Prussian S 5.1
| Company type | Steam locomotive series |
|---|---|
| Industry | Railway |
| Founded | 1900 |
| Headquarters | Germany (Prussia) |
| Products | Express steam locomotives |
The S 5.1 was a series of express steam locomotives operated by the Prussian state railways, initially known as S 5, manufactured between 1900 and 1903 in two distinct models. It incorporated a four-cylinder compound locomotive engine utilizing Vapor–liquid equilibrium saturated steam and featured a 2'B (2-2-0) wheel configuration. Following World War I, only a single S 5.1 was incorporated into the Polish State Railways fleet, where it was classified as Pd3. A comparable model was also deployed by the railways of Alsace–Lorraine.
Development history
Toward the end of the 19th century, four-cylinder compound engines were regarded as optimal for express locomotives due to their high power output, operational economy, and superior balance relative to two-cylinder alternatives.[1] This made them especially suitable for high-speed services. In Germany, this approach gained traction independently through the efforts of August von Borries from the Hanover Prussian railway administration—designer of the well-known Prussian Prussian S 3 express locomotive—and Alfred de Glehn, who pioneered the first four-cylinder compound locomotive worldwide in 1886.[1] De Glehn, who directed the Belfort workshops affiliated with the Alsatian Machine Factory Illkirch-Graffenstaden, located in German-controlled Alsace, constructed the initial 2'B four-cylinder compound locomotive for France’s Nord railway in 1891.[2]
To evaluate this design in practice, the Prussian railways commissioned a trial express engine with a 2'B wheel setup, assigned number Berlin 37 and built by Grafenstaden in 1894 (factory number 4550). This was Prussia's first locomotive equipped with a four-cylinder compound engine.[3] Later renamed Erfurt 37 and from 1906 reclassified as Erfurt 501 within the S5 series (though it never bore the S 5.1 designation),[2] it followed de Glehn’s blueprint featuring high-pressure cylinders mounted externally near the midpoint of the locomotive, driving the second coupled axle just behind the leading bogie.[3] The low-pressure cylinders were positioned inside the frame beneath the smokebox and powered the first driving axle through a crank axle mechanism. This arrangement ensured both driving axles were powered, thereby distributing mechanical load more evenly.[2] The engine employed an external Heusinger valve gear and a Belpaire firebox with a heating surface of approximately 110 m² and a grate area of about 2.05 m². Its bogie had an external frame design. Originally fitted with a minimalist French-style cab, it was later modified to conform to Prussian standards. The locomotive ran with a three-axle tender holding 15 m³ of water and five tonnes of coal.[2]
The production series, labeled S 5 starting in 1906 and reclassified as S 5.1 from 1911 following introduction of the (S 5.2) variant, comprised two main versions: one produced at Grafenstaden and another at Hannover.[4]
S 5.1 Grafenstaden Version
The Prussian railways commissioned 22 locomotives utilizing de Glehn's four-cylinder compound system. Of these, 10 were produced in 1902 at Grafenstaden, while Henschel & Son in Kassel constructed 12 units in 1903. Although based on de Glehn's original design, these models featured a sturdier construction and incorporated an improved Belpaire boiler with a heating surface of 122 m², a grate area of 2.3 m², and an elongated smokebox. The boiler was elevated by 19 cm, positioning its centerline at 245 cm instead of the previous 226 cm. While the engine's fundamental dimensions remained consistent, the driving wheel diameter was reduced to 1.98 m, aligning with the standard for German 2'B locomotives since the Prussian S 3. The maximum speed capability increased from 90 km/h to 100 km/h. The spacing between coupled axles stayed at 3 m; however, the bogie axle distance expanded to 2.05 m on Grafenstaden models and to 2.1 m on those from Henschel. Notably, the Grafenstaden variant incorporated a hemispherical steam dome, contrasting with Henschel’s cylindrical design. Both versions were paired with a standard Prussian four-axle tender (Musterblatt III-5f), which held 16 m³ of water and carried up to 5 tons of coal.
These locomotives operated within several Prussian railway divisions, including Altona (which housed 11 units), Erfurt, Magdeburg, and from 1906 onwards, Hanover and Danzig, bearing numbers from 501 to 600. No further production occurred after this batch due to the arrival of the S 7 series, which was regarded as the ultimate development in this class.
Grafenstaden also manufactured 54 comparable locomotives for the Alsace-Lorraine railways, reflecting the factory’s geographical position. Production spanned from 1902 to 1904 for the initial 50 units, with an additional four built in 1913 for reasons not clearly documented given the model’s obsolescence at that time. These engines were initially classified as A18, later renamed S 3 in 1906, and eventually designated S 5 in 1912. They operated at a higher boiler pressure of 15 atm and featured French-style safety valves. The first batch of twenty included 226 fire tubes yielding a heating surface of approximately 121.96 m²; later units had fewer but larger tubes—104 in total—providing a heating surface of around 169.85 m². Surpassing the Alsace-Lorraine fleet of Prussian S 3 locomotives (which numbered forty), these machines served express routes from Strasbourg until their retirement in 1937.
S 5.1 Hannover Version
The second variant of the S 5.1 was engineered by von Borries and assembled by Hanomag in Hanover, resulting in a total of seventeen locomotives. The prototype was completed in 1900 and earned the Grand Prix at the Paris World Exhibition that same year. Following this success, sixteen additional units were manufactured between 1902 and 1903, all allocated to Hanover and numbered consecutively from 501 to 517.
Von Borries’ design featured left and right cylinder pairs cast together beneath the smokebox near the bogie’s midpoint. The low-pressure cylinders were mounted externally and drove the first coupled axle directly; meanwhile, high-pressure cylinders placed internally also powered this axle via a crank axle mechanism. This arrangement simplified some mechanical aspects but introduced stress on curves that sometimes caused deformation issues. An internal Heusinger valve gear controlled valve timing, complemented by von Borries’ own starting valve system. Contrary to some reports, von Borries supported superheaters and intended to equip the prototype with a Schmidt chamber superheater; however, Robert Garbe opposed this plan due to his preference for simpler twin-cylinder superheated locomotives.
Evolving from the Prussian S 3 model, this locomotive retained essential dimensions such as driving wheels measuring 1.98 m in diameter, coupled axle spacing of 2.7 m, bogie axle spacing of 2.2 m, and a boiler heating surface of approximately 119 m². It utilized the same Musterblatt III-5f tender as its predecessors. Distinctive features included a tall steam dome shifted towards the rear and an additional cylindrical air reservoir at the front (later replaced by a horizontal type), with a conspicuous sandbox positioned between these components.
Service following World War I and in Poland
Following the conclusion of World War I, the Prussian locomotives were incorporated into the German Railways fleet. The majority of S 5.1 engines from both versions were retired between 1919 and 1920, with the remaining units being decommissioned shortly thereafter; none were assigned new identification numbers by the German Railways.
A single S 5.1 locomotive of the de Glehn type (manufactured by Henschel, factory number 6447, Danzig 513, previously Magdeburg 501) was transferred to Poland and classified as Pd3-1 by the Polish State Railways. This unit was withdrawn from service prior to 1926 and stands as the only S 5.1 example operated outside Germany.
References
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Bibliography
- Rauter, Herbert; Scheingraber, Günther (1991). Preußen-Report. Band 2: Die Schnellzuglokomotiven der Gattung S 1 – S 11 [Prussia Report. Volume 2: Express Locomotives of Classes S 1 – S 11] (in Deutsch). Hermann Merker Verlag. ISBN 3-922404-16-2.