South African Class 10A 4-6-2

The South African Class 10A 4-6-2 of 1910 is a South African steam locomotive from the pre-Union era in the Transvaal.

In 1910 the Central South African Railways placed ten Class 10-2 4-6-2 Pacific type steam locomotives in service, of which five were built with and five without superheaters. In 1912, when the five non-superheated locomotives were assimilated into the South African Railways, they were renumbered and reclassified to Class 10A.^[3][4][5][6]

Manufacturer

Ten heavy 4-6-2 Pacific type passenger locomotives, designed by Central South African Railways (CSAR) Chief Mechanical Engineer (CME) G.G. Elliot and based on the Class 10 design of his predecessor, CSAR Chief Locomotive Superintendent P.A. Hyde, were ordered from the North British Locomotive Company (NBL) and delivered in 1910. They had plate frames, Belpaire fireboxes and Walschaerts valve gear and were delivered in two variants, five of them using saturated steam while the rest were superheated. They were all classified as Class 10-2 by the CSAR, numbered in the range from 665 to 674, and entered service in March 1910.^[5][3]

Characteristics

The Class 10A locomotives were similar to the Class 10, except that their boilers were arranged 7.5 inches (191 millimetres) further forwards and their firebox throats and back plates were sloped instead of being vertical. Like the Class 10, they had 62 inches (1,570 millimetres) driving wheels, the largest yet used in South Africa.^[3]

While the Class 10 had outside admission valves, the Class 10A used inside admission piston valves. The valve gear was reversed by means of a vertical steam reversing engine placed on the right-hand running board in line with the steam dome. Two Trevithick exhaust steam feedwater heaters were mounted on the running boards on either side of the smokebox, and a Weir’s feedwater pump was mounted on the left-hand side of the firebox. The feedwater heaters and the feedwater pump were removed after a few years since the feedwater heaters proved to be troublesome.^[3][7]

Reclassification

The Union of South Africa was established on 31 May 1910, in terms of the South Africa Act, enacted by the Parliament of the United Kingdom. One of the clauses in the Act required that the three Colonial Government railways, the Cape Government Railways, the Natal Government Railways and the CSAR, also be united under one single administration to control and administer the railways, ports and harbours of the Union. While the South African Railways (SAR) came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways required careful planning and was only implemented with effect from 1 January 1912.^[4][8]

When they were assimilated into the SAR in 1912, the five saturated steam locomotives, numbered in the range from 665 to 669, were reclassified as Class 10A and renumbered in the range from 747 to 751. The five superheated locomotives were designated Class 10B.^[4][5]

Watson standard boilers

In the 1930s many serving locomotives were reboilered with a standard boiler type designed by then CME A.G. Watson as part of his standardisation policy. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification.^[2][5]

All five of the Class 10A locomotives were eventually reboilered with Watson Standard no. 1 boilers. Since the original difference between the Class 10A and Class 10B lay only in the fact that their respective boilers were constructed without or with superheaters, distinction between the two types became unnecessary after reboilering and the reboilered Class 10A locomotives were reclassified to Class 10BR along with similarly reboilered Class 10B locomotives.^[2][5]

An obvious visual difference between an original and a Watson Standard reboilered locomotive is usually the rectangular regulator cover just to the rear of the chimney on the reboilered locomotive. In the case of the Class 10BR locomotives an even more obvious visual difference was the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.^[2]

Service

The Class 10A was placed in service hauling passenger trains out of Johannesburg. In service, it was found that the superheated Class 10B sister locomotives could handle almost 25% more load than the saturated steam Class 10A, so much so that double heading passenger trains in the Orange Free State became unnecessary with the Class 10B.^[3]

The Class 10A was therefore soon taken off mainline passenger service and put to good use on suburban work. After reboilering and reclassification to Class 10BR, most of the rest of their working lives were spent on the Cape Midlands system, where they were used on the mainline out of Port Elizabeth.^[5]

Two worked as station pilots at Kimberley, but in 1960 they joined the rest of the Class that were by then working the suburban between Port Elizabeth and Uitenhage. In later years they again served on the Reef’s suburban routes while a few were used in the same service around Cape Town, until they were eventually relegated to shunting work. They were scrapped in 1974.^[5]

Service illustrated

The main picture shows Class 10BR (ex Class 10A) number 751, ex CSAR Class 10-2 number 669.

• 

  Class 10BR (ex Class 10A) no. 750, ex CSAR Class 10-2 no. 668, plinthed at Roodepoort Station

See also

• List of South African locomotive classes
• South African Class 10 4-6-2
• South African Class 10B 4-6-2
• South African Class 10C 4-6-2
• South African Class 10D 4-6-2
• South African locomotive history
• Tender locomotive numbering and classification
• The 4-6-2 "Pacific"
• Watson Standard boilers

References

Wikimedia Commons has media related to: South African Class 10A (4-6-2)

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