In 1903 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:...

 placed two Karoo Class steam locomotive

Steam locomotive

A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...

s with a 4-6-2

4-6-2

4-6-2, in the Whyte notation for the classification of steam locomotives, represents the wheel arrangement of four leading wheels on two axles , six powered and coupled driving wheels on three axles, and two trailing wheels on one axle .These locomotives are also known as Pacifics...

 Pacific wheel arrangement in passenger service. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 5A.

Design

The Karoo Class of the Cape Government Railways (CGR) was the first locomotive with a 4-6-2 Pacific wheel arrangement to be introduced in Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

. It was the logical development of the CGR Class 6 2-6-2

South African Class 6Y 2-6-2

In 1903 the Cape Government Railways placed two Class 6 steam locomotives with a 2-6-2 Prairie wheel arrangement in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6Y.-Manufacture:...

 that later became the Class 6Y on the South African Railways (SAR). Designed by CGR Chief Locomotive Superintendent H.M. Beatty at the Salt River shops in Cape Town

Cape Town

Cape Town is the second-most populous city in South Africa, and the provincial capital and primate city of the Western Cape. As the seat of the National Parliament, it is also the legislative capital of the country. It forms part of the City of Cape Town metropolitan municipality...

, it was acquired to cope with the increasing weight of passenger trains on the one in eighty gradients between Beaufort West

Beaufort West

Beaufort West is a town in the Western Cape province in South Africa. It is the largest town in the arid Great Karoo region, and forms part of the Beaufort West Local Municipality, with 37 000 inhabitants in 2001....

 and De Aar.

Since Beatty was very cautious about raising the boiler’s centre line to more than twice the rail gauge, or 7 feet (2.134 m), and in this case also to accommodate the large 60 inches (1,524 mm) driving wheels, he resorted to cutting the boiler shell and installing specially shaped pockets to obtain the required clearance. The locomotive had a bar frame, Stephenson valve gear

Stephenson valve gear

The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for all kinds of steam engine. It is named after Robert Stephenson but was actually invented by his employees....

 and used saturated steam.

Manufacturer

Two locomotives were built by Kitson and Company in 1903, immediately after building the two Class 6Y locomotives since their works numbers follow in sequence. They were numbered 903 and 904, but were not allocated class numbers by the CGR and instead became known as the Karoo Class, from the region of the Western System that they were designed to work in.

The 4-6-2 Pacific wheel arrangement was not used in other parts of Africa, but Kitson later used the Karoo design as basis for a batch of Pacifics it built for the Midland Railway of Western Australia.

Class 5 sub-classes

When these two locomotives were assimilated into the newly established SAR in 1912, they were renumbered 721 and 722 and reclassified to Class 5A. The rest of the CGR’s Karoo Class locomotives were grouped into two more sub-classes by the SAR.

Service

In service the Class 5A locomotives performed excellently. Beatty’s annual report for 1905 stated that they ran 159000 miles (255,885.1 km) before a failure occurred, that failure being a hot box. They spent most of their working lives in the Karoo, until they were displaced by larger locomotives and placed in suburban service around Cape Town. They were withdrawn by 1940.

Gallery

See also

• South African Class 5 4-6-2
  South African Class 5 4-6-2
  In 1912 four Enlarged Karoo Class 4-6-2 Pacific passenger steam locomotives that had been ordered by the Cape Government Railways the year before, were placed in service by the newly established South African Railways...
  
  
• South African Class 5B 4-6-2
  South African Class 5B 4-6-2
  In 1904 the Cape Government Railways placed four Karoo Class 4-6-2 Pacific passenger steam locomotives in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and classified as Class 5B.-Manufacturer:...
  
  
• South African Class 6Y 2-6-2
  South African Class 6Y 2-6-2
  In 1903 the Cape Government Railways placed two Class 6 steam locomotives with a 2-6-2 Prairie wheel arrangement in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6Y.-Manufacture:...
  
  
• Tender locomotive numbering and classification
• The 4-6-2 "Pacific"
• List of South African locomotive classes