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Re: 4ped vs. 2ped maneuverability (was Re: A fundimental conundrum ...)

Mickey P. Rowe wrote:

> >> Rob, can you provide *any* evidence whatsoever that [bipeds can make
> >> tighter turns than quadrupeds]?

Mickey and all,
  The CG on a human has all of the mass of the human balanced along a
very narrow vertical area which is the area they control in a spin.  The
quadruped's area centered around it's CG is spread out along it's body. 
If you watch dogs catch frisbees (the world championship kind) they leap
up and 'stand' on their hind limbs which effectively reduces the mass
they have to move in a spin to that which is closest to their CG.
Barrel-racing Quarterhorses also do this and move into a more vertical
shape to turn faster.
  But to add some weight (sorry), dogs are better at catching frisbees
than people are, so it's probably not a biped/good-quadruped/bad
  And dinosaurs CG is not as well centered as humans are, so sorry
again.  It's that teeter-totter/see saw shape which causes problems.

> Give us something concrete, Rob: come up with two animals -- one a
> biped and one a quadruped -- both with equivalent mass and both
> capable of attaining similar speeds.  Then give us data indicating
> that the biped *due to its lesser inherent stability* can make tighter
> turns.  I'll believe you're on to something when the data indicate it.
> At the moment you're completely ignoring little things like the fact
> that a four-footed animal can push off with all four of its feet.

sorry I didn't do that.  It's not a biped thing but a vertical weight
mass distribution thing.  Less area to move around the area of spin
means easier spins.

> The differences in acrobatic ability between dogs and humans has much
> less to due with the dog's inherent stability than it does with our
> ability to grasp high wires and to drastically alter our moment of
> inertia by tucking in our arms and legs while arching our backs in.

Or our damn-foolery.  It's hardly a survival trait to do something so
stupid as triple back flips.

-Betty Cunningham