Cable Sling Resources

Friction between the individual wires and strands, as a consequence of their twist, further compensates for any flaws.

HISTORY

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. laid (or 'twisted') together like a helix. Each strand is likewise made of metal wires laid together like a helix. Initially wrought iron wires were used, but today steel is the main material used for wire ropes.

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 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.

Manufacturing a wire rope is similar to making one from natural fibers. 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 fibers 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.

Cable Sling is wire rope that consists of several strands

The specification of a wire rope type – including the number of wires per strand, the number of strands, and the lay of the rope – is documented using a commonly accepted coding system, consisting of a number of abbreviations.

Example. 6x19 FC RH OL FSWR

Each of the sections of the wire rope designation described above is variable. There are therefore a large number of combination of wire rope that can be specified in this manner. The following abbreviations are commonly used to specify a wire rope

Abbr.

FSWR

IWR

IWRC

SWL

WLL

Description

Fibre core

Flexible steel wire rope

Filler wire

Independent wire rope

Independent wire rope core

Jute (fibre)

Left hand lay

Lang's lay

Non-rotating

Ordinary lay

Right hand lay

Seale

Seale filler wire

Seale Warrington

Safe working load

Triangular strand

Warrington

Warriflex

working load limit

Warrington Seale

Warrington differs from the other types (Filler Wire and Seale construction) in that the outside layer of wires in each strand of the wire rope is composed of wires alternately large and small. The outside wires of both the Filler Wire and Seale construction ropes are uniform in size. The fundamental difference between these types is that the layer of wires underneath the outside layer in the Seale type is made up of wires all of the same size. The wires under the outside layer of the Filler Wire rope are made up of a combination of main wires, each of the same size, and smaller filler wires, each of the same size, nested between the main wires. The outside layer of wires, therefore, is supported partly by the main inside wires and partly by the filler wires.Some ropes have shaped or formed (triangular) wires to improve the wear and bearing properties of the outer layers (rather than circular drawn wire).

By having different lay directions of the strands and wire (left and right - also known as S and Z), it is possible to balance the torque value - resulting in a rope that does not tend to untwist when load is applied. This is called torque balanced or non-rotating rope.