Ot1

Ot1-18, photographed near Jelenia Góra in 1970s; photo by Frank Engel (www.frank-engel.de) – thanks for permission!

DR class 41 side drawing by K.-E. Hertam (TB vol.1).

Development of the BR41: TCDD 46059, photographed at the Çamlık museum on September 30, 2007.

DRG 41 182, Orenstein & Koppel 13174/1938. Photo from my collection. This engine after WWII served with DR, later was re-designated 41 1182-9 and withdrawn in September 1986.

German class 41 locomotive was designed in 1934 to fulfill the demand for a fast freight machine, capable of maintaining relatively high speed while not exceeding maximum axle load of 18 tonnes. It was intended to succeed DRG class 56^20-29 (ex-Prussian G8²). Four designs with the 1-4-0 axle arrangement were submitted to this specification, but none of them found favor; the choice fell instead on a 1-4-1 machine, designed by Schwartzkopff – partly because it utilized the same boiler as the class 03 express locomotive then in production. This very machine was standarized as BR (Baureihe, or class) 41, however, with boiler pressure increased from 16 to 20 bar. This demanded new materials and St47K steel was widely used. Soon it turned out that this steel was prone to premature ageing and after few years boiler pressure had to be reduced to 16 bar – the same was the case with several other types then in use with DRG. It should be noted here that experiments with even higher boiler pressure, then actively pursued in Germany, in general proved unsuccessful.

Class 41 featured drivers of untypical diameter – 1600 mm, larger than adopted in Germany for freight locomotives (1400 mm) but smaller than that of typical passenger machines (1750 mm). Furthermore, maximum axle load could be increased from 17.6 to 19.7 tonnes by simply repositioning bolts in levers connecting idle axes with driven axles. These features contributed to versatility: the machine could be used for fast freight trains as well as for passenger and even express ones, the more so that front Krauss-Helmholtz bogie facilitated easy running even at 100 km/h.

Two prototypes were built in 1936 and series production started in 1938 to last until 1941, when war needs dictated shifting to heavier locomotives. Production machines differed from prototypes in some details, mainly concerning boiler accessories. In all, 366 examples were built by nine companies: Borsig (73), Esslingen (35), Henschel (86), Jung (40), Krauss-Maffei (18), Krupp (31), MBA – formerly Orenstein & Koppel (21), Schichau (37) and Schwartzkopff (25). Orders for further 24 machines from Schichau and 46 from Schwartzkopff were cancelled in 1941. Very soon these locomotives acquired a somehow contemptuous nickname of ‘Oschenlok’ (literally ‘ox loco’), as they were widely used with express freight trains transporting livestock.

In 1937, Turkish state railways TCDD ordered from Henschel eleven engines, derived from BR41, for fast passenger trains. These locomotives were slightly lighter and had modified boilers with larger superheaters; diameter of drivers was increased to 1750 mm and cylinder bore to 650 mm. Designated No.46051 through 46061, they served mainly at the Istanbul-Ankara line. No.46059 (Henschel 23659/1937) has been preserved at the steam locomotive museum in Çamlık.

After WWII most class 41 machines remained in Germany. 220 examples served with DB and DR had 119. One engine, 41 153, was taken over by Czechoslovak railways, but probably was not allocated a service number; in 1955 it was transferred to an industrial operator. Soviets took six machines, but nothing is known about their further service. PKP took over 19 locomotives of this class (some sources give 18 – probably because the last one was accepted as late as in 1948). One more (41 076, Borsig 14797/1939) was handed over by DR in 1946, but this machine was not restored in service and had no PKP number. Contrary to pre-war DRG practice, they were used almost exclusively with passenger trains, hence their designation Ot1. Just as with those operated by DR and DB after WWII, boiler pressure was soon reduced to 16 bar, although some tests with higher pressure were in fact performed. Most Ot1s were used in Lower Silesia, but as electrification progressed, many of them were shifted to Lublin, to replace elderly and never entirely satisfactory Os24s.

Premature ageing of boiler elements was an inherent flaw of these otherwise successful machines, therefore reconstruction was the only means to keep them in service. In West Germany, 103 machines were fitted between 1957 and 1961 with new welded boilers of high efficiency, which radically changed their silhouettes. Forty of them were converted to oil firing and re-designated class 042; last of them was withdrawn in October 1977. Last original machines (not reconstructed – class 041) were written off in 1971. In East Germany, 21 machines were fitted with reconstructed welded boilers (otherwise identical with the original ones) and, from 1961 onwards, eighty were rebuilt with entirely new boilers of indigenous design. Last DR machines survived in service until 1984. PKP had only nineteen Ot1s, so launching a dedicated reconstruction program was perhaps considered unjustified. Thus, when signs of intensified deterioration of material properties had been discovered during major overhauls in late 1960s, this meant a death sentence. All machines of this class were written off between August 1969 and March 1973; the last of them was Ot1-17 (ex DRG 41 313, Orenstein & Koppel 13272/1940). This meant that, in effect, these modern and efficient locomotives were outlived in service by older ones. Unfortunately, no Polish Ot1 has been preserved (nothing particularly shocking for a railway fan in Poland!). In contrast, as many as 23 machines of this type (most of them, if not all, in reconstructed versions) have survived in Germany; four of them (41 018, 41 144, 41 231 and 41 360) are in working order and there are plans to restore further two in service. 41 105 (Krupp 1927/1938) has had an eventful career: after 31 years with DB it was sold in 1976 to The Netherlands and served as a stationary boiler in Vlissingen until 1979. Sold to Stoom Stichting Nederland, Rotterdam, it was restored in service in 1980 and ran with special trains until 1991, when boiler certificate expired. There are plans to bring it back to the working order.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1936 – 1941
2.	Total built / used in Poland	-	366 / 19^2)
3.	Tender class	-	34D44
4.	Axle arrangement	-	1-4-1
5.	Design maximum speed	km/h	90
6.	Cylinder bore	mm	2 X 520
7.	Piston stroke	mm	720
8.	Engine rating	kW/hp	1360 / 1850 (?)
9.	Tractive effort	kG	14 950
10.	Boiler pressure	MPa	1.63^1)
11.	Grate dimensions	m X m	2.609 X 1.57
12.	Firebox heating surface	m^2	16.15
13.	Distance between tube plates	mm	6 800
14.	Number of flue tubes	-	85
15.	Heating surface of flue tubes	m^2	114.5
16.	Number of smoke tubes	-	20
17.	Heating surface of smoke tubes	m^2	69.62
18.	Evaporating surface, total	m^2	200.27
19.	Superheater heating surface	m^2	72.22
20.	Diameter of drivers	mm	1600
21.	Diameter of idlers front/rear	mm	1000 / 1250
22.	Total weight, empty	kg	92 840
23.	Total weight, working order	kg	101 900
24.	Weight on drivers, working order	kg	78 000^3)
25.	Weight with tender, empty	kg	122 740
26.	Weight with tender, working order	kg	176 100
27.	Maximum axle load	T	19.7^3)
28.	Axle base (with tender)	mm	20 175
29.	Overall length (with tender)	mm	23 905
30.	Brake type	-	Knorr

1) Initially 2.04 MPa, later reduced.

2) Some sources give 18 – probably because Ot1-19 was accepted later than other examples.

3) Repositioning of undercarriage lever bolts allowed for reducing weight on drivers to 70 000 kg and maximum axle load to 17.6 T.

References and acknowledgments

Comprehensive account of this class history and design can be found in the monographic article by Paweł Terczyński in SK vol.2/2001. Brief description can be found in TB vol.1. TB vol.1. Description of BR 42 development and service can be found at http://www-personal.umich.edu/~khmiska - this website is maintained by Kurt H.Miska. Information on individual examples has been taken from the impressive Ingo Hütter’s locomotive database (available at www.lokomotive.de).