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The Maschinenfabrik Esslingen, the "in-house supplier" to K.W.St.E., supplied the first five machines of the Class AD Württemberg express train in 1899. 98 locomotives had been delivered by 1907.
K.W.St.E. had started using the locomotives of the axle series 2B, i.e. with a front bogie and two driven axles, and exclusively purchased machines of this type in the period between 1845 and 1865. Then, due to the arrival of a new senior machine master and his ideas, preference was shown to other construction types.
When K.W.St.E. needed a new express locomotive shortly before the turn of the century, they once again returned to the double coupled machine with a front bogie. By now, this construction type had established itself as an express locomotive. The Maschinenfabrik Esslingen, the "in-house supplier" to K.W.St.E., supplied the first five machines of the Class AD in 1899.
The locomotives with a typical connection pipe between the domes, had traction wheels with a diameter 1800 mm, which allowed a top speed of 100 km/h. On flat stretches they could move a 150 t train weight at top speed. The low maximum axle load of only 14 t allowed them to be used on all Württemberg lines. The machines were fitted with the two-axle standard tender with 10 cm³ of water.
A total of 98 locomotives of differing construction series were delivered by 1907. Actually, there should have been 100 but the last two locomotives were fitted with a superheater in 1907 and delivered as hot steam locomotives of the class ADh. This technology seemed to be successful and a further 15 hot steam locomotives had followed by 1909. By now the weight of the express trains had increased so much that they could hardly be moved anymore by the light 2B locomotives. The class AD moved into the passenger service.
As an experiment, a superheater was also fitted to one of the wet steam locomotives, the 1506. Although the performance of the locomotive was increased, no other locomotives were refitted because they were due to be taken out of service shortly. The last Württemberg express locomotives AD and ADh remained in service until 1932.
bu da link:
http://www.brawa.de/en/products/h0/locomotives/steam-locomotives/0640-br-ad.html