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A gin pole used to install a weather vane atop the 200-foot steeple of a church Roof trusses being assembled with gin poles. The gin pole is derived from a gyn, and considered a form of derrick, called a standing derrick or pole derrick, [2] distinguished from sheers (or shear legs) by having a single boom rather than a two-legged one.
The mechanical advantage is 2, requiring a force of only 50 N to lift the load. A block and tackle is characterized by the use of a single continuous rope to transmit a tension force around one or more pulleys to lift or move a load. Its mechanical advantage is the number of parts of the rope that act on the load. The mechanical advantage of a ...
A number of pulleys are assembled together to form the blocks, one that is fixed and one that moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies that force applied to the rope. [4] In order to determine the mechanical advantage of a block and tackle system consider the simple case of a ...
Examples of rope and pulley systems illustrating mechanical advantage. Consider lifting a weight with rope and pulleys. A rope looped through a pulley attached to a fixed spot, e.g. a barn roof rafter, and attached to the weight is called a single pulley. It has a mechanical advantage (MA) = 1 (assuming frictionless bearings in the pulley ...
Vitruvius, a military engineer writing about 28 BC, defined a machine as "a combination of timber fastened together, chiefly efficacious in moving great weights."About a century later, Hero of Alexandria summarized the practice of his day by naming the "five simple machines" for "moving a given weight by a given force" as the lever, windlass, screw for power, wedge, and tackle block (pulley).
F/n = 23 kN per anchor during initial lift (n = 2 lifting anchors) Transport loads in the yard and on-site Suction due to casting bed adhesion is not considered, as the calculation takes into account the lifting device dynamic coefficient. S = (W x Ksl x Kd) / n = (64.8 x 1.16 x 1.2) / 2 = 45.1 kN load resistance required per anchor
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A lifting hook is usually equipped with a safety latch to prevent the disengagement of the lifting wire rope sling, chain or rope to which the load is attached. A hook may have one or more built-in pulley sheaves as a block and tackle to multiply the lifting force. Lifting hook attached to sheave suspended by wire rope from boom of crane