South African Class Exp 1 4-6-2
Encyclopedia
In 1907 the Cape Government Railways
placed a single experimental three cylinder compound steam locomotive with a 4-6-2
Pacific wheel arrangement in service, based on the second series of the Karoo Class locomotives. In 1912, when it was assimilated into the South African Railways, it was renumbered and classified as Class Experimental 1.
and was numbered 900, but it was not classified by the CGR and was simply referred to as the Three Cylinder Compound.
The cylinders were arranged in the "Smith" system of compounding, with a single high pressure cylinder situated between the two low pressure cylinders. The Smith system of compounding was developed from the two-cylinder Worsdell
-von Borries
compound system. Walter Mackersie Smith
, a Scottish engineer, improved on this system by developing a three cylinder compound system with one high pressure cylinder inside and two low pressure cylinders outside. It permitted the locomotive to be worked in either compound, semi-compound or simple mode.
The locomotive had a bar frame, Walschaerts valve gear and used saturated steam.
After having been in service for a few years, however, experienced drivers of the Three Cylinder Compound found that, if treated and handled properly, the compound locomotive could outperform a simple in terms of power as well as fuel and water consumption. One driver described how judicious injections of live steam in the low pressure cylinders (semi-compound mode) on heavy grades enhanced the locomotive’s performance and how the life of the high pressure big-end bearings, which initially proved troublesome, could be prolonged by mixing castor oil in with the ordinary oil that was used on all the bearings and the valve motion.
on the section between Beaufort West
and De Aar. It performed well, provided the centre high pressure big-end bearings were given adequate care and frequent lubrication.
In 1912, when it was assimilated into the South African Railways (SAR), it was classified as Class Experimental 1 and renumbered to 764. It continued working passenger trains through the Karoo until it was withdrawn in 1933.
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 a single experimental three cylinder compound steam locomotive 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 service, based on the second series of the Karoo Class locomotives. In 1912, when it was assimilated into the South African Railways, it was renumbered and classified as Class Experimental 1.
Manufacturer
In the first few years of the twentieth century H.M. Beatty, Locomotive Superintendent of the Cape Government Railways (CGR), experimented with various forms of compound steam locomotives. One of these locomotives was delivered by the North British Locomotive Company (NBL) in 1907. It was based on the second version of the CGR’s Karoo ClassSouth 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:...
and was numbered 900, but it was not classified by the CGR and was simply referred to as the Three Cylinder Compound.
Characteristics
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.The cylinders were arranged in the "Smith" system of compounding, with a single high pressure cylinder situated between the two low pressure cylinders. The Smith system of compounding was developed from the two-cylinder Worsdell
Thomas William Worsdell
Thomas William Worsdell was a British locomotive engineer. He was born in Liverpool into a Quaker family.-Family:...
-von Borries
August von Borries
August Friedrich Wilhelm von Borries was one of Germany's most influential railway engineers, who was primarily concerned with developments in steam locomotives....
compound system. Walter Mackersie Smith
Walter Mackersie Smith
Walter Mackersie Smith was a Scottish engineer who made an important contribution to the development of the compound steam locomotive. His middle name has sometimes been mis-spelt Mackenzie . He was born at Ferry-Port on Craig, Fife....
, a Scottish engineer, improved on this system by developing a three cylinder compound system with one high pressure cylinder inside and two low pressure cylinders outside. It permitted the locomotive to be worked in either compound, semi-compound or simple mode.
The locomotive had a bar frame, Walschaerts valve gear and used saturated steam.
Performance
During 1907 extended comparative tests were carried out with the Three Cylinder Compound and a simple expansion "Karoo" two cylinder locomotive. Initial results showed that, while the compound locomotive displayed no marked economy of fuel over the simple, it could take a heavy train up a long continuous grade at a much higher speed.After having been in service for a few years, however, experienced drivers of the Three Cylinder Compound found that, if treated and handled properly, the compound locomotive could outperform a simple in terms of power as well as fuel and water consumption. One driver described how judicious injections of live steam in the low pressure cylinders (semi-compound mode) on heavy grades enhanced the locomotive’s performance and how the life of the high pressure big-end bearings, which initially proved troublesome, could be prolonged by mixing castor oil in with the ordinary oil that was used on all the bearings and the valve motion.
Service
The Three Cylinder Compound was placed in service in the KarooKaroo
The Karoo is a semi-desert region of South Africa. It has two main sub-regions - the Great Karoo in the north and the Little Karoo in the south. The 'High' Karoo is one of the distinct physiographic provinces of the larger South African Platform division.-Great Karoo:The Great Karoo has an area of...
on the section 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. It performed well, provided the centre high pressure big-end bearings were given adequate care and frequent lubrication.
In 1912, when it was assimilated into the South African Railways (SAR), it was classified as Class Experimental 1 and renumbered to 764. It continued working passenger trains through the Karoo until it was withdrawn in 1933.
See also
- South African Class 5B 4-6-2South African Class 5B 4-6-2In 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 Exp 2 2-8-0South African Class Exp 2 2-8-0In 1902 the Cape Government Railways placed a single experimental 2-8-0 Consolidation type tandem compound steam locomotive in service, based on its Schenectady built Class 8 of 1901. In 1912, when the locomotive was assimilated into the South African Railways, it was renumbered and classified as...
- South African Class Exp 3 2-8-0South African Class Exp 3 2-8-0In 1903 the Cape Government Railways placed a single experimental 2-8-0 Consolidation type tandem compound steam locomotive in service, based on its Schenectady built Class 8 of 1901. It was similar to the tandem compound delivered a year earlier, but with a larger firegrate and an increased...
- South African Class Exp 4 2-8-2South African Class Exp 4 2-8-2In 1903 the Cape Government Railways placed two Class 9 steam locomotives with a 2-8-2 Mikado wheel arrangement in service. In 1912, when these locomotives were assimilated into the South African Railways, they were renumbered and classified as Class Experimental 4.-Manufacturer:The Cape Class 9...
- South African Class Exp 5 2-8-2South African Class Exp 5 2-8-2In 1906 the Cape Government Railways placed a single experimental steam locomotive with a 2-8-2 Mikado wheel arrangement in service. In 1912, when this locomotive was assimilated into the South African Railways, it was renumbered and classified as Class Experimental 5.-Manufacturer:The Cape Mikado...
- South African Class Exp 6 4-8-0South African Class Exp 6 4-8-0In 1906 the Cape Government Railways placed a single experimental Class 10 steam locomotive with a 4-8-0 Mastodon wheel arrangement in service on the Cape Eastern System. In 1912, when this locomotive was assimilated into the South African Railways, it was renumbered and classified as Class...
- The 4-6-2 "Pacific"
- List of South African locomotive classes