RE: Weighing T. rex model

["Stewart, Dwight" <Dwight.Stewart@VLSI.com>]

Hi, Ralph, Et All;

   Well, when we did the hydrostatic weighing, we HAD the live subject there
to dry weigh ahead of time.  But, I can tell you that the amount of air in
those sacs is CRUCIAL... absolutely crucial.  Allow me to give you a very
modest example.  We had to weigh a 340 pound offensive lineman, because the
training coach wanted this 2.05 meter tall guy on a "fat loss" diet. :-)
The question was: how much of his weight WAS "fat".  So another grad student
& I did the hydrostatic weighing, ONLY the huge guy was afraid to submerge
his head, so we couldn't get him to expel the air from his lungs; not very
well.  We weighed him 5 times & came up with body fat percentages of from 18
to 36%!!!  I remember this because a post Doc stepped in & tried (assuming
WE were the problem) & he did no better than we did.  The thing is, he
LOOKED more like the 18% number.  We were accustomed to weighing subjects &
one develops a pretty good eye for these things.  But, to recap what I said
yesterday, IN HUMANS, 50/50 fast/slow twitch muscle fibers weigh 2.5 times
what an equal volume of adipose tissue weighs.  Air is even lighter than
that (of course),
But throws the calculation off by just as much, because it is a bit more
buoyant than adipose tissue.  I was taught that everything else in the human
body is heavier than water, including the water within the tissues, because
it contains heavier elements.  
   As far as HOW muscular a Tyrannosaur or any other dinosaur was, you need
to ask Dr. Holtz.  To my eyes, the current reconstructions  of T. rex look
very mesomorphic.

Dwight 

        -----Original Message-----
        From:   Ralph Miller III [SMTP:gbabcock@best.com]
        Sent:   Tuesday, September 22, 1998 7:52 AM
        To:     dinosaur@usc.edu
        Subject:        Weighing T. rex model

        How much drilling for air sacs and shaving down for leanness is
required to
        properly weigh a Boston Museum of Science / Battat 1/40 scale
        _Tyrannosaurus_ model using water displacement?  If not 1:1, what is
the
        presumed density of tyrannosaurid flesh as compared to that of
water?  

        I ask these questions because when I tried to weigh _T. rex_ using
water
        displacement directly from the Battat model, multiplying the weight
of the
        water by 40 x 40 x 40 (64,000), I came up with a figure that was way
too
        high.  I recognize that the questions I ask are subject to a high
degree of
        leeway (i.e. how much muscle exactly was on those bones?), but I'd
like to
        hear what others have concluded.

        -- Ralph Miller III     gbabcock@best.com