OKi1

OKi1-28, photographed at the Railway Museum in Warsaw on May 25, 2005.

The same engine, photographed on September 5, 2006.

A drawing from the LHW catalogue card shows LBE No.125 ‘Fuchs’ (Linke-Hofmann 334/1906). This engine was sold to the Altona-Kaltenkirchen-Neumünster railway in 1923 and served there as No.18 until 1953. From my collection.

Class 74^0-3 side drawing, © Lokomotiv-Revue; source: TB vol.2.

Prussian state railways KPEV designated both passenger and freight tank engines with capital T, for Tenderlokomotive. After steam superheating had been introduced, it was decided to use even and odd number for engines running on superheated and saturated steam, respectively. Thus, T9 was a freight locomotive with 1350 mm drivers and maximum speed set at 60 to 65 km/h, built in large numbers and three main variants. Next was T10, a modern passenger engine for suburban traffic with 2-3-0 axle arrangement, 1750 mm drivers and maximum speed of 100 km/h, of which only twelve were built. T11, designed by renowned Robert Garbe as a development of class T9³, in fact preceeded T10 by a few years and was a less advanced design, with 1500 mm drivers, single-axle Krauss-Helmholtz lead truck, tractive effort of 8.6 tonnes and maximum speed of 80 km/h. Prototype was completed by Union-Gießerei of Königsberg in 1903 and 470 examples were built for KPEV until production terminated in 1910. The majority came from Union (364 examples), the rest being supplied by Borsig, Hohenzollern and Vulcan. Furthermore, Linke-Hofmann Werke built nine almost identical machines for Lübeck-Büchener Eisenbahn (LBE) in three small batches, between 1906 and 1908. Most T11s ran with suburban trains; S-Bahn in Berlin alone received 141 examples.

Robert Garbe was one of the keenest advocates of single-expansion engines running on superheated steam; no wonder, thus, that such derivative of T11 appeared even before the latter was ordered in quantity. In 1905 it was accepted as class T12 and was eventually destined to outnumber its predecessor: over 1000 were built until 1923. T12 offered more power and much better economy and therefore almost immediately started to supplant its older kinsman.

After WWI, newly-formed DRG were left with 358 T11s, classed 74^0-3. In 1926 twenty were rebuilt with steam superheating, but this program was not proceeded with, as electrification of suburban lines rendered these engines surplus. In particular, electrification of the S-Bahn between 1924 and 1933 left a few hundred tank engines with no job. While more modern T12s were relegated to secondary lines and switching, many T11s were withdrawn. In late 1920s and early 1930s as many as 204 locomotives of this type were written off, some after less than twenty years in service. Two more followed during WWII; furthermore, a few were sold to various private local railways. Similarly, of nine examples in the LBE inventory (which had not been taken over by DRG), seven were written off between 1926 and 1932 or sold; only two survived until 1953. After WWII, DB were left with just 65 engines of this type, most were withdrawn in early 1950s. DR had sixty; a few soldiered on until late 1960s, quite a lot went to industry. Four examples were taken over by Soviet MPS (Ministry of Transport), but their service was probably very short.

Polish railways were a major recipient of T11s after WWI. As many as 56 examples were taken over and impressed into service. They were classed OKi1 and given service numbers from 1 to 52; four operated in Gdańsk were designated OKi1-1Dz through –4Dz, where Dz stood for ‘Danzig’ (in fact, all four had been operated in Gdańsk by KPEV before 1918). Most of these obsolescent, but reliable engines served in Upper Silesia on local lines. Two (OKi1-5 and OKi1-24) were withdrawn before 1936, the rest survived until the next war. In September 1939 the majority were taken over by DRG and given service numbers after those withdrawn before the war; six fell into Soviet hands (one after a brief period with Lithuanian railways LG), but five of them were later re-captured by Germans. After 1945, thirty-six were returned to PKP, but one (former OKi1-3Dz) was not given new service number and written off in 1946. Furthermore, a number of DRG engines were taken over. According to the Ingo Hütter’s database (www.locomotive.de), they numbered 22, of which five were not given service numbers and shared the fate of the OKi1-3Dz. It seems possible, however, that two of them might be impressed into service as OKi1-47 and OKi1-48, on which information is lacking. Anyway most reliable sources agree that post-war class OKi1 numbered 52 examples. These comparatively weak engines performed best on flat-profile lines, so all were assigned to the regional railway management in Gdańsk. Some were later relegated to auxiliary duties and switching. Their withdrawal started in early 1950s and only eleven survived with PKP until 1960. Between 1952 and 1959 sixteen were transferred to various industrial establishments and some enjoyed there a few years’ lease of life. Last three OKi1s in the PKP service were withdrawn in 1966. One of them (OKi1-28, Borsig 5424/1904, KPEV ‘Berlin 7560’, then OKi1-14 and 74 104) has been preserved and can now be seen at the static display in the Railway Museum, Warsaw. As far as I know, only one more engine of this type still exists. Union 1602/1908 (KPEV ‘Hannover 7512’, then DRG 74 231) was kept by DR after WWII and remained in service until 1968, when it was transferred to an industrial plant. Plinthed at a railway school premises in Erfurt in 1974, it was finally transferred to Museums-Eisenbahn Minden in 2000 and sometimes runs with special trains.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1903 – 1910
2.	Total built / used in Poland	-	479 / 56^1) – 52^2)
3.	Tender class	-	-
4.	Axle arrangement	-	1-3-0
5.	Design maximum speed	km/h	80
6.	Cylinder bore	mm	2 ´ 480
7.	Piston stroke	mm	630
8.	Engine rating	kW/hp	382 / 520
9.	Tractive effort	kG	8 600
10.	Boiler pressure	MPa	1.22
11.	Grate dimensions	m X m	1.75 ´ 0.99
12.	Firebox heating surface	m^2	8.7
13.	Distance between tube plates	mm	4000
14.	Number of flue tubes	-	209
15.	Heating surface of flue tubes	m^2	104.27
16.	Number of smoke tubes	-	-
17.	Heating surface of smoke tubes	m^2	-
18.	Evaporating surface, total	m^2	112.97^3)
19.	Superheater heating surface	m^2	-
20.	Diameter of drivers	mm	1500
21.	Diameter of idlers front/rear	mm	1000 / -
22.	Total weight, empty	kg	48 300
23.	Total weight, working order	kg	62 600
24.	Weight on drivers, working order	kg	47 400
25.	Weight with tender, empty	kg	-
26.	Weight with tender, working order	kg	-
27.	Maximum axle load	T	16.0
28.	Axle base (with tender)	mm	6 350
29.	Overall length (with tender)	mm	11 190
30.	Brake type	-	Knorr

1) After WWI.

2) Plus six more with no service numbers, written off in 1946.

3) Some sources give 116.4 sq.m.

References and acknowledgments

Concise information can be found in TB vol.2 and LP. Information on individual examples has been taken from the impressive Ingo Hütter’s database (www.locomotive.de).