PRR S1

The locomotive of the class S1 of the Pennsylvania Railroad was by far the largest and most powerful express steam locomotive in the world and also the only one with the wheel arrangement 3'BB3 '. The streamline locomotive was built in 1939 in the railway-owned shops in Altoona. The internally billed for production costs amounted to 669 780 U.S. dollars.

Technology and dimensions

The S1 was one of the few duplex locomotives. In this design, two groups of coupled axles are rigidly mounted in a common framework. The advantage of this design was that the individual engines had to endure lower forces the piston, could therefore be built lighter and quieter running at higher speeds. By a short stroke low piston speeds could be achieved.

A constructive weak point was that only 45 percent of the locomotive weight load on the driving wheels. With 32 tons axle load to the drive wheels while the regular measure of the load on the rails was reached, however, resulted from the fact that especially the starting tractive effort was less than the capacity of the boiler would have allowed it. The centrifugal tendency was high therefore especially when starting. In addition to that changed in the separate engines of the time of the originally uniform displacement of the piston dead center positions, difficult making it for the engineer to determine the basis of the then covering exhaust noise if one of the two engines went through alone and finish this in time. The result was stronger wear and tear damage to the tires and rails.

The large wheelbase of the driving axles was also a problem since you ordered the cylinder of the rear engine between the two driving wheels on. The also possible arrangement behind the rear wheels dome had several drawbacks, such as long vapor trails and an unfavorable position of the cylinder near the firebox.

Nevertheless, it looked for the S1 very large driving wheels with 2134 mm ( 84 " ) diameter ago, the largest that have ever been used on a locomotive with more than three axles powered, with the exception of kuk StB series 210/310 ( 2140 mm coupled wheel / axle arrangement 1'C 2 '). This results in a hilltop stand salmon of about 8.3 m returned (for comparison, in the DR series 06, it was at 2000 mm driving wheel diameter 6.75 m).

In addition, in the front bogie of the S1 was before the front cylinders, and not lower, so that the engine ( without tender ) was 24.5 m long with a Gesamtachsstand of about 19.5 m. To improve the Kurvenläufigkeit the first and third coupled axle respectively to 57.2 mm were slid sideways.

The locomotive had a Heusinger control. The frame was the largest up to that cast by General Steel Castings frame and weighed 44.5 tons.

The tender of S1 had eight axes and was 23.6 tons of coal and 91.7 cubic meters of water absorb. In addition, he decreed as the PRR usual, a water pumping device. Its service weight was 205 t; Locomotive and tender are brought together 481 t on the scale.

The locomotive was disguised streamlined, the shoe was designed by Raymond Loewy.

Operation

After its completion in late January 1939, the S1 from late April to late October was shown in 1939 and also from mid-May until the end of October 1940 at the World Fair in New York. They stood on rollers so that they could be run in stand before the audience.

From December 1940, the S1 was used on the route between Chicago and Pittsburgh in passenger transport. It soon turned out that the locomotive tended in a relatively tight curve just before the station in Pittsburgh derailed. Therefore, it was used only on the part of the route between Chicago and Crestline (Ohio ), about 2 /3 of the originally planned distance. Even in their home - depot Crestline they jumped more often in a triangular track from the track, which had been built for them because they did not fit on the turntable.

Due to the centrifugal tendency of the vehicle, there were always problems when starting, especially since you started the engine because of their great power often face the heaviest trains. The resulting delays were, however, offset by the train drivers by a correspondingly excessive speed easily again.

The locomotive was out too big in every respect, therefore, the successor type T1 was already ordered when the S1 was still standing at the World Fair in New York. Your operating as a single piece was very uneconomical. By the end of 1945, the locomotive was used for heavy express and Postzugdienst and 1949 scrapped.

S1 and T1, the fastest steam locomotive in the world?

In the German trade press and literature a report of an unwanted record run of S1 has been regularly appeared and quoted, after which co-moving in the train officials of the ICC in March 1946 at a speed of 141 mph (227 km / h) should have stopped. While experts agree on the fact that the locomotive could reach the claimed speed well, there is still no evidence for such a journey. Several specified details such as the date or the procedure of the ICC, can appear implausible this report. Similar reports, however, from American sources, speaking of such speeds associated with the T1 locomotives. Neither S1 nor T1 have ever been extended with a measuring carriage.

The S2

Related to S1, but no duplex locomotive was the class S2, a steam locomotive with the wheel arrangement 3'D3 '. It was somewhat shorter than the S1, but had the same bogies. The class names of the PRR were awarded after the wheel arrangement of locomotives, and S1 and S2 of the same group were assigned, although the wheel arrangement only visually consistent.

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