The Mechanical Handling and Storing of Material

490 THE MECHANICAL HANDLING OF MATERIAL the hoisting and lowering of the load at any speed. These winches will handle a If- cub. yd. bucket weighing 4,000 lb. filled with 1 ton of coal, with 150 lb. steam pressure. The rated capacity of the winches is 100 tons per hour. The actual capacity attained under test as mentioned was 138 tons per hour. The average time occupied by each trip of the bucket is twenty seconds. In the first installations for the U.S. colliers “Vestal,” “Prometheus,” and “ Hector ” the winches were of the metallic friction drum type, each being controlled by its own operator. In the latest development of the marine transfer the winches are <9 Fig. 684. The Marine Transfer as Installed on U.S. Colliers “Neptune,” “Jason,” and “ Orion.” so designed that they can be controlled by a single operator by two hand and one foot levers; a second foot lever is provided but is only used occasionally for the adjustment of the lines. These ships have very tall masts, thus providing a very high point of support for the overhead block, which is desirable as it greatly reduces the strain in the booms and rigging. The record of the official test for the two operators with their two winches is 190 tons per hour from a single hatch, made in 1909 with the collier “ Hector.” The later installations for two winches (see Fig. 686) with one operator are equipped on the U.S. colliers “Neptune,” “Orion,” and “Jason,” Structural steel A-frames are