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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]
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 ...
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.
A crane was needed which could set larger and heavier blocks, up to 30 tons. The Hercules design combined aspects of both the earlier fixed-jib gantry cranes built for works at Manora and that would later be used for a slewing jib crane at Port Alfred. A horizontal jib was added, with the ability to slew sideways.
The jib has a radius (reach) of 35 feet (11 m) and a height of 40 feet (12 m). The crane weighs 120 tons. A vertical boiler inside the cab operates at 100 psi and supplies two twin-cylinder steam engines: one for slewing (turning) the crane, a larger one for winding the lifting chain. The winding drums can be driven by their gearing at four ...
In 1881, Stothert and Pitt constructed a horizontal jib crane for Sir John Coode's harbour building work on the Kowie River at Port Alfred in South Africa. [6] This was a rail-mounted steam crane, with a fixed horizontal jib carrying a movable trolley or 'crab'. The crane, including the steam plant, could slew on a central king post bearing ...