The pulleys, usually placed side by side, have wrought-iron arms, the rim and central boss being generally of cast iron. They should be placed with proper regard to the lead of the ropes off the drum to the pulleys, so that the angle of the rope to each is equal. The rim is made to suit the kind of rope to be used, and is grooved accordingly. Pulleys are usually from 10 to 20 feet in diameter. In deciding on a suitable size, it must be borne in mind that ropes receive more injury from working over small pulleys than over large ones, and consequently wear out quicker. A good plan is to have the pulleys the same size as the drum of the winding engine, a rule for ascertaining which is given later in this Chapter. Provision must always be made for their adjustment and oiling.

Fig. 67 shows a Pit-head frame which is elegant in appearance and of great strength, as made by Messrs. Thornewill & Warham, Engineers, of Burton-onTrent, and erected at the Earl of Carnarvon's New Hall Park Collieries, near Burton-on-Trent. The general arrangement of the pit bank is also shown in the Figure.

The height from pulley centres to pit bank is 40 feet, the pulleys being 15 feet in diameter. The legs are of open lattice work with 4" x 4" x 1" angle iron bars connected by flat bars 21"x", and are suitably cross-braced and stiffened by plate girders and spandrils of various sections.

The platform around the pulleys is fenced, and access thereto is obtained by a stairway on one of the back-legs.

The pulleys are of the usual type, having cast-iron rims and bosses with wrought-iron arms, and are fitted with steel spindles having journals running in pedestals with adjusting screws and ample lubricating boxes attached.

The legs are provided with cast-iron plates at their feet, bedding on stone blocks mounted on brick pillars, and secured by large foundation bolts.

For lighter loads and small plants the frames are constructed of I and iron sections and are very neat, and strong, and preferable to wood.

When required for shipment the frames are erected, and marked before being taken to pieces, and the necessary bolts provided for locking together in reerection.

ROPES are now usually made of steel wire of different qualities, all being stronger than iron for the same size; and they may be round or flat. The round are preferable and certainly the most popular. Ropes of hemp are also used, but only to a limited extent, and are gradually falling into disuse for winding.

Wire ropes should be carefully protected with best water-proof grease. The safe working load of ropes may be taken at from th to th of the breaking strain. A close approximation to the safe working load of ordinarily-made wire ropes moving at high speeds is found by multiplying the weight of the rope per fathom in pounds by 5 for iron wire, and by 8 for steel wire, and consider the product as hundredweights. Thus, an iron wire rope, weighing 16 lbs. a fathom, has a safe working load of 16×5 = 80 cwt.; a steel wire rope of the same weight, 16 x8 = 128 cwl. These are only rough approximations-rules that can be easily carried in the memory. André, in his Treatise on Coal Mining, gives the following rules to find the safe working load:-C=√4 L for iron wire and C = √√2'4 L for steel wire, where C = the circumference of the rope in inches and L= the safe working C2 C2 load, and therefore L = for iron wire and for steel wire. 4 2'4

The following rules were at one time used by some rope manufacturers, but the difference in quality of the materials used renders the rule of little practical value. Owing to this difference probably, there is a want of uniformity in the strength of similarly-sized ropes quoted by manufacturers. Let B = breaking weight in tons, and W= weight per fathom in pounds. Then for hemp ropes W = B; for iron wire ropes W=55 B; and for steel wire ropes W=33 B. Or,

=

where C circumference of rope in inches (where the ropes are flat C will answer for the perimeter) and B = breaking weight in tons.

Then for hemp ropes B = 25 C2; for iron wire ropes B 1'5 C2; and for steel wire ropes B = 2.5 C2.

The working or safe load is for- Round

Flat

Suppose, then, it becomes necessary to know the diameter of wire rope which would be equal in strength to a hemp one of 4 inches diameter, it would be found thus the ratio that the square of the diameter of an iron wire rope bears to a hemp one in point of strength is as 15: 25. Therefore as 1'5:25:: 4o: 2·6, and √2.6 = 1633 inch as the diameter of the iron wire rope. Similarly, if it be required to know the diameter of steel wire rope which would be equal in strength to the hemp one of 4 inches in diameter and the iron wire rope of 1.633 inch in diameter, the reasoning would be thus: the ratio that the square of the diameter of the steel wire rope bears to the hemp one in point of strength is as 25 : ·25 :: 4o : 1·6 and √1·6 = 1265 inch as the diameter of the steel wire rope.

The duration of a rope depends upon circumstances. If placed in a wet shaft where the water is impregnated with mineral acids, or in an upcast shaft where gases injure the ropes, they will not last so long as those working in dry shafts. Ropes subjected to rapid winding are injured more than where slow speeds of winding prevail. The average duration of flat wire ropes is usually taken at one year, and that of round ropes at a year and a half; but it is impossible to fix a hard and fast line, on account of the great difference in circumstances under which ropes work. The speed of winding, freedom from chemical action, careful attention and greasing, the number of hours used per day and the number of days per year, are all elements affecting the duration. In putting on a rope care should be taken to pass it through the exterior of the drum on an easy curve, and then to coil it round the drum-shaft once or twice before securing it thereto. A rope should be long enough to admit of a couple of coils on the drum when the cage is lowered to the pit-bottom. The other end of the rope is secured to the cage by "capping."

The most frequently used method of "capping" a round wire rope is as follows: A strip of iron is worked into suitable shape to form the cap. The central portion is well rounded for a few inches, sufficient when the two ends are afterwards bent over towards each other to form a strong loop or bow to take the D link which holds the cage bridle-chains. The two sides of the cap are rather smaller at the ends than next the loop, and are curved to receive the rope between them. Rivet-holes are drilled opposite each other in the two sides. Besides this socket, two rings of iron are prepared of such sizes as to afterwards fit tightly over the joint. These rings are closed before going on, and fit somewhat loosely over the rope; they are passed over the end whilst hot. About 2 feet back from its end a piece of copper wire is now bound round the circumference of the rope. The wires at the extremity are then opened and folded back upon the rope, the fold taking place at the copper-wire binding. Another length of copper wire is carefully and tightly wound over the folded wires so as to bring them into close contact with the rope and prevent any wires from projecting. As the binding proceeds upwards the folded wires are thinned gradually by cutting off a few at a time, until, when the binding has reached the top, a cone has been thereby formed at the extremity of the rope. In this state the rope is inserted between the two sides of the socket, which are easily spread open for the purpose. The sides are then, by means of clamps, pressed tightly against the rope and held firmly so, whilst rivets are driven through the socket and the heads formed on

the rivets. The operation of riveting is attended with some practical difficulty. The holes are not drilled recklessly through the rope, as a drill in advancing straight across would sever many of the wires obliquely crossing its course, and so weaken the rope. To avoid cutting the wires and yet obtain a passage through them and past the cores without injury, a short needle is used, having a point at one end and a head and eye at the other. The needle is struck by a hammer or turned by passing a short rod through the eye, whilst attempts are made to direct it to form an opening between the wires and past the cores, without cutting them, in line to the corresponding rivet-hole on the opposite side. Frequently the needle, after piercing the rope, reaches the other side considerably off the desired point, and many fruitless attempts are made before the object sought is accomplished. When the rivets, usually three in number, are closed, the larger of the two rings, which was put over the rope last, is brought down over the joint and firmly pressed into its position on the socket near its bottom end. The other ring is then served similarly. It takes up a position near the top of the joint. As the rings cool they contract and tightly grip the socket.

Fig. 68 (A) shows the capping on a rope performed in this way. The object of the rings is to prevent the socket from opening or parting from the rope. They give additional security to the rivets by resisting the force within the joint (resulting from lifting and raising the cages); and after the rope has been running some time, if the rivets give way, the rings still have considerable grip on the rope, because the bottom end of the socket is larger in diameter than the top (due to the folded and cut wires), and the strain caused by lifting the cages tends to pull the rope through, and so wedge into closer contact the rope, socket and rings.

At some collieries the practice is to put the rings on in a cold condition. Where put on hot, it often happens that the time taken to bind the copper wire and drive the needles has allowed the rings to cool. They may, however, be heated again whilst on the rope before being dropped into place on the socket.

Another method of capping a round wire rope is shown in Fig. 68 (в). A piece of round iron sufficiently long to form the socket and of slightly tapered form, has a conical opening bored through it. Near its lower extremity, which has also the larger diameter, a bolt-hole is cut, the two circular openings being opposite each other. The rope is threaded through the aperture from its upper end, the opening being just large enough to allow of this. The lower extremity is slightly larger. The wires of the rope are folded back when the rope is well through the socket, and the end, as now shaped, pulled back into the aperture. The two bindings of copper wire should be wound as in the previously described method.

The folded wires prevent the rope from being pulled farther than a point sufficiently clear of the bolt-hole. Molten lead is now poured from a ladle in through the larger diameter of the aperture, the socket being inverted for the purpose. The lead fills up all the interstices between the rope and the inner sides of the socket. It is then allowed to cool, when the lead and rope form a hard solid mass within the aperture strong enough without rivets to resist the strains put upon it afterwards. A D shaped link for the reception of the cage chains is secured by a square-headed bolt passed through the bolt-hole in the socket and kept firmly in place by a cottar, driven down vertically at the tail end of the bolt. Besides the molten lead, a plug with a thread formed on it is screwed into the socket on the under side.

A third method of capping a round pit-wire rope consists in preparing a wrought-iron socket with the loop formed at its lower extremity and welding the socket down one side, leaving the central conical opening as in the other methods. Rivet-holes are then drilled in the socket, and the manner of further procedure is much the same as in the first described method. The first given method of capping is preferable, as it allows of the rope within the socket to be partially

examined, whereas in the other methods the rope at the cap is quite hidden from view.

At some collieries it is customary to fix the cappings without the use of rivets. Where this practice is followed, three or four rings or hoops are used, according to the size of the rope, the weight to be lifted, and the length of the cap. After slipping the hoops up the rope in their proper order according to size, the rope may be prepared in one or two ways. Small wire is tightly bound round the rope

removed.

two feet from the end, the strands are untwisted and the core of the rope The wires are then bent back the opposite way to the strand, care being taken to tuck them under every other strand, and also to cut off some wires between each tuck so as to make the rope taper for receiving the cap; or it may be done after cutting away the core by bending back the whole of the wires around the rope, thinning them out to the required taper. In each case after the tucking or turning back is completed, small wire is wound round outside so as to make the rope as solid and uniformly taper as possible. The cap, having been made hot at the bow, is then laid to the rope and by means of clamps pressed down tightly to it; the hoops are then slipped down over the cap and driven home.

Caps should be made of the best selected iron, and those for round ropes be made upon a tapered mandrel, so that they may be well shaped.

In frosty weather, the first cage journey should not be started with a full load -it is much better to give the ropes one or two runs with light loads before starting full work.

The systems of capping round pit wire-ropes are adopted also on incline and engine plane ropes, except that in their cappings the rings, or hoops, which would be inconvenient, are omitted.

With flat wire ropes, the method of capping differs from any just described. Fig. 68 (c) illustrates the plan adopted. A portion of the end of the rope is doubled back over a wooden roller (protected by a thin covering of iron) through the centre of which is a bolt-hole. Above the roller, the surface of the doubled back portion of the rope is pressed firmly against the surface of one side of the rope. It is secured in this position by a series of glands placed about a foot apart. The gland consists of a three-sided strip of flat iron except at the extremities where it is rounded, and a thread cut to take a nut. Another flat plate, which is a straight plate rather longer than the width of the rope, is passed over the ends of the three-sided plate whilst the latter is in position, accurately fitting round the joined portion of rope. A nut is then run on the thread prepared at either side of the gland, and the doubled rope is tightly gripped within the two plates, as it is enclosed by their four sides.

Two discs or cheeks of thin iron, having bolt-holes cut to correspond with that in the roller, are bolted one at either side of the roller, each bolt going through the two discs and the roller. The diameter of the discs is sufficient to form flanges to the roller and keep the rope securely on it. A D shaped link is then fastened by means of a bolt to the underside of the roller and this link receives the cage chains.

In some instances, a short iron cylindrical tube is used without the interior packing of wood, round which the rope is passed, and the D link secured below by a bolt passed through the interior of the tube. No flanges are used, the ▷ link at the bottom of the rope preventing its slipping from the iron roller, which is slightly longer than the width of the rope. This is a very simple method of capping, but not quite so safe as some others.

Another method of capping flat wire ropes is by using a wooden block of a pear-shaped instead of a circular section. The thin end is placed upwards, and it is bored with a central hole. Where the rope passes round this wooden block long or short clamps are used. The clamps are shaped to suit the blocks, and are provided with bolt-holes to receive bolts and nuts above and below the wooden block for securing the rope. With a long pair of clamps. there may be one bolt below and three or four pairs above. With a short pair of clamps, one bolt is placed below and a pair above the block. Above the short clamps two or three separate pairs of short plates, rather longer than the width of the rope, are placed, each pair being provided with bolt-holes through which, by means of two bolts and nuts, they are brought to bear upon the rope between them. Before being tightened, oval-shaped pieces of wood are inserted between the two surfaces of the doubled rope at points intermediate to the pairs of plates. These bulge the rope out and form it into wedge-shaped portions which tend to keep the rope tight against the plates and so prevent it from slipping.

At some collieries, a practice, which is to be recommended, is to re-cap the ropes periodically, say every 3 months or so, whether there is any apparent necessity

or not.

When fixing a new rope it should be carefully uncoiled off a reel used for the purpose.

The following observations for users of wire-ropes, which have been issued by