| South African Class 4A 4-8-2 & South African Class 4AR 4-8-2 |
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|---|---|
| SAR Class 4A 1559 at Hutchinson, Cape Province, 11 November 1916 | |
| Power type | Steam |
| Designer | Cape Government Railways |
| Builder | North British Locomotive Company |
| Serial number | 20225-20234[1][2] |
| Model | CGR 4-8-2 |
| Build date | 1913 |
| Total produced | 10 |
| Configuration | 4-8-2 "Mountain" |
| Gauge | 3 ft 6 in (1,067 mm) Cape gauge |
| Leading wheel diameter |
28.5 in (724 mm) |
| Driver diameter | 54 in (1,370 mm) |
| Trailing wheel diameter |
33 in (838 mm) |
| Wheelbase | Total: 58 ft 5.375 in (17.815 m) Engine: 6 ft 2 in (1.880 m) pilot 14 ft 5 in (4.394 m) coupled 32 ft 2 in (9.804 m) total Tender: 4 ft 7 in (1.397 m) bogie 16 ft 1 in (4.902 m) total |
| Length | 66 ft 3.675 in (20.210 m) |
| Height | 12 ft 10 in (3.912 m) as built 12 ft 11.25 in (3.943 m) reboilered |
| Axle load | 15.6 long tons (15.9 t) on 2nd driver as built 14.55 long tons (14.8 t) on 1st driver reboilered |
| Weight on drivers | 62.7 long tons (63.7 t) as built 57.55 long tons (58.5 t) reboilered |
| Locomotive weight | 85.4 long tons (86.8 t) as built 81.45 long tons (82.8 t) reboilered |
| Tender weight | 47,920 lb (21.7 t) empty 47.25 long tons (48.0 t) w/o |
| Locomotive & tender combined weight |
171,136 lb (77.6 t) empty 132.65 long tons (134.8 t) w/o as built 128.7 long tons (130.8 t) w/o reboilered |
| Tender type | XM - XC, XC1, XD, XE, XE1, XF, XF1, XF2, XJ, XM, XM1, XM2, XM3, XM4, XP1, XS permitted * 2 axle bogies * Wheels 34 in (864 mm) dia * Length 25 ft 1.125 in (7.649 m) |
| Fuel type | Coal |
| Fuel capacity | 8 long tons (8.1 t) |
| Water capacity | 4,000 imp gal (18,000 l) |
| Boiler | As built: 5 ft 6.375 in (1.686 m) int dia 18 ft 3 in (5.563 m) int length 7 ft 6 in (2.286 m) pitch Reboilered: 5 ft 7.5 in (1.715 m) int dia 19 ft 4 in (5.893 m) int length, steel firebox 19 ft 3.625 in (5.883 m) int length, copper firebox 8 ft (2.438 m) pitch |
| Boiler pressure | 180 psi (1,240 kPa) |
| Firegrate area | 37 sq ft (3.437 m2) |
| Heating surface: Tubes |
As built: 144 tubes 2.25 in (57.2 mm) ext dia 22 tubes5.125 in (130 mm) ext dia 2,126 sq ft (197.512 m2) Reboilered: 81 tubes 2.5 in (63.5 mm) ext dia 30 tubes5.5 in (140 mm) ext dia 1,933 sq ft (179.582 m2) |
| Heating surface: Firebox |
184 sq ft (17.094 m2) as built 142 sq ft (13.192 m2) reboilered |
| Heating surface: Total |
2,310 sq ft (214.606 m2) as built 2,075 sq ft (192.774 m2) reboilered |
| Superheater area | 470 sq ft (43.664 m2) as built 497 sq ft (46.173 m2) reboilered |
| Cylinders | Two |
| Cylinder size | 21.5 in (546 mm) bore 28 in (711 mm) stroke |
| Valve gear | Walschaerts |
| Tractive effort | 32,360 lbf (143.9 kN) at 75% boiler pressure[3] |
| Career | South African Railways |
| Class | Class 4A, Class 4AR |
| Number in class | 10 |
| Number | 1551-1560 |
| Delivered | 1913-1914 |
| First run | 1913 |
| Withdrawn | 1974[4] |
| Disposition | Retired |
In 1913 and 1914 ten Class 4A steam locomotives with a 4-8-2 Mountain wheel arrangement were placed in service by the South African Railways.[4]
Contents |
The Class 4 Mountain locomotive was designed as a heavy mixed traffic locomotive by H.M. Beatty, the last Chief Locomotive Superintendent of the Cape Government Railways (CGR), at the Salt River shops. Soon after the South African Railways (SAR) was established in 1912, an order was placed with North British Locomotive Company (NBL) for a further ten locomotives of this type. They were delivered in 1913 and 1914 and became the Class 4A.[4]
The Class 4A locomotive was an improved version of the predecessor Class 4. It had a superheater added, which further resulted in the Stephenson valve gear having to be replaced with piston valves and Walschaerts valve gear. Like their two forerunners, they were excellent steamers and, with the modifications, gave a much better performance.[1][4]
In the 1930s many serving locomotives were reboilered with a standard boiler type designed by then Chief Mechanical Engineer (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][4]
When all ten Class 4A locomotives were eventually reboilered with Watson Standard no. 2 boilers, they were therefore reclassified to Class 4AR. In the process they were also equipped with Watson cabs, with their distinctive slanted fronts compared to the conventional vertical fronts of their original cabs.[3][4]
An obvious visual difference between an original and a Watson Standard reboilered locomotive is usually a rectangular regulator cover just to the rear of the chimney on the reboilered locomotive, but this was not always the case, as illustrated in the gallery below. In the case of the Class 4AR an even more obvious visual difference is the Watson cab.[3]
Their first ten years of service were spent working both passenger and goods trains on various sections of the Cape main line. At first they worked out of Cape Town, but when more powerful locomotives became available they were transferred to the Karoo, working between Touws River and Kimberley and also northward from Kimberley to Mafeking. They were then transferred to the Reef, from where they regularly served on the Zeerust, Breyten and Volksrust lines while also being employed in a variety of suburban and local train workings.[1][4]
During the Second World War Class 4A number 1554 was equipped with temporary protective armour to serve as the locomotive of an armoured train that was based at Mapleton Camp. The photograph alongside shows the locomotive and armoured train being inspected during 1942 by the Honourable F.C. Sturrock, M.P., South Africa’s Minister of Transport at the time.
The last Class 4AR was withdrawn from shunting operations on the West Reef in 1974. Some remained working in industrial service for several more years, the last one being finally retired from Apex Colliery in 1983.[4][5]
A lighter version of the Class 4A was built by NBL for the Rhodesian Railways (RR). It became the RR Class 10 and was used on the long section south of Bulawayo in Southern Rhodesia (now Zimbabwe) through Bechuanaland Protectorate (now Botswana) to Mafeking in the Cape Province.[5]
Like the SAR Class 4A, the RR Class 10 had combustion chambers, the only RR locomotive class with this feature.[5]
The main picture shows SAR Class 4A 1559, as built, on the Cape Town-Johannesburg train, taking water at Hutchinson in the Karoo on 11 November 1916.[1]
In the pictures of reboilered Class 4AR locomotives below, one locomotive has the rectangular regulator cover just to the rear of the chimney, while the other, Class 4AR 1554, has a bolted on cover plate flush with the boiler cladding instead. Both have Watson cabs, while the pictures of Class 4A locomotives display their original cabs with conventional vertical fronts.[3]
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