of the tramroads is usually from 18 to 30 inches. In a few collieries the gauge is 3 feet. Small trams are much more easily moved about than the heavier ones, and this allows of sheet iron being laid at the junctions of roads in the workings, whereas for the heavier trams there must be turn-tables or else no break in the continuity of the rails. Small trams may be taken from the end of engine-planes or horseroads to the working faces by putters without horses if the gradients of the roads are suitable. Large trams usually have to be taken to the face by horses, and the hauliers are men. Boy drivers are often employed where the trams are light, as they are able to lift the empties on the rails when necessary. The large trams used in South Wales are adopted to meet the circumstances prevailing, and tend to economy in the haulage. The reduction of the length of the working day by legislation or otherwise tends to the use of larger trams. If a large quantity must be raised in a short time in deep shafts requiring great ventilating capacity, both necessities are most simply met by the use of large shafts and large trams. The deeper the shaft and the shorter the day for winding, the greater is the need for large trams for a given output. There are, however, limits to the size of tram which can be used, owing to the difficulty of maintaining underground roads beyond a certain width, and this difficulty increases with the depth and the inclination of the seams. The larger the tram in use the greater is the necessity Fig. 279.-DOG SPIKES HOLDING Fig. 280.-NOTCHED RAIL FOR Fig. 281.-LIVESEY'S for the underground tramroads to be carefully and skilfully laid, approximating, as far as circumstances will allow, to the construction of a surface railway. If the crush is great, the displacement of timbers and rails is increased in proportion to the width of the road. Usually, seams in which roads may be made a width to take a double line of rails have only a slight inclination, and are worked by means of comparatively shallow shafts. A serious drawback to the use of large trams is the greater liability to accidents as compared with that of small ones. If the surface tramway is to be worked by an ordinary light locomotive, or the underground by an electrical or a compressed air locomotive, the gauge of the way should not be less than 2 feet; if by a stationary engine the gauge should not be less than 18 inches. Any gauge above 3 feet is really a railway and beyond what is ever required in the mine. The double-headed rail is not much used in mines because it cannot be kept securely in place without the use of chairs and fish-plates. There is the same objection to the introduction underground of the bull-headed type. The flat-bottomed rail is the one most frequently used on engine-planes and the chief horse-roads underground. It is secured to wooden sleepers placed from 2 to 3 feet apart by dog spikes, or to steel sleepers by wooden keys, bolts or clips. The spikes are not driven vertically into the sleeper but slightly slanting, one on each side of the rail, as shown at A A in Fig. 279, so that their heads may have proper contact with the sloping surface at the base of the rail. The spikes are sometimes made with a projection at the back, or with ears at the side, to facilitate their withdrawal. When driven as described they do not prevent the rail from moving in the direction of its length, to avoid which the rail is sometimes notched as shown in Fig. 280. The spikes are driven at the notches and prevent the rail from moving in the same way as nails driven through nail-holes in the flanges of bridge-rails do. The weight of the rails used will vary according to the capacity of the tubs, and also with the distance the sleepers are placed apart. If the floor is soft and springy in any section of the road, the sleepers are placed closer together, and in extremely bad cases it may be necessary to lay longitudinal timbers under the transverse sleepers to distribute the weight. The rails laid on these main roads are usually in 4-yard, 5-yard, or 6-yard lengths, longer rails being inconvenient to handle in the roadways. Fish-plates should be used with flat-bottomed rails for permanent work. In countries where wood is abundant, it makes the most economical sleeper, but steel sleepers seem to be coming more and more into use owing to their Fig. 282.-FAST AND LOOSE CLIPS MADE At Tredegar. greater durability and reduced cost of maintenance. Different forms of metallic sleepers have been used in making surface railways in other countries, and to a limited extent in this. Their use is sure to increase as the forest supplies dwindle, and increased attention has of late years been given to their design. The flat-bottomed rail is usually secured to steel sleepers by some form of clip, and the joints of the rails for permanent roads are usually fished. Fig. 281 shows Livesey's patent clips, from which it will be seen that there are two clips, the larger one of which is corrugated on the inside to correspond with the corrugations on the loose key. Both clips are riveted to the sleeper at the steel-works, so that there is very little fitting of parts on the railway. The rail is simply canted in or out of place at the fixed clips, after which the key is driven to secure the rail. The corrugations prevent its working loose, but in order to give it greater holding power it is sometimes made longer, with the end turned downward so as to fill the space between the rail and the clip. Fig. 282 is an illustration of fast and loose clips for a light steel sleeper, which has been largely made at Tredegar for gauges from 2 feet and upwards. The outside clip is riveted on at the works so that the gauge is always maintained by this, the loose clip on the other side being secured by a bolt. Some clips are independent of bolts and rivets, and where they do not introduce a number of loose parts have much to recommend them. Colquhoun's clips, Fig. 283, are made on this principle. When the clip is passed through the two holes in one side of the sleeper and brought into its proper position with the inner end of the clasp gripping the base of the rail, a wooden key is driven; the rail, sleeper and clip are thus all fastened firmly together. It has been extensively used on engine-planes at collieries. In Wood's clips the sleeper and rail are gripped together without the use of Fig. 283.-COLQUHOUN'S CLIPS. bolts or rivets. They are formed in one piece, and are so shaped that the driving of an ordinary wooden key is made the means of security. In Raffarel's patent sleeper there are two cast-iron or steel brackets, and the Fig. 284.-Metallic SleepERS FOR AN UNDERGROUND ROADWAY. driving of a single key ingeniously fastens together the rail, sleeper, and brackets. The brackets are in contact with the rail at the flange and under the head. This sleeper for a 2' 9" gauge weighs 16 lbs. or, inclusive of fastenings, 22 lbs. A sleeper which has been much used in the South Wales collieries is shown in Fig. 284. There are no loose parts, but a clip is formed at one end of each sleeper. The position of the clips is different on adjacent sleepers, but the same on alternate ones. The sleepers formed with inside clips are first laid obliquely across the road in the position of the dotted lines in the illustration, and when turned until they are at right angles with the rails they form locking sleepers, and together with the sleepers having outside clips, hold the rail securely in place. A sleeper with the chairs or gripping jaws formed out of its own material, and without loose pieces of attachment, is the simplest and most economical. Fig. 285 shows a steel sleeper of this kind which has been used in the collieries of South Wales. The rail may be canted into place between the rigid upturned metal, after which the wooden key is driven to hold it firmly in place. This sleeper allows of great rapidity in laying a tramway. The drawback to the use of steel sleepers having smooth surfaces for horse-roads is the increased liability to horses slipping on them, but a better foot-hold for the horses is obtained if a corrugated form of sleeper is used. Fig. 285.-STEEL SLEEPER WITH Messrs. J. & F. Howard, of Bedford, who are makers of portable railway plant for mining and other purposes, have adopted the form of sleeper shown in Figs. 286 and 287. The sleeper is made of plate steel corrugated and flanged in order to give the greatest strength with the least weight of material. In constructing the sleeper the chairs for the rails are formed by pressure on the crown HOWARD Fig. 286.-STEel Sleeper, KEY AND RAIL. of the sleeper, none of the metal being removed or cut away, but, on the contrary, the parts of the chairs upon which the rails are intended to rest are increased in thickness and durability. The chairs are formed on the sleepers by special hydraulic machinery with a precision of position in all sleepers that ensures accuracy of gauge being afterwards obtained. The rails rest upon the whole width of the sleeper, thus having a great bearing surface. No bolts, dogs, rivets, or fish-plates are required, the only fastening being the simple metal key shown in the drawing, and this is serrated on one side to fit into the cheeks of the chair when driven home. For underground work a modified form of sleeper can be used, threaded on to the rails, and the use of keys is thus dispensed with. The method of laying the line is shown in Fig. 287. The jointing sleepers are formed in the same manner as the single sleepers, except that two corrugations are rolled on one plate; the chairs or rail seats are pressed out of each corrugation in such a manner that the rail ends abut and are held in each seating respectively by its own serrated key. The keys are so arranged that either of them may be taken out without disturbing the others. This method of securing and joining the lengths of rails enables the laying down, and also the taking up, of the road for removal and re-layal to be effected with the greatest ease and expedition. The corrugated form of sleeper allows the ballast to settle down very firmly under it, and the rail seats being below the crown of the sleeper, prevent any Fig. 287.-PORTABLE RAILWAY, SHOWING JOINTING SLEEPERS. HOWARD Fig. 288.-THREE-WAY POINTS. tendency for it to shift sideways on curves. For lines worked by horses this is the strongest form of sleeper, as the corrugation prevents any bending likely to be caused by the constant treading of the animals employed, and also gives a good foothold, thus preventing the slipping which so frequently occurs on flat-crowned sleepers. The advantages of a portable line of rails of this form may be summed up as follows: Simplicity, strength, and durability. |