crane

In engineering, a machine for raising, lowering, or placing in position heavy loads. The three main types are the jib crane, the overhead travelling crane, and the tower crane. Most cranes have the machinery mounted on a revolving turntable. This may be mounted on trucks or be self-propelled, often being fitted with caterpillar tracks.

The main features of a jib crane are a power winch, a rope or cable, and a movable arm or jib. The cable, which carries a pulley block, hangs from the end of the jib and is wound up and down by the winch. The overhead travelling crane, chiefly used in workshops, consists of a fixed horizontal arm, along which runs a trolley carrying the pulley block. Tower cranes, seen on large building sites, have a long horizontal arm able to revolve on top of a tall tower. The arm carries the trolley.

Cranes can also be mounted on barges or large semisubmersibles for marine construction work.