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Crane

cranes, post, jib, traveler, power, electricity, tons, gauntry and tracks

CRANE, a hoisting and transporting ma chine, consisting essentially of a central post on which is mounted rigidly a crosswise arm or jib; together with a winding apparatus and a device for rotating the entire structure upon a pivot or on a circular track. The jib is com monly supported at or near its outer end by a strut footed against the lower part of the post or by a tie to the top of the post. The jib is usually so arranged as to carry a traveler, by which the load may be transported toward or away from the post as the case may be. The crane differs from the derrick in that the latter has a boom hinged to the post instead of a jib rigidly at tached. In the derrick-crane the jib and the post form one continuous structure, either curved or cranked, and this is hinged to the revolving base.

Cranes are of very many types, and the largest ones are quite individual in character and construction, as they are erected for par ticular uses. They may, however, be grouped into three general classes: Fixed cranes, port able cranes, and traveler cranes. Each of these classes is susceptive of subdivisions, depending upon their peculiarities of structure and the power used to operate them.

Fixed cranes, as their name implies, are built to operate in the where erected, within a fixed radius. This class includes the common foundry or quarry crane, suitable for lifting and moving loads up to 10 or 15 tons, and often operated by hand; the whip cranes used in warehouses and commercial establishments, lift ing up to five tons and operated by hand or electricity; the wall crane, built like a bracket pivoted against the face of a wall; and wharf cranes, erected substantially at the waterside and often far inland—for loading and unload ing the cargoes of vessels and of railroad trains. Some of these are of great power lifting up to 100 tons. They are operated variously by steam or electricity or pneumati cally with water or oil.

Portable cranes are also known as Thalance because of the heavy weights which are placed on the of the smaller sizes to counterbalance the load. They are mounted on a truck with wheels to run on a track. This type is in common use by railroads for remov ing wreckage, and in bridge building and simi lar work. Instead of the counterbalancing weights, it is usual to mount the hoisting engine and machinery on the tail of the crane. For railroad work, the post and jib are commonly in one piece, and demountable for convenience in transportation. The operating power is steam or electricity. Frequently the machinery is so arranged as to make the crane self-pro pelling, and it is then called a locomotive crane.

Traveling cranes are of two general types: the overhead gauntry crane and the gauntry crane which runs on the ground. In the former a bridge-like structure runs on elevated tracks placed lengthwise of a yard or building, and on this bridge a traveler runs transversely, thus covering the entire space within the tracks. In

small installations the motive power is often a chain worked by hand, but these cranes have been greatly elaborated, and electricity is gen erally used, though there are instances of the employment of compressed air and also pneu matic installations. In very large plants the traveler frequently carries a cargo in which the operator sits, controlling every motion from a switchboard. Some of these cranes employed in shipbuilding yards and locomotive works are of great power, handling a load of 100 tons with ease and speed. The gauntry cranes, which run on tracks laid on the ground, partake of the type seen in the portable crane in some cases, mounted on an elevated gauntry, the base of which is fitted with trucks to run on the tracks. Another type resembles the overhead traveler crane. Combination structures are numerous and various, including the cantilever crane, in which the jib is extended on both sides of the post into a long trussed arm of the cantilever type; the bridge crane, in which one end of the long jib is supported on a track running on an elevated rail, with a traveler running on this bridge arm; the Titan crane, often built upon a float for harbor use, with its long arm sup ported by several guys from the top of the tall mast; and the coal and ore (tips)" for raising and emptying whole cars, operated generally by hydraulic power. For the multitude of specific details of construction and operation of these indispensable machines, consult Boettcher, A„ 'Cranes' (Tolhausen's translation and addi tions, London 1908) ; Hill, C. W., 'Electric Crane Construction> (London 1911) ; Marks, E. C. R., 'The Construction of Cranes and Other Lifting Machinery' (Manchester 1904) ; Wilda, H., 'Cranes and Hoists: Their Con struction and Calculation' (Salter's translation, London 1913).

or species of Tipula, etc., of the dipterous family Tipulidte. These flies are very common and known by their large size and long sprawling leis. They can usually be distinguished from midges and mosquitoes by their size, and always by a V-shaped mark on the back of the thorax. The antenna are rather long and slender, and the hind-body long, slender and cylindrical. They possess a distinct ovipositor, with two pairs of long, horny, pointed valves. The larva is a footless grub, like a maggot, which lives under stones in brooks or in damp soil; its head is distinct, and in this respect the kirva is more primitive and generalized than are those of most flies. It breathes by a pair of spiracles situated at the, extremity of the body. There are many species of crane-flies in the United States.