Oi102

An unknown N^w, photographed probably somewhere in Russia, date unknown. Source: www.en.wikipedia.org. Class N^W had larger drivers, but was otherwise very similar externally.

Locomotive As-56 (later re-classed N^u), photographed in Nizhny Novgorod in 1911. Source: www.commons.wikimedia.org.

An unidentified N^W from Kolomna works, location and date unknown. Source: Die Lokomotive August 1912.

Class N side drawing by Artur Przęczek (used by permission – many thanks!).

In 1892 Aleksandrovskiy Zavod built two prototype 1-3-0 passenger locomotives with 1900 mm drivers. Designed by Nikolai Shchukin with the assistance of Belgian engineer Alfred Belpaire, these engines were originally intended to replace earlier class K (2-2-0) and avoid double-heading with heavier passenger trains. Following positive experience with class O freighters, it was decided to use compound steam engine. Although axle load turned out to be higher than expected by almost two tonnes, new locomotive was finally accepted and classed N (H in Russian script). According to some sources this designation came from the Nikolaevskaya railway that placed first orders. In fact at this time all railways, state-owned and private, had their own numbering schemes. In 1912, after unification had been introduced, this designation was retained as this was the first vacant letter in the Russian alphabet.

First variant featured Joy valve gear, hence after 1912 it was re-designated N^D (H^Д); production totaled 127 examples. N^W (H^B, upper case superscript) had Walschaert gear and Bissel pony truck instead of the Adams axle. It was built in 167 examples, all for government railways. N^w (H^b, lower case superscript) featured 1700 mm drivers, sacrificing speed for tractive effort; it was the most numerous sub-type, 589 engines being built between 1903 and 1911. N^u (H^y) was the ‘strengthened’ version with modified boiler and low-pressure cylinder bore increased to 750 mm. It appeared in 1910 and was built in 121 examples. There were nine more sub-types, most with 1700 mm drivers, built in much smaller numbers; some were fitted with single-expansion steam engines and steam superheaters, the latter being distinguished by subscript or superscript P, or П in Russian script. Total output was 1083 examples, built by all major Russian locomotive manufacturers, apart from six delivered by German Union works. The latter, classed N^R (H^P), ran on saturated steam, featured 1800 mm drivers and single-expansion steam engines; due to poor economy this version was not ordered in quantity. After WWI all remaining engines of this type were converted to singles and fitted with superheaters. Last survived in service until 1950s, but not a single example has been preserved.

According to LP, after WWI Polish railways obtained seven locomotives of this type. Their numbers are not known, nor is to which sub-types they belonged. Locomotive specifications list published by the Ministry of Transport in 1927 (see references) lists just one, which had been renumbered Oi102-1. This engine is of the N^W sub-type and its year of manufacture is given as 1904. If this is correct, it might have been built by Luganskiy Zavod or Sormovskiy Zavod, which in 1904 delivered six and fifteen examples, respectively, to railways in the area which became part of Poland in 1918 – but this is just a conjecture. Oi102-1 disappeared from the PKP rosters before 1936 and most probably was scrapped. All remaining engines of this type were probably not re-designated and written off before 1926.

A captured and partially armored class N engine was used by Polish troops on the Eastern Front with the ‘Generał Konarzewski’ armored train between 1919 and 1920. During retreat in July 1920 it was scuttled in the Berezyna river and destroyed.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1903 – 1909
2.	Total built / used in Poland	-	1083 (167^1)) / 7
3.	Tender class	-	23D101
4.	Axle arrangement	-	1-3-0
5.	Design maximum speed	km/h	100
6.	Cylinder bore	mm	500 / 730
7.	Piston stroke	mm	650
8.	Engine rating	kW/hp
9.	Tractive effort	kG	6500
10.	Boiler pressure	MPa	1.21
11.	Grate dimensions	m x m	2.2 m^2
12.	Firebox heating surface	m^2
13.	Distance between tube plates	mm
14.	Number of flue tubes	-	278
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	138.0
19.	Superheater heating surface	m^2	-
20.	Diameter of drivers	mm	1900
21.	Diameter of idlers front/rear	mm	1030 / -
22.	Total weight, empty	kg
23.	Total weight, working order	kg	59 000
24.	Weight on drivers, working order	kg	45 000
25.	Weight with tender, empty	kg
26.	Weight with tender, working order	kg	114 000
27.	Maximum axle load	T	15.4 / 15.5^1)
28.	Axle base (with tender)	mm	16 222
29.	Overall length (with tender)	mm	18 994
30.	Brake type	-	Westinghouse

Note: all data except total built refer to the N^W version.

1) N^W version only.

References and acknowledgments

- LP;

- LOZD vol.1;

- Charakterystyka parowozów (Steam Engine Specifications) by A. Czeczott (Ministry of Transport, 1927);

- Monographic article on the ‘Generał Konarzewski’ armored train by Krzysztof Margasiński and Artur Przęczek (SK vols. 9/2019 and 10/2109).