Wetli roller wheel system
The Wetli roller wheel system was an alternative to cog railways developed by the Zurich canton engineer and railway pioneer Kaspar Wetli . It was tested in the 1870s on the Wädenswil-Einsiedeln railway in Switzerland, which was under construction . After a serious accident during the test drive on November 30, 1876, no one was willing to use the system.
history
In 1868 Kaspar Wetli had developed the Wetli roller wheel system under the title Basic Features of a New Locomotive System for Mountain Railways. It is a roller wheel system that works similarly to a gear system and is characterized by the arrow-shaped rail sections between the guide rails. The roller engages in these arrow-shaped pieces of rail. He had submitted this system to the Zurich Polytechnic for assessment, which, however, saw no particular or major advantages for a mountain railway.
This system was intended to provide a higher tractive effort uphill. For this reason, it should be used on the Wädenswil-Einsiedeln-Bahn (WE), because the route was laid out with five percent, which at the time was almost unsuitable for pure adhesion operation for a full line. When going downhill, the roller should not intervene and the train should be braked with the normal block brake. The test locomotive with a roller for the Wetli system was delivered by the Winterthur locomotive factory in 1874 . It had to be rebuilt several times and never really convinced, especially because of the excessive pressure drop in the roller system. The test drives were therefore limited to a little bit above Wädenswil; the locomotive was sold and scrapped in 1880. Nevertheless, based on the experience gained, the system could be regarded as functional.
However, the delays in the construction of the railway did not allow test runs to be started along the entire route until late autumn 1876. Based on the experience gained with the test locomotive, the NOB ordered three steam locomotives of type Ed 2/2 with a drive roller for the Wetli system from the Esslingen machine factory .
Misfortune and the abandonment of the Wetli system
On November 30, 1876, the main rehearsal of the Wetli system was announced. The ascent with the 253 locomotive and an attached, two-axle wagon loaded with rails was promising. On the way back from Schindellegi there were problems with the roller and they were picked up because it was not absolutely necessary to operate it on the descent. On the further descent to Wädenswil, however, the train could not be braked with the locomotive or wagon brakes or with counter steam. The accident was foreseeable for the passengers, in addition to the engine driver and two stokers, ten other people on the rail car. Some of them tried to jump to safety, others were thrown from the car, including the brakeman. A stoker climbed from the locomotive to the wagon to tighten the wagon brake even more, and then returned to the locomotive. About 1.5 km from Wädenswil station, the freight wagon derailed and the clutch tore. The car came to a stop, the people still on it were rescued, including Wetli himself. The locomotive, on the other hand, continued to accelerate and had an estimated speed of 120 km / h when entering the Wädenswil station. The locomotive derailed on a turnout sequence, the boiler was torn down and the locomotive overturned. One stoker died, the engine driver and the second stoker were injured. Another person who was in the train station was also killed. Of the people who jumped or fell from the car, one was killed and all the others injured.
A first expert report fundamentally criticized the Wetli system and suspected that, in addition to spinning drive wheels as a result of excessive counter-steam, carbonized wooden brake blocks and a graphite film on the wheels that resulted from this were the cause. A second report clearly disproved charred brake pads as the cause and instead showed that traces of oil had been found on the rails, wheels and the brake pads. The authors came to the conclusion that leaked oil of unknown origin must be the cause of the brake failure. They criticized, among other things, the late examination of parts of the line, inadequate tests on the brakes and the fact that the author of the first report had never spoken to the driver. They gave the recommendation that “we should work towards bringing in professional experts from the outset in similar cases”.
The system was no longer used after this accident. For the Wädenswil-Einsiedeln railway, a pure adhesion railway was later realized.