Wire Ropes. — Wire ropes are used about collieries for haulage and winding, and occasionally for the transmission of power. The ropes in general use are usually made of steel wire, but in a few cases iron wire is used in their construction. Two classes of steel wire ropes are commonly used: (a) Crucible Steel, and (b) Plough Steel. 'Crucible Steel Ropes' is the name given by the trade to ropes made from steel wire, having an ultimate strength of from 70 to 90 tons per square inch. Plough steel ropes are made from steel wire having an ultimate strength of from 100 to 120 tons per square inch. In some cases where steel wire of over 120 tons per square inch ultimate tensile strength is used in the construction of a rope, the rope goes by the trade name of an Improved Plough Steel Rope. These names are merely trade designations, and it would be much more satisfactory if the ultimate strength of the steel wire used in the manufacture of the rope were specified.

Wire ropes consist of a number of strands, each composed of an equal number of single wires, these strands being twisted round a hemp core to form the finished rope. The hemp core is saturated with a lubricant, which tends to prevent rusting. Besides causing less internal friction than a wire core would, the hemp core gives greater flexibility, a quality that is necessary in most ropes used for mining purposes. The strands are six in number, and they may be spun with seven, nineteen, or thirty-seven wires. Ropes for mining purposes usually consist of six strands of nineteen wires each (6 x 19).

The lay of a rope is the direction in which the strands are twisted into the rope. Ropes are either right-hand or left-hand. The strands are twisted in a right-hand direction in the usual lay. There are two types of lay in general use: Ordinary lay and Lang's lay. (See Fig. 91.) In the ordinary lay the wires forming the strands are twisted in the opposite direction to the strands in the rope, while in Lang's lay the wires are twisted into the strands in the same direction as the strands are twisted into the rope. The chief advantages of Lang's lay are that the wires and the strands being twisted in the same direction a uniform surface is obtained, which distributes wear, and the wires being straighter the rope is rendered more flexible. The disadvantages arc their greater tendency to untwist and the trouble that arises in using them if any of the wires are broken.

Lang's lay ropes are usually adopted for haulage, or winding where the cage works in guides. They are not suitable for sinking as they cause undue spinning of the kettle.

Locked Coil Rope. — Ropes of this class are made with a centre of round wire, which is covered with layers of wire of rectangular section, and, finally, by a layer of shaped wires which fit or lock into each other. A section of this type of rope is shown in Fig. 92.

The rope presents a smooth uniform surface which gives it the appearance of a flexible bar rather than a rope. Although not quite so flexible as the ordinary type it is somewhat lighter for similar strength. Locked coil ropes are non-spinning and therefore suitable for use in shaft sinking. Their shape adds to their durability, and for winding purposes they give extremely satisfactory service.

Flattened Strand Ropes. — Ropes of this class have a large and comparatively smooth-wearing surface, which tends to increase their durability. In these ropes (Fig. 93) the strands have an elliptical or triangular cross section, which is determined by the shape of the metal centre of the strand. The rope itself may have either a hemp or a wire core. It is claimed for this rope that the internal friction between the strands, when being coiled on a drum or when running over a wheel, is less than with any other type.

This class of rope is extremely flexible, is not liable to kink, and is free from all tendency to spin.

Flat Ropes. — These are formed from a number of small ropes, usually six or eight, each made up with four strands of seven wires. They are plaited and then sewn together by stitches of single wire, which cross in a transverse direction. This class of rope (see Fig. 94) is not much used, as weight for weight it is greatly inferior in strength to round or flattened strand ropes, and does not wear nearly so well. It has one advantage over a round rope, that is, it can be wound on a reel, layer after layer resting on the top of each other. By this means a certain amount of balancing is obtained during the wind, and the rope being always in the same plane as the headgear pulley, side friction is eliminated.

Storage and Use of Ropes. — Wire ropes should always be carefully stored in a good storeroom, and the reel on which they are wound should be raised above the floor level to protect them from damp. Ropes should be greased at intervals with a suitable grease, free from acid, e.g., a paste made by mixing flaked graphite with linseed oil. To comply with the Mines Act, all winding ropes must be recapped at intervals of not more than six months, and no winding rope must be used for more than three and a half years. The caps or sockets in general use are of the conical type (Fig. 95), and are fixed to the rope in the following manner. The rope is pushed through from the small end and allowed to project about twice the length of socket. It is then wrapped firmly with wire about half-way to the end, each strand is untwisted and the wires bent back upon themselves, a few being cut away so as to allow the rope end to assume the form of a conical knob. The rope is drawn back into the socket and run in with white metal, the melting-point of which must not be above 750° Fahrenheit. The breaking load of a winding rope must be ten times the working load, and the capping must stand against a load seven times greater than the maximum working load. A special type of socket, into which the rope is secured by wedges, must be used for locked coil wire ropes.

Safety Hooks. — In the event of an overwind the cage is drawn past the landing stage and over the wheels, or up against the cross beams of the headgear, should these be in the way. The usual result in the latter case is the breaking of the rope with the consequent fall of the cage down the shaft. To prevent this the Coal Mines Act makes the use of safety hooks compulsory on all vertical shafts. There are several types of these so-called safety hooks, but all aim at setting the rope free in the event of an overwind, while at the same time providing for the suspension of the cage from a beam which sets the liberating mechanism into action.

One of the best is that known as Walker's (Fig. 96). The supporting ring, through which the rope is threaded, is fixed in a wooden beam or between iron girders placed below the pulleys in the headgear. The hook itself consists of a pair of jaws hinged at the centre and clasping the pin of the rope capping in a circular hole in their upper end. The jaws are held together and prevented from releasing the rope by a clamp, which entirely surrounds them and is kept in position by two copper pins. In the event of an overwind the hook is carried up through the supporting ring, but the clamp is caught and forced back, the two copper pins for holding it in position being shorn. As the clamp is forced back, the top parts of the jaws are opened and forced over the edge of the ring before the rope is released. The rope when freed passes over the pulley, and the cage remains suspended from the ring in the cross-beams.

Safety Catches. — Catches have been designed for the purpose of arresting the descent of the cage should the rope break during the wind.

These catches are complicated appliances, and the question of whether their use is desirable is still undecided. Meantime British mining engineers favour reliance upon rope inspection' and renewal at frequent intervals.

Cages. — The cage is the receptacle which is attached to the end of the winding rope for carrying the loaded or empty tubs, and for holding men while they are being raised or lowered in the shaft. Cages must be provided with catches to prevent tubs falling out, and when used for raising and lowering men the top must be completely covered and the two sides constructed so as to prevent anything projecting outwards into the shaft. Suitable gates must be fixed at each of the open ends, and these gates must be closed when men are riding in the cage.

Cages are made from strong angle or strip steel, and the top and sides covered with light steel plates. The top plate is either sloped from the centre down to each side or is of semicircular shape. One, two, or sometimes three decks or platforms are provided for holding the tubs, and one, two, or four tubs may be carried on each deck. The number of tubs carried depends on the size of cage provided. A cage with two decks is shown in Fig. 97.