Vertical caving terminology and methods > General hardware
A rope made from strands of wire, typically steel or stainless steel. "Cable" generally refers to thicker cables, and "wire" generally refers to thinner cables, but either term can be used for any sized cable. Cable is much heavier than a rope of the same diameter, but it is also much stronger than a rope, and far more resistant to abrasion. The strength and weight depend on the material it is made from, but as a general rule, a stainless steel cable is about 2.2 times as strong as a nylon rope of the same diameter, but weighs 6 times as much. A very thin version is used to make electron ladders. Much thicker ones are too heavy to carry normally, but are sometimes installed as fixed aids, particularly as traverse lines for wire traverses. Because they do not have dynamic properties like a rope would, they can produce much higher forces if they are subjected to shock loads, so they are generally used in situations where shock loading is considered unlikely. They may be used in places where rub points could become a problem for ropes. Cables have historically been used for prusiking by Russian cavers, and winches would typically use cables rather than rope. Cables cannot have knots tied in them, so they rely on swaged eyelets, cable clamps and splices. Cables dramatically lose their strength when bent around sharp corners. A bend around a bar the same thickness as the cable can result in 50% of the strength being lost, and the loss increases exponentially for tighter bends. The distance it wraps around the bar is unimportant, and even a small deflection can cause the loss of strength if the radius of the bend is significant. As a result, loops or eyelets should have thimbles. Pulling on a cable directly using a carabiner is likely to reduce its strength by about half, depending on the thickness of the cable and carabiner, which negates most of the strength benefit from using cables.
Cables are made from a number of strands, where each strand is made up from a number of individual wires. The strands normally have a central core wire, with six wires twisted around it, so 7 wires in total. They can then optionally have another 12 wires wrapped around the outside of those, giving 19 wires in total. For low strength purposes, they may be used as a single strand like this, known as a 1×7 or 1×19 wire rope (sometimes written with a * or / instead of the × symbol). To make better cables, these may be used like a hawser laid rope, with three strands twisted together. However, it is more common for cables to have a central core strand with six similar strands twisted around it, known as a 7×7 wire rope or 7×19 wire rope, depending on how many wires are used per strand. Some manufacturers confusingly describe this as a 6×7 structure, while stating that it also has a wire core, which shows that the central strand is only there to hold the right shape, and is not load bearing. Thicker cables may then have 12 strands wound around the inner strands, known as a 19×7 or 19×19 wire rope, or they could have 6 much thicker strands wound around the inner strands, where they tend to be named only by taking the outer-most layer into account, such as 6×36 wire rope, ignoring the 7×7 inner structure. Other structures are possible, but these are the most common.
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