Württemberg Tss 4

The class Tss 4 referred to a small series of only three tank locomotives for 750 mm gauge, which was derived from the Ts 4 for 1,000 mm, which was also built only three times. They were used on the Bottwartalbahn from Heilbronn to Marbach, where they were used until they were replaced in the 1920s.

In order to improve the running characteristics on radii of up to 80 meters, the locomotives were designed with a complicated Klose chassis. In this case, only the second axle was fixed and the fourth axle, which was offset far to the rear, steered the first and third axles by a maximum of 31 mm each via a lever system. A lever system was also used to transmit power to the last coupled axle, which changed the length of the coupling rods depending on the curve radius. A special feature was the outer frame, because of which inside and inclined cylinders were also used. However, the coupling rods and the valve gear were outside the frame, since a lot of space was needed for the lever mechanism. The power was transmitted via Hall cranks and the water tanks had the cut-outs typical of Klose locomotives to provide enough space for the mechanics.

The three machines were given the operating numbers 11 to 13 and were named after localities along the 37 km long route. The latter were Großbottwar, Oberstenfeld and Beilstein. The Tssd 42 in a simpler Mallet design followed just five years after it was put into service, so no further Tss 4s were ordered. Nevertheless, the three machines remained in use and by the early 1920s were already showing clear signs of wear. At that time, after the establishment of the Reichsbahn, the Saxon VI K was also introduced on this line, so that the first machine was retired as early as 1923. The others still received the Reichsbahn numbers 99 621 and 99 622 and were retired by 1928.