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



Rob Meyerson wrote (quoting me):

>> Rob, can you provide *any* evidence whatsoever that [bipeds can make
>> tighter turns than quadrupeds]?
>
>I have no documented info, just things I have observed.  Think of a
>game of "keep-away": 

Your examples were totally useless in terms of the point you're trying
to make.  Suppose I told you that Doritos are much better than
Pringles and when you asked me how I knew I told you that I'd tasted
Doritos and they were really good.  Without pitting the two things
against each other you can't say you've made a comparison.  If you
respond to this message with a similarly unsupportive statement I'll
ignore you.

> Usually, the more stable the form, the more manuverable it becomes
> (for the same reason that Air Force aircraft are built for
> unstability).  

You meant "unstable" at the beginning of the sentence, but it doesn't
help you much.  In any design there are tradeoffs, and your "analysis"
here is so superficial as to have virtually no bearing on any real
life situation.  Which aircraft is more stable, the Fokker Dr-1 (the
"triplane" made famous by the Red Baron) or the F-16 Fighting Falcon?
I'll give you a hint: the F-16 is so unstable in pitch that if its
flight computers fail it will nose up or down catastrophically (i.e.
the resultant stresses will rip apart its airframe) in about 1/40th of
a second.  Which of the two aircraft is more maneuverable?  The Dr-1.
It can make much tighter turns at low airspeeds where the F-16 wasn't
designed to operate.

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.

> Therefore, a deer or dog will never be able to pull off
> the moves that a human is able to do.  Granted, a dog can do some
> pretty acrobatic things (like when it goes after a frizbee), but it
> isn't going to be doing any triple backflips off the high wire.

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.

>>> Further, being quadrepedal has a disadvantage in terms of being a
>>> high speed creature

> The point is that the power provided by the front limbs is minor
> compared to the power of the hind limbs.

No, your point was that forelimbs getting in the way of the hindlimbs
was a drawback to being a quadrupedal runner.  That's just ludicrous.
I'm not going to bother continuing that discussion.  If you want to
keep digging yourself in deeper feel free.

--
Mickey Rowe     (mrowe@indiana.edu)