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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.
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.
A jib crane is a type of crane - not to be confused with a crane rigged with a jib to extend its main boom - where a horizontal member (jib or boom), supporting a moveable hoist, is fixed to a wall or to a floor-mounted pillar. Jib cranes are used in industrial premises and on military vehicles.
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 ...
The operator's cabin hosts a display showing the tower crane's position, movement and operating area. Where the tower crane’s operating area overlaps with other cranes or prohibited zones these are also displayed. The system alerts the operator when the crane is approaching a prohibited area or another crane. [9]
A ring crane is a form of large construction crane with a luffing jib. It is distinguished by its slew pivot [ i ] being in the form of a ring-shaped track, rather than a narrow central spindle. The broad base this gives to the slewing section above allows it to slew whilst carrying extremely heavy loads.
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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]