South African Class 6Z 2-6-4
Encyclopedia
In 1901 the Cape Government Railways
placed four Class 6 steam locomotive
s with a 2-6-2
Prairie wheel arrangement in service, that were soon modified to a 2-6-4
Adriatic wheel arrangement. In 1902 another four locomotives were placed in service, built with the 2-6-4 wheel arrangement. These latter four were the first tender locomotives in the world to be built with this wheel arrangement. In 1912, when they were assimilated into the South African Railways, these eight locomotives were renumbered and reclassified to Class 6Z.
locomotive was designed at the Salt River works of the Cape Government Railways (CGR). It was a further development of the very successful Class 6 4-6-0
locomotive that began as an experimental redesign of the Class 6 with a 2-6-2 Prairie wheel arrangement.
To overcome this problem, CGR Chief Locomotive Superintendent H.M. Beatty prepared designs for a new locomotive with a 2-6-2 wheel arrangement, in which the frame terminated in front of the firebox, where it connected to a casting termed the "bridle casting". This casting extended out on either side and had wider spaced frames attached to it which allowed a wider and deeper firebox.
Because of the widened frames, trailing carrier wheels were incorporated to take the weight of the firebox. Unlike usual practice, they were not arranged as a bissel truck, but the outside axle boxes worked in hornblocks bolted to the frames. The result was that the fixed wheelbase was extended backwards beyond that of the coupled wheels. The driving wheels were also located further forward to accommodate the deeper firebox and as a result the two axle pilot bogie was replaced by a single axle bissel truck.
It was the first time that such a method of widening the frame had been used and it proved to be extremely successful, being widely copied by both the Natal Government Railways
(NGR) and the Central South African Railways
(CSAR). The design was applied to South African locomotives for many years to come, until boiler centre lines were raised to a height that permitted the main frames to be reduced in depth and therefore to continue right through to the rear buffer beam.
Another four locomotives incorporating this modification were ordered from Neilson, Reid later in 1901. They were numbered 274 to 277 upon delivery 1n 1902. The change in design was found to have made a marked improvement in the locomotive’s stability at speed and the first four locomotives were therefore also modified accordingly.
The 2-6-4 wheel arrangement was usually used only on tank locomotive
s, with only two exceptions. These eight locomotives were the world’s first tender locomotives with the 2-6-4 wheel arrangement. They remained unique in the world until 1908, when the Austria
n Class 210 express locomotives appeared, followed by their Class 310 in 1911, both designed by Karl Gölsdorf
. The 2-6-4 type therefore became known as the Adriatic wheel arrangement, named for the Adriatic Sea
which bordered Austria-Hungary
.
The rest of the CGR’s Class 6 locomotives, together with the CSAR’s Classes 6-L1 to 6-L3 locomotives that had been inherited from the Oranje-Vrijstaat Gouwermentspoorwegen (OVGS) via the Imperial Military Railways (IMR), were grouped into thirteen more sub-classes by the SAR. The 4-6-0 locomotives became Classes 6, 6A to 6H and 6J to 6L, and the 2-6-2 locomotives became Class 6Y.
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 four Class 6 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 2-6-2
2-6-2
Under the Whyte notation for the classification of steam locomotives, 2-6-2 represents the wheel arrangement of two leading wheels, six coupled driving wheels and two trailing wheels.Other equivalent classifications are:...
Prairie wheel arrangement in service, that were soon modified to a 2-6-4
2-6-4
Under the Whyte notation for the classification of steam locomotives, a 2-6-4 locomotive has two leading wheels, six coupled driving wheels and four trailing wheels...
Adriatic wheel arrangement. In 1902 another four locomotives were placed in service, built with the 2-6-4 wheel arrangement. These latter four were the first tender locomotives in the world to be built with this wheel arrangement. In 1912, when they were assimilated into the South African Railways, these eight locomotives were renumbered and reclassified to Class 6Z.
Manufacture
The Cape Class 6 2-6-42-6-4
Under the Whyte notation for the classification of steam locomotives, a 2-6-4 locomotive has two leading wheels, six coupled driving wheels and four trailing wheels...
locomotive was designed at the Salt River works of the Cape Government Railways (CGR). It was a further development of the very successful Class 6 4-6-0
4-6-0
Under the Whyte notation for the classification of steam locomotives, 4-6-0 represents the wheel arrangement of four leading wheels on two axles in a leading truck, six powered and coupled driving wheels on three axles, and no trailing wheels. This wheel arrangement became the second-most popular...
locomotive that began as an experimental redesign of the Class 6 with a 2-6-2 Prairie wheel arrangement.
Design innovation
Good though the Class 6 4-6-0 locomotives were, the requirement grew for larger and more powerful locomotives. It was becoming increasingly apparent at the time that such locomotives would require boilers with larger grate areas, which was not possible with the existing type of frame.To overcome this problem, CGR Chief Locomotive Superintendent H.M. Beatty prepared designs for a new locomotive with a 2-6-2 wheel arrangement, in which the frame terminated in front of the firebox, where it connected to a casting termed the "bridle casting". This casting extended out on either side and had wider spaced frames attached to it which allowed a wider and deeper firebox.
Because of the widened frames, trailing carrier wheels were incorporated to take the weight of the firebox. Unlike usual practice, they were not arranged as a bissel truck, but the outside axle boxes worked in hornblocks bolted to the frames. The result was that the fixed wheelbase was extended backwards beyond that of the coupled wheels. The driving wheels were also located further forward to accommodate the deeper firebox and as a result the two axle pilot bogie was replaced by a single axle bissel truck.
It was the first time that such a method of widening the frame had been used and it proved to be extremely successful, being widely copied by both the Natal Government Railways
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...
(NGR) and the Central South African Railways
Central South African Railways
From 1902 to 1904, the area of power of Lieutenant-Colonel Sir Percy Girouard later also included the lines of The Netherlands-South African Railway Company; together this dominion covered all lines in the Transvaal that belonged to NZASM ....
(CSAR). The design was applied to South African locomotives for many years to come, until boiler centre lines were raised to a height that permitted the main frames to be reduced in depth and therefore to continue right through to the rear buffer beam.
Redesign
The first order for four locomotives was placed with Neilson, Reid and Company in 1901 and delivered in that same year. They were numbered 270 to 273 for the Western System of the CGR and subjected to exhaustive testing, during which it was found that, while they were good locomotives, they were inclined to be unsteady at speed. The locomotive design was therefore modified by replacing the trailing carrier wheels with a two axle bogie.Another four locomotives incorporating this modification were ordered from Neilson, Reid later in 1901. They were numbered 274 to 277 upon delivery 1n 1902. The change in design was found to have made a marked improvement in the locomotive’s stability at speed and the first four locomotives were therefore also modified accordingly.
The 2-6-4 wheel arrangement was usually used only on tank locomotive
Tank locomotive
A tank locomotive or tank engine is a steam locomotive that carries its water in one or more on-board water tanks, instead of pulling it behind it in a tender. It will most likely also have some kind of bunker to hold the fuel. There are several different types of tank locomotive dependent upon...
s, with only two exceptions. These eight locomotives were the world’s first tender locomotives with the 2-6-4 wheel arrangement. They remained unique in the world until 1908, when the Austria
Austria
Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
n Class 210 express locomotives appeared, followed by their Class 310 in 1911, both designed by Karl Gölsdorf
Karl Gölsdorf
Karl Gölsdorf was an Austrian engineer and locomotive designer.-Early Life:Karl Gölsdorf was born on 8 June 1861 in Vienna, the son of Louis Adolf Gölsdorf. Even as a schoolboy he was introduced to locomotive design by his father, the chief mechanical engineer of the Imperial and Royal Southern...
. The 2-6-4 type therefore became known as the Adriatic wheel arrangement, named for the Adriatic Sea
Adriatic Sea
The Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges...
which bordered Austria-Hungary
Austria-Hungary
Austria-Hungary , more formally known as the Kingdoms and Lands Represented in the Imperial Council and the Lands of the Holy Hungarian Crown of Saint Stephen, was a constitutional monarchic union between the crowns of the Austrian Empire and the Kingdom of Hungary in...
.
Class 6 sub-classes
In spite of their totally different appearance and wheel arrangement, the CGR designated these locomotives as Class 6 as well, possibly because they were intended as an "Improved Class 6". When they were assimilated into the newly established South African Railways (SAR) in 1912, they were renumbered 713 to 720 and reclassified to .The rest of the CGR’s Class 6 locomotives, together with the CSAR’s Classes 6-L1 to 6-L3 locomotives that had been inherited from the Oranje-Vrijstaat Gouwermentspoorwegen (OVGS) via the Imperial Military Railways (IMR), were grouped into thirteen more sub-classes by the SAR. The 4-6-0 locomotives became Classes 6, 6A to 6H and 6J to 6L, and the 2-6-2 locomotives became Class 6Y.
Service
In SAR service the eight Class 6Z locomotives gave good service on the Cape main line and later in suburban service, until they were withdrawn and scrapped in 1934.Gallery
The main picture shows ex CGR Class 6 271, SAR Class 6Z 714, circa 1912.See also
- South African Class 6 4-6-0South African Class 6 4-6-0In 1893 and 1894 the Cape Government Railways placed forty Class 6 4-6-0 steam locomotives in service, twenty-two on its Western System and eighteen on its Midland System. In 1897 ten of them were sold to the Oranje-Vrijstaat Gouwermentspoorwegen. At the end of the Second Boer War in 1901, these...
- South African Class 6A 4-6-0South African Class 6A 4-6-0In 1896 and 1897 the Cape Government Railways placed a second batch of fifty Class 6 4-6-0 steam locomotives in service, forty-one on its Western System, six on its Midland System and three on its Eastern System. During the Second Freedom War four were transferred to the Imperial Military Railways...
- South African Class 6B 4-6-0South African Class 6B 4-6-0In 1897 and 1898 the Cape Government Railways placed a third batch of fifty-five Class 6 4-6-0 steam locomotives in service, thirty-two on its Western System, twenty-one on its Midland System and two on its Eastern System. During the Second Freedom War seven were transferred to the Imperial...
- South African Class 6C 4-6-0South African Class 6C 4-6-0Between 1896 and 1898 the Oranje-Vrijstaat Gouwermentspoorwegen placed twenty-four new Cape Class 6 steam locomotives with a 4-6-0 wheel arrangement in service...
- South African Class 6D 4-6-0South African Class 6D 4-6-0In 1898 a fourth batch of thirty-three Class 6 4-6-0 steam locomotives were placed in service by the Cape Government Railways. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6D....
- South African Class 6E 4-6-0South African Class 6E 4-6-0In 1898 the Oranje-Vrijstaat Gouwermentspoorwegen ordered its final six new Cape Class 6 locomotives. When British forces invaded the Orange Free State during the Second Freedom War, these locomotives were taken over by the Imperial Military Railways and after the war they were renumbered into the...
- South African Class 6F 4-6-0South African Class 6F 4-6-0In 1900 two redesigned Class 6 4-6-0 steam locomotives were placed in service by the Cape Government Railways. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6F.-Manufacturers:...
- South African Class 6G 4-6-0South African Class 6G 4-6-0In 1901 eight redesigned Class 6 4-6-0 steam locomotives were placed in service by the Cape Government Railways. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6G.-Manufacturer:...
- South African Class 6H 4-6-0South African Class 6H 4-6-0In 1901 twenty-one Class 6 4-6-0 steam locomotives were placed in service by the Cape Government Railways, built to the older Class 6 designs with plate frames...
- South African Class 6J 4-6-0South African Class 6J 4-6-0In 1902 fourteen Class 6 bar framed steam locomotives with a 4-6-0 wheel arrangement were placed in service by the Cape Government Railways. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6J....
- South African Class 6K 4-6-0South African Class 6K 4-6-0In 1901 ten American built Class 6 bar framed steam locomotives with a 4-6-0 wheel arrangement were placed in service by the Cape Government Railways. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6K.-Manufacturer:The Class 6 was...
- South African Class 6L 4-6-0South African Class 6L 4-6-0In 1904 the Cape Government Railways placed its last two Class 6 4-6-0 bar framed steam locomotives in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and reclassified to Class 6L.-Manufacturer:...
- South African Class 6Y 2-6-2South African Class 6Y 2-6-2In 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 2-6-4 "Adriatic"
- List of South African locomotive classes