Sliding weights

fearn · 30th June 2005, 09:34 PM

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 · 30th June 2005, 09:41 PM

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

30th June 2005, 09:34 PM	#1
fearn Member Join Date: Dec 2004 Posts: 1,247	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

30th June 2005, 09:41 PM	#2
fearn Member Join Date: Dec 2004 Posts: 1,247	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