The reference for locomotives and railcars
Palatinate Railways P 5 and Bavarian Pt 3/6
German Reichsbahn class 770-1
Germany | 1908 | 41 produced
Die Lokomotive, June 1921

When a powerful passenger train locomotive was needed for the Palatinate network, the main lines with many stops and turning points were considered, and so the decision was made in favor of a large tank locomotive. The locomotive developed as the Palatinate P 5 only achieved its greatest number of units after it was taken over by the Bavarian State Railways and is therefore primarily known under its Bavarian designation Pt 3/6.

The P 5 was the first 2-6-4 tank locomotive on the European mainland. The rear bogie was primarily used to carry the weight of the supplies and had the effect that as the amount of coal decreased, there was still almost the same weight on the coupled axles. The reserves in the first variant included 16 cubic meters of water and 5.2 tons of coal, which was more than in older, three-axle tenders. The three coupled axles were used to be able to carry a heavy boiler and have a high tractive power available.

Due to this arrangement, it had become necessary to bring the leading axle as close as possible to the first coupled axle. Therefore, an extremely unusual arrangement of the Krauss-Helmholtz bogie was used, in which the leading axle was connected to the second coupled axle instead of the first. In addition, the cylinders were arranged relatively high and inclined, since there was no longer enough space in the usual position.

The first production lot included twelve engines, which had been delivered in 1908 as the P 5 with saturated steam. After the takeover, the state railway procured another 29 units between 1911 and 1923, which were already running on superheated steam. The remaining engine were finally also equipped with a superheater in 1925. In comparison, the maximum train load of the saturated engines at two percent and 30 km/h was 140 tonnes, while this could be increased to 180 tonnes with superheater

At the Reichsbahn, the older engines were given the numbers 77 001 to 77 012, while the newer ones became 77 101 to 77 129. The engines procured for Bavaria continued to be used on the express route between Garmisch-Partenkirchen and Munich, since these had similar characteristics to the routes for which the P 5 had originally been developed. Almost all of the locomotives of the newer series survived the Second World War, with only one eventually going to the Reichsbahn and the rest to the Bundesbahn, where they were used until 1956 and 1954 respectively. The nine remaining examples of the first series were sold to various private railways immediately after the war.

VariantP 5Pt 3/6
Axle config2-6-4T (Adriatic) 
Gauge4 ft 8 1/2 in (Standard gauge)
Dimensions and Weights
Length43 ft 1 5/16 in44 ft 1 15/16 in
Wheelbase30 ft 10 1/16 in30 ft 0 1/4 in
Fixed wheelbase11 ft 9 3/4 in
Empty weight141,096 lbs
Service weight204,809 lbs208,998 lbs
Adhesive weight110,231 lbs107,585 lbs
Axle load36,817 lbs35,935 lbs
Water capacity4,227 us gal3,698 us gal
Fuel capacity11,464 lbs (coal)9,921 lbs (coal)
Power sourcesteam
Indicated power849 hp (633 kW)
Estimated power1,006 hp (750 kW)
Optimal speed21 mph25 mph
Top speed56 mph
Starting effort26,044 lbf
Power Plant
Driver diameter59.1 in
Boiler pressure188 psi
Expansion typesimple
Cylinderstwo, 20 7/8 x 22 1/16 in
Grate area25.2 sq ft
Firebox area107 sq ft111.1 sq ft
Tube heating area1,497.3 sq ft1,083.1 sq ft
Evaporative heating area1,604.3 sq ft1,194.1 sq ft
Superheater area376.7 sq ft
Total heating area1,604.3 sq ft1,570.9 sq ft
Calculated Values
steam locomotive
tank locomotive
last changed: 01/2022

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