Pu29

Pu29-3 (HCP 200/1931), Kościerzyna loco depot, August 2000.

The same machine, February 5, 2003 – note missing ash-pan side boxes.

The same machine, February 5, 2003 – note flat smoke-box door.

Pu29 – drawing by M.Ćwikła (from SK vol.4/2000).

Still bearing the Pu29-1 service number, the sole surviving example was photographed in Bydgoszcz in June 1964. Photo from my collection.

In late 1920s locomotives used for express passenger trains by PKP represented a diverse group of machines, almost exclusively of German or Austrian origin. Most of them were obsolete. Older machines, such as Prussian classes S3, S4, S5 and S6 or Austrian 108 and 308, had only two driven axles. Austrian classes 210 and 310, with three driven axles, were suitable only for light trains. Even Prussian class S10 locomotives, considered superior to previously mentioned ones, were too weak. Polish Os24 and Ok22 machines were used with express trains, but certainly this was an interim measure. There was a need for a powerful, fast machine for heavy express trains, so in early 1929 two prototypes were ordered, one from the Cegielski works (HCP) of Poznań and one from Fablok.

All above-mentioned express locomotives of foreign origin had two-axle lead trucks and this was then considered in Europe almost a must for a fast locomotive. Four driven axles were mandatory, in order keep axle load within acceptable limits. Finally it was decided to adopt the 2-4-1 axle arrangement for one prototype and 1-4-1 for the other, in order to compare their characteristics in service. The former layout was quite widespread. In the USA, 2201 such machines were built between 1911 and 1948 (according to Guide to North American Steam Locomotives by George H. Drury), used for passenger as well as for fast freight trains; the heaviest of them exceeded 192 tonnes. They were known as Mountains or Mohawks. Locomotives of this layout, which combined good running qualities and high tractive effort at moderate axle load, were also used in Europe (with a notable exception of Germany) – mainly in France and Spain.

Three prototypes of the 2-4-1 locomotive, designated Pu29, were built by HCP in 1931 (serial numbers 198 through 200); new large four-axle tenders, class 32D29 (the largest built in Poland before WWII), were designed for these machines. First test runs took place in September 1931. Performance was good: with nineteen four-axle passenger cars, weighting 818 tonnes, 105 km/h could be maintained and maximum speed reached 112 km/h. Due to the axle arrangement, running was very smooth. Crews praised good visibility and easy access to the running gear and brakes. Fuel consumption, despite live-steam injectors of excessive output, was comparatively low. There were only few minor shortcomings, easy to rectify. The machine looked impressive and powerful, measuring almost 25 metres with tender. This length, however, eventually turned out to be crucial for the final fate of this otherwise very successful design. Axle base was over 21 metres and only few turntables in Poland could accept machines exceeding 20 metres. Pu29 was simply too long. With the appearance of the 1-4-1 contender, the Pt31 from Fablok, the choice obviously fell on the latter type – only slightly smaller and less powerful, but due to axle base reduced by just 960 mm much more handy. It should be noted that two competing prototypes, although built by different companies, had much in common, including steam engine and drivers; steam parameters were also the same.

All three Pu29s remained in use until September 1939, mainly in northern Poland. Pu29-3 was captured by the Germans and impressed into DRG service as 12 201. Both remaining examples were taken over by the Soviets. Pu29-1 fell into German hands at the Eastern Front, to be given DRG service number 12 202 (this locomotive remained with DB and was written off in May 1952). Pu29-2 was converted for the 1524 mm track and retained its original designation, written in Russian script (ПУ29-2). Its ultimate fate remains unknown; according to some Russian sources, it was wrtitten off in 1958 (information from PNPP). After WWII, only the 12 201, found in Czechoslovakia, returned to Poland and was restored in service in 1950 as Pu29-1 (initially it was erroneously designated Pt31-46). After twenty years, again mainly in Northern Poland, it was withdrawn in March 1970. It was decided to keep this machine as a museum exhibit, but eight years passed before this could be effected. In the meantime it was slightly damaged and subsequent restoration – apart from fitting plates with the pre-war service number Pu29-3 – did not bring it up to its original condition. In particular, convex smoke-box door with central lock was replaced by a flat one and ash pan side-boxes are missing (removed probably in early 50s). This machine is now at the locomotive depot in Kościerzyna.

It is worth reminding here that Pu29 was the largest and heaviest Polish steam locomotive ever built for domestic service: even the impressive and powerful Ty51 was lighter by almost four tonnes (in working order) and considerably shorter.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1931
2.	Total built / used in Poland	-	3 / 3
3.	Tender class	-	32D29
4.	Axle arrangement	-	2-4-1
5.	Design maximum speed	km/h	100^1)
6.	Cylinder bore	mm	2 X 630
7.	Piston stroke	mm	700
8.	Engine rating	kW/hp	1334 / 1820
9.	Tractive effort	kG	13 500
10.	Boiler pressure	MPa	1.53
11.	Grate dimensions	m X m	2.78 X 1.78
12.	Firebox heating surface	m^2	18.5
13.	Distance between tube plates	mm	6 500
14.	Number of flue tubes	-	103
15.	Heating surface of flue tubes	m^2	132,0
16.	Number of smoke tubes	-	26
17.	Heating surface of smoke tubes	m^2	80.0
18.	Evaporating surface, total	m^2	230.5
19.	Superheater heating surface	m^2	86.8
20.	Diameter of drivers	mm	1850
21.	Diameter of idlers front/rear	mm	860 / 1200
22.	Total weight, empty	kg	102 800
23.	Total weight, working order	kg	113 800
24.	Weight on drivers, working order	kg	72 600
25.	Weight with tender, empty	kg	129 300
26.	Weight with tender, working order	kg	182 300
27.	Maximum axle load	T	18.5
28.	Axle base (with tender)	mm	21 195
29.	Overall length (with tender)	mm	24 595
30.	Brake type	-	West

1) Some sources give 110 km/h

References and acknowledgments

Comprehensive account of this class history and design can be found in the monographic article by Paweł Terczyński in SK vol.4/2000. Description can also be found in PNPP.