A crane can be described as a machine which is capable of lowering and lifting heavy objects and also moving them horizontally the difference between a crane and hoist is that hoist can lift objects vertically but cant move them horizontally. The word crane is taken from the fact that these machines have a shape similar to that of the tall, long-necked bird of the same name.
As early as the first century, cranes were built which were powered by animals or human beings .these types of cranes had a boom connected to a rotating base. It had a treadmill which powered the drum around the rope was wounded. The rope was attached to the pully at the top of the boom and to a hook or holder which lifts the load or weight.
A great advancement was made in crane design during Middle Ages when an horizontal arm called the ‘jib’was attached to the boom in a way which allowed it to pivot, allowing for an increased range of motion
Cranes continued to be operated by human being until middle of the 19th century when steam engines were developed. Electric motors and internal combustion engines were used to power cranes . During the first half of twenth century cranes were developed is such a way that it had tall slender towers with the boom and the operator on the top of the tower. During the 1950s, the availability of stronger steels, combined with an increased demand for taller buildings, led to the development of cranes with very long booms attached to small trucks, or to crawlers with caterpillar treads. Mobile cranes and tower cranes of many different kinds are used extensively in construction sites around the world.
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