Bromberg 72 (Henschel 7082/1905), factory photo.
Side drawing of the S7 Bauart Grafenstaden, third
production variant; source: Lokomotiv-Archiv Preußen
vol. 1 (see References).
In 1902 Prussian state railways KPEV introduced new express locomotive, with the 2-2-1 axle arrangement and four-cylinder compound engine. It was intended as a replacement for class S51, which was built in comparatively small numbers. New class S7 in fact included two different types, known as Bauart Hannover and Bauart Grafenstaden. The former was eventually standardized, but total output was moderate: just 159 examples in four years. The latter was even less successful.
Bauart Grafenstaden, designed by Alfred de Glehn, drew on experience gained with engines built for French railways, which favored four-cylinder compounds. Prototype (5269/1902) was followed by further five examples from Grafenstaden and 21 from Henschel. In 1904 Grafenstaden delivered ten engines with steam pressure increased from 14 to 15 bar, slightly enlarged boiler and improved lead truck. Third and final production variant, which appeared in 1905, featured further boiler modifications and boiler pressure increased to 16 bar. It was built by Grafenstaden (19) and Henschel (23). Later production examples had modified boilers, with 131 flues instead of 257 (increased in outer diameter from 50 to 70 mm). Total output of all variants was thus 79 examples. Despite all improvements, this engine was not considered successful. It was slightly weaker than Bauart Hannover and improvement over class S51 was in fact small. Both variants were superseded by class S9 with much larger boiler, which – although basically successful – was not built in large number, as its concept was already obsolescent. Ultimate improvement was achieved only with class S6, which ran on superheated steam.
After WWI seventeen locomotives of this type were taken over by Belgian railways and five by French (Chemin de fer de l’Est). German railways DRG withdrew them completely in early 1920s and no new Bauart designation was assigned. Polish state railways acquired only three engines, classed Pf2 – all belonged to the third production variant, two were built by Henschel and one by Grafenstaden. All were withdrawn between 1927 and 1936 and scrapped. No locomotive of this type has been preserved.
Main technical data1)
1) All data for the third production version.
2) Increased to 110 km/h in 1907.
3) First/second batch.
References and acknowledgments
- Lokomotiv-Archiv Preußen Band 1 by Andreas Wagner, Dieter Bäzold, Rainer Zschech and Ralph Lüderitz (Bechtermünz Verlag, 1996);