Abstract
In this paper the author discusses the several types of cranes used on docks for removing cargoes from ships and placing the articles handled, that is, crates, barrels, bundles, etc., at the points desired. Two general types of cargoes must be handled: namely, bulk cargo and general cargo. The disadvantages of some of the common types are mentioned, and the manner in which these have been eliminated in later designs are pointed out. The types of loads best handled by different types of equipment are mentioned, and recommendations as to proper equipment are made. It is shown that, while in some cases as high as 50 tons must be lifted, the most popular general-cargo crane is of from three to five tons’ capacity. The author emphasizes the importance of proper attention to dock conditions in the determination of wheel loads, and therefore, the crane capacity, in the case of existing docks, and where new construction is contemplated the desirability of adequate strength to take care of the maximum load likely to be imposed. The hoisting rope receives considerable attention in the paper. The disadvantages of the two-strand fall are pointed out, and it is recommended that it be avoided wherever possible. A disadvantage of the ordinary luffing crane is that when the jib is luffed in the load suspended from the jib head is simultaneously raised, resulting in wasted work and requiring a more powerful motor than otherwise would be necessary. Level-luffing cranes are described which overcome this objectionable feature and permit more flexible operation. The various arrangements of compensators and counterweights to permit this are described.
