Pn11

 

 

Pn11-8 (ex 210.09, BMMF 358/1910), photographed in Kraków in March 1937. Source: National Digital Archives (www.nac.gov.pl). Used by permission. This engine was returned by DR in 1955 and scrapped.

 

 

 

 

 

Development of steam locomotives in Austro-Hungary was influenced by two important factors: comparatively poor quality of many tracks and low calorific value of domestic coals. The former implied axle load limit of 14.5 tonnes; the latter called for large fireboxes, in order to achieve sufficient steam production and parameters. These factors influenced the Austrian school of locomotive design. Many achievements of this school are connected with the name of Karl Gölsdorf (1861-1916).

During the last decade of the 19th century there was a considerable tendency to increase speed and comfort of the most prestigious passenger trains, which resulted in many new designs. Austro-Hungarian state railways KkStB (Kaiserlich-königliche österreichische Staatsbahnen) were no exception, although the above-mentioned factors resulted in somewhat specific design features. These were clearly seen in the first express locomotive standardized by this service, class 6. Designed by Gölsdorf, it went into production at three factories (WLF, Wiener Neustadt and StEG) in 1894 and during next four years 68 examples were built. This machine had high-pitched boiler and large drivers (2000 mm in diameter), which provided space for a huge firebox. Despite quite good performance, class 6, with two driven axles, soon became obsolete. It was developed further, into classes 106 (126 examples), 206 (89 examples) and 306 (only five); while retaining the same axle arrangement (2-2-0), 2100 mm drivers and general layout, they differed considerably, but soon it became evident that more powerful machines were necessary. It was not possible to maintain low axle load while substantially increasing boiler size and capacity with the 2-2-0 arrangement, so new designs concepts were tried: class 9 (2-3-0), class 108 (2-2-1), class 110 (1-3-1) and class 280 (1-5-0).

In 1906, Gölsdorf began to design a new express locomotive, intended to haul trains of overall weight 400 tonnes on a 10‰ gradient track at 60 km/h. He decided to place the firebox behind the drivers, in order to match the ‘wagon-top’ boiler of peculiar shape and large firebox with 2100 mm drivers. For that purpose, he reverted the 2-3-1 axle arrangement (then widely used in the USA and known there as Pacific).  Rear truck, with two idle axles, could support the weight of the large firebox without excessive axle load. This arrangement, later named Adriatic, was never used again in a tender locomotive; it was featured in five tank engines, rebuilt in Czechoslovakia from class 354.0, ex KkStB class 229, in 1936 and re-classed 353.1, and in two DB class 66 tank engines of 1950.  Experiments with two rear idle axles, however, continued in some countries for quite a long time. Specific boiler shape, large drivers and axle arrangement combined to give a unique silhouette. Even today, many railway fans (including myself) consider this machine one of the most beautiful steam locomotives ever built – an almost perfect blend of grace and power – while other (few!) describe it as simply awkward. De gustibus non est disputandum...

New locomotive, in line with Gölsdorf’s preference for compounds, was fitted with a four-cylinder compound steam engine. It went into production for KkStB as class 210 in 1908. Gölsdorf did not decide to introduce steam superheating, as he was afraid that high-grade lube oil, necessary for lubrication with high steam temperature, would be in short supply in Austria-Hungary. Steam dryer of the Gölsdorf-Clench type was installed in the smoke box, but this layout did not prove satisfactory and, in the end, advantages of reheat prevailed. Only eleven class 210 machines had been built, six by WLF and five by BMMF – the latter factory is also known as PÈM, this abbreviation being derived from its Czech name – before production switched in 1911 to class 310 with steam superheating.

During WWI, two captured engines (210.01 and 210.10) briefly served in Ukraine and then were taken over by the Russians. Later they were transferred to the Vladikavkaz Railway, but their final fate is unknown; nor are their Soviet service designations, although some sources report that they were assigned. The remaining nine survived in the KkStB service until 1918 and then went to PKP. Classed Pn11, they remained in service in southern and later eastern Poland until 1939. Later, during overhauls, they were modified and fitted with steam superheaters, but it is not clear if this was completed before WWII. Although they became similar to class Pn12 (ex-KkStB 310), their designation remained unchanged.

In 1939 three examples (Pn11-2, -6 and -9) were captured by Germans and re-numbered 16 051 through 053. They were used mainly in Austria. The rest fell into Soviet hands, but all except two became German booty after Fall Barbarossa. Pn11-4 (ex 210.05, WLF 1929/1910) was converted to the 1524 mm track, but retained its Polish service number, albeit written in Russian script. Its final fate is not known. German ex-Pn11s were returned after the war. Four came from Czechoslovakia and one from Austria between 1947 and 1948: neither ÖBB nor ÈSD had assigned them any service number. They were given new PKP numbers, but saw no service; all were written off in 1950. Pn11-8 (ex 210.09, BMMF 358/1910), returned by DR in 1955, was scrapped without being entered into the PKP rosters. Moreover, six Pn12s returned after the war were initially erroneously designated Pn11-7 through 12.

Class 210 was certainly among the best and most advanced European express locomotives running on saturated steam, but appeared when superheating had already proven its advantages and had become a well-established design feature. In fact they served as a starting point for Gölsdorf’s most famous brainchild, class 310. No engine of this type has survived until today. 

 


Main technical data

 

No.

Parameter

Unit

Value

1.

Years of manufacture

-

1908 – 1910

2.

Total built / used in Poland

-

11 / 9 – 71)

3.

Tender class

-

21D11

4.

Axle arrangement

-

1-3-2

5.

Design maximum speed

km/h

100

6.

Cylinder bore

mm

2 X 390 /

 2 X 660

7.

Piston stroke

mm

720

8.

Engine rating

kW/hp

1155 / 1570

9.

Tractive effort

kG

9 300

10.

Boiler pressure

MPa

1.53

11.

Grate dimensions

m X m

4.62 m2

12.

Firebox heating surface

m2

15.1

13.

Distance between tube plates

mm

5 750

14.

Number of flue tubes

-

291

15.

Heating surface of flue tubes

m2

207.45

16.

Number of smoke tubes

-

-

17.

Heating surface of smoke tubes

m2

-

18.

Evaporating surface, total

m2

222.553)

19.

Superheater heating surface

m2

-

20.

Diameter of drivers

mm

21002)

21.

Diameter of idlers front/rear

mm

995 / 995

22.

Total weight, empty

kg

77 100

23.

Total weight, working order

kg

83 800

24.

Weight on drivers, working order

kg

43 800

25.

Weight with tender, empty

kg

92 600

26.

Weight with tender, working order

kg

133 800

27.

Maximum axle load

T

14.6

28.

Axle base (with tender)

mm

18 236

29.

Overall length (with tender)

mm

21 538

30.

Brake type

-

Hardy / Westinghouse

 

1)      After WWII, including one not restored in service (no number assigned).

2)      Some sources give 2140 mm – probably due to different standards used by KkStB.

3)      Data on heating surfaces have been taken from KT vol.1; data from other sources differ slightly. 

 

References and acknowledgments

 

-        Monographic article by Pawe³ Terczyñski (SK vol. 1/2003);

-        KT vol. 1, EZ vol. 2;

-        www.pospichal.net/lokstatistik (website by Josef Pospichal).