Pfalzbahn / Bavaria 2-6-4 Locomotives in Germany

Class Details by Steve Llanso of Sweat House Media

Class Pt 3/6 // BR 77.1 (Locobase 5755)

Data from Christian Lindecke's website [] (visited 28 Nov 2003). Additional data from US Military Railway Service Equipment Data Book -- German Locomotives supplied by Allen Stanley from his extensive Rail Data Exchange in March 2004. Supplemented by [], last accessed 14 May 2011, last accessed 14 May 2011 and from cnum_8XAE739, Exposition universelle, Groupe VII. Classes 39 et 40: Industrie des Transports-Chemins de fer et Tramways. Exposition internationale des industries et du travail de Turin 1911 (Paris: Comite Francais des Expositions a l'Etranger, 1911), p. 18.

These 90-km/h (55 mph) engines were the superheated version of the 1908 P5s. Taking advantage of the greater efficiency of the superheater, the design had a lower boiler pressure (13 bar vs 14 bar). Fire-side tube diameter was 40 mm and the flues measured 124 mm internally. Those measurements a combined tube-and-flue heating surface area of 100.62 sq m (1,083 sq ft); Locobase shows the water-side diameters and areas. The design's trailing load on a 2% grade rose from 140 tons to180 tons.

They were built in two batches. The first nine were delivered to the Pfalzbahn in 1911-1913; see Locobase 5754. The last ten came to the Bavarian in 1923 as Pt3/6.16 class; these operated expresses between Garmisch and Partenkirchen to Munich.

Very quickly all were taken into the newly formed DRG as the BR 77.10 class. Those that were still fitted with the unsatisfactory Pielock superheater (see Locobase 13565 for a detailed description of this unit) were retrofitted with the Schmidt version in 1925. An impressive number of these Munich-based tanks served through World War II, being retired in 1950.

Principal Dimensions by Steve Llanso of Sweat House Media

ClassPt 3/6 // BR 77.1
Locobase ID5755
RailroadPfalzbahn / Bavaria
Number in Class19
Road Numbers77 110-77 129
Number Built19
Valve GearWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)
Engine Wheelbase (ft / m)30.02 / 9.15
Ratio of driving wheelbase to overall engine wheelbase
Overall Wheelbase (engine & tender) (ft / m)30.02 / 9.15
Axle Loading (Maximum Weight per Axle) (lbs / kg)35,935 / 16,300
Weight on Drivers (lbs / kg)107,585 / 48,800
Engine Weight (lbs / kg)208,998 / 94,800
Tender Loaded Weight (lbs / kg)
Total Engine and Tender Weight (lbs / kg)208,998 / 94,800
Tender Water Capacity (gals / ML)3696 / 14
Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT)5 / 5
Minimum weight of rail (calculated) (lb/yd / kg/m)60 / 30
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)59.10 / 1500
Boiler Pressure (psi / kPa)188.50 / 13
High Pressure Cylinders (dia x stroke) (in / mm)20.87" x 22.05" / 530x560
Tractive Effort (lbs / kg)26,037 / 11810.20
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.13
Heating Ability
Tubes (number - dia) (in / mm)135 - 1.772" / 45
Flues (number - dia) (in / mm)21 - 5.236" / 133
Flue/Tube length (ft / m)13.12 / 4
Firebox Area (sq ft / m2)111.08 / 10.32
Grate Area (sq ft / m2)25.19 / 2.34
Evaporative Heating Surface (sq ft / m2)1310 / 121.70
Superheating Surface (sq ft / m2)377 / 35
Combined Heating Surface (sq ft / m2)1687 / 156.70
Evaporative Heating Surface/Cylinder Volume150.05
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation4748
Same as above plus superheater percentage5793
Same as above but substitute firebox area for grate area25,545
Power L111,183
Power MT687.48

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