| South African Class MC1 2-6-6-0 | |
|---|---|
| SAR Class MC1 1642, circa 1914 | |
| Power type | Steam |
| Designer | American Locomotive Company |
| Builder | North British Locomotive Company |
| Serial number | 20442-20456[1][2] |
| Model | NGR Mallet |
| Build date | 1913-1914 |
| Total produced | 15 |
| Configuration | 2-6-6-0 Mallet |
| Gauge | 3 ft 6 in (1,067 mm) Cape gauge |
| Leading wheel diameter |
28.5 in (724 mm) |
| Driver diameter | 45.5 in (1,160 mm) |
| Wheelbase | Total: 60 ft (18.288 m) Engine: 8 ft 4 in (2.540 m) per coupled set 33 ft 5 in (10.185 m) total Tender: 4 ft 7 in (1.397 m) bogie 16 ft 9 in (5.105 m) total |
| Length | 68 ft 5.125 in (20.857 m) |
| Height | 12 ft 5.1875 in (3.789 m) |
| Axle load | 16.2 long tons (16.5 t) on 6th driver |
| Weight on drivers | 89.95 long tons (91.4 t) |
| Locomotive weight | 97.9 long tons (99.5 t) |
| Tender weight | 50.9 long tons (51.7 t) |
| Locomotive & tender combined weight |
148.8 long tons (151.2 t) |
| Tender type | 2 axle bogie Wheels 34 in (864 mm) dia |
| Fuel type | Coal |
| Fuel capacity | 10 long tons (10.2 t) |
| Water capacity | 4,250 imp gal (19,300 l) |
| Boiler | 5 ft 8 in (1.727 m) int dia 16 ft 2.75 in (4.947 m) int length 7 ft 6 in (2.286 m) pitch |
| Boiler pressure | 200 psi (1,380 kPa) |
| Firegrate area | 42.5 sq ft (3.948 m2) |
| Heating surface: Tubes |
152 tubes 2.25 in (57.2 mm) ext dia 27 tubes 5.375 in (137 mm) ext dia 2,060 sq ft (191.380 m2) |
| Heating surface: Firebox |
154 sq ft (14.307 m2) |
| Heating surface: Total |
2,214 sq ft (205.687 m2) |
| Superheater area | 580 sq ft (53.884 m2) |
| Cylinders | Four |
| High-pressure cylinder size |
18 in (457 mm) bore 26 in (660 mm) stroke |
| Low-pressure cylinder size |
28.5 in (724 mm) bore 26 in (660 mm) stroke |
| Valve gear | Walschaerts[3] |
| Tractive effort | 46,414 lbf (206.5 kN) at 50% boiler pressure[1] |
| Career | South African Railways |
| Class | Class MC1 |
| Number in class | 15 |
| Number | 1634-1648[1] |
| Delivered | 1914 |
| First run | 1914 |
| Withdrawn | 1939[3] |
| Disposition | Retired |
In 1914 the South African Railways placed fifteen Class MC1 Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in service.[1][3]
Contents |
Orders for an improved version of the Class MC were placed with the North British Locomotive Company (NBL) in 1913. When the fifteen locomotives were delivered and placed in service in 1914, they were classified as Class MC1 and numbered 1634 to 1648.[1][3]
The improvements in the Class MC1 consisted mainly of a redesigned boiler that included a superheater, instead of the saturated steam boiler of the Class MC, and 0.5 inches (12.7 millimetres) larger diameter low pressure and high pressure cylinders. The result was a much better performing locomotive with an increased tractive effort brought about by the larger cylinders.[1][3]
In a compound locomotive steam is expanded in phases. After being expanded in a high pressure cylinder and having then lost pressure and given up part of its heat, it is exhausted into a larger volume low pressure cylinder for secondary expansion, after which it is exhausted through the smokebox.[4]
In the compound Mallet locomotive, the rear set of coupled wheels are driven by the smaller high pressure cylinders which are fed steam from the steam dome. Their spent steam is then fed to the larger low pressure cylinders that drive the front set of coupled wheels. By comparison, in the more usual arrangement of simple expansion, steam is expanded just once in any one cylinder before being exhausted through the smokebox.[1][3]
The Class MC1 was placed in service on the coal line from Witbank to Germiston. In later years some also saw service on the Natal main line and the Cape Midlands System, while a number of them were transferred to the Cape Western System where they served as banking locomotives up the Hex River Pass between De Doorns and Touws River. They remained there until they were withdrawn from service by 1939.[1][3]
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