Peter,
'Well, I'm not sure but....' they are fundamentally different I'll try and put
into words what I think I know:
Power is a measure of the rate of doing work (work per unit time) and is
normally measured in watts
Work is the product of force and the distance moved by the point of
application. Work also has the same units
as energy so power can be seen as the rate of producing energy. (units
therefore force x distance /time)
(Horsepower is a good old British unit equivalent to 746 watts.)
Torque is a measure of the rotational FORCE produced by the crankshaft and is a
direct measure of the explosive
force of the gases in the combustion chamber that pushes the piston downwards.
The length of the crank also
comes into this because a longer crank would produce more torque at a lower
rotational speed (i.e. same force
acting at a greater distance - think of levers - but the point of action -the
big-end - travelling at the same
instantaneous speed so taking longer to complete a revolution). As revs
increase the combined effect of the
successive explosions causes more and more torque to be generated up to the
peak figure, after which the
effects of incomplete combustion start to be noticed and the torque begins to
fall away.
It just so happens that power and torque curves have a similar shape probably
for the reason mentioned, but I
suppose it is possible to design engines with high torque but relatively power.
Diesels fit this description, don't
they, due their high compression ratios producing a greater explosive force?
> Both apparently refer to the ability to do a certain amount of work within a
> specific time, and they seem to max out at different RPMs, but other than
> these two sophomoric opinions, I'm stumped. Anyone really know??
I know the physicists and mechanical engineers will shoot this down in flames,
but I don't care any more!
Phil
From: Phil Willson
Electronic Engineering
Queen Mary and Westfield College
London E1 4NS
Tel +44 (0)171 975 5338
Fax +44 (0)181 981 0259
email p.j.willson@qmw.ac.uk
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