Gantry crane
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Both overhead travelling cranes and gantry cranes are types of Crane which lift objects by a hoist which is fitted in a trolley and can move horizontally on a rail or pair of rails fitted under a beam. An overhead travelling crane, also known as an overhead crane or as a suspended crane, has the ends of the supporting beam resting on wheels running on rails at high level, usually on the parallel side walls of a factory or similar large industrial building, so that the whole crane can move the length of the building while the hoist can be moved to and fro across the width of the building. A gantry crane has a similar mechanism supported by uprights, usually with wheels at the foot of the uprights allowing the whole crane to traverse.
A Portainer crane is a specialised version of the gantry crane in which the horizontal gantry rails and their supporting beam are cantilevered out from between frame uprights spaced to suit the length of a standard freight container, so that the beam supporting the rails projects over a quayside and over the width of an adjacent ship allowing the hoist to lift containers from the quay and move out along the rails to place the containers on the ship. The uprights have wheels which run in tracks allowing the portainer crane to move along the quay to position the containers at any point on the length of the ship.
Overhead travelling cranes and gantry cranes are particularly suited to lifting very heavy objects and huge gantry cranes have been used for shipbuilding where the crane straddles the ship allowing massive objects like ships' engines to be lifted and moved over the ship. Two famous gantry cranes built in 1974 and 1969 respectively, are Samson and Goliath, which reside in the largest dry dock in the world in Belfast, Northern Ireland. Each crane has a span of 140 metres and can lift loads of up to 840 tonnes to a height of 70 metres, making a combined lifting capacity of over 1,600 tonnes, one of the largest in the world.
However, gantry cranes are also available running on rubber tyres so that tracks are not needed, and small gantry cranes can be used in workshops, for example for lifting automobile engines out of vehicles.
