Within less than a year it was obvious that the B9A, despite its increased power, offered no real advantage over the original class S (later B9). A second, more comprehensive rebuild produced the B9B, which was useful both as a motive power unit and as a basis for Belčamin's ongoing development programme. The precursor of the most important characteristic of the 4-4-0s of 1906, namely the boiler with high superheat, can already be seen. Other improvements were new piston-valve cylinders, stronger mainframes and axle journals and more generously-dimensioned valve gear, plus a higher running plate and a shortened version of the Belčamin cab. A standard tender was attached. The balancing still left much to be desired and caused strong surging in the following train. This problem was instrumental in motivating Belčamin to give up tandem compounds once and for all and to apply only the De Glehn and Von Borries arrangements in his later designs. The B9B remained in use until 1911.

Text and graphics © Norman Clubb 2012