At 06:15 PM 8/26/2009, Rolf Lockwood wrote...
>  Torque is defined as an engine's ability to do work, characterized
> by the twisting motion off the end of the crankshaft.

No. Work is done by power over time, not force (torque). Try lifting a
1000 lb. weight. You can tug and tug, and you will be applying a lot of
force. You might even "work up" a sweat, but unless you actually lift
that 1000 lbs. off the ground, you haven't done any work.

>  Horsepower is a purely calculated value that measures only the speed
> at which the work is done. So the ONLY thing that gets you over the
> crest of a hill is torque,

Nope. You need to study some physics. Force only does work when it
actually moves something. Work over time is power.

>Torque is an absolutely 'tangible' value, horsepower a mere
>calculation.

No. One HP is the amount of power it takes to raise 550 pounds 1 foot
in 1 second. (foot-pounds, not to be confused with pounds-feet, which
is a measure of torque) Power is the rate at which work is done. You're
probably confused by the fact that one can convert torque to HP with
the formula RPM x Torque x 5252 = HP. But you can just as easily start
with HP: HP / 5252 / RPM = Torque.

When a car is put on a dynamometer, it is power which is measured (the
amount of work needed to turn a weight or heat a liquid, and how long
it takes to do so), and torque is calculated.

Moving a Vanagon up a 1000 foot hill is the same amount of work,
whether you're going 10 or 60 MPH. But, to go 60 MPH, you need more
power, which allow you to do the same amount of work in less time.

Here's a pretty good explanation. Don't feel discouraged, it confuses a
lot of people:
http://auto.howstuffworks.com/auto-parts/towing/towing-capacity/information/fpte.htm