South African Class H 4-10-2T

The South African Class H 4-10-2T of 1899 is a South African steam locomotive from the pre-Union era in the Natal Colony.

Between 1899 and 1903 the Natal Government Railways placed one hundred and one tank steam locomotives with a 4-10-2T wheel arrangement in service. In 1912, with the establishment of the South African Railways, the ninety-three Class C Reid Tenwheelers that survived unmodified were designated Class H.^[3][4]

Manufacturers

Increasing traffic on the new Natal Government Railways (NGR) mainline into the interior, with its sharp curves and severe 1 in 30 gradients, led to the requirement for a tank locomotive that could haul at least one and a half times as much as a Dübs A 4-8-2T locomotive. This resulted in the design of a 4-10-2T tank locomotive by G.W. Reid, Locomotive Superintendent of the NGR at the end of the nineteenth century.^[1][4]

Since there was no precedent for such an enormous Cape gauge tank locomotive, the design was the subject of some severe criticism and various objections were put forward against its introduction. It was therefore decided to order only one experimental locomotive from Dübs and Company. It was delivered in 1899 and numbered 149.^[1]

In 1900 the General Manager of the NGR reported that the trials of the 4-10-2 locomotive had proven successful beyond anticipation. As a result, orders were placed for another one hundred locomotives between 1901 and 1903. The first ninety-five of these locomotives were built in four batches by Dübs and were numbered in the range from 150 to 244.^[1]

Since Dübs and a number of other Scottish locomotive builders were merged to form the North British Locomotive Company (NBL) while the locomotives were being built, the last five were delivered as having been built by the newly established NBL, numbered in the range from 245 to 249. On the NGR the locomotive type became known as the Reid Tenwheeler and when a locomotive classification system was introduced, they were designated Class C.^[1][5][6]

Characteristics

In order to negotiate sharp curves, both the first and fifth pairs of coupled wheels were flangeless. The locomotives used saturated steam and were equipped with Allan straight link valve gear, which was chosen chiefly because it required less space than the more usual Stephenson lifting link gear and was simpler in construction. The trailing Bissel truck was of the Cartazzi type that allowed the axle some lateral movement.^[1][4]

The portion of the crankpins for the connecting rod big-ends was turned 1.5 inches (38.1 millimetres) eccentric to obtain the longest possible piston stroke that the wheel diameter would permit. The piston rods and crossheads were forged in one piece, so the connecting rod small-ends had to be forked.^[1]

Modifications

NGR Class C no. 149, SAR Class H no. 232, c. 1900

The main shortcoming of the Reid Tenwheeler was a tendency to derail while reversing, particularly over points, since the trailing drivers were flangeless. This was overcome by increasing the tyre width from 6 inches (152 millimetres) to 7 inches (178 millimetres), after which the locomotives proved successful in service.^[1]

When some were withdrawn from mainline service and put in branchline and shunting service where smaller radius curves were encountered, they were modified to 4-8-2T locomotives by removing the fifth pair of coupled wheels.^[1][4]

Renumbering

The Union of South Africa was established on 31 May 1910, in terms of the South Africa Act. One of the clauses in the Act required that the three Colonial Government railways, the Cape Government Railways, the NGR and the Central South African Railways, 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.^[3][7]

In 1912 ninety-three as yet unmodified Class C Reid Tenwheelers were designated Class H on the SAR and renumbered in the range from 232 to 324, while the modified 4-8-2T engines were designated Class H2 and renumbered in the range from 227 to 231. Three locomotives, NGR numbers 194, 195 and 214, were scrapped prior to 1912 and did not come under the renumbering scheme.^[1][4][3]

The SAR Class H locomotives were subsequently gradually also modified to a 4-8-2T wheel arrangement. The first three of these, SAR numbers 240, 294 and 305, were renumbered again to 329, 330 and 331 respectively, but the rest retained their Class H numbers after modification. Their builders, works numbers and renumbering are set out in the table.^[1][3]

Service

The Reid Tenwheelers were employed on the lower section of the Natal mainline. Most of them continued to work there even after more powerful locomotives were placed in service. In the SAR era some were relocated to De Doorns in the Cape Province for banking service up the Hex River Pass. They had a long service life and some, modified to 4-8-2T, remained in service until 1977.^[4]

Other operators

Imperial Military Railways

In 1902, during the Second Boer War, the Imperial Military Railways (IMR) placed orders for altogether thirty-five locomotives of the Reid Tenwheeler type with Dübs and Company and Neilson, Reid and Company. In SAR service, these locomotives were designated Class H1 in 1912.^[1][4]

Industry

A final order for one new Reid Tenwheeler type locomotive was placed by Witbank Collieries as late as 1927. The total of 137 locomotives that were built to this design was about double the number of all other 4-10-2 locomotives in use elsewhere in the world, all of which were tender locomotives serving mainly in the United States of America and Brazil.^[5]

See also

• South African Class H1 4-8-2T
• South African Class H2 4-8-2T
• The 4-10-2 "Reid Tenwheeler"
• South African locomotive history
• List of South African locomotive classes

References

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

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