Os24
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Südbahn 570.02 (StEG 4001/1915), location and
date unknown. This type was the basis for the Os24 design. 570.02 remained in
Austria and after Anschluss became DRG 33 002; returned after the
war and re-numbered 133.02, it was withdrawn in January 1954. Source: Die Lokomotive
December 1915.
Factory photo of the Os24 from the Fablok leaflet (source: www.commons.wikimedia.org).
Os24-10 (in fact Os24-7),
Another picture of the only surviving Os24, taken on
...and yet another, taken on
Os24 drawing by M.Ćwikła,
from SK
vol.6/1999.
Os24-59. My data give ‘location unknown, October
1959’, but judging from the service number this is a pre-war picture. Photo
from my collection.
Decorated Os24-7 (Fablok
121/1926), double-heading with another locomotive of this type, leaves Kraków to inaugurate the service to Miechów;
November 1934. This engine fell into Soviet hands in 1939 and was later
captured by Germans. Impressed into the DRG service
as 33 214, it was returned in 1945 and re-numbered Os24-4, to be written off
in April 1949. Source: National Digital Archives (www.nac.gov.pl). Used by permission.
Of poor quality, but interesting, this photo
of an Austrian class 113 engine fitted with the Dabeg
feedwater pump and heater was published in the Technika Parowozowa
monthly, vol. 1/1929.
Another picture of the Os24-7, photographed
probably shortly after her transfer to the Railway Museum. Photo by J. Szeliga (postcard from my collection).
Original Class 570 design was later developed
into BBÖ Class 113. Prototype 113.01 (StEG 4693/1923) later became DRG 33 101; returned after the war and re-numbered 33.101,
it was withdrawn in October 1960. Location and date unknown; source: Die Lokomotive
December 1924.
Os24-7 again: Railway Museum (now Stacja Muzeum),
Warsaw, July 6, 2023. |
Steam
locomotives with the 2-4-0 axle arrangement were first designed and built in
the USA, but never achieved much popularity there; from somehow awkward Centipede of 1855 to five machines
supplied by Baldwin to Ferrocarriles Nacionales de
Mexico in 1935, only about 600 were built, not many by American standards.
They were known as Mastodons or
simply Twelve-Wheelers. This layout
eventually found much more favor with European railways. As it combined
considerable tractive effort with moderate axle load and satisfactory running
qualities, it was destined primarily for passenger traffic in mountain
regions with comparatively weak tracks. No wonder, thus, that one of the main
protagonists of this axle arrangement were the Austro-Hungarian state
railways kkStB
and later their descendants, ČSD
and MÁV; beside these, many engines
of this layout were purchased by Spanish RENFE. In
1915, StEG
(Maschinenfabrik der priv. österreichisch-ungarischen Staatseisenbahnen-Gesellschaft)
of Vienna designed a 2-4-0 locomotive for Südbahn, designated class 570,
mainly for heavy passenger trains running across the Semmering
pass between Vienna and Graz. These large locomotives – in fact first
passenger engines with four driven axles – were fast and powerful, but prone
to snaking, so running above 80 km/h was somehow uneasy. Only two were built,
plus five more for the KDB railway
in northern Slovakia (classed I t); the latter were taken over by
Czechoslovak ČSD after WWI as class
455.0 and remained in use until 1959. Between 1923 and 1928 further forty
engines of slightly modified design were built for Austrian BBÖ railways as class 113; despite
certain modifications, their running qualities still left much to be desired
and consequently their maximum speed was reduced to 85 km/h in 1934. Much
more – about 500 – locomotives of similar design were also built after WWI in
Hungary as class 424. When
the First Locomotive Factory in Poland,
later known as Fablok, was founded in Chrzanów in May 1919, technical assistance was provided
by StEG;
no wonder, thus, that Austrian designs were favored. Although first five Ok22
passenger locomotives had already been supplied by Hanomag,
it was felt that these engines, with axle load of 17 tonnes,
were not suitable for many railway lines in southern and eastern Poland,
characterized by weak tracks. StEG suggested a design based on wartime class 570 – not
on modified class 113 – and in 1924 first twenty locomotives were ordered and
classed Os24. First of them was commissioned on January 23, 1926, and the
last in May. Two subsequent orders, each for twenty engines, followed and the
last of these was delivered in 1927. Os24
locomotives, large and impressive, were pre-war PKP’s pride and glory, at least until the end of 1920s, when new
Pu29s and later Pt31s made their appearance. Impressive they were, mainly due
to high-pitched boiler (firebox had to be located very high with such axle
arrangement) and quite pleasant silhouette; they were not, however,
trouble-free. Despite their designation, they were initially used mainly with
express trains, but soon it was found that, just as their Austrian ancestors,
they had a pronounced tendency to snaking and uneasy running at higher
speeds, above 50 km/h. Moreover, it soon turned out that passing tight curves
resulted in frame fractures between cylinders and first coupled axle. Poor
manufacture quality was suggested as the main reason; it was also argued that
valve gear design was faulty and resulted in excessive dynamic load on
connecting rods and side sills. Other specialists pointed out that load distribution
between lead truck and first coupled axle was improper. No modifications
were, however, undertaken. On the other hand, some new design concepts were
tested on these engines. Two (Os24-19 and Os24-20) had their typical valve
gears replaced by the Lentz-type poppet-valve ones. In 1927 four (Os24-16,
Os24-17, Os24-18 and Os24-20) were fitted with Dabeg
feedwater heaters and pumps, driven by third pair
of drivers. Last two examples had Worthington-type feedwater
pumps. Despite certain advantages none
of these novelties was accepted for widespread use. An account of the tests
with Dabeg pumps, published in 1928, stated
that they presented no advantage compared to steam injectors then in common
use, providing that the latter were properly adjusted and operated by skilled
personnel. Moreover, pumps were considerably heavier than injectors. All
engines of the Os24 class were used in eastern and south-eastern Poland. With
gradual improvement of track quality and mounting supplies of superior Pt31s
of indigenous design they were shifted to passenger trains; in this role,
however, Ok1 (Prussian P8) and Ok22 (its direct derivative) proved much
better. In the end, class Os24 was judged too heavy and powerful for its
ultimate role and in general rather unsuccessful. This also explains why this
layout was not developed further; no other Polish locomotive had the 2-4-0
axle arrangement. Os24s were coupled with four-axle 27D24 tenders – then the
heaviest locomotive tenders built in Poland. In
1939, two examples (Os24-17 and Os24-31) were destroyed and ten were taken
over by the Germans. In 1941 they were re-numbered 33 201 through 210 –
their Austrian counterparts were designated class 330 (ex-570) and
331 (ex-113) – and served mainly with Ostbahn. The remaining 48
engines were taken over by the Soviets. According to PNPP, thirty were converted to the 1524 mm track; in 1941 they
were evacuated eastwards and never returned. The remaining 18 were captured
by Germans after Fall Barbarossa.
They were in a very poor condition, so only six were repaired and restored in
service (DRG 33 211 through
216). Some unserviceable Os24s, brought by DRG to Warsaw and awaiting repair, were destroyed during
hostilities. Most German engines of this type were transferred to Austria during
the closing stages of WWII, so in 1945 only four were taken over by Polish
railways (two left by DRG in Poland
and two captured by the Soviets, but not impressed into the NKPS service). However, eleven more
soon followed from Austria. After the war, Soviet railways had 34 examples,
which retained their original service numbers, written in Russian script
(OC24). According to PNPP, last
were withdrawn in 1962. Just
as before the war, all fifteen machines of this type were based in eastern
Poland, namely in Lublin, Chełm and Rozwadów. They were known by the affectionate name ‘Osa’ (Wasp), derived from its designation. Their service
was not very long and lasted only until late 60s. One locomotive of this type
– the sole surviving example – has been preserved in the Railway Museum in
Warsaw. Despite bearing plates with Os24-10 service number, it is in fact the
Os24-7 (Fablok 147/1926, pre-war Os24-39),
captured by Soviets in 1939. This engine later fell into German hands and
became DRG 33 215 in 1944. Taken over
by ÖBB in 1945, it was again taken by the Soviets in July 1948 and
immediately handed over to PKP. This locomotive was withdrawn from use
on April 17, 1970, as the last of this class, and thoroughly reconditioned in
1983. Main
technical data
1)
Some sources give 25D24. 2)
Some sources give about 217 m2, which is
incorrect. List of vehicles can be found here.
References
and acknowledgments
-
Monographic article by Paweł
Terczyński (SK vol. 6/1999); -
PNPP,
LP; -
www.beitraege.lokomotive.de
(locomotive database by Ingo Hütter). |
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