Ok102

Factory photo of the KWStB 422 (Esslingen 2912/1898). Source: www.commons.wikimedia.org.

Side drawing of class D. Source: Lokomotiv-Archiv Württemberg (see References).

Class AD 2-2-0 of the Königlich Württembergischen Staats-Eisenbahnen (KWStE) proved too weak for heavy passenger trains on the demanding Ulm-Stuttgart-Bretten line. Thus, between 1898 and 1905, the railway took delivery of fourteen class D passenger locomotives from Maschinenfabrik Esslingen. They ran on saturated steam and featured four-cylinder compound steam engines of the de Glehn type. Prototype was 2911/1898 and the locomotives were assigned service numbers from 421 to 434. These engines, although successful and possessing satisfactory characteristics, were complex and demanded skillful drivers. In fact they were quickly surpassed by more modern types running on superheated steam.

Four-cylinder compounds were not favored by newly-created German state railways, so eight locomotives of this type that remained in Germany saw very little service, despite comparatively young age. DRG service numbers 38 101 through 108 were reserved for them, but never actually assigned, as all were withdrawn until 1924 and scrapped. KWStB 426 and 429 went to France and were taken over by Chemins de Fer de l’État, becoming 230.985 and 230.986. Four-cylinder de Glehn compounds were quite widespread in France, so both enjoyed longer service runs, the former being withdrawn only in 1934 and the latter around 1930. According to Lokomotiv-Archiv Württemberg (see References), the remaining four locomotives (KWStE 423, 425, 430 and 432) were taken over by PKP. Due to the same axle arrangement as in popular Prussian P8, they were initially classed P8^w, where the upper index indicated the land of origin. In 1926 they were re-classed Ok102. However, LP gives only three examples; KWStE 423 is missing, so this locomotive was either never taken over by PKP or withdrawn before 1926. The official list of steam engine types, issued by the Ministry of Transport in 1927, also gives three examples then in use. Be as it was, this class disappeared from the PKP rosters before 1936. No locomotive of this type has survived until today.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1898 – 1905
2.	Total built / used in Poland	-	14 / 4 (3?)
3.	Tender class	-	13C102
4.	Axle arrangement	-	2-3-0
5.	Design maximum speed	km/h	90
6.	Cylinder bore	mm	2 X 380 / 2 X 600
7.	Piston stroke	mm	560
8.	Engine rating	kW/hp
9.	Tractive effort	kG
10.	Boiler pressure	MPa	1.43
11.	Grate dimensions	m X m	2.3 m^2
12.	Firebox heating surface	m^2	12.1
13.	Distance between tube plates	mm	3 990
14.	Number of flue tubes	-
15.	Heating surface of flue tubes	m^2	149.9
16.	Number of smoke tubes	-	-
17.	Heating surface of smoke tubes	m^2	-
18.	Evaporating surface, total	m^2	162.0
19.	Superheater heating surface	m^2	-
20.	Diameter of drivers	mm	1 650
21.	Diameter of idlers front/rear	mm	850 / -
22.	Total weight, empty	kg	57 300
23.	Total weight, working order	kg	64 400
24.	Weight on drivers, working order	kg	44 800
25.	Weight with tender, empty	kg
26.	Weight with tender, working order	kg	96 500
27.	Maximum axle load	T	15.0
28.	Axle base (with tender)	mm	14 075
29.	Overall length (with tender)	mm	16 920
30.	Brake type	-	steam^1)

1) Westinghouse brakes were latter fitted. 

References and acknowledgments

- LP;

- www.pl.wikipedia.org;

- www.de.wikipedia.org;

- Lokomotiv-Archiv Württemberg by Hermann Lohr and Georg Thielmann (Transpress, Berlin, 1988).