|
Historically wire rope evolved from steel 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. Friction between the individual wires and strands, as a consequence of their twist, further compensates for any flaws. This method of minimising the effect of flaws may also be seen in Damascus steel, employing multiple folding or laminations Modern wire rope was invented by the German mining engineer Wilhelm Ducay 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 to ropes made of hemp or to metal chains, such as had been used before. Wilhelm Albert’s first ropes consisted of wires twisted about a hemp rope core, six such strands then being twisted around another hemp rope core in alternating directions for extra stability. Earlier forms of wire rope had been made by covering a bundle of wires with hemp. In America wire rope was later manufactured by John A. Roebling, 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. Manufacturing a wire rope is similar to making one from natural fibres. The individual wires are first twisted into a strand, then six or so such strands again twisted around a core. This core may consist of steel, but also of natural fibres such as sisal, manila, henequen, jute, or hemp. This is used to cushion off stress forces when bending the rope. This flexibility is particularly vital in ropes used in machinery such as cranes or elevators as well as ropes used in transportation modes such as cable cars, cable railways, funiculars and aerial lifts. It is not quite so essential in suspension bridges and similar uses. Wire rope is often sold with vinyl and nylon coatings. This increases weather resistance and overall durability, however it can lead to weak joints if the coating is not removed correctly underneath joints and connections 
Wire rope construction 
This image of a fraying wire rope shows some individual wires. A chain is a series of connected links which are typically made of metal. A chain may consist of two or more links. Chains are usually made in one of two styles, according to their intended use:
From Wikipedia, the free encyclopedia : Manufacture of wire, chain and springs |
