South African 4-8-4

The first railway in South Africa was built to British standard gauge, but for ease of construction in hilly territory the choice eventually fell on a gauge of 3 ft. 6 in., and all subsequent South African railways, with the exception of some 2-ft. track, were built to this standard.

Despite this, South African locomotives were among the largest and most powerful in the world; a wide variety of Beyer-Garratt types were at work, and the most powerful of these developed almost 80,000-lb. tractive effort and weighed no less than 214 tons.

Of all contemporary S.A.R. locomotives, however, the most impressive were the immense Class ' 25 ' 4-8-4s, fifty of which were built by Henschel and North British in 1953; with two 24 in. x28 in. cylinders and 225lb. pressure they developed a tractive effort of over 51,000 Ib. and were the most powerful non-articulated 3ft 6in gauge engines in the world.

The original engines were followed by ninety similar machines with condensing tenders, and one of these is seen here at Cape Town. Instead of exhausting the used steam to atmosphere, it passes from the cylinders back into the tender, where it is condensed for further use. This feature enables the locomotives to work over long desert stretches without replenishing their water supply.