PRR class S1
| PRR class S1 | |
|---|---|
 PRR class S1
|
|
| Number: | 1 |
| Type : | 3'BB3 'h4 |
| Gauge : | 1435 mm ( standard gauge ) |
| Length over buffers: | 42,700 mm |
| Service mass: | 276 t |
| Service mass with tender: | 487.5 t |
| Friction mass: | 127.7 t |
| Wheel set mass : | 32.0 t |
| Top speed: | 193.1 km / h |
| Driving wheel diameter: | 2134 mm |
| Impeller diameter front: | 914 mm |
| Rear wheel diameter: | 1067 mm |
| Cylinder diameter: | 660 mm |
| Piston stroke: | 559 mm |
| Boiler overpressure: | 21.2 bar |
| Grate area: | 12.3 m² |
| Superheater area : | 193.7 m² |
| Evaporation heating surface: | 525.9 m² |
The class S1 locomotive of the Pennsylvania Railroad was by far the largest and most powerful express train steam locomotive in the world and also the only one with a 3'BB3 ' wheel arrangement. The streamlined locomotive was built in 1939 in the railway's own workshops in Altoona . The internally billed manufacturing costs for this were $ 669,780.
Technology and dimensions
The S1 was one of the few duplex locomotives . In this design, two sets of are coupled axles rigidly in a common frame stored. The advantage of this design was that the individual engines had to withstand lower piston forces , so they could be built lighter and ran more smoothly at higher speeds . A short piston stroke made it possible to achieve low piston speeds.
A constructive weak point was that only 45 percent of the locomotive weight was on the driving and coupling axles . With 32 tons of axle load on the driving and coupling axles, the permissible load on the superstructure was used , but it turned out that, above all, the starting tractive effort was lower than the boiler output would have allowed. The tendency to skid was therefore particularly high when moving off. In addition, the originally even offset of the piston dead center positions in the separate engines changed over time, which made it difficult for the engine driver to determine from the overlapping exhaust noise whether one of the two engines went through alone and to stop it in time . The consequence was greater wear and tear on the wheel tires and rails.
The large fixed wheelbase was also a problem, because the cylinders of the rear engine were arranged between the two groups of coupled axles. The also possible arrangement behind the rear coupling axle had several disadvantages, such as long steam paths and an unfavorable position of the cylinders in the immediate vicinity of the fire box .
The S1 drive wheels with a diameter of 2134 mm (84 ″) were planned, the largest ever used on a locomotive with more than three coupled axles.
In addition, the front bogie of the S1 was in front of and not under the front cylinders, so that the locomotive (without tender ) was 24.5 m long with a total axle distance of approx. 19.5 m. The first and third coupling axles could each be laterally displaced by 57.2 mm to improve the arc's mobility.
The locomotive had a Heusinger control . The integral cast frame was the largest ever cast by General Steel Castings and weighed 44.5 tons.
The S1's tender had eight axles and could hold 23.6 t of coal and 91.7 m³ of water . In addition, as usual with the PRR, it had a water scoop . His service weight was 205 tons; The locomotive and tender together weighed 481 t.
The locomotive was clad in a streamlined manner, the design came from Raymond Loewy .
business
After its completion at the end of January 1939, the S1 was shown at the world exhibition in New York from the end of April to the end of October 1939 and also from mid-May to the end of October 1940 . She stood on roles so that she could run in front of the audience.
From December 1940, the S1 was used on the route between Chicago and Pittsburgh in passenger traffic. It soon turned out that the locomotive tended to derail in a relatively narrow arc just before the train station in Pittsburgh . Therefore it was only used on the part of the route between Chicago and Crestline (Ohio) (283 miles / 446 kilometers), about 2/3 of the originally planned distance. In her home depot, Crestline, she often derailed in a triangular track that was built especially for her because it did not fit on the turntable .
Because of the tendency of the vehicle to skid , there were always problems starting, especially since the locomotive was often used in front of the heaviest trains because of its high performance . The resulting delays could, however, be easily compensated by the train drivers by increasing the speed accordingly.
The locomotive was too big in every respect, which is why the successor type T1 was already ordered when the S1 was still at the world exhibition in New York. Operating them as a single item was very uneconomical. By the end of 1945, the locomotive was in serious Quick - and Postzugdienst used and 1949 scrapped.
S1 and T1, fastest steam locomotives in the world?
In the German-language specialist press and literature , a report about an unwanted record run of the S1 appeared and was quoted several times, according to which ICC officials on the train were said to have stopped a speed of 141 mph (227 km / h) in March 1946. While experts agree that the locomotive was able to achieve the claimed speed, there is still no evidence of such a journey. Several details given, such as the date or the procedure of the ICC, make this report appear unreliable. Similar reports, albeit from American sources, speak of such speeds in connection with the T1 locomotives. Neither the S1 nor the T1 have ever been driven out with a measuring vehicle.
The S2
Related to the S1, but not a duplex locomotive, was the S2 class , a steam turbine locomotive with a 3'D3 'wheel arrangement. It was slightly shorter than the S1, but had the same running bogies. The class designations of the PRR were assigned according to the wheel arrangement of the locomotives, and S1 and S2 were assigned to the same group, although the wheel arrangement only matched visually.
Trivia
On the cover of the album 'Play it Straight' by the Danish pop group Laid Back , the S1 is shown, but in a red shade that the machine never wore.
literature
- Wilhelm Reuter: record locomotives . Motorbuch Verlag, Stuttgart, ISBN 3-87943-582-0
- David P. Morgan: Duplex drives . In: Trains . 11/59, Kalmbach Publishing Co., pp. 16-25, ISSN 0041-0934
