Erfurt 52 (later Erfurt 403 and Bromberg 407, Henschel 7601/1905, first variant with chamber-type superheater. After 1918 this locomotive became Pd2-6. Factory photo (source: Lokomotiv-Archiv Preußen Band 1, see References).
Side drawing of the S4 Normalbauart by M.Kratochvil (source: TB vol. 1).
In 1893 Wilhelm Schmidt patented his steam superheater for a stationary engine. The idea of its application in a steam locomotive found a keen advocate in Robert Garbe, then in charge of the design and procurement of locomotives at the Preußische Eisenbahndirektion. Garbe firmly believed that superheating provided an optimal means to improve steam engine output and efficiency. First locomotive fitted with the superheater was a modified Prussian S3 Hannover 74, built by Vulcan (s/n 1643) and delivered to KPEV in April 1898. It retained the original compound steam engine. A modified P41 (Cassel 131) from Henschel followed suit. First superheater variant, in the form of one smoke tube of large diameter, was far from perfect, suffering from problems with tightness and difficult cleaning. Its advantages, however, immediately became obvious. In 1899 Vulcan delivered next experimental locomotive, again developed from S3 (s/n 1732, Hannover 86), this time with a chamber-type superheater in the smoke-box and single-expansion steam engine. Another experimental locomotive was Berlin 74, built by Borsig (s/n 4800/1900) and awarded Grand Prix at the 1900 World Fair in Paris After eliminating problems resulting mainly from higher steam temperature, including introduction of piston valves instead of slide ones and development of suitable lubricants, this variant was accepted for production. Between 1902 and 1909 three manufacturers (Borsig, Humboldt and Henschel) delivered 40, 10 and 54 examples, respectively – 104 in all, the first locomotives with steam superheating built in quantity. They were referred to as Normalbauart, in order to distinguish them from three experimental engines. In 1906 they were classed S4 (this class included also two earlier locomotives from Vulcan and one from Borsig). Those built from 1906 onwards were fitted with improved superheater with smoke tubes, which later found widespread use, and cylinders slightly increased in diameter. They were standardized as Musterblatt XIV-2. Thirty-five earlier examples with chamber-type superheaters were later also rebuilt to this standard. These locomotives were typically coupled with 2’2’T16, 3T13 and 3T15 tenders. Class S4 was successful, but produced only in limited numbers, as much more powerful S6 with the same axle arrangement appeared in 1906.
First DRG renumbering plan of 1923 included 44 S4s, but only four were actually renumbered two years later. Classed 135, they were withdrawn until 1927; their service numbers were later used again in 1939, for ex-PKP Pd5s. Six engines, all from Bromberg regional management (today Bydgoszcz) were handed over to the Polish railways and classed Pd2. Initially they were based in Łódź and later transferred eastwards, to the Rawa Ruska depot, where their comparatively low axle load was an advantage. Pd2-4 was withdrawn in October 1932, but not scrapped. In 1939 one engine (Pd2-3) became German booty; renumbered 13 401, it was returned by DR in December 1955 and scrapped. Five Pd2s (including withdrawn Pd2-4) fell into Soviet hands and were taken over by NKPS, but all were captured by Germans after Fall Barbarossa. Four were renumbered 13 401 through 404, while Pd2-4 served with Ostbahn and retained its original number; ultimate fate of this locomotive is unknown. Two were returned in 1946, but saw no service; one was handed over by DR along with Pd2-3 and was also scrapped. Pd2-5 remained in Easter Germany and was written off in 1948. Despite its considerable historical significance, no locomotive of this type has been preserved.
Main technical data1)
1) Technical data for the ultimate production variant (Normalbauart).
2) Excluding experimental locomotives.
3) Increased to 110 km/h in 1907.
4) Equivalent to Prussian 4T16.
5) With the 4T16 tender.
References and acknowledgments
- Lokomotiv-Archiv Preußen Band 1 by Andreas Wagner, Dieter Bäzold, Rainer Zschech and Ralph Lüderitz (Bechtermünz Verlag, 1996);
- LP, TB vol. 1;