Among the various means proposed of late years for building lines of
railroad on the steep slopes of mountains, that of M. Wetli, of
Zurich, Switzerland, has attracted considerable attention from
European engineers. We have already laid before our readers the system
of central toothed rails used on the Righi and other mountain roads in
Europe. In the Wetli system, instead of this rail and the pinion on
the vehicle engaging it, there is a drum having a helicoidal thread
which engages with triangular rails. This drum is attached to the
locomotive. The construction will be readily understood from the
illustrations given herewith, which we take from _La Nature_. The
thread on the drum is precisely that which would be formed could a
rail similar to one of the central angular rails be wrapped around it;
so that it always is in contact with the mid rails, and necessarily
prevents any bodily sliding or rolling of the vehicles over the
regular track when the drum is held motionless. The V-shaped mid rails
are securely fastened to horizontal iron ties, which rest on wooden
traverses. The angle of the V is 50°; the distance between any two
traverses is 2.8 feet.
[Illustration: Fig. 1.--THE WETLI MOUNTAIN RAILROAD.]
The locomotive has three coupled axles, on the mid one of which the
drum is attached so as to be raised or lowered to engage the rails at
the will of the engineer: it being possible to cause it to act on the
rails with a pressure of 3.7 tons. The diameter of the drum is 2.14
feet. Its spiral thread is of steel, very solidly attached, and so
made as to grip the rails to a distance of 0.6 inch below the level of
the track. In order to insure this contact, on the drum axle are two
pulleys which run on the exterior road, and of which the diameter
determines the depth of the hold of the threads. These pulleys are
34.7 inches in diameter, while the driving wheels are very slightly in
excess, to provide for the use of tyres.
M. Wetli's invention, as we have described it, was placed between
Woedensweil and Einsiedlen, Switzerland. The difference in altitude
between these points is 1,513 feet, the distance 9.6 miles. The grade
is from 4 to 5 per cent over the first six miles of the way, and
subsequently decreases to 1 per cent. The Wetli railroad was
established last October only on the heavy grade, that is, the first
six miles.
[Illustration: Fig. 2.]
Early in November, trial trips were made which did not prove
satisfactory. Sometimes the drum thread gripped the triangular rails
properly and acted well; again it would wedge itself upon them, and
often would simply roll over their tops without engaging at all. After
the first trials, during which very many of the rails were broken, M.
Welti re-adjusted the drum thread. Finally, he concluded that he had
overcome all difficulties in his apparatus; and accordingly a formal
trial was arranged on November 30. For about four and a half miles of
the ascent the drum worked well; and the hoarfrost, with which the
rails were thickly covered, showed good contact. Afterward it worked
irregularly; but the station of Schindelleghi, a distance of five
miles, was reached without accident, the locomotive dragging a car
loaded with 20 tons of rails. It was then attempted to make the
descent by the aid of the helicoidal drum; but this jumped the rails,
and broke them almost immediately. By the aid of back pressure of
steam and brakes, the locomotive was stopped. Then, unfortunately, the
engine was started again; but hardly had the descent been resumed when
it was evident that the drum was not holding, and that the speed was
accelerating rapidly. Brakes and steam were both found useless, and
the engine went tearing over the rails at the rate of a mile a minute.
Of the fourteen persons in the vehicles, three were thrown out and
killed, and the rest were more or less seriously injured. The heavily
loaded car left the track, and tore up both central and side rails
until its coupling broke. The engineer, with great intrepidity, clung
to his engine, coolly giving signals to open switches so that the
locomotive might run upon the level track and so expend its momentum;
but the engine left the rails at a sharp curve, destroyed the track
for about a hundred feet, and finally stopped a mass of ruins, with
its brave engineer mortally wounded. Whether the Wetli system can be
made to work as intended by the inventor is regarded as doubtful by
the engineers who have examined into the causes of the disaster.
* * * * *