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Path: utzoo!utcs!mnetor!clewis
From: clewis@mnetor.UUCP (Chris Lewis)
Newsgroups: net.origins
Subject: Re: more on dinosaurs and load-bearing
Message-ID: <2128@mnetor.UUCP>
Date: Tue, 10-Sep-85 12:38:22 EDT
Article-I.D.: mnetor.2128
Posted: Tue Sep 10 12:38:22 1985
Date-Received: Tue, 10-Sep-85 14:16:25 EDT
References: <391@imsvax.UUCP>
Reply-To: clewis@mnetor.UUCP (Chris Lewis)
Organization: Computer X (CANADA) Ltd., Toronto, Ontario, Canada
Lines: 76
Summary: 

In article <391@imsvax.UUCP> ted@imsvax.UUCP (Ted Holden) writes:
>     There are  two articles  on the  net now having to do with the capacity of
>the really heavy sauropod dinosaurs to bear weight,  one by  myself and another
>by Stanley Friesen.  Some comments:

>     The notion that the dinosaurs thighs were more efficient than Kazmier's is
>simply wrong by a very wide margin.  The  thigh muscles  in the  human would be
>pulling   fairly   straight,   while   the   outer  layers  of  muscle  in  the
>disproportionately much wider thigh of the sauropod would  not only  be pulling
>at a  vector angle,  they would  be pulling  THROUGH the inner layers of muscle
>i.e. the  different  layers  of  muscle  in  such  a  wide  limb  would  get in
>eachother's way.  

I think you've missed part of what he was saying.  It is perfectly possible
to have the bones and muscles to be arranged in such a way as to provide a 
LOT MORE leverage.  Consider, when a human is standing with leg thus:

		O <- hip
		 \
		  A
		   \
		    O    <- knee
		   /
		  B
		 /
		 ==== <- foot

For all intents and purposes, the leg muscles for the knee are connected
between A and B around the knee.  The leverage for the purpose of
straightening the leg is pretty poor because most of the muscle contraction
force is wasted trying to shorten the bones because most of the force
is parellel with the bones.  Engineers never build mechanical
systems with that sort of inefficiency built-in.  

Consider a better system:
		
		O <- hip
		 \
		  A
		   \
		    O    <- knee
		   /---B
		  /
		 /
		 ==== <- foot

If the muscle was connected between A and B (on the tip of a bone spike),
you'd get lots more leverage.  Lots of dinosaur bones show such adaptation 
to get more leverage.  If you were to measure the straight-line pull 
strength of a thigh muscle, it would be far higher than the force
exertable when installed in a human being.  Also, consider things like 
the primates, when you consider that a chimp or orangutan weighing less 
than a hundred pounds can rip the door off of a car without any trouble
with its scrawny arms, you find the mistake in trying to scale up humans 
to explain limits in animals.

>Basically,  he  claims  that  a Mr. R.M. Alexander has computed "load factors",
>based on the stress that BONES can take, and determined  thereby that dinosaurs
>could function  normally in  our world.   

>Nonetheless, if I kept my back and legs straight, and two of these friends were
>kind enough to put a bar with five or six hundred pounds on it on my shoulders,
>I could  stand with  it;   the bones  would not  break.  Mr. Alexander would no
>doubt then conclude that I could function quite well at 700 or 800 lbs  (my 200
>plus the bar). 

And he'd be right.  There are lots of people well over 500 or 600 pounds.  
Ever hear of "Haystacks Calhoun"?  I don't imagine that his bones are any 
bigger than yours, nor is he any taller, and he gets around pretty 
well.  Last I heard he was 750 pounds or so.  I used to watch a lot of 
wrestling back in my younger days (his high smashes were awesome - I
think he broke through the wrestling ring once)....
-- 
Chris Lewis,
UUCP: {allegra, linus, ihnp4}!utzoo!mnetor!clewis
BELL: (416)-475-8980 ext. 321