South African Railways 2-10-4 Locomotives in South_Africa

Class 21 (Locobase 13101)

Data from Holland, Volume II (1972), p. 24-25; Cdr J Plomer, "A Long Line of Mountains", The Railway and Locomotive Historical Society Bulletin, No. 122 (April 1970), pp. 7-25; and South African Locomotive Diagrams supplied in August 2013 by Allen Stanley from his extensive Rail Data Exchange collection. Works number was 24379 in 1937.

AG Watson's aversion to articulated locomotives led to his adoption of what was known in the United States as the Texas wheel arrangement for this branch-line freight engine to travel on 60-lb/yard (30-kg/metre) rail. The boiler and firebox were essentially identical to the 15E Mountains (Locobase 2962).

Watson planned to use RC Poppet valves as he had in his other new locomotives, but his retirement before the locomotive's delivery led quickly to the substitution of Walschaert's constant-lead radial valve gear. Despite the Locomotive Superintendent's hopes, service results showed that the rigid-wheelbase 5-coupled couldn't compete with the Garratts.

(Plomer took the opportunity presented by his detailed review in the L&RHSB to note that most heavy locomotives and tenders castings "had to come from America." He cited three reasons: Britain's largest producer of such castings failed during the Great Depression, the ship builders who could cast such items preferred to make their own forgings, and continued English preference (for the most part) for plate frames prevented making such cast frames from ever making economic sense.

As a result: "Baldwin's subsidiary which produced such castings shipped many to England, and other countries, when customers included them in their specifications." So, despite the absence of locomotive orders from American builders in South Africa, "Baldwin continued to ride the rails in many countries even if few were aware of it.")

Class 22 (Locobase 2963)

Although never built, this engine -- designed by the SAR's WAJ Watson -- illustrates what a little self-confidence and a high axle loading might lead to on the Cape gauge.

Unfortunately for the Class 22, it was too narrowly defined as a heavy hauler when what the SAR needed was a general mixed-traffic type. Moreover, says Holland (1972, II), sidings were not long enough to accommodate this behemoth. It remained a concept only. Note the large superheater flue diameter.