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April 1, 1868.] THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 103 THE WORKING OF STEEP GRADIENTS AND SHARP CURVES ON RAILWAYS.♦ Captain Tyler said there was one interesting question to which he had only briefly alluded, and that was with regard to the engines for working both severe gradients and sharp curves, which were advocated by M. Thouvenot, in France, and Mr. Fairlie, in this country. The latter adopted the principle of attaching the boilers of two engines together, firebox to firebox, and carrying them upon two bogie frames, the wheels under these frames being respectively coupled together and worked by separate cylinders. The former, by using peculiar cranks and coupling chains, proposed to transmit the power obtained by his double engines to the wheels of the carriages. There was no doubt much in favour of Mr. Fairlie’s form of locomotive for certain purposes. Captain Tyler considered there was frequently a certain amount of extra risk in the employment of tank engines. He had always been of opinion that they were not calculated ro run safely at high speeds, especially with passenger trains, and he thought such engines might properly be superseded, at all events for passenger traffic, by engines of a construction somewhat similar to that advocated by Mr. Fairlie. At the same time, tank engines were found to be convenient for the mineral traffic of short lines, for heavy gradients, and for frequent stoppages. In working steep inclines, one tank engine was often placed in front, and another at the tail of the train ; and this was in one re spect a safe mode of working, inasmuch as if a coupling gave way there was an engine as well as a break-van behind to prevent any of the wagons from running back. He had omitted all notice of the Pneumatic system, because he did not think it applicable to the working of very steep gradients. It might perhaps be usefully employed in tunnel lines for metropolitan passenger traffic, on account of the absence of steam and smoke; and he thought it was a pity it had not been tried in practice for that pur pose. In contrast to the working by the central rail system on the Mont Ccnis, he would refer to some practical results of the working of a steep gradient on a railway which he had recently visited, viz., the Naviga tion incline of the Taff Vale Railway, near the Aberdare Junction, 16 miles from Cardiff. He was accompanied by the Engineer of the line, Mr. George Fisher, who had furnished him with the following par ticulars of the incline, and of the engines with which it was worked. The gradients were, in ascending, successively, 1 in 28, 1 in 21’80, 1 in 20’74, for shorter distances, and then 1 in 67’80 for 420 yards. The average of the whole was about 1 in 20 for half a mile. The system of traction by rope, on which this portion of line was formerly worked, was abandoned two years ago, and since that time locomotives had been employed. The expense for six months was £900 with the locomotives against £700 with the rope and stationary engine. The tank engines, specially employed for working the traffic up this incline, ■weighed in working order 36 tons. They had six wheels, all coupled, 4 feet in diameter. The diameter of the cylinder was 16 inches, with a stroke of 24 inches. The pressure of steam in the boiler was 130 lbs. The maximum load was 45 tons, and the regulated load 25 tons : the former giving one-eighth and the latter one-tenth as the coefficient of adhesion. It was interesting to compare these results with the working of the engines on the central rail system. On the Navigation incline, the engine weighed 36 tons, taking a regulated load of 25 tons up an incline of 1 in 20; whereas, on the central rail system, an engine weighing only 20 tons could take a load of 40 tons up an incline of 1 in 12. In fact, the programme of working the Mont Cenis Railway provided for an average gross load, exclusive of the engines, of 40 tons for goods trains, and 25 tons for passenger trains; and the cost of locomotive power was found to be nearly a penny per ton per mile, for goods, in cluding fuel, grease, wages and maintenance. Similarly, for passenger traffic, the cost for locomotive power for one journey from St. Michel to Susa was estimated at 96 francs, which gave a little more than a farthing (1’2 farthing) per mile for each passenger. Mr. Fell said he was glad to have the opportunity of describing some details of the engine, and the improvements to which Captain Tyler had referred. When this project of crossing Mont Cenis by a railway was first laid before the Italian Government, it was proposed to divide the line into two distinct sections, one section being from St. Michel to Lanslebourg, and the other from Lanslebourg to Susa. It was proposed to work the first portion of the line by an engine with three or four cylinders, one pair driving the four outside wheels, and the other pair, or one cylinder, driving the four horizontal wheels, so that the relations of the interior and exterior wheels might be distinct. By that means wheels of comparatively large diameter could be used for the ordinary driving wheels, and small and more powerful ones for the climbing wheels. With the same speed of piston a higher velocity could then be obtained, and time saved in the journey, or more time could be allowed for ascending the heaviest gradients. It would be seen that, with an engine of so novel a kind, the best form adapted for such a line as this could only be determined after a long series of ex- * See page 13, ante. periments. There were many requirements which could only be ascer tained by actual trial. The Directors of the railway had determined to adopt one type of engine only for working both sections of the line, and the second engine having only one pair of cylinders, had consequently been modified with that view. Originally there was no connection between the two pairs of wheels working on opposite sides of the centre rail. Some method of connecting the two was, however, found to be necessary; and on the experimental engine this was produced by the introduction of a series of toothed wheels. The adhesion on the centre rail gave continuity of movement, and when one crank was at mid stroke it helped the other over the dead point. When running off the centre rail this was not the case, on account of the play between the toothed wheels; consequently the crank on the midstroke passed that point more rapidly than the one on the dead point, thereby producing a shock upon the engine. This shock would not take place if the inside wheels were driven by an independent pair of cylinders; but the pistons, being tied together where only one pair of cylinders was used by the outside gearing, moved in a way which produced that injurious effect. It thus became necessary to substitute some other system in place of the toothed wheels, which were weak and liable to rupture. Various plans had been proposed, out of which two were selected by Mr. Brunlees for experiment. One was the system of levers, jointed to the outside frames of the engine, connected in the centre by a side block and with two offset cranks by connectihg rods. The offset cranks were respectively placed at an angle of 45° with the driving cranks, which gave a leverage of GS inches, as compared with 8 inches the leverage at midstroke or 90°, which was enough to carry the cranks over the dead points. The relative position of the four cranks being such, that when one driving crank was at midstroke, and the other on the dead point, the off set cranks were each at an angle of 45° with the driving cranks, and acting with the above-named leverage of 6 J inches. This arrangement had been tried on the Mont Cenis, and had proved successful in carry ing the cranks over the dead points without the shock, and without the danger of fracture, which was unavoidable in the case of the toothed wheels; and it was therefore the plan of engine now adopted for the Mont Cenis Railway. Trials had been made of another plan, which had been devised for the same object, but which had the disadvantage of increased weight. The adaptation of the levers added only about 6 cwt. to the weight of the engine, while the other plan, which consisted of a combination of toothed wheels, combined with frictional gearing, added 9 cwt. to its weight, having besides the disadvantage of greater risk of fracture. Some other alterations had also been made. The rocking shafts were originally placed in front of the cylinders, in which position they worked very well, but to examine the cylindersand take oft' the covers, it was necessary to take down the slide bars; it had therefore been decided to move the rocking shafts to a position behind the cylinders. At present they were hung immediately under the boiler. There was another point of importance, viz., the general insecurity and instability of tank engines at high speed, which had been alluded to by Captain Tyler. It was necessary to consider this point, particu larly in an engine with an overhang which exceeded the length of the wheel base. 'I here appeared to be a risk attending such an arrange ment, and the question having been considered, it had been decided to adopt a third pair of wheels with a lateral movement, by which it was believed sufficient stability would be obtained to make the engine per fectly safe, but with the disadvantage that 12 cwt. would be added to the weight of the engine, and 2 tons of the adhesion obtained from its weight would be sacrificed. Another point of great importance was the action of the breaks in descending the inclines. As had been stated, a great amount of break power was necessary for these trains, and this could be obtained by the centre rail system, which might in fact be considered almost unlimited. It had been decided to have centre rail breaks as well as the ordinary breaks, attached not only to the engine, but to each carriage and each wagon of the train ; and probably the action of the combined breaks on a single carriage would be sufficient, or could be made so, to stop the whole train on any incline on the line. Then came the question of wear and tear upon the rails. The breaks now proposed were sledge breaks, forced on to the rails by a transverse screw or lever, which would produce a certain amount of wear. Another plan was under consideration for applying the breaks to the horizontal wheels, by which method it was believed the wear upon the centre rail would not be greater than upon the bearing rails. With regard to the compara tive economy of the two systems of working inclines, some persons were under the impression that the cost of traction by the centre rail system, when a given summit had to be attained, was greater than under the ordinary system, but it was not so. Supposing an elevation of 2,000 feet had to be attained, it could be shown that in the case of a gradient of 1 in 30, without the centre rail, and in another case, with a gradient of 1 in 12 with the centre rail, the locomotive power, though con siderably greater in the latter, being required for a proportionally diminished distance, the expense of working would not be increased, and time would be saved in the journey. There were two modes of dispensing with the centre rail at level crossings: one in which it disappeared altogether; the other a simple