| South African Class 16 4-6-2 & South African Class 16R 4-6-2 |
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| Class 16 800, Braamfontein, circa 1930 | |
| Power type | Steam |
| Designer | South African Railways |
| Builder | North British Locomotive Company |
| Serial number | 20430-20441[1][2] |
| Model | Class 16 |
| Build date | 1914 |
| Total produced | 12 |
| Configuration | 4-6-2 "Pacific" |
| Gauge | 3 ft 6 in (1,067 mm) Cape gauge |
| Leading wheel diameter |
30 in (762 mm) |
| Driver diameter | 60 in (1,520 mm) |
| Trailing wheel diameter |
33 in (838 mm) |
| Wheelbase | Total: 58 ft 11.875 in (17.980 m) Engine: 6 ft 2 in (1.880 m) pilot 10 ft 9 in (3.277 m) coupled 29 ft 5.5 in (8.979 m) total Tender: 6 ft 2 in (1.880 m) bogie 20 ft 5 in (6.223 m) total |
| Length | 66 ft 11.5 in (20.409 m) total |
| Height | 12 ft 10 in (3.912 m) as built 12 ft 11.25 in (3.943 m) reboilered |
| Frame | Plate frame |
| Axle load | 18 long tons (18.3 t) on 1st & 2nd drivers as built 17.75 long tons (18.0 t) on 2nd & 3rd drivers reboilered |
| Weight on drivers | 53.9 long tons (54.8 t) as built 53.15 long tons (54.0 t) reboilered |
| Locomotive weight | 83.65 long tons (85.0 t) as built 82.95 long tons (84.3 t) reboilered |
| Tender weight | Type MP1: 49,452 lb (22.4 t) empty 51.05 long tons (51.9 t) w/o Type MT: 61,520 lb (27.9 t) empty 66 long tons (67.1 t) w/o |
| Locomotive & tender combined weight |
With Type MP1: 170,716 lb (77.4 t) empty 149.65 long tons (152.1 t) w/o With Type MT: 182,784 lb (82.9 t) empty 149.05 long tons (151.4 t) w/o |
| Tender type | MP1 - MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted Type MP1: * 2 axle bogies * Wheels 34 in (864 mm) dia * Length 25 ft 10.75 in (7.893 m) Type MT: * 2 axle bogies * Wheels 34 in (864 mm) dia * Length 28 ft 5.375 in (8.671 m) |
| Fuel type | Coal |
| Fuel capacity | Type MP1: 12 long tons (12.2 t) Type MT: 10 long tons (10.2 t) |
| Water capacity | Type MP1: 6,000 imp gal (27,000 l) Type MT:4,250 imp gal (19,300 l) |
| Boiler | As built: 5 ft 4.625 in (1.641 m) int dia 18 ft 3 in (5.563 m) int length 7 ft 9 in (2.362 m) pitch Reboilered: 5 ft 7.5 in (1.715 m) int dia 18 ft 4 in (5.588 m) int length, steel firebox 18 ft 3.625 in (5.578 m) int length, copper firebox 8 ft (2.438 m) pitch |
| Boiler pressure | 190 psi (1,310 kPa) |
| Firegrate area | 37 sq ft (3.437 m2) |
| Heating surface: Tubes |
As built: 131 tubes 2.25 in (57.2 mm) ext dia 24 tubes 5.5 in (140 mm) ext dia 2,040 sq ft (189.522 m2) Reboilered: 87 tubes 2.5 in (63.5 mm) ext dia 30 tubes 5.5 in (140 mm) ext dia 1,636 sq ft (151.989 m2) |
| Heating surface: Firebox |
146 sq ft (13.564 m2) as built 142 sq ft (13.192 m2) reboilered |
| Heating surface: Total |
2,186 sq ft (203.086 m2) as built 1,978 sq ft (183.762 m2) reboilered |
| Superheater area | 515 sq ft (47.845 m2) as built 472 sq ft (43.850 m2) reboilered |
| Cylinders | Two |
| Cylinder size | 22 in (559 mm) bore 26 in (660 mm) stroke |
| Valve gear | Walschaerts |
| Tractive effort | 29,890 lbf (133.0 kN) at 75% boiler pressure[3] |
| Career | South African Railways |
| Class | Class 16, Class 16R |
| Number in class | 12 |
| Number | 790-801 |
| Delivered | 1914 |
| First run | 1914 |
| Disposition | Retired |
In 1914 the South African Railways placed twelve Class 16 steam locomotives with a 4-6-2 Pacific wheel arrangement in passenger train service.[4]
Contents |
The Class 16 4-6-2 Pacific locomotive was designed by D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922, and was built by the North British Locomotive Company in Glasgow, Scotland, who delivered twelve locomotives in 1914, numbered 790 to 801.[1][4]
The design of the Class 16 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.[1][4]
When built in 1914, the Class 16 was considered a very large and powerful express locomotive, even when compared to British locomotives built to run on 4 feet 8½ inches (1,435 millimetres) Standard gauge. As built with 60 inches (1,520 millimetres) driving wheels, the ratio of wheel diameter to rail gauge was the same as that of a Standard gauge locomotive having 81 inches (2,060 millimetres) driving 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 4-6-2 The Great Bear on the Great Western Railway and equalled, also at 85% boiler pressure, that of Gresley’s later Great Northern Pacifics. This made the Class 16 the most powerful express passenger locomotive design yet to have been built in Great Britain at the time.[5]
During the 1930s many serving locomotives were reboilered with a standard boiler type designed by A.G. Watson, CME of the SAR from 1929 to 1936, as part of his standardisation policy. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification.[3][4]
Eventually all twelve Class 16 locomotives were reboilered with Watson Standard no. 2B boilers and reclassified to Class 16R. Early conversions were equipped with copper and later conversions with steel fireboxes. 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. In the case of the Class 16 and Class 16R locomotives two even more obvious visual differences are the Watson cab and the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.[3][4]
Intended for fast passenger trains in the Transvaal, Orange Free State and the upper sections of Natal where the gradients were not as severe, the Class 16 Pacifics were placed in suburban passenger service working between Pretoria and Johannesburg and in main line service on the section from Johannesburg to Volksrust on the line to Natal. In later years, after being withdrawn from main line passenger service, many of these locomotives were employed in suburban and shunting service.[1][4][5]
The main picture shows Class 16 number 800, as built with a Belpaire firebox and Type MP1 tender, on interurban service with a destination board for Pretoria below its headlight, at Braamfontein, circa 1930.
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