Guides. — In its passage up and down the shaft the cage runs in guides, which are fixed in the shaft from top to bottom. These guides may be of (1) Wood, (2) Channel or other shaped steel section, (3) Wire ropes.

Wood guides are usually made of pitch pine, 4 inches by 4½ inches in section, and of length varying from 24 to 36 feet. With large cages and heavy loads, the section of the guides may be increased to 5 inches by 7 inches. Wood guides are largely used in fitting rectangular shafts, but they also make capital guides for a circular shaft if wood buntons are provided for their support. It is desirable to have these guides in as long lengths as possible so as to reduce the number of joints. The joints are always the weakest part, and they should be made so as to lose as little of the total strength of the section as possible. Various forms of joints are used, one of the best being the butt joint, which is shown in Fig. 98.

Steel guides are now extensively used, although they do not give as smooth running as wood guides. They are best formed from a good stiff section, and they must be carefully fitted and their joints properly aligned. Various shaped sections arc used, but a rail section with a round top and a flat bottom is common. The weight may be 40 to 50 lbs. per yard for light work, but for large cages and heavy loads sections weighing 80 to 90 lbs. per yard are commonly used. These guides are supported from iron girders built into the walling of the shaft. The method of fixing the guides to these cross girders or buntons is shown in Fig. 99.

Rope guides are widely used in circular shafts. They require no buntons, being suspended from the headgear, and kept tight by weights fixed at their lower end. The wire ropes used for cage guides differ from winding or haulage ropes by having heavy steel wire rods twisted together in place of the lighter wires used in the manufacture of an ordinary rope. A steel guide rope and a section showing its construction is illustrated in Fig. 100, and the method of fixing them to the headgear in Fig. 101.

The speed at which the cages are raised or lowered in the shaft depends on the depth of the shaft and the power of the winding apparatus. A maximum speed of 60 feet per second is rarely exceeded, and the average speed varies from 20 feet per second in shallow shafts to 45 or 50 feet per second in deep shafts. To attain these speeds with safety all the shaft fittings must be regularly examined and maintained in perfect order.

Headgear. — The headgear is the erection at the top of the shaft to support the wheels over which the winding ropes run. It consists of a frame, usually of steel, supporting two large pulleys placed above the centre of the shaft. The frame is generally formed of six principal members:

Two uprights placed close to the shaft on the side nearest the winding engine — these two uprights carry the greatest part of the weight; two uprights on the opposite side of the shaft and connected to the pair already mentioned by cross-beams, to which the guides are fixed and in which the detaching ring of the safety hook is fixed; two back stays, inclined at an angle to resist the pull of the winding ropes as they pass from the headgear pulleys to the winding drums. These principal members are braced together by light ties so as to give stability to the whole structure. The height must be such as will allow for banking about 20 feet above ground level, and provide the necessary clearance between the cage and the pulleys. This clearance varies with the type of cage and position of the detaching hook, but is usually such as to give a total height of 55 to 65 feet to the headgear. A modern headgear is shown in Fig. 102.

Winding Engines. — As a rule horizontal engines having two cylinders coupled at an angle of 90 degrees to the drum shaft are best for winding. Such engines are usually fitted with some form of link motion which operates an ordinary slide valve in the case of the smaller engines. Large engines are usually fitted with cornish valves or valves of the corliss type. Of late quite a large number of compound winding engines have been adopted and are working quite satisfactorily and giving economical results. A pair of coupled horizontal winding engines, made by Messrs. Barclay, Kilmarnock, are shown in Fig. 103.

In winding, the common practice is to attach two ropes to the same drum, and place them so that while one is being wound on the other is being run off. This arrangement requires two winding spaces in the shaft, a loaded cage ascending in one, while another similar cage containing empties is descending in the other. On the arrival of the loaded cage at the top, the tubs containing the coal are removed and replaced by empties, while simultaneously the empty tubs are removed from the cage at the pit bottom and replaced by loaded ones. When starting from the pit-bottom, unless some system of balancing be adopted, the load on the engine is greater by the weight of the rope than it is at the middle of the wind. When the wind is completed the load upon the engine has diminished by twice the weight of the rope. This is caused by the whole of the upcoming rope being wound on to the drum and its weight eliminated, while at the same time the downgoing rope has been reeled off and its weight transferred to the other side, thus producing the difference mentioned.

In a deep mine where a heavy rope is used, the weight of the rope may be greater than that of the coal raised. In such cases the weight of the descending rope tends to drag on the engine at the end of the run, and necessitates the use of the brake, or live steam to bring the cages to rest at the proper place. This condition of matters does not tend to rapid or economical winding, and to overcome the difficulty several systems of balancing the weight of the rope have been introduced. These are: (1) Pirns and fiat ropes, (2) Spiral drums, (3) Balance chains, (4) Tail rope, (5) Methods which get over the difficulty without actually balancing the weight of the rope, e.g., (a) Pneumatic Winding, and (b) Electric Winding on some regenerative system.

Pirns and Flat Ropes. — In this system a narrow drum or pirn the width of the rope to be used is provided. The rope is kept in position by radial arms fixed to the drum and caused to wind upon itself, hence the effective diameter of the drum is increased by twice the thickness of the rope at each revolution. This gives a gradually increasing moment for the load side, and a gradually decreasing one. for the empty side, and by suitably selecting the diameter of the drum and the thickness of the rope it becomes possible to obtain a perfectly uniform load on the engine throughout the wind. So far as the question of balance is concerned the method can be made quite satisfactory, but owing to the necessity of having to use a flat rope it is seldom adopted. The reason for not using this system more extensively, is the high cost and short useful life of fiat wire ropes.

Spiral Drums. — These drums are of conical shape and are fitted with a spiral groove into which the winding rope passes. (See Fig. 104.) At the beginning of the wind, when the loaded cage is at the pit-bottom, the rope is resting on the small diameter of the drum. As the wind takes place the rope gradually travels up the spiral groove until finally, at the completion of the wind, it is resting on the large diameter. By suitably proportioning the drum, the moment of the load at every part of the wind may be made approximately the same, thus providing a balanced system. Spiral drums are largely used for winding from deep shafts, their only drawback being their weight, which causes loss of both speed and energy at starting and stopping.

Balance Chain. — This method of counterbalancing the weight of the winding rope is occasionally applied under suitable circumstances, but under ordinary conditions the cost is too high. It requires an auxiliary shaft, and it is only in certain cases where such auxiliary shafts have been sunk for the purpose of pumping water while the main shafts were being sunk and tubbed through waterbearing beds, that it can be profitably applied.

Tail Rope System. — This method of balancing is used in conjunction with plain cylindrical drums, and consists of attaching a rope of the same weight as the winding rope to the bottom of each cage. This rope may pass round a pulley at the pit-bottom, but it is better to provide an extra fathom or so depth of shaft and simply allow the weight of the rope to form a loop in this part while running. If this be done, a space wide enough for the rope is boarded in so that the loop is prevented from kinking. The general arrangement of this system is shown diagrammatically in Fig. 105.

Tail Rope, Koepe's System. — This is practically an endless rope system where a single-grooved pulley is substituted for the heavy winding drum. The rope is carried from the driving pulley to the cage at the top, from that cage down the shaft, round a wheel in the pit-bottom, and is fixed to the cage there. It then passes up the shaft and on to the driving pulley whence it started. The Koepe system, although extensively employed on the Continent, has not found favour in this country. Owing to the rope having only half a turn resting in the throat of the driving pulleys the system cannot be employed with keps, as the rope tends to slip when relieved of the weight of the cage. This slipping on the pulley disturbs the indicator and would also disturb the setting of the controller, which must now be fitted to winding engines to comply with the law. A diagram of the Koepe system is given in Fig. 106.

Whiting System. — When mineral has to be raised from great depths the problem of winding becomes more intricate. Flat ropes, as already stated, are not successful, largely on the score of cost. A round rope requires a large drum, since it is not good practice to coil the rope upon it in more than one layer. These objections are both overcome in a system devised by Mr. S. B. Whiting, which closely resembles the method used in cable tramways. In this system the rope passes several times round two drums, which, as a rule, are both driving drums. One end of the rope is fixed to the cage, while the other end passes round an idle pulley located on a carriage, and from thence to the other shaft compartment. The lack of balance in the system itself makes the use of a tail rope imperative.

Other Systems. — Both pneumatic and electrical system of winding have been devised, and while not giving a balanced wind they get over the difficulties due to lack of balance by other means. They are, however, too complicated for description in an elementary book.

Controllers. — In addition to the safety hooks already described, it is necessary, to comply with the Mines Act, to provide an effective automatic contrivance which will prevent overwinding should the depth of the shaft exceed 100 yards. Various forms of these contrivances, which now go under the name of controllers, are in use. They are arranged to come into operation should the person in charge of the engine fail to shut off steam when nearing the end of the wind; should he raise the cage at too high speed; should he draw the cage beyond the stopping place even at a low speed; should he start away in the wrong direction. In each case the automatic gear shuts off the steam and applies a powerful brake, thus bringing the engine to rest before damage is done.

Visual Indicators. — To comply with the general regulations some form of indicator that will record the signals given to the winding engineman must be fitted to his engine. A difference of opinion as to what is really required here has arisen, and it is questionable if any of the appliances so used comply fully with the stated requirements. Whether or not some form of sight indicator must be provided, and perhaps the best way to deal with the matter is to adopt a type which will satisfy the Mines Inspector, who after all is the person who must either accept or condemn.