page_title: 4-6-2
section_title: South African Railways
hierarchical_section_title: 4-6-2 / Usage / South Africa / Cape gauge / South African Railways
caption_attribution_description: English: SAR Class 16B 805 (4-6-2) Location: Johannesburg
context_page_description: Under the Whyte notation for the classification of steam locomotives, 4-6-2 represents the wheel arrangement of four leading wheels on two axles, six powered and coupled driving wheels on three axles and two trailing wheels on one axle. The 4-6-2 locomotive became almost globally known as a Pacific type.
context_section_description: Seven Class 16 variants were introduced on the South African Railways (SAR) between 1914 and 1935.
  The Class 16 Pacific was designed by Hendrie, CME of the SAR from 1910 to 1922, and was built by NBL, who delivered twelve locomotives in 1914. The design closely followed that of the Class 15 4-8-2 Mountain type that was introduced at the same time from the same builders, and many parts were made interchangeable. They had Walschaerts valve gear, were superheated and had Belpaire fireboxes. At the time, it was considered a very large and powerful express locomotive, even when compared to British locomotives built to run on 4 ft 8 ¹⁄₂ in (1,435 mm) standard gauge. With 60 inches (1,524 millimetres) coupled wheels, the ratio of wheel diameter to rail gauge was the same as that of a Standard gauge locomotive having 81 inches (2,057 millimetres) coupled wheels. Their tractive effort of 29,890 pounds-force (133.0 kilonewtons) at 75% boiler pressure exceeded the 27,800 pounds-force (123.7 kilonewtons) at 85% boiler pressure of Churchward's The Great Bear on the Great Western Railway and equalled, also at 85% boiler pressure, that of Gresley's subsequent Great Northern Pacifics. This made the Class 16 the most powerful express passenger locomotive design yet to have been built in Britain at the time.
  The Class 16A four-cylinder simplex Pacific of 1915 was designed by Hendrie and built by NBL. Two locomotives were delivered, identical in most respects to their predecessor Class 16 except that they had four cylinders instead of the usual two. All four cylinders were arranged in line below the smokebox and were the same size, with the outer cylinders driving the centre coupled wheels while the inner cylinders operated on a cranked leading coupled wheel axle. The result was a very smooth running locomotive, capable of very fast running, but since the available space on a Cape gauge locomotive prevented larger cylinders from being fitted, the four-cylinder design was never repeated by the SAR.
  The Class 16B Pacific, also designed by Hendrie, was also built by NBL, who delivered ten locomotives in November 1917. They were identical to the predecessor Class 16 and successor Class 16C in most respects, except that they had wider cabs than the Class 16, while the Class 16C had a combustion chamber in the firebox. All ten were eventually reboilered with Watson Standard no 2B boilers and Watson cabs with slanted fronts, and reclassified to Class 16CR.
  Ten Class 16C locomotives, also designed by Hendrie and built by NBL, were delivered in 1919 with another twenty following in 1922. Identical to predecessors Class 16 and Class 16B in most respects except for the addition of a combustion chamber, they proved to be excellent free-steaming, fast and reliable locomotives with a reserve of power greater than either of the predecessors. All thirty were later reboilered with Watson Standard no 2B boilers and also reclassified to Class 16CR.
  Seven Class 16D Pacific locomotives were built for the SAR by Baldwin Locomotive Works in 1925 and 1926. The Class was designed for working the Union Limited and Union Express fast passenger trains, forerunners of the Blue Train, between Johannesburg and Cape Town. The builders conformed to SAR requirements, but also incorporated the latest American railway engineering practices and introduced several new features to the SAR, such as top feeds to the boiler, self-cleaning smokeboxes, Sellar's drifting valves, grease lubrication and arch tubes to support the brick arch and improve circulation. It had a bar frame extending from the front buffer beam to the rear dragbox, while its size earned it the nickname Big Bertha. In 1926, no. 860 made locomotive history by hauling the Union Limited over the 956 miles (1,539 kilometres) from Johannesburg to Cape Town in 29 hours.
  When orders for more Pacific locomotives were placed in 1928, the Class 16D design was modified by the CME, Colonel F.R. Collins DSO, who shortened the frame to end at the front of the firebox and added a bridle casting. This resulted in a wider frame 
caption: Class 16B No. 805 restored to its as-delivered appearance
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