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A block and tackle [1] [2] or only tackle [3] is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads.. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and one moves with the load.
A pulley may have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain. The earliest evidence of pulleys dates back to Ancient Egypt in the Twelfth Dynasty (1991–1802 BC) [1] and Mesopotamia in the early 2nd millennium BC. [2]
In stricter senses, the term wire rope refers to a diameter larger than 9.5 mm (3 ⁄ 8 in), with smaller gauges designated cable or cords. [1] Initially wrought iron wires were used, but today steel is the main material used for wire ropes. Historically, wire rope evolved from wrought iron chains, which had a record of mechanical failure.
Some cable ferries use a wire rope on the upstream side in order to hold the position and a chain on the downstream side for propulsion. A special type are electrically powered overhead-cable ferries like Straussee Ferry , which have an onboard propulsion unit and can float free, but are connected to the overhead wire for the power supply ...
Wire ropes were occasionally used, but cotton, hemp, manila hemp and flax rope saw the widest use. Typically, the rope connecting two pulleys with multiple V-grooves was spliced into a single loop that traveled along a helical path before being returned to its starting position by an idler pulley that also served to maintain the tension on the ...
A crane is a machine used to move materials both vertically and horizontally, utilizing a system of a boom, hoist, wire ropes or chains, and sheaves for lifting and relocating heavy objects within the swing of its boom. The device uses one or more simple machines, such as the lever and pulley, to create mechanical advantage to do its work.
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