South African Class ME 2-6-6-2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Class ME no. 1618, c. 1912 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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The South African Railways Class ME 2-6-6-2 of 1912 was a steam locomotive.
In 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. [1] [2] [3] [4]
A steam locomotive is a type of railway locomotive that produces its pulling power through a steam engine. These locomotives are fueled by burning combustible material – usually coal, wood, or oil – to produce steam in a boiler. The steam moves reciprocating pistons which are mechanically connected to the locomotive's main wheels (drivers). Both fuel and water supplies are carried with the locomotive, either on the locomotive itself or in wagons (tenders) pulled behind.
Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a 2-6-6-2 is a locomotive with one pair of unpowered leading wheels, followed by two sets of three pairs of powered driving wheels and one pair of trailing wheels. The wheel arrangement was principally used on Mallet-type articulated locomotives, although some tank locomotive examples were also built. A Garratt type locomotive with the same wheel arrangement is designated 2-6-0+0-6-2.
During 1911, the Central South African Railways (CSAR) placed an order for a single experimental simple expansion Mallet articulated steam locomotive with the North British Locomotive Company (NBL). The locomotive was intended for test purposes on branch lines with light 45 pounds per yard (22 kilograms per metre) rail. [1] [2] [3] [5]
The Central South African Railways (CSAR) was from 1902 to 1910 the operator of public railways in the Transvaal Colony and Orange River Colony in what is now South Africa. During the Anglo-Boer War, as British forces moved into the territory of the Orange Free State and the South African Republic, the Orange Free State Government Railways, the Netherlands-South African Railway Company and the Pretoria-Pietersburg Railway were taken over by the Imperial Military Railways under Lieutenant-Colonel Sir Percy Girouard. After the war had ended, the Imperial Military Railways became the Central South African Railways in July 1902, with Thomas Rees Price as General Manager. With the creation of the Union of South Africa in 1910, the CSAR was merged with the Cape Government Railways and the Natal Government Railways to form the South African Railways.
The North British Locomotive Company was created in 1903 through the merger of three Glasgow locomotive manufacturing companies; Sharp, Stewart and Company, Neilson, Reid and Company and Dübs and Company, creating the largest locomotive manufacturing company in Europe and the British Empire.
By the time it was delivered in January 1912, the CSAR had already become part of the newly established South African Railways (SAR). The locomotive was therefore classified as the sole Class ME and numbered 1618 on the SAR roster. [1] [2] [3] [4]
Having been built for branch line working, the engine's maximum axle load was 9 long tons 18 hundredweight (10,060 kilograms) and it was delivered with the 6 long tons (6.1 tonnes) coal capacity version of the Type XF tender. Its Belpaire firebox extended over the second and third coupled wheels of the rear engine unit. [2] [6] [7]
The South African type XF tender was a steam locomotive tender from the pre-Union era in Transvaal.
The Belpaire firebox is a type of firebox used on steam locomotives. It was invented by Alfred Belpaire of Belgium in 1864. Today it generally refers to the shape of the outer shell of the firebox which is approximately flat at the top and square in cross-section, indicated by the longitudinal ridges on the top sides. However, it is the similar square cross-section inner firebox which provides the main advantages of this design i.e. it has a greater surface area at the top of the firebox where the heat is greatest, improving heat transfer and steam production, compared with a round-top shape.
Compared to other Mallet locomotives which were placed in service during the first decade of the SAR’s existence, the Class ME was unique in being arranged as a simple expansion (simplex) locomotive with four high-pressure cylinders instead of the more usual compound expansion arrangement of two high-pressure and two low-pressure cylinders. [1] [3] [8]
The cylinders were arranged outside the plate frames and the 6 inches (152 millimetres) diameter trick-ported piston valves, designed for inside admission, were actuated by Walschaerts valve gear. Each engine unit was equipped with an independent Wakefield mechanical lubricator to supply oil to the valves and pistons. [2]
The Walschaerts valve gear is a type of valve gear invented by Belgian railway mechanical engineer Egide Walschaerts in 1844 used to regulate the flow of steam to the pistons in steam engines. The gear is sometimes named without the final "s", since it was incorrectly patented under that name. It was extensively used in steam locomotives from the late 19th century until the end of the steam era.
An automatic lubricator, is a device fitted to a steam engine to supply lubricating oil to the cylinders and, sometimes, the bearings and axle box mountings as well. There are various types of automatic lubricator, which include various designs of displacement, hydrostatic and mechanical lubricators.
The comparatively low boiler pressure of 170 pounds per square inch (1,172 kilopascals) is indicative of the opinion held at the time that the economies to be gained from superheating did not require high boiler pressure. The boiler was equipped with a Schmidt superheater. Steam distribution to the four cylinders was rather unique, being led from the superheater header in the smokebox to a steam collector box which was arranged between the two cylinders of the rear engine unit, from where a branch was led to the cylinders of the front engine unit by a central steam pipe with flexible joints, since this engine unit could move sideways in relation to the boiler barrel. This pipe took the place of the usual receiver pipe on compound Mallets. [2]
The blast pipe had separate outlets for the exhaust steam from each engine unit, with the rear engine unit's exhaust feeding through an annulus arranged around the exhaust from the front engine unit. A device was installed by which either engine unit could be cut out whilst running so that steam could be admitted to one pair of cylinders only when running light engine. [2]
The Class ME proved to be successful in operation and, even though it was acquired as an experimental locomotive, remained in service for 25 years. It spent its last years working on the line from Nelspruit to Sabie in the Eastern Transvaal Lowveld, until it was withdrawn and scrapped in 1937. [1]
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