The driving cog-wheel and the other cog-wheels fitted to the locomotive and carriages are fur nished with powerful brakes, which, when ap plied, 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 car riages encircle the top flange of each side-piece of the rack, and thus secure the train from leav ing 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 2% 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 auto matic brake comes into action.
Another form of rack consists in cutting the edge of a flat steel bar, so as to provide a uni form 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. con sisting 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 Alit 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 con structed in 1892. This railway rises 2765 feet in a length of rive miles, and it is laid to meter gauge, with a ruling gradient of 1 to 4.55. The rack on gradients not exceeding I in con sists 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 intro ducing a distance piece between the angle bars, so as to form two or three parallel racks with a small interval between 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 cogwheel at the same time. The speed of the trains ranges from
to miles an hour, according to the gradients, and averages 5 miles an hour.
A more complicated form of single rack, re sembling a flat-bottomed rail in its low portion, and widened out considerably for the teeth at the top, called the Strub system. after its de signer. 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 of 7 3-5 miles, with gradients ranging from 1 in up to 1 in 5: and the upper 6 1-5 miles are to be in tunnel, while the final ascent to the sum mit is to be effected by a vertical lift. of 241 feet. The central rack rails, 111. feet long, are joined together at their ends by fish-plates, like ordi nary flat-bottomed rails. A brake is provided, which encircles and grips the widened-out head of the rack.
The Abt system consists essentially of two or three steel rack bars, from 11-16 inch to 1 13-16 inches thick. and 2 to inches deep, placed nearly two inches apart, and so arranged that the teeth are not opposite each other. but as it were break joints, causing the cog-wheels to en gage in a tooth in front on one rack before leav ing the tooth behind on the adjacent rack, which renders the motion smoother, and increases the security of the trains in descending, besides pro portioning the strength of the rack to the steep ness of the gradient by the addition of one or two bars. The Gcneroso railway in Italy and the Rothorn railway in Switzerland, 5 2-3 miles and 4 4-5 miles long, rising 4326 feet and 5515 feet, with ruling gradients of 1 in 4.55 and 1 in 5, and constructed in 1889-90 and 1891, respectively, are laid to a gauge of 2 feet inches with cast steel sleepers. and provided with a double Abt rack, in which cog-wheels on the driving axles work. The system has also been extended to mountain lines in several other countries. as. for instance, the Manitou and Pike's Peak Railway in Colorado. of standard gauge. rising, 7532 feet in a length of miles, with a maximum gra dient of 1 in 4.
Instances of the application of electricity as the motive power on mountain railways laid with the Abt rack, where water-power is readily available for generating the electrical current, are furnished by the Mont Saleve Railway near Geneva, and the Goruergrat Railway ascending from Zermatt. These railways, constructed in 1891 and 1S96-9S, respectively, have lengths of 5 3-5 miles and 5 4-5 miles, with rises of 2363 feet and 4600 feet, and are laid to the meter gauge. with gradients of 1 in 4 and 1 in 5. and a double line of rack. In all these rack railways. special care is always taken to anchor the track firmly down into the solid ground. so as to pre vent its creeping gradually downhill under the pressure of the cog-wheels on the rack.