Pf1

Hannover 628 (Hanomag 4156/1904), factory photo. Source: Lokomotiven der alten deutschen Staats- und Privatbahnen by Hermann Maey and Erhard Born (Transpress, 1983).

Side drawing of the S7 Bauart Hannover; source: Lokomotiv-Archiv Preußen vol. 1 (see References)..

First Prussian express locomotives with four-cylinder compound engines – class S5, later S5¹ – were considered an interim type and built in comparatively small numbers (93 examples in two distinct versions, known as Bauart Grafenstaden and Bauart Hannover). They served mainly with the railways of then-German Alsace-Lorraine. Their intended replacement was class S7, which differed mainly in being fitted with the Adams rear pony truck, in order to accommodate larger firebox (grate area increased by almost 20 percent).

As with its predecessor, class S7 was built in two versions. Of these, Bauart Hannover, designed by August von Borries and built by Hanomag (prototype 3768/1902), was standardized as Musterblatt III-2f. Between 1902 and 1906, 159 examples were built by Hanomag (123) and Linke-Hofmann (36). During first two years they were built in parallel with older types, S5¹ and even S3. Typically they were coupled with 4T21,5 standardized tenders (Musterblatt III 5h), sometimes with smaller 4T19s. Despite having been standardized, this engine was not considered entirely successful and did not find widespread use, as improvement compared to class S5¹ was below expectations. Bauart Grafenstaden fared even worse, only 79 being built (this locomotive is described under a separate entry). Both were superseded by class S9 with much larger boiler, but substantial improvement was achieved only with class S6. The latter, although having the same axle arrangement as S5¹, namely 2-2-0, ran on superheated steam and offered much better performance.

After WWI eight locomotives of this type were taken over by Belgian railways (SNCB service numbers 6704, 6705, 6711 and 6716 through 6720) and six by French. German railways DRG withdrew them completely until 1923, so no new Bauart designation was assigned. In fact they were outlived by older classes. Polish state railways acquired seven engines, classed Pf1 (four built by Hanomag and three by Linke-Hofmann). Assignment of individual service numbers is not known. Little is known about their service and all were withdrawn between 1927 and 1936. No locomotive of this type has been preserved.

Main technical data

No.	Parameter	Unit	Value
1.	Years of manufacture	-	1902 – 1906
2.	Total built / used in Poland	-	159 / 7
3.	Tender class	-
4.	Axle arrangement	-	2-2-1
5.	Design maximum speed	km/h	100^1)
6.	Cylinder bore	mm	2 X 360 / 2 X 560
7.	Piston stroke	mm	600
8.	Engine rating	kW/hp
9.	Tractive effort	kG	6 400
10.	Boiler pressure	MPa	1.43
11.	Grate dimensions	m X m	2.71 m^2
12.	Firebox heating surface	m^2	10.0
13.	Distance between tube plates	mm	4 550
14.	Number of flue tubes	-	241
15.	Heating surface of flue tubes	m^2	151.6
16.	Number of smoke tubes	-	-
17.	Heating surface of smoke tubes	m^2	-
18.	Evaporating surface, total	m^2	161.6
19.	Superheater heating surface	m^2	-
20.	Diameter of drivers	mm	1980
21.	Diameter of idlers front/rear	mm	1000 / 1000
22.	Total weight, empty	kg	54 100
23.	Total weight, working order	kg	60 200
24.	Weight on drivers, working order	kg	30 400
25.	Weight with tender, empty	kg
26.	Weight with tender, working order	kg
27.	Maximum axle load	T	15.2
28.	Axle base (with tender)	mm	15 500
29.	Overall length (with tender)	mm	18 405
30.	Brake type	-	Knorr

1) During tests 143 km/h was reportedly achieved. Officially increased to 110 km/h in 1907.

References and acknowledgments

- Lokomotiv-Archiv Preußen Band 1 by Andreas Wagner, Dieter Bäzold, Rainer Zschech and Ralph Lüderitz (Bechtermünz Verlag, 1996);

- LP;

- http://www.oocities.org/de/rolfwiso (website by Rolf Wisotzky);

- www.pl.wikipedia.org;