page_title: 2-10-2
section_title: South Africa
hierarchical_section_title: 2-10-2 / Usage / South Africa
caption_attribution_description: English: SAR Class 18 (2-10-2) at Germiston loco, with additional plating under the smokebox front
context_page_description: Under the Whyte notation for the classification of steam locomotives, 2-10-2 represents the wheel arrangement of two leading wheels, ten powered and coupled driving wheels, and two trailing wheels. In the United States of America and elsewhere the 2-10-2 is known as the Santa Fe type, after the Atchison, Topeka and Santa Fe Railway that first used the type in 1903.
context_section_description: On 3 ft 6 in (1,067 mm) Cape gauge, this wheel arrangement was first used by the South African Railways (SAR) in 1927. Two Class 18 steam locomotives, the most powerful non-articulated locomotives to see service on the SAR, were introduced on the line between Witbank and Germiston in an attempt to ease problems that were being experienced with increasingly heavy coal trains. It was designed by Colonel F.R. Collins DSO, Chief Mechanical Engineer of the SAR from 1922 to 1929, and built by Henschel and Son in Germany. They were three-cylinder locomotives, with the two outer cylinders using Walschaerts valve gear and the inner cylinder using Gresley conjugated valve gear, actuated by the motions of the outer cylinders.
  One more 2-10-2 locomotive, the Class 20, was designed for branch line work on light rail by A.G. Watson, Chief Mechanical Engineer from 1929 to 1936. Only one locomotive was built by the SAR at its Pretoria Mechanical Shops at Salvokop in 1935.
  In 1950, this sole Class 20 locomotive was modified to an experimental condensing locomotive, equipped with a condensing tender that was ordered from Henschel in Germany in 1948. Beginning in 1951, tests with the condensing Class 20 were conducted in the Eastern Transvaal and the Karoo. The positive results of the condensing trials proved the viability of condensing locomotives in South Africa and led to the introduction of the Class 25 4-8-4 condensing locomotive fleet in 1953.
caption: SAR Class 18
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