Wire rope is composed of as few as two solid metal wires twisted into a helix that forms a composite rope, in a pattern known as laid rope. Larger diameter wire rope consists of multiple strands of such laid rope in a pattern known as cable laid. Manufactured using an industrial machine known as a strander, the wires are fed through a series of barrels and spun into their final composite orientation. 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. 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. While flaws in chain links or solid steel bars can lead to catastrophic failure, flaws in the wires making up a steel cable are less critical as the other wires easily take up the load. While friction between the individual wires and strands causes wear over the life of the rope, it also helps to compensate for minor failures in the short run. Wire ropes were developed starting with mining hoist applications in the 1830s. Wire ropes are used dynamically for lifting and hoisting in cranes and elevators, and for transmission of mechanical power. Wire rope is also used to transmit force in mechanisms, such as a Bowden cable or the control surfaces of an airplane connected to levers and pedals in the cockpit. Only aircraft cables have WSC (wire strand core). Also, aircraft cables are available in smaller diameters than wire rope. For example, aircraft cables are available in 1.2 mm (3⁄64 in) diameter while most wire ropes begin at a 6.4 mm (1⁄4 in) diameter. Static wire ropes are used to support structures such as suspension bridges or as guy wires to support towers. An aerial tramway relies on wire rope to support and move cargo overhead.
History Modern wire rope was invented by the German mining engineer Wilhelm Albert in the years between 1831 and 1834 for use in mining in the Harz Mountains in Clausthal, Lower Saxony, Germany. It was quickly accepted because it proved superior strength from ropes made of hemp or of metal chains, such as had been used before. Wilhelm Albert's first ropes consisted of three strands consisting of four wires each. In 1840, Scotsman Robert Stirling Newall improved the process further. In America wire rope was manufactured by John A. Roebling, starting in 1841 and forming the basis for his success in suspension bridge building. Roebling introduced a number of innovations in the design, materials and manufacture of wire rope. Ever with an ear to technology developments in mining and railroading, Josiah White and Erskine Hazard, principal owners of the Lehigh Coal & Navigation Company (LC&N Co.) — as they had with the first blast furnaces in the Lehigh Valley — built a Wire Rope factory in Mauch Chunk (later renamed Jim Thorpe, Pennsylvania), in 1848, which provided lift cables for the Ashley Planes project, then the back track planes of the Summit Hill & Mauch Chunk Railroad, improving its attractiveness as a premier tourism destination, and vastly improving the throughput of the coal capacity since return of cars dropped from nearly four hours to less than 20 minutes. The following decades featured a burgeoning increase in deep shaft mining in both Europe and North America as surface mineral deposits were exhausted and miners had to chase layers along inclined layers. The era was early in railroad development and steam engines lacked sufficient tractive effort to climb steep slopes, so inclined plane railways were common. This pushed development of cable hoists rapidly in the United States as surface deposits in the Anthracite Coal Region north and south dove deeper every year, and even the rich deposits in the Panther Creek Valley required LC&N Co. to drive their first shafts into lower slopes beginning Lansford and its Schuylkill County twin-town Coaldale. The German engineering firm of Adolf Bleichert & Co. was founded in 1874 and began to build bicable aerial tramways for mining in the Ruhr Valley. With important patents, and dozens of working systems in Europe, Bleichert dominated the global industry, later licensing its designs and manufacturing techniques to Trenton Iron Works, New Jersey, USA which built systems across America. Adolf Bleichert & Co. went on to build hundreds of aerial tramways around the world: from Alaska to Argentina, Australia and Spitsbergen. The Bleichert company also built hundreds of aerial tramways for both the Imperial German Army and the Wehrmacht. In the latter part of the 19th century, wire rope systems were used as a means of transmitting mechanical power including for the new cable cars. Wire rope systems cost one-tenth as much and had lower friction losses than line shafts. Because of these advantages, wire rope systems were used to transmit power for a distance of a few miles or kilometers.
Construction
Wires Steel wires for wire ropes are normally made of non-alloy carbon steel with a carbon content of 0.4 to 0.95%. The very high strength of the rope wires enables wire ropes to support large tensile forces and to run over sheaves with relatively small diameters.
Strands In the so-called cross lay strands, the wires of the different layers cross each other. In the mostly used parallel lay strands, the lay length of all the wire layers is equal and the wires of any two superimposed layers are parallel, resulting in linear contact. The wire of the outer layer is supported by two wires of the inner layer. These wires are neighbors along the whole length of the strand. Parallel lay strands are made in one operation. The endurance of wire ropes with this kind of strand is always much greater than of those (seldom used) with cross lay strands. Parallel lay strands with two wire layers have the construction Filler, Seale or Warrington.
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