South African Class MC 2-6-6-0 - AbsoluteAstronomy.com

In 1912 the South African Railways placed ten Class MC Mallet articulated compound steam locomotives

Compound locomotive

A compound engine unit is a type of steam engine where steam is expanded in two or more stages.A typical arrangement for a compound engine is that the steam is first expanded in a high-pressure cylinder, then having given up heat and losing pressure, it exhausts directly into one or more larger...

with a 2-6-6-0

2-6-6-0

In Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-6-6-0 is a locomotive with one pair of unpowered leading wheels, followed by two sets of three pairs of powered driving wheels, and no trailing wheels...

wheel arrangement in service.

Manufacturer

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

North British Locomotive Company

The North British Locomotive Company was created in 1903 through the merger of three Glasgow locomotive manufacturing companies; Sharp Stewart and Company , Neilson, Reid and Company and Dübs and Company , creating the largest locomotive manufacturing company in Europe.Its main factories were...

(NBL) for ten locomotives that were very similar to the Class MB

South African Class MB 2-6-6-0

In 1910 the Natal Government Railways placed five 2-6-6-0 Mallet articulated compound steam locomotives in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and classified as Class MB.-Manufacturer:...

. They were delivered and placed in service in May 1912, classified as Class MC and numbered 1607 to 1616.

Characteristics

Like the previous Mallets

Mallet locomotive

The Mallet Locomotive is a type of articulated locomotive, invented by a Swiss engineer named Anatole Mallet ....

, these ten compound locomotives had Walschaerts valve gear and used saturated steam. Their tenders were similar to those of the Class 3

South African Class 3 4-8-2

In 1909 the Natal Government Railways placed its first true Mountain type locomotive in service when five Class Hendrie D 4-8-2 tender locomotives were commissioned. Twenty-five more were placed in service in 1911. In 1912, when they were assimilated into the South African Railways, they were...

, 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

Cape Government Railways

The Cape Government Railways was the government-owned railway operator in the Cape Colony from 1874 until the creation of the South African Railways in 1910.-Private 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.

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.

In the compound Mallet locomotive

Mallet locomotive

The Mallet Locomotive is a type of articulated locomotive, invented by a Swiss engineer named Anatole Mallet ....

, 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.

Superheating

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.

Service

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.

Manufacturer

Characteristics

Superheating

Service

See also