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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.
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.
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 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.
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 ...
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 ...
The base of the tower is hinged and the top of the tower is connected to a pulley system for load lifting. As this is a simple derrick system, it is recommended for use by some agencies as an improvised rescue derrick in an emergency situation where no suitable rescue derrick or crane is available. [1] [2]