Prussian P 4.1
{{Infobox locomotive
| name = Prussian P 4.1
PKP Od1
| bgcolor = 000000
| color = FFFFFF
| image = P4-1 KPEV 372.jpg
| alt = Prussian P 4.1 locomotive
| caption = Prussian P 4.1 locomotive
| powertype = Steam
| builder =
| builddate = 1891–1901 | whytetype = 4-4-0 | uicclass = 2'B n2 | gauge = Template:Track gauge | leadingdiameter = 908 mm (2 ft 11+3⁄4 in) | driverdiameter = 1,750 mm (5 ft 8+7⁄8 in) | length =
| over buffers =
- Erfurt variant: 15,615 mm (51 ft 2+3⁄4 in)
- Hannover variant: 16,411 mm (53 ft 10+1⁄8 in)
| height = 3,080 mm (10 ft 1+1⁄4 in) | axleload = 15 t (15 long tons; 17 short tons) | serviceweight = 47.6 t (46.8 long tons; 52.5 short tons) (earlier: 49.1 t (48.3 long tons; 54.1 short tons)) | firearea = 2.30 m2 (24.8 sq ft) | boilerpressure = 12 bar (1.20 MPa; 12.2 kgf/cm2; 174 psi) | fireboxarea = 117.9 m2 (1,269 sq ft) (earlier: 125.5 m2 (1,351 sq ft)) | cylindersize= 430 or 460 mm (16+15⁄16 or 18+1⁄8 in) | pistonstroke = 600 mm (23+5⁄8 in) |maxspeed = 90 km/h (56 mph) |maxspeed = 90 km/h (56 mph) |maxspeed = 90 km/h (56 mph) |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed = |maxspeed=
- max speed is 90 km/h in the original text.
- Therefore, we keep it as such.
Prussian P 4.1 locomotives were steam-powered passenger engines operated by the Prussian state railways (KPEV), produced from 1891 until 1901. Featuring a 2'B wheel configuration, these units utilized a twin-cylinder saturated steam mechanism. Following the Treaty of Versailles, Poland acquired 21 examples of this model, which were classified as Od1 by the Polish State Railways beginning in 1923. Within Germany, the Deutsche Reichsbahn Gesellschaft (DRG) cataloged them under the series number 3670.
History
The P 4 passenger locomotive's development was influenced by a study tour undertaken by German engineers to the United States and the United Kingdom, where they examined prevailing locomotive designs. This research contributed to a new generation of Prussian passenger and express engines characterized by a 2'B wheel arrangement—comprising a two-axle leading bogie plus two driving axles—with distinctions primarily in driver wheel diameter: 1,750 mm for passenger models and 1,980 mm for express variants. Earlier, less powerful locomotives with a 1B arrangement had been employed for both types of service.
In 1891, the railway directorate in Erfurt commissioned two prototype passenger locomotives from Henschel in Kassel. These prototypes featured driving wheels measuring 1,730 mm and twin-cylinder engines; simultaneously, two similar units equipped with compound engines (later known as series P 4.2 or Od2) and four express locomotives—both twin-cylinder and compound—were constructed. The initial twin-cylinder prototypes bore the numbers Erfurt 496 and 497 and were renumbered in 1906 as P 4 Erfurt 1801 and 1802.
Subsequent to these prototypes, Henschel manufactured a batch of 55 twin-cylinder passenger locomotives between 1891 and 1892, based on an enhanced design identified as the Prussian standard pattern (Musterblatt) III-1c. The majority (26 units) were assigned to the Erfurt directorate, while others were distributed among Berlin, Elberfeld, and Magdeburg divisions. Compared to the prototypes, these featured a slight increase in driving wheel diameter to 1,750 mm while maintaining internal Allan valve gear. From 1911 onward, they were classified as series P 4.1.
Further refinements followed, paralleling improvements made to the express S 3 series. The introduction of a Hanover-type leading bogie mounted further forward extended the wheelbase by 825 mm to reach a total length of 7,400 mm between axles. Cylinder diameter was increased from 430 mm to 460 mm, and external Heusinger valve gear replaced earlier mechanisms. This updated design—Musterblatt III-1d—resulted in production of 325 locomotives by Henschel between 1893 and 1901, complemented by an additional hundred units from other manufacturers: Hanomag (60), Borsig (25), Schwartzkopff (8), and Grafenstaden (7). Including the original prototypes, a total of 482 twin-cylinder passenger locomotives with a 2'B wheel arrangement were constructed for Prussian railways.
Operation
In 1906, the Prussian railway authorities categorized these locomotives under the P 4 series, which included compound engine models, and assigned them new numbers ranging from 1801 to 1900 within each railway directorate. By 1911, the twin-cylinder variants were reclassified as sub-series P 4.1, while those equipped with compound engines were designated as P 4.2. Initially, the P 4.1 locomotives served passenger routes and some express services, but they were soon surpassed in performance by the more robust P 4.2 units, followed by the introduction of newer classes such as the P 6 and P 8 on primary lines.
Following World War I, most Prussian locomotives were integrated into the German DRG. However, the majority of P 4.1 models were deemed outdated and retired. A renumbering plan in 1923 aimed to reclassify 157 locomotives, yet by 1925 only nine were assigned new DRG numbers as series 3670 (36 7001–7009), all of which were withdrawn from service between 1926 and 1927. After the war, Poland acquired 21 P 4.1 engines, which were classified by the Polish State Railways as series Od1; none remained in Polish service following World War II.
Some P 4.1 locomotives found new homes elsewhere: a limited number went to Lithuania, three units to Latvia, and four to Yugoslavia. In Latvia, these were classified under series An (2'B wheel arrangement) with numbers ranging from 32 to 34. Notably, locomotive An-33 remained operational until the Soviet annexation of Latvia in 1940, after which it was absorbed into the Soviet railway system.
On July 29, 1898, a Henschel-built locomotive known as Cassel 131 (classified under Musterblatt III-1d and later as P 4 Cassel 1846) was experimentally equipped with a Schmidt superheater, marking it as the second locomotive worldwide to feature this technology after the express S 4.
In 1907, five Musterblatt III-1c locomotives from the Frankfurt directorate underwent conversion to compound engines and were reclassified as P 4.2. Comparable locomotives were also procured by other German rail networks. Between 1903 and 1910, three Musterblatt III-1d units were constructed for the Royal Military Railways (Kgl. Militär-Eisenbahn)—one by Hanomag and two by Linke-Hofmann in Wrocław—although the reasoning behind ordering these somewhat outdated models remains unclear.
Hanomag manufactured nineteen similar locomotives for the Oldenburg railways between 1896 and 1902. These featured a shorter wheelbase of 6,250 mm, a reduced distance between the bogie and driving axles (2,150 mm between driving axles), lacked a steam dome (instead equipped with a box-shaped sandbox and safety valves), and measured a total length of 15,513 mm including a three-axle tender. In 1925, these engines were reclassified as DRG series 3612 (36 1201–1219) but were retired by 1931.
In 1904, the private Lübeck–Büchen railway (LBE) commissioned two locomotives inspired by the Prussian design but with shortened wheelbases to fit smaller turntables. Named Meteor and Comet, these locomotives remained in operation until their retirement in 1933 and 1935 respectively.
Design
The P 4.1 was a 2'B passenger steam engine equipped with a twin-cylinder saturated steam mechanism (2'B n2). It was produced in two main versions: the initial Musterblatt III-1c and the subsequent standard III-1d.[1] The boiler's centerline was positioned at 2,145 mm above the rail level (2,135 mm for the III-1c variant), featuring a diameter of 1,460 mm and a fire-tube length of 3,900 mm.[2] Its heating surface covered 117.9 m² (125.5 m² in the III-1c), supported by a grate area of 2.3 m² and operating at a steam pressure of 12 atmospheres.[1]
The spacing between the driving axles measured 2,600 mm, while the leading bogie axles were set 2,000 mm apart. The gap from the second bogie axle to the first driving axle was 2,800 mm, resulting in a total wheelbase of 7,400 mm.[2] In contrast, the III-1c variant had bogie axles spaced at 2,050 mm with a shorter distance between bogie and driving axles, culminating in a wheelbase of 6,575 mm. Axle loads registered at 14.6 tonnes and 15 tonnes on the driving axles, and 9 tonnes on the bogie axles (III-1c: 14.1 tonnes and 10.5 tonnes respectively).[1]
The locomotive’s twin cylinders measured 460 mm in diameter (430 mm for III-1c) with a piston stroke length of 600 mm. It employed external Heusinger valve gear (internal Allan type on III-1c), which actuated the crankpins on the first driving axle. Braking systems were installed on the driving wheels.[1]
Commonly paired with three-axle tenders, these included the Musterblatt III-5b (later classified as pr 3T12: carrying 12 m³ of water and 5 tonnes of coal, measuring 6,250 mm in length) or III-5c (pr 3T15: holding 15 m³ water and 5 tonnes coal, also 6,250 mm long). Subsequently, four-axle III-5k tenders were introduced (pr 2'2'T16: capacity of 16 m³ water and 7 tonnes coal, length of 7,350 mm).[3][4] When combined with the pr 2'2'T16 tender, the locomotive’s overall length was 17,511 mm,[4] while with three-axle tenders it measured 16,411 mm.[1]
According to a specification from 1924, a P 4.1 could pull a train weighing 160 tons at speeds up to 80 km/h; for a load of 310 tons, it could maintain 70 km/h; and for a heavier train of 500 tons, it managed speeds around 60 km/h on level track. On inclines such as a gradient of 2‰, both allowable load and velocity were reduced considerably—for example, hauling approximately 290 tons at a speed of 60 km/h.[1]