Crane (machine)
A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses one or more simple machines, such as the lever and pulley, to create mechanical advantage to do its work. Cranes are commonly employed in transportation for the loading and unloading of freight, in construction for the movement of materials, and in manufacturing for the assembling of heavy equipment.
The first known crane machine was the shaduf, a water-lifting device that was invented in ancient Mesopotamia (modern Iraq) and then appeared in ancient Egyptian technology. Construction cranes later appeared in ancient Greece, where they were powered by men or animals (such as donkeys), and used for the construction of buildings. Larger cranes were later developed in the Roman Empire, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbour cranes were introduced to load and unload ships and assist with their construction—some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron, iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first mechanical power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century.[1] Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
There are many different types of cranes, each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. Mini-cranes are also used for constructing high buildings, to facilitate constructions by reaching tight spaces. Large floating cranes are generally used to build oil rigs and salvage sunken ships.
Some lifting machines do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.
Etymology[edit]
Cranes were so called from the resemblance to the long neck of the bird, cf. Ancient Greek: γερανός, French grue.[2]
History[edit]
Ancient Near East[edit]
The first type of crane machine was the shadouf, which had a lever mechanism and was used to lift water for irrigation.[3][4][5] It was invented in Mesopotamia (modern Iraq) circa 3000 BC.[3][4] The shadouf subsequently appeared in ancient Egyptian technology circa 2000 BC.[5][6]
Failed crane in Sermetal Shipyard, former Ishikawajima do Brasil – Rio de Janeiro, caused by a lack of maintenance and misuse of the equipment
Cranes can mount many different fittings, such as hooks, blocks, spreader bars, and "choker" lines, depending on load (left). Cranes can be remote-controlled from the ground, allowing much more precise control, at the expense of the view from atop the crane (right).
Automobile crane of the Railway Troops of Russia
Truck mounted crane building a bridge
A truck-mounted crane in road travel configuration
Crane operators are skilled workers and heavy equipment operators.
Key skills that are needed for a crane operator include:
History of cranes