Chopping tests- an index

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Neil Frankish

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Apr 23, 1997, 3:00:00 AM4/23/97
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A thought occurred to me (it happens sometimes) on the way to work. Mr.
Swaims chopping tests, which I read with interest, didn't take into
account length or mass. I was just thinking that maybe the Kukri didn't
perform as well as tha machete was because of a difference in length (or
moment). Would it be possible to divide the time or number of cuts by
the length (maybe length times mass of one end past the balance point)
to get a more comparable figure? or am I being over complicated?

Neil.

Mike P. Swaim

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Apr 25, 1997, 3:00:00 AM4/25/97
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>Neil.

Hi Neil,
Glad you liked my humble efforts. I really like the idea of
establishing a predictor for knife potential. If we had enough folks
test different things in exactly the same manner and post results,
then we might be able to establish a sort of rough guide for
predicting the working characteristics of other implements not yet
tested. That, in itself, may sound overly complicated, and unneeded,
but I think that I've found enough 'annomalies', already to somewhat
question some of the accepted conventional wisdom. I'm no where near
reaching any real sort of conclusions, yet, and hope to sporadically
continue to post 'test' results for quite some time to come as time
allows.

Anyway, to get more to the specifics of your questions:

US GI Machete= 17 7/8" blade length, (nominally 18") / 22.5oz.

Ontario SP8 Survival Machete= 10" blade, but only 7 7/8" usable edge /
29 oz.

CS LTC Kukri = 12 1/4" blade, 11 1/2" edge / 17 oz.

Now, just looking at the above, there are going to be at least three
factors, that I feel play a major role, that are not evident. They are
1) Length of "Sweet Spot" ( the area of the blade that is most
efficient for actual chopping/hacking), 2) Blade contour (or included
angle of all planes leading from edge to where blade flattens or
widens), 3) Weight distribution.

The CS Kukri has a "Sweet Spot" of something about like 4". One of
it's features is an "S" curvature to the blade, but this means that
less of the blade is available for use on a simple downward strike
against a fixed horizontal plane. As for blade contour, from the edge,
the blade slowly rizes over a 3/4" plane to a thickness of just over
1/8". Note how shallow this edge angle is compared to the GI Machete.
It's very 'weight forward'.

The SP8 Survival Machete has a "Sweet Spot" of aprox. 4". It's blade
rises from edge to full thickness of 1/4" in 11/16". It's also very
blade heavy, but has that weight much more evenly distributed than the
Kukri.

The US GI Machete has a "Sweet Spot" of perhaps 9". It reaches max
blade thickness of 1/8" in just 5/16". It is also very 'weight
forward', but that weight is quite well distributed over most of the
length. It balances at about 5 1/2--6" forward of the handle.

One thing that I noticed from the above data, is that the machetes
have a steeper bevel angle than the Kukri. They are more like a
hatchet or ax, than a knife in that regard, whereas the Kukri is more
like a knife, with it's longer sloping bevel.

Something that I've wondered about since the first tests has to do
with why the hatchets didn't do as well as the machetes. I, and
others, have questioned whether the more wedge shaped hatchets would
eventually surpass the machetes as the work thickness increases.
However, there is clearly a point of diminishing returns for even that
line of thinking, since chopping wood with a very heavy triangular
splitting maul is worse than with a slimmer, lighter ax.

Something that I'll probably do in the next several months, is a
chopping test of something much thicker than 2x2's. It may not be
anytime soon.

I've got some ideas of where all this may lead, floating around in my
head, but won't share them at this time, except to say that I think
that it may be possible to come up with the sort of index or guide
that I think you're referring to that might allow one to more
accurately _theorize_ how potential blade shapes might perform in
various media. I know that a lot of folks _think_ they can do that
already, but I also know that alot of us were rather surprised by some
of the actual results as posted earlier. I'd like to see something a
little bit more in depth than the standard "use a steeper angle to
chop with, and a shallower angle to slice with", but that's what it
may come down to.

Cheers, and sorry to drone on so long, but I'm encouraged that I've
got others thinking.
Mike P. Swaim


Robert Allen

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Apr 25, 1997, 3:00:00 AM4/25/97
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In article <5jrdg5$u...@camel2.mindspring.com> mi...@cphl.mindspring.com writes:
+
+Now, just looking at the above, there are going to be at least three
+factors, that I feel play a major role, that are not evident. They are
+1) Length of "Sweet Spot" ( the area of the blade that is most
+efficient for actual chopping/hacking), 2) Blade contour (or included
+angle of all planes leading from edge to where blade flattens or
+widens), 3) Weight distribution.

Your "Sweet Spot" seems to be what's been previously defined as
the "semi-strong" area of a sword. Sir Richard Burton covered
this in his first (and only) book on swords which is available
as a reprint. In the context of swords the blade part nearest
the user is the 'strong' area, followed by 'semi-strong' and
'weak' as you move out to the point. The different areas
are used differently by the attacker and defender, but I believe
the attacker uses the semi-strong area to beat the opponents
blade (the defender blocks with the strong area of her blade).
It doesn't surprise me that the semi-strong area is best for
chopping, but keep in mind that it may not be optimal for
snap cuts, etc. Perhaps a saber fighter can comment if they
use the weak or semi-strong area for strikes.

Robert

Mike P. Swaim

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Apr 26, 1997, 3:00:00 AM4/26/97
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r...@batcomfs.Eng.Sun.COM (Robert Allen) wrote:


>Your "Sweet Spot" seems to be what's been previously defined as
>the "semi-strong" area of a sword. Sir Richard Burton covered
>this in his first (and only) book on swords which is available
>as a reprint.

Hey, I've got that book. Your post prompted me to re-read sections of
it. Thanks. Dang shame that ole Sir Rick saw fit to expire prior to
completing Vol.s II and III. He was just getting up to periods that
interest me.

He mentions that Henry Wilkinson came up with a way to predict blades
"centre of percussion without the tedious process of experimenting
with each and every blade." His notion of comparing them to the
vibrations expressed by a thin rod with a ball afixed, leaves me a
little perplexed. I think I see where he's going, but it seems like
more effort than just using the blade to chop stuff with. Some of his
other observations are certainly bang on.

This was the first book that made me realize the usefullness of a
purely thrusting weapon like a rapier or epee. Prior to seeing his
simple diagrams, I'd sorta figured that those were primarily for
French Fops. ;-) ;-)

Cheers,
MiAim

David Kelleher

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Apr 26, 1997, 3:00:00 AM4/26/97
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Mike P. Swaim wrote:
Dang shame that ole Sir Rick saw fit to expire prior to
> completing Vol.s II and III. He was just getting up to periods that
> interest me.
> Cheers,
> MiAim

He did write them for the most part. The night he died his wife burned
everything.
daithi

Neil Frankish

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Apr 28, 1997, 3:00:00 AM4/28/97
to

Mike P. Swaim wrote:
>
snip
snip

> I've got some ideas of where all this may lead, floating around in my
> head, but won't share them at this time, except to say that I think
> that it may be possible to come up with the sort of index or guide
> that I think you're referring to that might allow one to more
> accurately _theorize_ how potential blade shapes might perform in
> various media. I know that a lot of folks _think_ they can do that
> already, but I also know that alot of us were rather surprised by some
> of the actual results as posted earlier. I'd like to see something a
> little bit more in depth than the standard "use a steeper angle to
> chop with, and a shallower angle to slice with", but that's what it
> may come down to.
>
> Cheers, and sorry to drone on so long, but I'm encouraged that I've
> got others thinking.
> Mike P. Swaim


Keep thinking and "drone" on as much as you like. I find it interesting
that a tool that has been with mankind for so long still has the
potential for research and development.

Neil.

Mike P. Swaim

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Apr 30, 1997, 3:00:00 AM4/30/97
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Neil Frankish <{removethis}nfrn...@mail.tcd.ie> wrote:

>Keep thinking and "drone" on as much as you like. I find it interesting
>that a tool that has been with mankind for so long still has the
>potential for research and development.

>Neil.

Never before in history has information flowed so readily, rapidly and
cheaply. Also, never before has it been so simple for an average
commoner to appreciate cutlery goods from a myriad of sources from
around the world. Likewise, never before has it been so easy for a
rank amatuer hobbiest to make knives borrowing from whatever features
or cultures one can imagine, using anything from the materials of long
ago, to the latest space age alloys. Whether all that will lead to
improvements, or just a finer appreciation for past developments,
remains to be seen. ;-)

MiAim

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