1.It is desired to market a small air-driven hoist in which the load is supported on a single line of wire rope and the rated design load is ton (750 lb). The wire rope is to be wrapped on a drum of 7.0 inches diameter. The hoist should be able to lift and lower the full-rated load 16 times a day, 365 days a year, for 20 years before failure of the rope occurs.
a. If a special flexible improved plow steel (IPS) rope is to be used, what rope size should be specified?
b. With the rope size determined in (a), it is desired to estimate the “additional stretch” that would occur in the rope if a 750-lb load were being lowered at the rate of 2 ft/sec, and when the load reaches a point 10 feet below the 7.0-inch drum, a brake is suddenly applied. Make such an estimate.
