Horsepower

["Marsee Skidmore" <heyred@email.msn.com>]

I can offer the motorhead perspective. Electric motors and internal
combustion engines are rated very differently. Electric motors are quite
linear in output, while IC engines are quite "peaky." Since electric motors
are killed by heat, EE's rate them at the low end of the curve, to ensure
long life at 100% duty cycle. Since hp ratings sell cars, ME's rate IC
engines at the peak of the output curve. Not only that, but they strip off
all of the the silly little parasitic drags on horsepower, like the fuel
pump, water pump, alternator, and cooling fan before they put it on the
dynamometer. As a result, you can pull the 100 hp (rated) engine out of a
car, replace it with a 20 hp (rated) electric motor, and get darn near the
same performance. Getting from horsepower to prop thrust is an issue of
great wackiness, and I can't discuss that one with the same confidence. :-o
Joe