South African Class 20 2-10-2
Encyclopedia
In 1935 the South African Railways placed one Class 20 steam locomotive
with a Santa Fe wheel arrangement in service. In 1950 it was modified to an experimental condensing locomotive.
.
Watson disliked articulated locomotives and his aim with the Class 20 was to build an as powerful as possible non articulated locomotive with a maximum 12 long tons (12.2 t) axle load. The end result could be considered as Watson’s answer to the Class GCA 2-6-2+2-6-2
Garratt locomotive, having very similar weight and tractive effort capacities.
The Class 20 carried more water and coal than the Garratt and was about 20 long tons (20.3 t) heavier with 33080 pound-forces (147.1 kN) tractive effort, compared to the 28470 pound-forces (126.6 kN) of the Class GCA. Even so, only one Class 20 was produced and the design was not repeated.
locomotive that had been equipped with a Watson Standard no. 1A boiler. The driving wheels were from scrapped Class 8
locomotives. The bar frames and cylinders were imported, the cylinders with Rotary Cam Poppet valve gear being those of a Class 19C
, but with the stroke reduced from 26 inches (660.4 mm) to 24 inches (609.6 mm) by means of deep spigots on the modified cylinder covers. The trailing pony truck was similar to that of the Class 19C, but the leading Bissel truck was specially designed.
and that eventually culminated in the procurement of the Class 23 4-8-2
fleet in 1939.
, even though freight traffic volumes in that territory were hardly enough to justify such a powerful locomotive. It entered service there in 1935 but was soon returned to South Africa and allocated to Pretoria
, where its power capacity could be used more productively. The Pretoria drivers considered the Class 20 to be one of their best locomotives since it was free-steaming, more than usually trouble-free and able to handle any load they gave it.
for use in Argentina
and Germany
. In pre-war days it was considered to modify a Class 12A
into a condensing locomotive, but this never realised.
In 1950 the Class 20 was modified to an experimental condensing locomotive, equipped with a condensing tender that was ordered from Henschel in 1948. This condensing tender, with Henschel works number 28388, was designed for a Deutsche Reichsbahn
Class 52 condensing locomotive. It was modified slightly and regauged to Cape gauge
.SAR Klasse 20 2485 on Kondenslok (German)
The tender was designed in such a way that it could also be used on a modified Class 19D
or Class 24
, however, this was never done. The tender was capable of condensing 27000 pounds (12,247 kg) of exhaust steam per hour in maximum operating temperatures of between 100 and 110 °F (37.8 and 43.3 C).
Beginning in 1951, tests with the condensing Class 20 were conducted in the Eastern Transvaal and the Karoo
. It proved the viability of condensing locomotives in South Africa
, attaining a water saving of between 88% and 93% as well as a lower coal consumption, the latter brought on by the higher temperature of the condensed feedwater. Depending on the operating conditions, a water range of between 400 and 680 mi (643.7 and 1,094.4 km) was achieved.
At the end of 1951 the locomotive was relocated to Touws River
, where it was used for further condensing tests and occasionally put to work in regular service. The positive results of the condensing trials led to the introduction of the Class 25 4-8-4
condensing locomotive fleet in 1953.
At that time number 2485 was again relocated, this time to De Aar, for service on the section via Prieska to Upington on the line to Windhoek
in South West Africa. It remained in service there until 1958. Even though its service record and uniqueness justified preservation, it was scrapped in 1961.
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...
with a Santa Fe wheel arrangement in service. In 1950 it was modified to an experimental condensing locomotive.
Design
The Class 20 2-10-2 Santa Fe type steam locomotive was designed in 1934 by A.G. Watson, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1929 to 1936, and was built by the SAR at its Koedoespoort shops in PretoriaPretoria
Pretoria is a city located in the northern part of Gauteng Province, South Africa. It is one of the country's three capital cities, serving as the executive and de facto national capital; the others are Cape Town, the legislative capital, and Bloemfontein, the judicial capital.Pretoria is...
.
Watson disliked articulated locomotives and his aim with the Class 20 was to build an as powerful as possible non articulated locomotive with a maximum 12 long tons (12.2 t) axle load. The end result could be considered as Watson’s answer to the Class GCA 2-6-2+2-6-2
South African Class GCA 2-6-2+2-6-2
In 1927 the South African Railways placed thirteen Class GCA Garratt articulated steam locomotives with a 2-6-2+2-6-2 wheel arrangement in branch line service...
Garratt locomotive, having very similar weight and tractive effort capacities.
The Class 20 carried more water and coal than the Garratt and was about 20 long tons (20.3 t) heavier with 33080 pound-forces (147.1 kN) tractive effort, compared to the 28470 pound-forces (126.6 kN) of the Class GCA. Even so, only one Class 20 was produced and the design was not repeated.
Construction
The sole Class 20 locomotive was numbered 2485. It was a hybrid with a boiler inherited from a Class 19ASouth African Class 19A 4-8-2
In 1929 the South African Railways placed thirty-six Class 19A steam locomotives with a 4-8-2 wheel arrangement in service. Five of them were later reboilered and reclassified to Class 19AR.-Manufacturer:...
locomotive that had been equipped with a Watson Standard no. 1A boiler. The driving wheels were from scrapped Class 8
South African Class 8 4-8-0
In 1902 and 1903 the Cape Government Railways placed twenty-three Class 8 steam locomotives with a 4-8-0 Mastodon wheel arrangement in service, three on the Cape Western System, eight on the Cape Midland System and twelve on the Cape Eastern System...
locomotives. The bar frames and cylinders were imported, the cylinders with Rotary Cam Poppet valve gear being those of a Class 19C
South African Class 19C 4-8-2
In 1935 the South African Railways placed fifty Class 19C steam locomotives with a Mountain wheel arrangement in service.-Manufacturer:When the need for more branch line locomotives became apparent in 1934, tenders were invited by the South African Railways for another fifty Class 19B locomotives...
, but with the stroke reduced from 26 inches (660.4 mm) to 24 inches (609.6 mm) by means of deep spigots on the modified cylinder covers. The trailing pony truck was similar to that of the Class 19C, but the leading Bissel truck was specially designed.
Legacy
The construction of this sole Class 20 locomotive marked the beginning of a research process that was continued two years later with the construction of the sole Class 21 2-10-4South African Class 21 2-10-4
In 1937 the South African Railways placed one Class 21 steam locomotive with a Texas wheel arrangement in service, designed as a mixed traffic locomotive suitable for light rail. A simultaneously proposed heavier main line version Class 22 never materialised....
and that eventually culminated in the procurement of the Class 23 4-8-2
South African Class 23 4-8-2
In 1938 and 1939 the South African Railways placed one hundred and thirty-six Class 23 steam locomotives in service. The Class 23 was the last and the largest 4-8-2 Mountain locomotive to be designed by the South African Railways.-Manufacturers:...
fleet in 1939.
Service
The locomotive was intended for goods traffic on light rail in South West AfricaSouth West Africa
South-West Africa was the name that was used for the modern day Republic of Namibia during the earlier eras when the territory was controlled by the German Empire and later by South Africa....
, even though freight traffic volumes in that territory were hardly enough to justify such a powerful locomotive. It entered service there in 1935 but was soon returned to South Africa and allocated to Pretoria
Pretoria
Pretoria is a city located in the northern part of Gauteng Province, South Africa. It is one of the country's three capital cities, serving as the executive and de facto national capital; the others are Cape Town, the legislative capital, and Bloemfontein, the judicial capital.Pretoria is...
, where its power capacity could be used more productively. The Pretoria drivers considered the Class 20 to be one of their best locomotives since it was free-steaming, more than usually trouble-free and able to handle any load they gave it.
Condensing trials
The arid nature of a large part of South Africa and the consequent difficulty to ensure adequate and suitable water supplies for steam locomotives led to a decision to experiment with condensing locomotives. Such locomotives had by then already been built by Henschel and SonHenschel & Son
Henschel & Son was a German company, situated in Kassel, best known during the 20th century as a maker of transportation equipment, including locomotives, trucks, buses and trolleybuses, and armoured fighting vehicles and weapons....
for use in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. In pre-war days it was considered to modify a Class 12A
South African Class 12A 4-8-2
Between 1919 and 1929 the South African Railways placed sixty-seven Class 12A steam locomotives with a 4-8-2 Mountain wheel arrangement in service.-Manufacturers:...
into a condensing locomotive, but this never realised.
In 1950 the Class 20 was modified to an experimental condensing locomotive, equipped with a condensing tender that was ordered from Henschel in 1948. This condensing tender, with Henschel works number 28388, was designed for a Deutsche Reichsbahn
Deutsche Reichsbahn
Deutsche Reichsbahn was the name of the following two companies:* Deutsche Reichsbahn, the German Imperial Railways during the Weimar Republic, the Third Reich and the immediate aftermath...
Class 52 condensing locomotive. It was modified slightly and regauged to Cape gauge
Cape gauge
Cape gauge is a track gauge of between the inside of the rail heads and is classified as narrow gauge. It has installations of around .The gauge was first used by Norwegian engineer Carl Abraham Pihl and the first line was opened in 1862.- Nomenclature :...
.SAR Klasse 20 2485 on Kondenslok (German)
The tender was designed in such a way that it could also be used on a modified Class 19D
South African Class 19D 4-8-2
Between 1937 and 1949 the South African Railways placed two hundred and thirty-five Class 19D steam locomotives wirh a 4-8-2 Mountain wheel arrangement in service...
or Class 24
South African Class 24 2-8-4
In 1949 and 1950 the South African Railways placed one hundred Class 24 branch line steam locomotives with a 2-8-4 Berkshire wheel arrangement in service.-Design:...
, however, this was never done. The tender was capable of condensing 27000 pounds (12,247 kg) of exhaust steam per hour in maximum operating temperatures of between 100 and 110 °F (37.8 and 43.3 C).
Beginning in 1951, tests with the condensing Class 20 were conducted in the Eastern Transvaal and the Karoo
Karoo
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...
. It proved the viability of condensing locomotives in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, attaining a water saving of between 88% and 93% as well as a lower coal consumption, the latter brought on by the higher temperature of the condensed feedwater. Depending on the operating conditions, a water range of between 400 and 680 mi (643.7 and 1,094.4 km) was achieved.
At the end of 1951 the locomotive was relocated to Touws River
Touws River (town)
Touws River is a small railway town of 6,800 people in the Western Cape province of South Africa. It is located on the river of the same name, about north-east of Cape Town.-History:...
, where it was used for further condensing tests and occasionally put to work in regular service. The positive results of the condensing trials led to the introduction of the Class 25 4-8-4
South African Class 25 4-8-4
Between 1953 and 1955 the South African Railways placed ninety Class 25 condensing steam locomotives with a 4-8-4 Northern wheel arrangement in service...
condensing locomotive fleet in 1953.
At that time number 2485 was again relocated, this time to De Aar, for service on the section via Prieska to Upington on the line to Windhoek
Windhoek
Windhoek is the capital and largest city of the Republic of Namibia. It is located in central Namibia in the Khomas Highland plateau area, at around above sea level. The 2001 census determined Windhoek's population was 233,529...
in South West Africa. It remained in service there until 1958. Even though its service record and uniqueness justified preservation, it was scrapped in 1961.
See also
- Tender locomotive numbering and classification
- The 2-10-2 "Santa Fe"
- South African Class 25 4-8-4South African Class 25 4-8-4Between 1953 and 1955 the South African Railways placed ninety Class 25 condensing steam locomotives with a 4-8-4 Northern wheel arrangement in service...
- List of South African locomotive classes