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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.
This specific example uses a level luffing mechanism to maintain the load at approximately the same vertical height as the jib moves through its range of travel. 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]
Rather than slewing (rotating) the crane to reach the delivery hopper on-shore, a kangaroo crane has its own in-built hopper beneath the jib, that slews with it as the crane rotates. Dumping the grab contents into the hopper now only requires the quicker luffing movement, without needing to slew for each load.
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. [1]
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. Ring cranes are rare.
The process of rotating a telescope to observe a different region of the sky is referred to as slewing. The term slewing is also found in motion control applications. Often the slew axis is combined with another axis to form a motion profile. In crane terminology, slewing is the angular movement of a crane boom or crane jib in a horizontal plane.
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