The Bavarian Class Gt 2×4/4 (bayerische Gt 2x4/4) engine of the Royal Bavarian State Railways (Königlich Bayerische Staats-Eisenbahnen or K.Bay.Sts.B.), was a heavy goods train tank locomotive of the Mallet type. It was later designated the DRG Class 96 (Baureihe 96) by the DRG, DB and DR.
Description
The Gt 2x4/4 Mallet locomotive was equipped with two sets of compound-configured running gear, the front one, pivoted on a 15 cm thick coupling pin, had large low-pressure cylinders, and the rear one, which was fixed, had smaller high-pressure cylinders. Both had one driven and three coupled axles. The designer of this heavy locomotive was the then senior engineer and director at Maffei, Anton Hammel, (1857-1925), who had also developed the famous S 3/6. Between 1913 and 1914 the first series of 15 vehicles was procured and they entered service in 1914. The locomotives caused quite a stir at that time and could be seen at the railway exhibitions frequently held in those days (e.g. the 1922 transport exhibition in Munich) - and, like the S 3/6, they were often painted with a blue or ochre yellow photographic livery and adorned with a crowned chimney. As the first one of the second series, no. 5766 (96 016) was even spruced up with brass bands on the crowned chimney and boiler as well as brass decorations on its front cylinders, and certainly made an impression. A similar thing was carried out on the same locomotive after the rebuilding of the second series in 1926. Otherwise, the first series had a narrow chimney with a cap similar to the Prussian P 8. The operational livery of the K.Bay.Sts.B. locomotives was green with yellow lettering and a black chassis.
Due to the advent of the Prussian T 20 (DRG Class 95) in 1922 with its 1'E1' axle arrangement and better qualities than the initial Gt 2x4/4 series, a second series was built and deployed between 1922 (no. 5766) and 1923 (nos. 5767–5775). They were improved in comparison with their predecessors: greater evaporative heating area, capable of holding half a ton of coal more, greater axle load and service weight, short chimney (without a cap). Both series were later modified in different ways after being taken over by the Deutsche Reichsbahn, and incorporated into its classification scheme as Class 960. All locomotives were equipped with a Westinghouse compressed-air double brake, operating on all wheelsets from the front, the sand pipes initially served the second and fourth wheelsets of the front drive. After the modification of the second series in 1926, they were additionally fitted with a Riggenbach counter-pressure brake, and seven axles sanded to increase adhesion. To begin with the locos ran with three headlights at the front, but just two after 1926.
Rebuild
In 1925/1926 all the engines were rebuilt and strengthened, those of the first series being modified to a lesser extent (e.g. chimney enlargement, coal capacity increased from 4 to 4.5 t, boiler data, ride) than those of the second series. The following table shows the main changes that were made to second series:
High-pressure cylinder extended from 520 mm to 600 mm diameter
Blastpipe set lower and diameter increased
Chimney widened and shortened a little
Reduction in the number of heating tubes and increase in the number of smoke tubes Reduction in the total tube heating area Increase in the superheater area Installation of a feedwater heater (Oberflächenvorwärmer) in front of the stack Installation of a second air pump next to the first Installation of Riggenbach counter-pressure brake Increased coal bunker capacity from 4.5 t to 5 t Modified boiler fittings (sandbox, steam dome) Modifications to improve the ride ('slipping' of the front LP running gear) Sand pipes for 7 instead of 2 wheelsets Increase in adhesive weight from 123.2 to 131.1 Mp Increase in the centre coupled axle's axle load from 15.4 Mp to 16.4 Mp