South African Class MJ1 2-6-6-0 - AbsoluteAstronomy.com

In 1918 the South African Railways placed eight Class MJ1 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 branch line service.

Manufacturer

Because of the difficulties experienced by the usual British and German suppliers to build new locomotives during World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, orders for the Class MJ1 2-6-6-0 Mallet articulated compound steam locomotive were placed with Montreal Locomotive Works

Montreal Locomotive Works

Montreal Locomotive Works was a Canadian railway locomotive manufacturer which existed under several names from 1883–1985, producing both steam and diesel locomotives. For a number of years it was a subsidiary of the American Locomotive Company...

(MLW) in Canada. The locomotive was designed by MLW, based on the specifications for the Class MJ

South African Class MJ 2-6-6-0

Between 1914 and 1921 the South African Railways placed eighteen Class MJ Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in branch line service.-Manufacturers:...

Mallet that was designed by D.A. Hendrie, the Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922. Eight of these branch line locomotives were built and delivered by MLW in November 1918, numbered 1666 to 1673.

They were superheated, had Walschaerts valve gear and, like the Class MJ Mallets, had Belpaire firebox

Belpaire firebox

The Belpaire firebox is a type of firebox used on steam locomotives. It was invented by Alfred Belpaire of Belgium. It has a greater surface area at the top of the firebox, improving heat transfer and steam production...

es but slightly larger boilers. When compared to the Class MJ, a distinguishing feature of the Class MJ1 was the sandbox mounted on the boiler in North American style. In general appearance they were similar to the Class 14C

South African Class 14C 4-8-2

Between 1918 and 1922 the South African Railways placed seventy-three Class 14C steam locomotives with a 4-8-2 Mountain wheel arrangement in service...

and Class 15B

South African Class 15B 4-8-2

Between 1918 and 1922 the South African Railways placed ten Class 15B steam locomotives with a 4-8-2 Mountain wheel arrangement in service.-Manufacturer:...

4-8-2 locomotives that were also built by MLW in 1918.

The Class MJ1 was the last Mallet locomotive class to be placed in service by the SAR and all its subsequent new articulated locomotives were to be Modified Fairlies and Garratts.

Compound expansion

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. 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.

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.

Service

The Class MJ1 was also intended for branch line working and joined the Class MJ Mallets in service in the Eastern Cape. All eight were still in service by March 1948, but they were all withdrawn from service by 1960.

Manufacturer

Compound expansion

Service

See also