From: robertdf@microsoft.com (Robert Del Favero)
Subject: armor, physics, and aluminum
Date: 23 Dec 92 22:43:00 GMT
Organization: Microsoft Corp.


Aelfgar von Echternach writes:
>	The purposes of SCA armor seem to me to be:  1) functional and
>2) to _look_ authentic.  That's one of the nice things about aluminum, that
>it will look like shiny steel, and is also quite functional in it's role
>to protect.  The definition of functional is:  able to withstand the abuse
>of a rattan mock sword, or other mock weapon.  These constraints 
>necessarily divert our attentions from authentic armor.

1. Aluminum doesn't look or sound like steel. Even Mr. O'Connor says so.
(Stainless doesn't look like real steel either, but that's *my* problem.)

2. You seem to be arguing that the prevalent armor technology of the middle 
ages was unable to protect its users from the abuse of a rattan sword, 
which we use because it is so much less lethal than the real thing. One 
could conclude that medieval armor was therefore unable to protect its 
users from the more lethal abuse of a steel sword or halberd, and therefore 
the armored fighters of our period wasted their time and money buying and 
wearing armor. What have I missed?

3. In other words, "Steel can't stand up to rattan, so we shouldn't use it."
As someone who made and fought in steel armor of authentic weight and shape, 
and knows many (>20) people with similarly authentic steel armor,
I have trouble accepting this argument. My armor stood up to the attentions of
rattan weapons just fine, with the occaisional dent. I estimate that it required
no more than sixteen hours a year of additional work to keep the steel in good
repair. Keeping it from rusting added no more than a few minutes to the 
time I spent putting it away at the end of a session of fighting.  As an 
armor repair lackey for my shire over a period of several years, I saw 
numerous armor failures. Almost all were failure in the leather used to hold 
the pieces together, and that failure would happen no matter what material the 
plates were made from. Armor requires maintenance no matter what it's made of.

Trebor Stephenson writes:
>I've been in the society for 4 years and have been actively,seriously training
>to fight since last april. I'm currently wearing a pickle bucket lourka (sp?)
That's "lorica". Most Roman armors are "lorica something", so I assume 
that lorica is Latin for "armor". Yours is probably a lorica segmentata,
an armor made of overlapping horizontal bands of metal or leather. There 
are other kinds of lorica made in other ways, including the lorica squamata, 
a which used tongue-shaped overlapping scales.

>I am working on replacing this with a velveteen coat of plates w/plastic
>plates.[...] it's light so I will be less likely to go down with a heat 
>emergency at war (this is a large concern,I've had problems in the past)
Don't jump to conclusions. The problem with wearing armor in the heat isn't so
much the weight as the fact that air isn't circulating over your body and
cooling it by evaporating sweat. Lighter armor means less exertion, true, but
you'll still sweat if it's even moderately warm, and your body will heat up.

Yet another gentle wrote inquiring about the physics of fighting, but I didn't
save his article. The previous paragraph about overheating in armor is a
good example of basic thermodynamics. Another good physics investigation
would involve attempting to answer the question "How does armor protect?"
There are many ways in which it does so, including:
1. Spread the force over a large area, so that the force on any part of the
    area is too small to do damage. Plate armor is good for this.
2. Move, thereby dissipating the force of the blow without transmitting it.
    The swinging skirts on Japanese armors are an example of this. Shields
    work on the same principle.
3. Deform, dissipating the force of the blow into the armor itself. Dents in
    plate are an example.
4. Glance the weapon away, thereby using the force of the blow to move the
    weapon away from the armored person. The 'frog-faced' tilting helm is the
    quintessential glancing surface.
For example, chainmail just doesn't cut very well, so it protects from cuts. 
It lacks the rigidity to spread the force of mass weapons, and lacks the 
mass to dissipate weapon force by motion. It deforms too easily to dissipate 
much force by that mechanism. It's not slippery enough to make blows glance off 
very often. Thus the interesting bruises.

About aluminum lamellar armor: I'm unfamiliar with Mongol armor,
but Japanese lamellar armor seems to rely partly on movement to mitigate the 
force of a blow. The Japanese leg and upper arm protection swings freely, 
and would move under a blow. In such a case, the mass of the armor comes 
into play. Lighter pieces made to period size and shape out of aluminum 
might not have the mass to work as effectively as their steel counterparts. 
Finding out through experimentation how heavy a piece has to be, to be 
effective, would give us a way to estimate the thickness of the iron 
used in such armor. Granted, such experimentation is most useful for those
who plan on making their next armor more authentic than their current
one, and less useful for those who want one armor in a hurry.

Also, someone suggested using epoxy-based paint to replace lacquer on 
Japanese armors. I've seen it done, and it does approximate the look of
lacquer better than any anodizing I've seen. (True, it's no more authentic.)
If you try it, take the recommended precautions for handling epoxy 
very seriously. It is possible to develop a chemical sensitivity to the 
stuff that eventually will keep you from using it all. The home-built 
aircraft magazines always have a few ads from people selling half-built 
planes that they can't work on anymore because of epoxy sensitivity.

Vittorio del Fabbro
----------------------------------------------------------------------------
Robert Del Favero	robertdf@microsoft.com        Redmond, WA
The above is my personal opinion, and does not reflect the policies or opinions
of my employer.
Newsgroups: rec.org.sca