Crane

/krayn/, n.

1. (Harold) Hart, 1899-1932, U.S. poet.

2. Stephen, 1871-1900, U.S. novelist, poet, and short-story writer.

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I

Any of 15 species (family Gruidae) of tall wading birds that resemble herons but are usually larger and have a partly naked head, a heavier bill, more-compact plumage, and an elevated hind toe.

In flight, the long neck stretches out in front and the stiltlike legs trail behind. Cranes are found worldwide, living in marshes and on plains, except in South America. Many populations are endangered by hunting and habitat destruction. Cranes eat small animals, grain, and grass shoots. Two well-known species are the whooping crane and the sandhill crane.

Crowned crane (Balearica pavonina [regulorum]).

K.B. Newman

II

Any of a diverse group of machines that lift and move heavy objects.

Cranes differ from hoists, elevators, and other devices intended for vertical lifting, and from conveyors, which continuously lift or carry bulk materials such as grain or coal. Cranes have been widely used only since the introduction of steam engines, internal-combustion engines, and electric motors in the 19th century. They range in type and function from the largest derrick cranes to small, mobile truck cranes. Most derrick cranes can lift 5–250 tons (4.5–230 metric tons). Floating cranes, built on barges for constructing bridges or salvaging sunken objects, may be able to lift 3,000 tons (2,700 metric-tons). Small truck cranes are mounted on heavy, modified trucks; they make up in mobility and ease of transport what they lack in hoisting capacity.

III

(as used in expressions)

crane flower

crane fly

Crane Harold Hart

Crane Stephen

Crane Walter

sandhill crane

whooping crane

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▪ bird

 any of 15 species of tall wading birds of the family Gruidae (order Gruiformes). Superficially, cranes resemble herons but usually are larger and have a partly naked head, a heavier bill, more compact plumage, and an elevated hind toe. In flight the long neck is stretched out in front, the stiltlike legs trailing out behind.

      Cranes form an ancient group, the earliest fossils having been recovered from Eocene deposits in North America. Living forms are found worldwide except in South America, but populations of many are endangered by hunting and habitat destruction.

 These graceful terrestrial birds stalk about in marshes and on plains, eating small animals of all sorts as well as grain and grass shoots. Two olive-gray eggs spotted with brown are laid in a nest of grasses and weed stalks on drier ground in marsh or field. The same nest may be used year after year. The brownish, downy young can run about shortly after hatching. The trachea (windpipe) is simple in the chick but lengthens with age, coiling upon itself like a French horn. It lies buried in the hollow keel of the breastbone and reaches a length of 1.5 m (5 feet) in the adult whooping crane (Grus americana).

 The sandhill crane (G. canadensis) breeds from Alaska to Hudson Bay; it formerly bred in south-central Canada and the Great Lakes region of the United States but is now rare in these regions. This brownish-gray crane is about 90 to 110 cm (35 to 43 inches) long. Its call is long, harsh, and penetrating. The Florida sandhill crane (G. c. pratensis), a smaller race, breeds in Florida and southern Georgia and is nonmigratory. Other subspecies of sandhills are classified as rare or endangered. The common crane (G. grus) breeds in Europe and northern Asia, wintering in large flocks in northern Africa, India, and China. The Australian crane, native companion, or brolga (G. rubicunda), lives in Australia and southern New Guinea. The demoiselle crane (Anthropoides virgo) breeds in Algeria, southeastern Europe, and Central Asia; the crowned crane (Balearica pavonina [regulorum]), over nearly all of Africa; and the wattled crane (Bugeranus carunculatus), in eastern and southern Africa.

 

▪ materials handling

      any of a diverse group of machines that not only lift heavy objects but also shift them horizontally. Cranes are distinct from hoists, passenger elevators, and other devices intended solely or primarily for vertical lifting and from conveyors, which continuously lift or carry bulk materials such as grain or coal. Cranes have come into their present widespread application only since the introduction of steam engines, internal-combustion engines, and electric motors, beginning in the 19th century.

 The most prominent component of that class of cranes known as derrick cranes is the jib, or boom; this is a long beam that is structurally reinforced so that it will not bend. The jib is supported or held aloft by guy wires running from its top to a vertical mast, or pillar, that is itself stiffly braced; the guy wires set the angle at which the jib leans. Along the entire length of the jib runs a pulley system whose cables or chains are wound and unwound around a drum, or cylinder, that is placed at the jib's base and is turned by a motor. The cable dropping from the top of the jib is attached to loads and lifts them vertically. The loads may also be moved from side to side by having the jib pivot, or rotate, on its base around the mast. A simple pivoting hand-operated jib crane is depicted in Figure 1—>.

 A traveling jib crane is one in which the pulley system is suspended from a trolley, or wheeled carriage, moving along the length of the jib, as illustrated in Figure 2—>. Such traveling cranes usually have lifting capacities of from 5 to 250 tons. A potentially more powerful derrick is the floating crane, which is built on a barge for such purposes as constructing bridges or salvaging sunken objects. The Musashi, a large crane of this type built in Japan in 1974, can lift a 3,000-ton load.

      Problems in maintaining stability always arise with jib cranes, and in the case of larger cranes that lift heavy loads at long outreaches, special care has to be taken to avoid tipping of the crane. For this purpose, besides the usual practice of mounting the hoisting machinery in such a way as to counterpoise part of the load on the boom, special ballast weights must be added to ensure that the crane will not be overturned.

 The cantilever crane, a type much used in the construction of ships and tall buildings, has a horizontal boom that rests upon and can rotate about a vertical mast. The load is suspended from a trolley that can move along a track on the boom. A cantilever crane used in shipyards is depicted in Figure 3—>. During the erection of a building of many stories, the mast of a cantilever crane may be extended upward repeatedly as the height of the building increases. (See also cantilever.)

 Bridge cranes comprise another important class of cranes in which the pulley system is suspended from a trolley that moves on tracks along one or two horizontal beams, called the bridge, that are supported at both ends. In most cases, the bridge itself can move along a pair of parallel rails, so that the crane can serve a large rectangular area. A circular space can be served by a rotary bridge crane, in which one end of the overhead beam is supported by a central pivot while the other end moves on a circular rail on the periphery of the area. The overhead traveling crane, a bridge crane for which the rails are mounted above the level of the ground or floor, has the advantage of causing no obstruction of the working area. Overhead traveling cranes are commonly used indoors, where their rails can be attached to the columns that support the roof. This type of crane is depicted in Figure 4—>. If the construction of overhead rails is impracticable, the ends of the bridge can be attached to upright towers that move on rails at the ground level; such cranes are called gantry, or goliath, cranes.

      A commonly used type of small movable crane is the truck crane, which is a crane mounted on a heavy, modified truck. Such cranes frequently use unsupported telescoping booms; these are made up of collapsible sections that can be extended outward like the sections of an old nautical telescope or spyglass. The extension of the boom is usually managed hydraulically. Truck cranes make up in mobility and ease of transport what they lack in hoisting capacity.

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