OKa1 / TKa242

This OKa1-1, ex Tk 235, the only surviving example, was photographed in Warsaw on May 25, 2005

Another picture, taken on the same occasion…

… and some cab interior details.

Side drawing of OKa1 by M.Ćwikła from SK vol.3/2002

In 1928, Latvian state railways (Latvijas Dzelzcels – LDZ) purchased three light passenger locomotives for 1524 mm track from Hohenzollern company of Düsseldorf. These peculiar machines, designated class Tk and given service numbers 231 to 233 (serial numbers 4635 to 4637), had 1-1-1 axle arrangement; this archaic layout was considered suitable for light passenger drafts, consisting of only two or three cars. Driven axle load could be increased, by means of a pneumatic cylinder, from 16 to 17 tonnes.

Latvian railways intended to purchase further examples and Polish locomotive industry even offered their supply, but orders were finally placed in 1931 with German companies: Krupp (serial numbers 1196 to 1198, service numbers 234 to 236) and Henschel (serial numbers 21994, 21995 and 22062, service numbers 237 to 239). Some sources claim that in fact these machines were assembled in Latvia from German parts. These somehow awkward locomotives must have been considered successful, as further eleven examples were built between 1932 and 1934 by Latvian railway workshops at Liepaja and Dinaburga (Daugavpils), in co-operation with Finnish companies Tampere and Locomo.

All twenty machines served with Latvian railways until WWII. During the war, some of them were captured by Germans and rebuilt for the 1435 mm track. In 1944 they were evacuated westwards (together with other Latvian and Lithuanian locomotives), but some anyway fell into Soviet hands. One of them was Tk 235 (Krupp 1197/1931, probably assembled by Fenikss company of Riga), captured in 1945 near Opole. This small and untypical machine must have been considered of little use for Soviet railways, as instead of being claimed Soviet property and taken by MPS (ministry of transport), which was a common practice, it was passed over to PKP in January 1945. Designated OKa1-1, it served until February 1969, with minor modifications (steel firebox instead of the copper one, modified lighting etc.). For most of that time it was based in Łazy and used with service trains. After 24 years of this useful, if not conspicuous service it was withdrawn, but fortunately – instead of being scrapped – it was transferred to the Railway Museum in Warsaw, where it can still be seen. As far as I know, this is the only surviving example of this interesting class.

Tk 242 (built by the Dinaburga workshops in 1933, serial number 3), also captured by Soviets, was passed over to PKP in January 1946. It would have been logical to designate it OKa1-2, but someone had an idea that this machine, built in Latvia, should be treated as ‘of origin other than German or Austrian’, so Tk 242 became TKa242 (although, formally, TKa101-1 would have been more appropriate). Anyway, apart from evident errors, this is the only case of two locomotives of the same class being assigned completely different designations in PKP service. TKa242 served until 1955 in Kutno and was used in the role very similar to that of OKa1-1 – with service trains. After a serious failure it was not repaired; written off in 1957, it was finally scrapped.

Contribution of these peculiar – and, frankly speaking, not very beautiful – machines into the history of Polish railways has been marginal, but they are certainly of interest, being the only standard-gauge steam locomotives with single driven axle ever used in Poland. By a strange decree of fate, one of them still exists, while many classes, even more numerous, have disappeared completely.

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Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1928 – 1934
2.	Total built / used in Poland	-	20 / 2
3.	Tender class	-	-
4.	Axle arrangement	-	1-1-1
5.	Design maximum speed	km/h	75
6.	Cylinder bore	mm	2 X 320
7.	Piston stroke	mm	520^2)
8.	Engine rating	kW/hp
9.	Tractive effort	kG
10.	Boiler pressure	MPa	1.43
11.	Grate dimensions	m X m	1.25 m^2
12.	Firebox heating surface	m^2
13.	Distance between tube plates	mm
14.	Number of flue tubes	-
15.	Heating surface of flue tubes	m^2
16.	Number of smoke tubes	-
17.	Heating surface of smoke tubes	m^2
18.	Evaporating surface, total	m^2	51.2
19.	Superheater heating surface	m^2	21.8
20.	Diameter of drivers	mm	1500
21.	Diameter of idlers front/rear	mm	1050 / 1050
22.	Total weight, empty	kg	32 200
23.	Total weight, working order	kg	37 200
24.	Weight on drivers, working order	kg	16 000
25.	Weight with tender, empty	kg	-
26.	Weight with tender, working order	kg	-
27.	Maximum axle load	T	16.0^1)
28.	Axle base (with tender)	mm	5 700
29.	Overall length (with tender)	mm	9 425
30.	Brake type	-	Knorr

1) Adjustable up to 17 tonnes.

2) Some sources give 530 mm.

References and acknowledgments

As it might be expected, few details are available. The most comprehensive description I know is given in an article on Latvian and Lithuanian locos in Polish service by Tomasz Roszak in SK vol.3/2002.