| South African Class MC 2-6-6-0 | |
|---|---|
| SAR Class MC 1608, circa 1912 | |
| Power type | Steam |
| Designer | American Locomotive Company |
| Builder | North British Locomotive Company |
| Serial number | 19577-19586[1][2] |
| Model | NGR Mallet |
| Build date | 1912 |
| Total produced | 10 |
| 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: 59 ft 3 in (18.059 m) Engine: 8 ft 4 in (2.540 m) per coupled set 33 ft 5 in (10.185 m) total Tender: 4 ft 6 in (1.372 m) bogie 16 ft 6 in (5.029 m) total |
| Length | 66 ft 9.75 in (20.364 m) |
| Height | 12 ft 5.1875 in (3.789 m) |
| Axle load | 14.65 long tons (14.9 t) on 6th driver |
| Weight on drivers | 86.55 long tons (87.9 t) |
| Locomotive weight | 95.3 long tons (96.8 t) |
| Tender weight | 43.5 long tons (44.2 t) |
| Locomotive & tender combined weight |
138.8 long tons (141.0 t) |
| Tender type | 2 axle bogie Wheels 30 in (762 mm) dia |
| Fuel type | Coal |
| Fuel capacity | 8.25 long tons (8.4 t) |
| Water capacity | 4,000 imp gal (18,000 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 |
258 tubes 2.25 in (57.2 mm) ext dia 2,462 sq ft (228.727 m2) |
| Heating surface: Firebox |
154 sq ft (14.307 m2) |
| Heating surface: Total |
2,616 sq ft (243.034 m2) |
| Cylinders | Four |
| High-pressure cylinder size |
17.5 in (445 mm) bore 26 in (660 mm) stroke |
| Low-pressure cylinder size |
28 in (711 mm) bore 26 in (660 mm) stroke |
| Valve gear | Walschaerts[3] |
| Tractive effort | 44,810 lbf (199.3 kN) at 50% boiler pressure[1] |
| Career | South African Railways |
| Class | Class MC |
| Number in class | 10 |
| Number | 1607-1616[1][4] |
| Delivered | 1912 |
| First run | 1912 |
| Withdrawn | 1934 |
| Disposition | Retired |
In 1912 the South African Railways placed ten Class MC Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in service.[1][3][4]
Contents |
In order to augment the Mallet operations across the more difficult sections of the Natal main line, the South African Railways (SAR) placed an order with the North British Locomotive Company (NBL) for ten locomotives that were very similar to the Class MB. They were delivered and placed in service in May 1912, classified as Class MC and numbered 1607 to 1616.[1][3][4]
Like the previous Mallets, these ten compound locomotives had Walschaerts valve gear and used saturated steam. Their tenders were similar to those of the Class 3, but they differed little from the previous Mallets in size, power and performance and may for all intents and purposes also have been classified as Class MB. It would seem that, compared to the Cape Government Railways (CGR) that tended to group locomotives in the same Class that were dissimilar even to the extent of having different wheel arrangements, the early SAR at times took locomotive classification to the other extreme.[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.[5]
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]
They were satisfactory locomotives, but like the earlier Mallet compounds they would have given a better performance if they had been superheated. Two of them, numbers 1612 and 1615, were equipped with superheaters at a later date, but no others were modified in this manner.[1][3]
The Class MC joined the Class MA and MB fleet on the Natal main line, working heavy coal trains between Estcourt and Highlands. In later years some were transferred to the Cape Western System, where they served into the 1930s as banking locomotives up the Hex River Pass between De Doorns and Touws River. Others were transferred to the Witwatersrand for general service and to haul coal on the Witbank line. They were withdrawn from service by 1934.[1][3]
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