Pt31

Pt31-64 + 32D29-37, Chabówka Rolling Stock Heritage Park, April 13, 2004

Another picture of the Pt31-64, taken on July 29, 2006.

Pt31-49 under restoration at the Jaworzyna Śląska depot; photo taken on August 4, 2004.

Side drawing of Pt31, taken from PNP.

Pt31-17, somewhere in Poland, September 1961. Photo from my collection.

Good color photos of Polish trains from 1970s are extremely rare. Pt31-32 with a passenger train from Rozwadów to Ostrowiec was photographed by Geoff Plumb on July 1, 1974 (http://geoff-plumb.fotopic.net – thanks for permission!). Note a draft of old German two-axle coaches, of which many were then still in use. Pt31-32 was completed by Fablok for DRG as 19 162 (s/n 791/1940) and returned in 1945.

After WWI, Polish railways took over about 350 express locomotives of German (mainly Prussian) and Austrian origin. Most of them, however, were obsolete and weak machines with only two driven axles. Those that could be considered modern included Austrian classes 210 and 310, re-designated Pn11 and Pn12, respectively (the former running on saturated steam) and Prussian classes S10, S10¹ and S10² (in Polish service, Pk1, Pk2 and Pk3); their total number was slightly over eighty machines. Production of freight and later also passenger locomotives was given priority. In late 20s, however, lack of express locomotives became obvious; Os24s, used with some express trains, were not satisfactory and their service speed had to be reduced, due to poor running qualities. Ok1s and Ok22s, used for the same purpose, were too slow and weak. New machine was thus necessary.

Locomotive design in Poland was, to a large extent, influenced by German patterns, which favored express locomotives with three driven axles. Two-axle lead truck was considered mandatory for a fast machine and, with a rear idle axle necessary to support the weight of a large firebox, this led to the 2-3-1 arrangement, or Pacific – one of the most common ones for express locomotives in Europe. It was, however, decided to use four driven axles, as new engine was intended for heavy drafts, 750 tonnes or even more. 2-4-1 axle arrangement resulted in a long machine, so it was suggested that for speeds up to about 100 km/h a single-axle lead truck might suffice. In order to resolve this question, Ministry of Transport ordered two prototypes: Pu29 (2-4-1) from HCP (Cegielski) of Poznań and Pt29 (1-4-1) from First Locomotive Factory in Poland (Fablok) of Chrzanów. Due to some delay – an order from Bulgarian state railways BDŽ had been given priority – Pt29 was re-designated Pt31. 1-4-1 axle arrangement was first conceived in the USA; known there as Mikado, it was very popular, mainly with freighters. In Europe Mikados were considered universal machines, but only French railways ordered them in large numbers; classes 141P and 141R were one of the last and best known steam locomotives operated by SNCF. Fablok had had some experience with 1-4-1s, having built locomotives with this axle arrangement for Morocco (class 141A, 12 examples) and above-mentioned for Bulgaria (class 01, 10 examples).

Pu29, although entirely successful, immediately proved too long for most turntables; despite good performance, its output was limited to three examples. Pt31 won by being shorter by just 76 centimeters. It was also lighter by seven tonnes, but maximum axle loads were comparable. Both these locomotives had much in common; in particular, their steam engines were the same, as was the diameter of drivers. Contrary to its larger competitor, Pt31 had beam-type frame and shorter boiler (by 300 mm); number of smoke tubes was, however, increased from 103 to 112 and number of flues from 26 to 38, so both total evaporating surface and superheater surface were slightly increased. Two-axle lead truck was supplanted by Krauss-Helmholtz single-axle truck; rear Bissel semi-truck was retained.

Three Pt31 prototypes were ordered and the first of them (s/n 518/1932) was rolled out in October 1932. Tests began immediately and results were satisfactory, overall efficiency being comparable to that of the state-of-the-art European machines. Crews praised ease of maintenance and good running qualities. After several minor modifications, Pt31 was accepted as a standard express locomotive for PKP and deliveries began in 1934. On January 1, 1939, PKP had 81 examples and further seventeen were delivered during next eight months. 54 Pt31s were captured by Germans in September 1939 and impressed into DRG service as 19 101 to 19 154 (these numbers were assigned in 1941). Further twelve examples, ordered by PKP but not completed before the war, were built by Fablok under German supervision and supplied to DRG as class 39¹⁰ (service numbers from 39 1001 through 1012, later re-classed 19 155 through 166), bringing the total output to 110 examples. No Pt31 was destroyed during hostilities and all remaining 44 machines were captured by Soviets. Some of them (probably 21) were converted to 1524 mm track and based in Lwów, retaining their Polish designations written in Russian script (ПТ-31). They were never returned and last were withdrawn in 1961. The remaining 23 engines were captured by Germans in 1941; according to PNPP, fourteen were impressed into DRG service as 19 167 through 180 and the rest were taken over by Ostbahn and withdrawn in 1944. Germans – with their unquestionable achievements in railway engineering – held Pt31s in surprisingly high esteem and considered them especially suitable for heavy drafts in mountainous regions – no wonder, thus, that most captured machines were soon transferred to southern Germany and Austria. In fact, DRG had no comparable locomotive of indigenous design: class 22 with the same axle arrangement was substantially weaker and numbered only 85 examples.

During the war, Pt31s were scattered around Eastern and Central Europe and in 1945 only a handful were regained by PKP. The rest served in a number of countries:

- Germany – five with DB, written off in 1951, and thirteen with DR, all except one returned to PKP (most in 1955);

- Austria – 26 with ÖBB, all but one returned in 1947 and 1948, plus three on former Südbahn lines, designated class 919 and withdrawn in 1961,

- Czechoslovakia – eight examples, five of them classed 488.0 with ČSD service numbers 488.0500 through 488.0504, all returned to Poland in 1947,

- Hungary – eight, returned in 1952 and 1953,

- Romania – one (from Ostbahn, subsequent fate unknown),

- USSR – 24, none returned.

Some engines that returned were in a very poor condition and were not restored in service. Total number with post-war PKP was 65 examples, but numbers ran up to 66, as the sole Pu29-3 was initially erroneously included in rosters as Pt31-46. They gave good service and remained in use until late 70s. Last of them, Pt31-49 (pre-war Pt31-73, s/n 715/1938), was withdrawn in February 1980 and then used for some time as a stationary boiler at a food industry establishment. This machine can now be seen at the Industry and Railway Museum in Jaworzyna Śląska (former loco depot); its condition is far from satisfactory, but restoration is under way. Pt31-64 (s/n 721/1938) is now on display at the Rolling Stock Heritage Park in Chabówka. No more machines have survived until today.

Many view Pt31 the best locomotive ever designed and built in Poland and this opinion is certainly justified. Shortly after the war it was decided to commence its production as the basic express engine for Polish railways – once again. After some modifications it emerged as Pt47 and 180 examples were built, both by Fablok and HCP. This machine, of which two examples are still operational, is described under a separate entry.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1932 – 1940
2.	Total built / used in Poland	-	110^1) / 98
3.	Tender class	-	32D29
4.	Axle arrangement	-	1-4-1
5.	Design maximum speed	km/h	110
6.	Cylinder bore	mm	2 X 630
7.	Piston stroke	mm	700
8.	Engine rating	kW/hp	1472 / 2000
9.	Tractive effort	kG	13 500
10.	Boiler pressure	MPa	1.53
11.	Grate dimensions	m X m	2.71 X 1.664
12.	Firebox heating surface	m^2	17.0
13.	Distance between tube plates	mm	6 200
14.	Number of flue tubes	-	112
15.	Heating surface of flue tubes	m^2	118.0
16.	Number of smoke tubes	-	38
17.	Heating surface of smoke tubes	m^2	99.0
18.	Evaporating surface, total	m^2	234.0
19.	Superheater heating surface	m^2	91.46
20.	Diameter of drivers	mm	1850
21.	Diameter of idlers front/rear	mm	1000 / 1200
22.	Total weight, empty	kg	95 800
23.	Total weight, working order	kg	106 200
24.	Adhesive weight, working order	kg	73 800
25.	Weight with tender, empty	kg	122 300
26.	Weight with tender, working order	kg	174 700
27.	Maximum axle load	T	18.3
28.	Axle base (with tender)	mm	20 235
29.	Overall length (with tender)	mm	23 835
30.	Brake type	-	Westinghouse

1) Including 12 examples supplied directly to DRG in 1939 and 1940.

References and acknowledgments

Detailed account of this class history, design and pre-war service can be found in the monographic article by Paweł Terczyński in SK vol.11/2003 Comprehensive descriptions can be found in AP and PNP.