South African Class MB 2-6-6-0
Encyclopedia
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.
(NGR) in 1909, a further five similar locomotives were ordered from the American Locomotive Company
(ALCO) in 1910. They were delivered later that same year and numbered 337 to 341.
, these five had Walschaerts valve gear, bar frames and used saturated steam. They differed little from the previous Mallet, basically only in respect of their larger boilers, which made them slightly heavier, and their tenders with a larger coal capacity.
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
, 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.
In 1912, when they were taken onto the South African Railways (SAR) roster, they were renumbered 1602 to 1606 and classified as Class MB. They were withdrawn from service by 1924.
Natal government railways
The Natal Government Railways was formed in January 1877 in the Colony of Natal.In 1877 the Natal Government Railways acquired the Natal Railway Company for the sum of £40,000, gaining the line from the Point to Durban and from Durban to Umgeni...
placed five 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...
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...
in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and classified as Class MB.
Manufacturer
Following on the satisfactory performance of the experimental Mallet compound steam locomotive that was acquired by the Natal Government RailwaysNatal government railways
The Natal Government Railways was formed in January 1877 in the Colony of Natal.In 1877 the Natal Government Railways acquired the Natal Railway Company for the sum of £40,000, gaining the line from the Point to Durban and from Durban to Umgeni...
(NGR) in 1909, a further five similar locomotives were ordered from the American Locomotive Company
American Locomotive Company
The American Locomotive Company, often shortened to ALCO or Alco , was a builder of railroad locomotives in the United States.-Early history:...
(ALCO) in 1910. They were delivered later that same year and numbered 337 to 341.
Characteristics
Like the previous Mallet locomotiveMallet locomotive
The Mallet Locomotive is a type of articulated locomotive, invented by a Swiss engineer named Anatole Mallet ....
, these five had Walschaerts valve gear, bar frames and used saturated steam. They differed little from the previous Mallet, basically only in respect of their larger boilers, which made them slightly heavier, and their tenders with a larger coal capacity.
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.
Service
The five locomotives joined the first Mallet in banking service, working heavy coal trains between Estcourt and Highlands on the Natal main line. To relieve coupler strain, they were used in three-locomotive trains and in this manner were able to haul 750 long tons (762 t) up the one in thirty gradients on that line.In 1912, when they were taken onto the South African Railways (SAR) roster, they were renumbered 1602 to 1606 and classified as Class MB. They were withdrawn from service by 1924.
See also
- Mallet locomotiveMallet locomotiveThe Mallet Locomotive is a type of articulated locomotive, invented by a Swiss engineer named Anatole Mallet ....
- South African Class MA 2-6-6-0South African Class MA 2-6-6-0In 1909 the Natal Government Railways placed a single 2-6-6-0 Mallet articulated compound steam locomotive in service. In 1912, when it was assimilated into the South African Railways, it was renumbered and classified as Class MA.-Manufacturer:...
- South African Class MC 2-6-6-0South African Class MC 2-6-6-0In 1912 the South African Railways placed ten Class MC Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in service.-Manufacturer:...
- South African Class MC1 2-6-6-0South African Class MC1 2-6-6-0In 1914 the South African Railways placed fifteen Class MC1 Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in service.-Manufacturer:...
- South African Class MD 2-6-6-2South African Class MD 2-6-6-2In March 1910 the Central South African Railways placed a single experimental Mallet articulated compound steam locomotive with a 2-6-6-2 wheel arrangement in service...
- South African Class ME 2-6-6-2South African Class ME 2-6-6-2In January 1912 the South African Railways placed a single Class ME Mallet articulated steam locomotive with a 2-6-6-2 wheel arrangement in service.-Manufacturer:...
- South African Class MF 2-6-6-2South African Class MF 2-6-6-2In 1911 the Central South African Railways placed nine Mallet articulated compound steam locomotives with a 2-6-6-2 wheel arrangement in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and classified as Class MF...
- South African Class MG 2-6-6-2South African Class MG 2-6-6-2In 1911 the Central South African Railways placed a single experimental Mallet articulated compound steam locomotive with a 2-6-6-2 wheel arrangement in service...
- South African Class MH 2-6-6-2South African Class MH 2-6-6-2In 1915 the South African Railways placed five Class MH Mallet articulated compound steam locomotives with a 2-6-6-2 wheel arrangement in service.-Manufacturer:...
- South African Class MJ 2-6-6-0South African Class MJ 2-6-6-0Between 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:...
- South African Class MJ1 2-6-6-0South African Class MJ1 2-6-6-0In 1918 the South African Railways placed eight Class MJ1 Mallet articulated compound steam locomotives with a 2-6-6-0 wheel arrangement in branch line service.-Manufacturer:...
- Articulated locomotive numbering and classification
- The 2-6-6-0 Mallet
- List of South African locomotive classes