Info Favorites Register Log in
myArmoury.com Discussion Forums

Forum index Memberlist Usergroups Spotlight Topics Search
Forum Index > Historical Arms Talk > Calculating a Sword's "Swing Weight" Reply to topic
This is a standard topic  
Author Message
Pat Kilbane




Location: Los Angeles, CA
Joined: 09 Apr 2014

Posts: 5

PostPosted: Wed 23 Apr, 2014 3:07 pm    Post subject: Calculating a Sword's "Swing Weight"         Reply with quote

I've read that experts in baseball mechanics use the term "swing weight" to describe the perceived weight of a bat independent of its actual mass. Two bats with the same mass but with varying weight distribution have different moments of inertia (MOI), and will therefore swing "heavier" or "lighter" than each other.

I thought it would be a helpful shorthand if the same term were used for swords and other hand weapons. Swing weight describes a weapon's handling much more specifically than simple weight or POB.

Here are some weapon swing weights I calculated based on their MOI as compared to a 32 oz major league bat:

Albion Swords Hersir Viking: 19.21 oz.

Angus Trim 1508: 20.01 oz.

Arms & Armor Iberian Mace: 28.43 oz.

Arms & Armor Nordland Axe: 13.56 oz.

24" 16oz Nylon Police Baton: 5.18 oz

Any thoughts?
View user's profile Send private message
Mark Moore




Location: East backwoods-assed Texas
Joined: 01 Oct 2003
Likes: 6 pages
Reading list: 1 book

Posts: 2,256

PostPosted: Wed 23 Apr, 2014 3:46 pm    Post subject:         Reply with quote

I find this interesting. I know one fact. There is a near 0% chance of swift recovery swingin' my Hanwei claymore. In other words....Don't stand behind me. I believe it weighs a little over four pounds....could be wrong. Maybe more. Beast of a sword. I'd like to know the actual PSI different swords deliver, as well as their actual speed at impact. Big Grin ......McM
''Life is like a box of chocolates...'' --- F. Gump
View user's profile Send private message
Timo Nieminen




Location: Brisbane, Australia
Joined: 08 May 2009
Likes: 1 page
Reading list: 1 book

Posts: 1,493

PostPosted: Wed 23 Apr, 2014 3:47 pm    Post subject:         Reply with quote

Could just give the MoI, rather than comparing with a "standard bat". Any of oz.inches^2 or lb.feet^2 or kg.m^2 should do.

MoI about what point? Usually, if one gave MoI without any information about what point, it would be assumed to be about the centre of mass. But a more useful default for a sword is about the grip. But mid-hand, or top-of-hand, or what?

Vincent Le Chevalier gives his MoI data as "dynamic length" and "blade weight" in hist article http://www.myArmoury.com/talk/viewtopic.php?t=21670 ; these have the advantage of us being more familiar with lengths and weights than quantitative measures of MoI. The disadvantage is that calculation is required to compare MoI of different swords based on these figures. Your comparison with the "standard bat" has the same advantage of familiarity, without requiring any further calculation for comparison.

"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
View user's profile Send private message Visit poster's website
Pat Kilbane




Location: Los Angeles, CA
Joined: 09 Apr 2014

Posts: 5

PostPosted: Wed 23 Apr, 2014 4:10 pm    Post subject:         Reply with quote

Mark Moore wrote:
I'd like to know the actual PSI different swords deliver, as well as their actual speed at impact. Big Grin ......McM


If you have the length, weight, POB and COP of the weapon, I can give you a pretty close approximation on tip velocity, velocity at COP, effective mass at COP and the resulting pounds force of impact.
View user's profile Send private message
Pat Kilbane




Location: Los Angeles, CA
Joined: 09 Apr 2014

Posts: 5

PostPosted: Wed 23 Apr, 2014 4:21 pm    Post subject:         Reply with quote

Timo Nieminen wrote:
MoI about what point? Usually, if one gave MoI without any information about what point, it would be assumed to be about the centre of mass. But a more useful default for a sword is about the grip. But mid-hand, or top-of-hand, or what?


I doubt I have the experience you do, but I'm a fan of using the point beneath the middle of the hand for one-handed weapons and the middle of the top hand for two-handed weapons. That point coincides with the axis of rotation of the vertical flexion of the wrist. Baseball studies have shown that before ball impact the arms are still swinging for a fraction of a second after the wrists are fully extended, meaning that the true axis of rotation is some inches beyond the bottom of the bat handle. Not so easy to test your COP from that point, though.

Timo Nieminen wrote:
Vincent Le Chevalier gives his MoI data as "dynamic length" and "blade weight" in hist article http://www.myArmoury.com/talk/viewtopic.php?t=21670 ; these have the advantage of us being more familiar with lengths and weights than quantitative measures of MoI. The disadvantage is that calculation is required to compare MoI of different swords based on these figures. Your comparison with the "standard bat" has the same advantage of familiarity, without requiring any further calculation for comparison.


That looks like an interesting read... thanks! Yeah, saying that a sword has an MOI of .18 kgm^2 takes some getting used to.
View user's profile Send private message
Pat Kilbane




Location: Los Angeles, CA
Joined: 09 Apr 2014

Posts: 5

PostPosted: Wed 23 Apr, 2014 5:33 pm    Post subject:         Reply with quote

Mark Moore wrote:
Beast of a sword. I'd like to know the actual PSI different swords deliver, as well as their actual speed at impact. Big Grin ......McM

Hey Mark, here's what I came up with based on the numbers at KnifeCenter.com. They listed the COP at a dubious 31" on the 41" blade, so the starting data may be suspect. Here is that link:

http://www.knifecenter.com/item/CISH2060N/cas...more-sword

And here are the resulting numbers:

Effective Mass at COP: .65kg (22.9oz)
Velocity at COP: 24m/s (53.7mph)
Tip Velocity: 29.1m/s (65mph)
Avg. Impact Force: 13,635N (3068 lbs force)
Peak Impact Force: 27,270N (6136 lbs force)

Note that the "pounds force" measurement of impact is not the same as pressure, which is measured in lbs/in^2. To go from force to pressure, you'd have to know how much of the blade was in contact with the target.

6138 lbs of peak force is huge for a sword! It's as much as a baseball bat, which is tough to do considering a bat has a proximal taper.
View user's profile Send private message


Display posts from previous:   
Forum Index > Historical Arms Talk > Calculating a Sword's "Swing Weight"
Page 1 of 1 Reply to topic
All times are GMT - 8 Hours

View previous topic :: View next topic
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum






All contents © Copyright 2003-2018 myArmoury.com — All rights reserved
Discussion forums powered by phpBB © The phpBB Group
Switch to the Basic Low-bandwidth Version of the forum