gradient of 1 in 15 for 2½ miles, and a total rise of 869 feet, opened about 1879, having a gauge, like the rest of the railway, of 3 feet 6 inches, and curves of 5 chains radius, was laid with a central rail, and the traffic on the incline has been worked continuously by a locomotive with horizontal wheels gripping the central rail. Each engine, weighing about 30 tons, can draw a maximum train load of 70 tons up the incline; and in order to avoid an undue strain on the draw-bars, the three engines employed for taking up a heavy train are so distributed between the carriages as to enable each to draw its own load. The system has proved safe and satisfactory, and well adapted for running around sharp curves; while the saving in cost of construction by adopting the incline on this particular railway, instead of a more circuitous course, to obtain flatter gradients, readily surmounted by ordinary locomotives, was estimated at £100,000.
A solid central rack was introduced for the first time in 1847 on an incline of the Madison and Indianapolis Railway near Madison, Ind. It was 1⅓ miles long, with gradients of 1 in 16½ to 1 in 17. The rack railway, however, which was the precursor of the numerous Swiss mountain railways for tourists, was the line, three miles in length, constructed up to the top of Mount Washington in New Hampshire in 1866-69, rising altogether to a height of 3000 feet, with ruling gradient of 1 in 3. The rack in this case was formed in lengths of 10 feet, with two parallel angle-irons, 4 inches apart, connected by a series of round wrought-iron bars constituting the teeth of the rack, which resembles a ladder laid on the ground. The locomotives, provided with a central cog-wheel working in the ladder-rack, push the vehicles up the mountain at a rate of about three miles an hour. The first rack railway carried out in Europe up a mountain slope was the Vitznau-Rigi Railway, constructed from Vitznau, on the Lake of Lucerne, to the summit of the Rigi in 1869-73, rising 4472 feet in its course of 4⅓ miles, with a ruling gradient of 1 in 4 for about a third of its length, and never less than 1 in 6, except at the stations. The locomotive on these mountain lines is always placed below the carriages, so as to push them up the inclines and control their descent, the speed of the trains on the Rigi line being limited to between three and four miles an hour.
The driving cog-wheel and the other cog-wheels fitted to the locomotive and carriages are furnished with powerful brakes, which, when applied, keep the cogs firmly engaged in the rack, so as to arrest the descent of the train; and an air brake acting on the piston of the locomotive serves to regulate the downward speed. Strong hooks attached under the locomotive and carriages encircle the top flange of each side-piece of the rack, and thus secure the train from leaving the rails or being blown over by the wind.
A steel rack rail with teeth on each side, in which horizontal cog-wheels work, was adopted for surmounting the exceptionally steep inclines of the Pilatus Railway, averaging 1 in 2.8, and attaining 1 in 2.08 in some places, preliminary trials having proved that the ladder-rack was unsuitable for such gradients. This railway opened in 1889, starts from Alpnach on the Lake of Lucerne, and rises 5363 feet in its length of 2¾ miles. The driving cog-wheels are actuated by spur gearing, and the two pairs of cog-wheels are controlled by hand brakes, which suffice to regulate the descent of the train or to stop it if necessary. An air brake acting on the pistons of the locomotive furnishes additional control of the train on its descending journey; and if at any time the speed in descending becomes more than three miles an hour, a reserve automatic brake comes into action.
Another form of rack consists in cutting the edge of a flat steel bar, so as to provide a uniform row of teeth on its upper side, and the strength of the rack can be increased for steeper gradients by increasing the thickness or the number of the bars. The rack is thus formed by a series of solid bars, with teeth shaped to the most convenient form for the working of the cog-wheel in them. This simple form of rack, consisting of successive lengths of single bars joined at their ends and laid in the centre of the track, has been employed on the flatter gradients of several rack railways, where the Abt system of two or more such bars, laid so that their teeth are not in line across the track, is resorted to on the steeper parts of the lines.
The Sant' Ellero-Saltino Railway, the first purely rack railway built in Italy, was constructed in 1892. This railway rises 2765 feet in a length of five miles, and it is laid to meter gauge, with a ruling gradient of 1 to 4.55. The rack on gradients not exceeding 1 in 8⅓, consists of two steel angle bars riveted together, 4 to 6 feet long, with teeth formed in them; but for steeper gradients up to the maximum of 1 in 4.55, two flat steel bars are introduced between the angle bars, increasing the thickness of the teeth and the rigidity of the rack, which latter can be still further augmented by introducing a distance piece between the angle bars, so as to form two or three parallel racks with a small interval lictween them, in which the cog-wheel works with a widened bearing. This Telfener rack is simpler in construction and cheaper than the Riggenbach and Abt racks; but it does not possess the special advantage of the Abt rack, of thoroughly engaging two or three successive teeth of the cog-wheel at the same time. The speed of the trains ranges from 5½ to 4⅓ miles an hour, according to the gradients, and averages 5 miles an hour.
TRACK CONSTRUCTION OF STRUB RACK RAILWAY.
A more complicated form of single rack, resembling a flat-bottomed rail in its low portion, and widened out considerably for the teeth at the top, called the Strub system, after its designer, has been recently introduced on the Jungfrau Railway, which is laid to the meter gauge, and was opened in 1899, the motive power being electricity generated by waterfalls on the mountain. This line rises 6657 feet in a length
