Re: aluminium (was: NEW RONIN Movie..)

[James Marriott <marriott@pophost.micron.net>]

At 10:31 PM 9/9/98 -0700, Ti Kan wrote:
>Orin Eman writes:
>> Brett Dikeman wrote:
>> > Aluminium is a great choice for weight reduction, but it means that
parking
>> > lots are going to be disasters.  Anyone seen the saturn commercial
with the
>> > baseball lesson?  Picture that with an A8 :o
>> 
>> The thing about aluminium is that you can get the _same_ strength with
>> less weight.  Without doing some calibrated bashing of an A8, I
>> personally couldn't say that it would hold up better or worse than steel
>> to your average parking lot door bashing.
>> 
>> Orin.
>
>Audi actually says that the tempered aluminum body panels makes the A8
>more dent resistant than steel panels.  This was in one of the A8
>brochures I have.
>
>Remember, the aluminum used in an A8 is not ordinary aluminum.  It is a
>special alloy that exceeds the strength of steel while retaining the
>lightness of aluminum.

FYI and all that, VERY FEW aluminum alloys exceed the yield strength (on a
volume basis) of even the weakest steel.

Ponderables:
Aluminum is 1/3 the density of steel. Aluminum is 1/3 the stiffness (one a
volume basis) of steel. On a weight basis they are ~the same stiffness.
Aluminum costs ~3X steel on a weight basis. Indeed a pound of primo alum
alloy (2024-T6, 7075, etc at ~50k PSI yield strength) can be stronger than
a pound of crappo steel (~38k PSI YS), but you're screwed if you try to
weld it or form it very much, and it's pretty easy to get steel to 150k PSI
(~Grade-5 bolt spec) or even 250 (Stainless 440A) or even 450 (music wire).
I think I'm getting a little tangential . . .

>The metallurgy, the Audi Space Frame design and
>their manufacturing processes are the culmination of some ten years of
>research done by Audi and Alcoa.  There is some serious technology in
>there, and definitely not "soda can" stuff.

A "cellular science" nit, but soda cans are where some _big_ R&D money is
spent. Since the USA uses one billion cans per day, even a micro-percent
reduction in usage amounts to plenty. The soda-can deep-drawing process is
indeed quite high tech and "at the limit."

Without meaning to denegrate the A8, which is truly a bitchin' and
patent-laden car, at all,
James
mech eng, geek, masochist (200q and 4kq)