Problem $1$

A passenger elevator for an office building can lift its maximum

rated load of $7000$ lb at a rate of $60f\frac{t}{m}in($Fig$.1-9).$ Find the

service factor for the drive, which consists of an electric motor,

a worm gear speed reducer $($efficiency is $90\%),$ and two roller

bearings. Select a motor that operates at $1200$ rpm $.($Hint: Use

Eq$.1-9,$ Fig. $1-6,$ and Tables $1-2$ and $1-3.).$