the point of balance will be fairly close to the center of the metal part, because the wood is much lighter. In a sword with a heavy pommel and lighter blade, you can put the center of gravity and/or inertia pretty much where you want it.

So far as longer blades having bigger sweet spots due to higher vibrational frequency, I'll admit that I'm confused too. I agree that the longer blade should have a bigger sweet spot, but I'd bet a fair amount that it would have a lower frequency, just because it's longer. This is the same reason that cellos generally play lower than violins: the frequency is lower, not higher, in a longer string. I'm guessing that the word we're looking for is longer wavelength and bigger amplitude.

However, I'm still very glad that we had an engineer look at it. Now, if someone will get out there with the PVC tub and ball bearings, and find out what a sliding weight feels like when you swing it, we can all rest easily....

[Rivkin]

1. With given definitions the center of gravity and the center of inertia will be the same.

2. If its possible, I would really like to see the formula they use for sword's frequency as a function of length (do they consider it a string ? a thin and long prism ?).

3. Concerning tang not being a b.c., or even a separate body, I would prefer to hold a vastly different opinion.

4. Concerning waves propagating in swords and nodes - propagating waves usually do not have nodes. When people talk about nodes, they usually speak about standing waves, i.e. steady state solutions etc.
I suspect that the logic was that if sword can be considered a string, than a full wavelength standing wave will have a node in the middle, but it will basically be true only for even halfwavelengths mode... Plus I'm really too lazy to calculate the modes of a string with a variable mass, so I don't know how big percentage of the waves will have nodes at the center of mass.

5. Concerning the center of percussion - as far as I remember (and I remember it very poorly), the center of percussian is when you hit it, all the momentum is transfered into the rotation movement of the sword, without any daggling down or up.

[Jens Nordlunde]

Hi Ian,

Thank you for using your time on this topic, and thank you to your colleagues for their time. I had in the start expected the problem to be les complicated than it is, and I cant say that I can follow all the explanations, so I will have to read it one or two more times and see if it helps.

Fearn, I don’t have a sword with a sliding weight, only one with steel balls, and swinging that, the moving of the balls does not make much difference, it would not as the balls are not very heavy.

I think the conclusion is, like several has stated, that sliding weights on swords are non existent, and should such a sword be found, then it must have been made as an experiment – not for use.

[fearn]

Hi Rivkin,

You're right, of course: I'm thinking of standing waves, aka, the way the sword flexes when it hits something. The nodes are where it flexes the least, and those are where you want to hold it, unless you enjoy hand shock.

Hi Jens,

Yep, I think we've settled it. It's a good thing, too. Otherwise, we'd next have to deal with the mechanical advantage that the Chinese gain by putting those nine rings on the back of the nine-rings dao :D :D

Fearn

[Rivkin]

You're right, of course: I'm thinking of standing waves, aka, the way the sword flexes when it hits something. The nodes are where it flexes the least, and those are where you want to hold it, unless you enjoy hand shock.


That's one of the things I don't understand - what is a node for one wave, will be a maximum for another wave.

[Ian]

Hi Kirrill:

You raise some interesting points and I will try to deal with them as best I can. My college physics is but a distant memory!

Both of my local contacts went on vacation on Friday, and will be out of the office for the next four weeks. Academics do very well with vacation time.:rolleyes: I will do my best.

Ian.

1. With given definitions the center of gravity and the center of inertia will be the same. As described above, the respective moments vary with distance of the various components of mass from the handle, raised to the power of 0 (the zero moment, which is simply the total mass); with distance raised to the power 1 (the first moment); and with distance raised to the power of 2 (the second moment). The center of gravity relates to the first moment, the center of inertia relates to the second moment. If mass is distributed uniformly along the length of the rod, then I believe that the center of gravity and center of inertia will be the same. When mass is distributed unequally, then the two will be different. The difference will be demonstrated by the two tests I listed.

2. If its possible, I would really like to see the formula they use for sword's frequency as a function of length (do they consider it a string ? a thin and long prism ?). Need the experts for this one. I believe they modeled this as a solid rod.

The frequency we are talking about, then, is the resonant frequency of a solid rod, which (if I recall correctly) for a given diameter varies with the density of the material and its length. When we talk about a string, there is also a factor for the rigidity of the material or tension applied (a taught string resonates at a higher frequency than a slacker string). The resonant frequency is fixed for a rod of given dimensions and homogeneous construction. The amplitude of the vibration varies with the distance the rod is struck away from the resonant node.

An interesting example is the aluminum (aluminium) baseball bat, which has an outer aluminum shell and an inner core that is air-filled. Striking a ball with such a bat produces a brief, high-pitched "ching," and a lower-pitched "thunk." The higher pitched sound reflects the resonant sound of the metal shell, and the lower-pitched sound comes from resonance in the air-filled chamber.

These sounds are hard to distinguish with the human ear but apparently have been measured with sophisticated recording equipment. The low frequency sound is just a few hundred cycles per second, approaching the limits of detection for the human ear.

3. Concerning tang not being a b.c., or even a separate body, I would prefer to hold a vastly different opinion. For full tang construction, there should be no boundary condition because the tang is essentially an extension of the blade. This is the same situation as a baseball bat, and the handle presents no boundary condition in that example.

As I mentioned above, there may be dampening of the vibrations by materials around the tang. For partial tang construction, I am unsure how much of a boundary condition there may be. It probably varies with the width and length of the tang, and again the wrapping materials will be important in how much dampening of the vibrations might occur for the user.

4. Concerning waves propagating in swords and nodes - propagating waves usually do not have nodes. When people talk about nodes, they usually speak about standing waves, i.e. steady state solutions etc.
I suspect that the logic was that if sword can be considered a string, than a full wavelength standing wave will have a node in the middle, but it will basically be true only for even halfwavelengths mode... Plus I'm really too lazy to calculate the modes of a string with a variable mass, so I don't know how big percentage of the waves will have nodes at the center of mass. This one requires the experts. The test described above speaks to a property of standing waves, I think, but the center so defined also identifies the "sweet spot" which relates to properties of propagated waves also -- at least that was how it was explained to me.

With respect to analogous models, I believe that a string as we usually think of it is probably not the correct one. A string can have variable tension. If we exert enormous tension on a string, and essentially make it highly inflexible or "rigid," then we may approach a more representative model. A metal rod has a high degree of rigidity, which is essentially constant for the purposes of this discussion.

5. Concerning the center of percussion - as far as I remember (and I remember it very poorly), the center of percussian is when you hit it, all the momentum is transfered into the rotation movement of the sword, without any daggling down or up. Could be, but we need the experts for this one too.

[Rivkin]

Hi Ian,

I don't think rod vs. string makes too much of a difference.

1. Equations are basically the same - they are basically the same for all oscillations. What is important is that we have oscillations around the equilibrium. Exapnding potential in Taylor's series, and taking derivative with respect to the displacement (which is going to give us force), we'll se that constant force is not there due to the equilibrium requirement (there are no forces in equilibrium, the derivative of energy is zero), force linearly proportional to the displacement is what gives us oscillations, force proportional to the displacement squared exist only in anisotropic bodies (asymmetric problem), cube will give us a nonlinear oscillator, and that is something we don't whant to deal with.

So it's always restoring force linearly proportional to the displacement.

2. Now the shape determinces boundary conditions - but if something is very long in one dimension, since if it would be infinite, it would have plane waves as a solution, if it's just long it has something similar to plane waves - sin or cos (basically sum of 2 plane waves propagating in the opposite directions).

Now for other dimensions - if it's a rod, it's most likely going to have a Bessel function or something like this (since it's like a drum). I think the problem is somewhere in the books on diff. equations.

I think plank is more suitable than rod in case of swords, but again - we are interested in transverse oscillations along the longest dimension.

Concerning additional b.c. - I meant that the tang is coupled to a human hand, so it's either unmovable, but under stress, or it's coupled to an oscillator.

I still don't agree to the rest of the things...

Sincerely yours,

Kirill Rivkin

[Jeff D]

Hi Rivkin

I would like to address some of your questions and hope it can add to Ian's excellent answers.

1. With given definitions the center of gravity and the center of inertia will be the same.

Inertia is the tendency for a body at rest to stay at rest or stay in uniform motion. It requires an external force to alter this state. With our sword example I think its relevance is more in the handling of the sword than in its ability to cut as per Jen's original question. So I would agree with you that for all intense purposes it would be OK to consider it the center of mass.

2. If its possible, I would really like to see the formula they use for sword's frequency as a function of length (do they consider it a string ? a thin and long prism ?).

I am not sure what model the engineers used, however I think it would be safe to use a bar with a clamped (fixed) end (similar to a hilt) as a model. Using this model the formula is;
F(1) = 0.162 {a/(L squared)} {the square root of(Y/d)} where a=thickness, L is the length of the bar, Y is Young's module (which is a variable of the elasticity of the material), and d is the density.

3. Concerning tang not being a b.c., or even a separate body, I would prefer to hold a vastly different opinion.

Using my model I would not consider the tang in the Length formula as the hilt and tang would be the fixed portion of the bar.

4. Concerning waves propagating in swords and nodes - propagating waves usually do not have nodes. When people talk about nodes, they usually speak about standing waves, i.e. steady state solutions etc.
I suspect that the logic was that if sword can be considered a string, than a full wavelength standing wave will have a node in the middle, but it will basically be true only for even halfwavelengths mode... Plus I'm really too lazy to calculate the modes of a string with a variable mass, so I don't know how big percentage of the waves will have nodes at the center of mass.

I think again we are confusing some of the issues. The vibrations only affect Jen's question in reguards to the energy transfer. The less vibration, the more energy transfered from the kinetic energy of the swing into cutting energy. If there is a lot of vibration then a lot of energy is wasted. The vibration will obviously affect the handling as well. I think a complex bar with varing thickness, fullers etc. would set up a series of standing waves that would cancel each other out so that there will be minimal palpable vibrations.

5. Concerning the center of percussion - as far as I remember (and I remember it very poorly), the center of percussian is when you hit it, all the momentum is transfered into the rotation movement of the sword, without any daggling down or up.

I am not sure of what your question here is but I think you are correct in that the center of percussion is where the blade strikes the sword, and should there for be where the resistance of the object balances.

Hope this adds a bit.
Jeff

[Ian]

Kirrill:

I have taken this way beyond my knowledge or comfort zone and cannot address your latest comments.

Much of what I have presented comes from the book that I referenced above by Robert Kemp Adair. He is presently Sterling Professor Emeritus of Physics at Yale University. You can find his contact information at http://www.yale.edu and using the search function for people on the home page.

Much of what you disagree with is cited in his book, including the comment that the resonant frequency of a baseball bat is related to its length and the thickness of the handle. He also points at that the centers of gravity, percussion and inertia are not the same and occur at different points along the length of a baseball bat.

BTW, Adair's book is available on the web for $1.00 plus shipping through this site http://www.abebooks.com

Ian.

[Jens Nordlunde]

In ‘The Indian Antiquary’, August 1873, page 217, W.F.Sinclair writes:

A common weapon among Hindustanis and Musalmans is a long steel rod with three or four small rings sliding on it. These, slipping forward as the weapon descends, add force to the blow, which is far more severe than might be supposed from the slender appearance of the weapon. It is also a good guard against sword-cuts.

[Andrew]

Hi Jens. :)

Interesting. Have you ever seen such a weapon?

How was your trip?

Best,
A

[Jens Nordlunde]

Hi Andrew,

I am not sure, as I seem vaguely to remember such a weapon. If I have seen one, it is very long ago, but from the description I think it must be a mace without a head, only with a rather long and slender haft with sliding weights. The weapon Sinclair describes is interesting, but if they made such a weapon, why not a mace with sliding weights?

The trip was terrific, we saw the reserves at V&A, but it is with time like with fire, it is a good servant but a brutal master. When we arrived we had hours ahead of us, but suddenly the time was running out fast. We did however see a lot of things, amongst other the Kitchener collection, which is fantastic. We met Robert Elgood and Jonathan Barrett, but again, the time – rather frustrating I must say. I hope to see them again next year when we go to England once more.

At the V&A I did notice something about some weapons from Kutch, and will write about it later.

Oh yes, I forgot to mention, how can a trip like that not be a success, when you have the best guide of all:).

Best

Jens

[kronckew]

this thread was linked to in another thread today about a blade with sliding balls incorporated.

as i read this thread (post 31) there appeared a rapier with a sliding section hailed as a sliding weight sword example. this is incorrect as it was actually created to solve a completely different problem.

as rapiers became fashionable, they increased in length to almost silly proportions.m some wielders went accompanied by a servant that would help them draw and re-sheath the blade as needed.

numbers of gentlemen carrying these long swords were quite a tripping hazard and cumbersome to manoeuvrer in crowds, and could actually provoke duels. laws were passed to limit blade lengths. i recall london set a maximum BLADE length of 40 inches.

guards at the city gates would actually measure blades, and if found too long the owner could be fined and/or his blade snapped off to make it fit the regs.

this sword posted earlier was a design to circumvent the law, as it's long blade was slid back to allow it to be sheathed without requiring a servant while also becoming a regulation blade length with a long grip to bypass the regs - which did not specify an overall length.

if drawn in anger, the blade was slid out and locked in place rather them sliding in and out freely.

overly long rapiers with thrusting only type blades were an affectation of society that died out fairly quickly - that's why so few examples exist. they didn't really work well in a duel, gentlemanly rules of engagement which covered the flaws thankfully were rarely carried over to military blades that stuck to a more practical carry & use length suitable for the no rules melee of hand to hand desperate combat.

[Jens Nordlunde]

Interesting discussions we had in the good ol' days :).

[kronckew]

luckily we keep on learning instead of stagnating. :D

[Jim McDougall]

Excellent Kronckew!!! Indeed, we DO keep learning, and mostly because of those here who contribute and share the remarkable knowledge they hold in their specialized fields. Also, that members like yourself revive old threads and topics like this one, bringing into them new evidence or simply new avenues of research on them.
Jens, we did have amazing discussions back in those days, and it always further amazes me at how far we have all grown because of them.

During these earlier discussions, it seems that the affectation of the 'pearls' in blade channels was included and found to have been from a Persian decorative innovation on blades. It was at some point transmitted to both Indian and Chinese cultural spheres, where they were popularized in recognized degree.

I do recall in rapier discussions several years ago the case of these 'adjustable' blades was brought up and as noted the blade length had become a 'legal' dilemma in Spain and I believe others. I believe this was also the basis for the folding knives well known as 'navaja'

It was interesting here to see discussions involving members who are sorely missed as well who have been long absent, and the depth of the discourse which brought examples, cases and empirical data to light versus some of the fascinating 'lore'.

Well done, thank you!

[ariel]

Good old days.....
When the water was wetter and the girls prettier....

[kronckew]

the trouble with water is that it is wet. if the man upstairs had wanted us to get wet he would have given us fins. i spent a few decades of my life ensuring i did not have to actually swim in the stuff by putting a large ship underneath me to separate myself from it. even our closets relatives, gorillas and chimps, cover themselves with leaves when it rains.

i haven't drunk water in years. i drink only a couple beers a year & don't touch the hard stuff. a glass of port on xmas. i do drink coffee and vast quantities of iced sweet tea with lemon or peach flavouring. OK, that all has water as an ingredient but i can ignore it. the occasional shower is unavoidable.

all women are beautiful. some more than others. i find the range of really beautiful women has expanded as i get older.

[Roland_M]

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.
================================================

[Ibrahiim al Balooshi]

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.
================================================

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]

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

[fernando]

... as rapiers became fashionable, they increased in length to almost silly proportions.m some wielders went accompanied by a servant that would help them draw and re-sheath the blade as needed....
I am truly amazed with such resource ... a sword drawing servant; would never dream of it. Do you racall the source where you read such passage, Wayne ?

[Ibrahiim al Balooshi]

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?seq=1#page_scan_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.