Posts: 871 Location: Paris, France
Wed 28 Jan, 2009 2:36 pm
Swords and trainers
Hello again!
With the new data sent by members here I've been able to draw a graphical representation of how real swords and training items differ in their mass distribution.
Here is the picture first:
[ Linked Image ]
From top to bottom I've plotted one-handed swords, one-handed trainers, two sorts of Japanese sword simulator, hand and a half swords, and hand-and-a-half trainers.
As you can see the wooden arming sword, and wooden swords in general, have their point mass a bit too far forward from the cross. My longsword (at the bottom), also from Purpleheart Armoury, is the most extreme in this sense. Their stick mass is also higher in proportion (the rectangles are darker). The Purpleheart Longsword belongs to Kyle H., who was unable to weight it. Therefore I've used the mass given on the website, 1.1kg. I doubt this is accurate, as I weighed mine and it is actually something like 700g. This changes only the area of the rectangle, not the point mass location nor the color.
The bokens are actually quite close to the iaito. I suspect this has to do with the way the japanese swords are balanced, shorter with not much taper. This balance seems to be easier to reproduce in wood. Boken 2 is a very heavy boken, very thick. As you can see it is almost purely a stick, and so the point mass location is not really relevant. Still, it lands very near the cross, as it does on the metal iaito.
The Hanwei has the opposite property, the point mass is too far towards the pommel. I think they were forced to do this by their blunt blade. The blunt blade has too much stick mass of its own, and they wanted a plausible CoG, so they added more mass at the pommel, but doing so they also pulled the point mass location further towards the pommel. It would be interesting to measure an Albion I33 to see how they settled that issue...
To sum things up, trainers are different from real swords in two aspects: they have a proportionally bigger stick (their mass is not as concentrated as that of the real thing), and the location of the point mass is off, either too far down the blade or too far up the handle. I think it sums up visually the complaints I've heard about these entry-level training items. Indeed they cannot really move as real swords do.
Measuring other training items, for example nylon wasters, Albion blunts, and the new line done by Mr Pearce and CAS/Hanwei, would be informative I think. I'm willing to bet the most sophisticated training gear manages to get really close to the swords on this kind of diagrams.
At the risk of repeating myself, note how the position of the point mass seems to be very tightly controlled on medieval swords. It is at the cross each time, within the accuracy of the measurements. Even for the Arms&Armour
Black Prince, kindly measured by David E. Farell, you just see very little mass in the stick (a clear rectangle), but the point mass stays at the cross. Actually I didn't believe it would do that; with that big pommel I expected the point mass to be more inside the handle, and I was ready to adjust the theory... In the end no need to do that :)
I wish to thank again Eric Spitler, Kyle H., Thom R. and David E. Farell, for feeding me some very valuable data :) Keep it coming :D !