NZASM 40 Tonner 0-6-2T
The NZASM 40 Tonner 0-6-2T of 1892 was a South African steam locomotive from the pre-Union era in Transvaal. In 1892 and 1893, the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM) of the Zuid-Afrikaansche Republiek (Transvaal Republic) placed twenty locomotives in mainline service. Since the railway classified its locomotives according to their weight, these locomotives were known as the . Manufacturer Although the completion of the line from Delagoa Bay to Pretoria was still more than three years in the future, a requirement for larger and heavier mainline locomotives was identified in 1891. The Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM) therefore ordered ten tank locomotives from Emil Kessler's Maschinenfabrik Esslingen. A second order for another ten followed later in 1891. The first batch of locomotives were delivered in 1892, numbered in the range from 41 to 50. Of the second batch, numbered in the range from 51 to 60, the last seven were built in 1892. Since the NZASM classified its locomotives according to their weight, these locomotives were known as the . In addition to being numbered, they were all named as well, with the names and numbers cast in brass and mounted on their tank sides. Characteristics The locomotive used Murdoch's D unbalanced slide valves, arranged horizontally above the cylinders outside the plate frames and actuated by Heusinger valve gear. These valves caused considerable wear on motion pins and were later replaced by Trick ported balanced slide valves. The boiler barrel was built up in three rings, arranged telescopically, with the smallest diameter at the firebox end. The rings were lap-jointed and double riveted on longitudinal seams. These boilers had a long life and required little expense in repairs. Five cross-stays were fitted in the steam space above the firebox. The safety valves were arranged above the firebox inside the cab, while a steam escape pipe was fitted above the valves and passed through the roof. The exhaust had an Adams' Vortex pattern annular nozzle. While this presented additional surface to the blast, the annular orifice had a tendency to become clogged, which increased back pressure, and the exhaust pipes therefore frequently had to be taken out for cleaning. As delivered, the locomotive had thick wooden buffer beams which were later replaced by thick steel plates. The distance between the locomotive's tyres, i.e. between the wheel flanges on the axle, was . This was greater than for engines of the Cape Government Railways and Natal Government Railways and, although the flanges were somewhat thinner, the resulting tightness to gauge was blamed for the rather high rate of flange wear. To obtain greater life from the leading coupled wheels, they were occasionally exchanged with the trailing coupled wheels during overhauls. The original coupled axles were in diameter and were inclined to fracture. This was remedied by increasing the diameter to on new axles. The trailing wheels also proved to be troublesome. The trailing wheels and axle were of the radial type and were attached directly to the frame, which gave the locomotive a rigid wheelbase. The