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A jib or jib arm is the horizontal or near-horizontal beam used in many types of crane to support the load clear of the main support. [1] [2] An archaic spelling is gib. [3] Usually jib arms are attached to a vertical mast or tower or sometimes to an inclined boom.
On March 15, 2008, a crane owned by New York Crane & Equipment collapsed during construction. Seven people were killed and 24 others were injured. [ 5 ] It was a luffing-jib tower crane manufactured by Favco that was 200 feet (61 m) tall at the time of the collapse.
The "hammerhead", or giant cantilever, crane is a fixed-jib crane consisting of a steel-braced tower on which revolves a large, horizontal, double cantilever; the forward part of this cantilever or jib carries the lifting trolley, the jib is extended backwards in order to form a support for the machinery and counterbalancing weight. In addition ...
The jib was slewed by a mechanism on the ground, and bearings at the top of the tower and where the extension met the ground allowed it to turn. [ 1 ] [ 2 ] The winch on each arm was powered by two 52 horsepower (39 kW) electric motors for hoisting and two 14 horsepower (10 kW) motors for slewing, and a 18 horsepower (13 kW) motor for slewing ...
A level-luffing crane is a crane mechanism where the hook remains at the same level while luffing: moving the jib up and down, so as to move the hook inwards and outwards relative to the base. [ 1 ] Usually the description is only applied to those with a luffing jib that have some additional mechanism applied to keep the hook level when luffing.
Ships had increased in size by this time and the jib could no longer reach far enough to remove engines or boilers for repair work. It was even considered raising the crane up on a stone tower, as for the smaller crane at Canons Marsh opposite, to increase the lift height. In 1892, hydraulic machinery, including cranes, appeared in the docks ...
In 2007, Tishman Construction Corporation of New York completed a row of steel columns at the perimeter of the construction site. Two tower crane bases were erected, each base containing a functioning luffing-jib tower crane. By the end of 2007, the tower's footings and foundations were nearly complete. [10]
Each crane has a span of 140 metres (459 ft) and can lift loads of up to 840 tonnes to a height of 70 metres (230 ft). Their combined lifting capacity of almost 1,700 tonnes is one of the largest in the world. Prior to commissioning, the cranes were tested up to 1,000 tonnes, which bent the gantry downwards by over 30 centimetres (12 in).