Sliding weights

[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

[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? ). 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

[Rick]

Originally Posted by Jens Nordlunde

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 .

[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.

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