South African Class 10A 4-6-2

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CSAR Class 10-2 4-6-2 Saturated
South African Classes 10A & 10BR 4-6-2
SAR Class 10BR 751 (4-6-2).jpg
Class 10BR (ex Class 10A) no. 751,
ex CSAR Class 10-2 no. 669
Type and origin
Power type Steam
Designer Central South African Railways
Builder North British Locomotive Company
Serial number 18971-18975
Model CSAR Class 10-2
Build date 1910
Total produced 5
Configuration 4-6-2 "Pacific"
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading dia 28.5 in (724 mm)
Driver diameter 62 in (1,575 mm)
Trailing dia 33 in (838 mm)
Wheelbase Total: 55 ft 8 in (16,967 mm)
6 ft (1,829 mm) bogie
10 ft 10 in (3,302 mm) coupled
30 ft 2 in (9,195 mm) total
4 ft 7 in (1,397 mm) bogie
16 ft 9 in (5,105 mm) total
Length 63 ft 10.875 in (19,479 mm)
Height 12 ft 10 in (3,912 mm) as built
12 ft 11 in (3,937 mm) reboilered
Frame Plate frame
Axle load 15.9 long tons (16.2 t) on 2nd driver as built
16.4 long tons (16.7 t) on 3rd driver reboilered
Adhesive weight 47 long tons (47.8 t) as built
48.15 long tons (48.9 t) reboilered
Loco weight 73.75 long tons (74.9 t) as built
76.1 long tons (77.3 t) reboilered
Tender weight 48,144 lb (21.8 t) empty
49.35 long tons (50.1 t) w/o
Loco & tender weight 151,984 lb (68.9 t) empty
125.1 long tons (127.1 t) as built
125.45 long tons (127.5 t) reboilered
Tender type XM2 - XC, XC1, XD, XE, XE1, XF, XF1, XF2, XJ, XM, XM1, XM2, XM3, XM4, XP1, XS permitted
* 2 axle bogies
* 34 in (864 mm) wheels
* Length 25 ft 11.625 in (7,915 mm)
Fuel type Coal
Fuel capacity 10 long tons (10.2 t)
Water cap 4,000 imp gal (18,000 l)
 • Firegrate area
34.6 sq ft (3.214 m2) as built
36 sq ft (3.345 m2) reboilered
Boiler As built:
4 ft 6.75 in (1,391 mm) inside diameter
18 ft 6.5 in (5,652 mm) inside length
7 ft 4 in (2,235 mm) pitch
5 ft (1,524 mm) inside diameter
17 ft 9 in (5,410 mm) int length
8 ft (2,438 mm) pitch
Boiler pressure 200 psi (1,380 kPa) as built
180 psi (1,240 kPa) reboilered
Feedwater heater Trevithick exhaust steam type
Heating surface 1,810 sq ft (168.155 m2) as built
1,620 sq ft (150.503 m2) reboilered
 • Tubes As built:
154 tubes 2.25 in (57 mm) diameter
1,682 sq ft (156.263 m2)
76 tubes 2.5 in (64 mm) diameter
24 tubes 5.5 in (140 mm) diameter
1,491 sq ft (138.518 m2)
 • Firebox 128 sq ft (11.892 m2) as built
123 sq ft (11.427 m2) reboilered
Superheater Saturated steam as built
 • Heating area 366 sq ft (34.003 m2) reboilered
Cylinders Two
Cylinder size 18.5 in (470 mm) bore as built
20 in (508 mm) bore reboilered
28 in (711 mm) stroke
Valve gear Walschaerts
Performance figures
Tractive effort At 75% boiler pressure:
23,180 lbf (103.1 kN) as built
24,390 lbf (108.5 kN) reboilered
Operators Central South African Railways
South African Railways
Class CSAR Class 10-2, SAR Class 10A
Number in class 5
Numbers CSAR 665-669, SAR 747-751
Delivered 1910
First run 1910
Retired 1974

The South African Railways Class 10A 4-6-2 of 1910 is a 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.[1][2][3][4]


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.[1][3][5]


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.[1]

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.[1][6]


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.[2][7]

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.[2][3]

Watson standard boilers[edit]

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.[3][8]

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.[3][8]

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.[8]


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.[1]

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.[3]

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.[3]


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


  1. ^ a b c d e Holland, D.F. (1971). Steam Locomotives of the South African Railways, Volume 1: 1859-1910 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 137–138. ISBN 978-0-7153-5382-0. 
  2. ^ a b c Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, pp. 9, 12, 14, 34 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
  3. ^ a b c d e f g Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 52. ISBN 0869772112. 
  4. ^ Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. p. 20. ISBN 978-0-7153-5427-8. 
  5. ^ North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
  6. ^ Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 10. ISBN 0715386387. 
  7. ^ The South African Railways - Historical Survey. Editor George Hart, Publisher Bill Hart, Sponsored by Dorbyl Ltd., Published c. 1978, p. 25.
  8. ^ a b c South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended