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June, 1918 hoist, with a maximum load, operating either independently or jointly will have a speed of 2.5 feet per minute. With no load, each main hoist will have a speed of 10 feet per minute. The auxiliary main hoist with a maximum load will have a speed of 12 feet per minute and with no load, 30. feet per minute. The speed of the trolley travel of each main hoist with a maximum load will be 12 feet per minute, and with no load, 100 feet per minute. The speed of the trolley. travel of the auxiliary hoist. with a maximum load will be 100 feet "per minute, and with no load, 150 feet per minute. eee The operating mechanism consists of an electric motor driving through THE MARINE REVIEW from steel castings, the face of the drums being machine scored. In order to operate the two main hoists in unison so as to insure equal hoisting speed when hoisting loads in excess of 175 tons the maximum capacity .of each individual hoist-- one of the intermediate shafts on each hoist is arranged for coupling so that the two motors drive through these coupled shafts. Change gears are provided on each hoist to permit varia- tion in the speed of hoisting. The first intermediate shaft on each hoist is equipped with a brake, 54 inches in diameter and with a 10-inch face." The object. of this brake is to provide mechanical means of brak- ing in addition to the electric brake. - main hoist. 235, trolley. A mill type hoist motor of _87 horsepower is used. The hoisting drum on the auxiliary hoist is 84 inches 'in diameter with a 102-inch face, machine scored. A mechanical emergency brake is provided as well as a solenoid brake on the' motor. The variations in hoisting speed with a maximum load and with no load is obtained by means of an_ electric speed control. : The auxiliary hoist racking or trav- -ersing mechanism follows the general design of that employed with the A mill type motor of 27% horsepower is used. The drum is cast iron, 36 inches in diameter and 54- inch face. The motor is provided with a-solenoid brake. The required 392 TON SHIPBUILDING CRANE ae) ROCKEFELLER BLOG. CLEVELANO,O. eoire 5 &1O TON SHIPBUILDING CRANE 1914 120 TON SHIPBUILDING CRANE NO" Raoiws y 1916 GRAPHIC COMPARISON OF SHIPBUILDING CRANE WITH MODERN BUILDING AND WITH TYPICAL HOISTING UNITS. properly connected gears and shaft- ings, four vertical pinions meshing 'swith: a. circular rack. The transmis- sion mechanism is interposed with three compensating gears so as to compensate the duty on the four slew- ing pinions. The controller is of the magnetic type. Two separate hoisting units are provided in duplicate. The design calls for a double lead from each hoisting drum to the trolley in order to reduce the rope strains by one-half as com- pared with the single lead. Each main cable will be equalized on a sheave at the outward end of the jib. A mill-type motor of 87 horse- power will be used for each hoisting unit. The hoisting drums are 10 feet in diameter and 14 feet 4 inches long. The drums are built up in sections \ The mechanical brake will be used in emergencies. The main hoist racking or travers- ing mechanism for the main hoist trolley which travels back and forth on the jib, consists of two duplicate rope drives, each unit operating one of the 175-ton hoists, A mill type motor of 27% horsepower is used for each racking unit. The racking drums are 48 inches in diameter with a 54- inch space. The intermediate shafts of the racking or traversing mechan- ism are arranged to couple together to insure trolley movements in uni- son when hoisting maximum loads. Change gears for securing speed changes are provided on the travers- ing mechanism. The motors have solenoid brakes. On the auxiliary hoist, double ropes lead from the hoisting. drum to the revolving structure. speed variations are electrically con- trolled. Slewing mechanism comprises an annular rack mounted on the rear of the roller path at the base of the The rack is cast steel with cast teeth. : The motor equipment includes two motors for the main hoist; two mo- tors for the main hoist trolley; one motor for the auxiliary hoist; one motor for the auxiliary hoist trol- ley; three motors for 'the overhead crane operating over the machinery floor, one motor for slewing and one for operating the vertical sliding door in the rear of the machinery house. The auxiliary hoist trolley operates the full length of the travel inde- pendent of the main hoist trolleys. . The trackway for the auxiliary trolley is located between the main hoist