South African Class MA 2-6-6-0

The South African Railways Class MA 2-6-6-0 of 1909 is a steam locomotive from the pre-Union era in the Natal Colony.

In 1909, the Natal Government Railways placed a single 2-6-6-0 Mallet articulated compound steam locomotive in service. In 1912, when it was assimilated into the South African Railways, it was renumbered and classified as Class MA.^[1][2][3][4]

Manufacturer

As a result of a visit to the United States of America by Natal Government Railways (NGR) Locomotive Superintendent D.A. Hendrie in 1909, to study Mallet type locomotives and also American locomotive design in general, the American Locomotive Company (ALCO) supplied the NGR with two experimental locomotives, which represented a radical departure from previous NGR locomotive designs. One was the NGR Class B America D, later to be designated the Class 3A on the South African Railways (SAR), while the other was the first Mallet type articulated compound steam locomotive in South Africa.^[1][4][5]

Mallet principles

Articulation

The object with an articulated locomotive is to distribute traction power over a larger number of driving wheels, with a flexible wheelbase. On the Mallet type, the boiler was fixed to the frame of the rear engine unit, as on a regular steam locomotive. The front engine unit carried the boiler barrel by means of a large supporting bracket, attached to the underside of the barrel and carried on a slide, fixed to the front engine unit's frame. On curves, the front engine unit could move several inches laterally under the boiler barrel. Side control springs acted as a centering device for the engine unit.^[2]

Compound expansion

In a compound expansion (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.^[1]

By comparison, in the more usual arrangement of simple expansion (simplex), steam is expanded just once in any one cylinder, before being exhausted through the smokebox.^[1]

In the compound Mallet locomotive, the rear set of coupled wheels are driven by the smaller high-pressure cylinders, from which spent steam is then fed to the larger low-pressure cylinders, which drive the front set of coupled wheels.^[1][2][4]

Characteristics

The NGR 2-6-6-0 Mallet locomotive had Walschaerts valve gear, a bar frame and used saturated steam. It was the first articulated compound steam locomotive to enter service in South Africa, and its design and large proportions represented a big advance in motive power on Cape gauge. At the time, it was the most powerful locomotive in the country.^[1][2][4]

Copper steam pipes, 4 ¹⁄₂ inches (114 millimetres) in internal diameter, were arranged from each side of the steam dome and passed vertically down the outside of the boiler, to the steam chests of the high-pressure cylinders. The exhaust from the high-pressure cylinders passed to a receiver pipe, 7 ¹⁄₂ inches (191 millimetres) in internal diameter, arranged along the centre line of the locomotive and with a ball-joint at the connection with the high-pressure cylinder casting. The front end of the pipe was fitted with an expansion joint, near the connection which led to the steam chests of the low-pressure cylinders. The exhaust from the low-pressure cylinders was carried by a pipe, also 7 ¹⁄₂ inches (191 millimetres) in internal diameter, with flexible connections leading into the smokebox.^[2]

An intercepting valve was arranged in the high-pressure cylinder casting, through which the engine could be worked in simplex mode, when required. Upon starting, the valve would feed boiler steam directly to the low-pressure cylinders for a few revolutions of the coupled wheels, just sufficient to give the engine additional power at starting, after which it automatically cut off and the working would become compound. By means of a steam cock in the cab, the driver could also admit boiler steam to the low-pressure cylinders for additional power, while ascending steep inclines.^[2]

The tender rode on diamond-frame four-wheeled bogies, and was equipped with a glass water gauge on the side of the tender tank, the first time such a device had been used in South Africa.^[2]

Performance

While the results obtained with the Mallet in service were encouraging, it might have been better than adequate if the locomotive had been superheated. Even so, the locomotive’s performance was good enough to warrant subsequent orders by the NGR for a further five slightly larger and more powerful compound Mallets.^[1][4]

The Mallet type gradually fell into disfavour, however, as a result of their high cost of repairs, low mileage between heavy repairs, high initial cost and the difficulties of obtaining a reasonably high sustained rate of speed from them, in comparison to the excellent performance of the non-articulated tender engines which were being introduced by D.A. Hendrie of the NGR and H.M. Beatty of the Cape Government Railways (CGR) at the time. The Mallets seemed to "choke" after a certain speed had been reached, a problem attributed to their long steam pipes and tortuous steam passages. In some cases, where Mallets worked on the same sections and to the same time schedules as non-articulated locomotives, they showed a higher rate of wear and tear and a higher rate of breakdown than the non-articulated types. Furthermore, when the four-cylinder simplex Garratt articutated type was introduced after World War I, it soon showed that it had definite advantages over the Mallet under South African conditions.^[2]

Service

The locomotive was placed in service as a banking engine, working heavy coal trains between Estcourt and Highlands on the Natal mainline. This section was about 28 miles (45 kilometres) long with a gradient of nearly 1 in 30 (3⅓%) uncompensated throughout, which made it, in effect, equivalent to a gradient of about 1 in 25 (4%).^[1][2][4]

When the Union of South Africa was established on 31 May 1910, the three Colonial government railways (CGR, NGR and Central South African Railways) were united under a single administration to control and administer the railways, ports and harbours of the Union. Although the South African Railways and Harbours came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways required careful planning and was only implemented with effect from 1 January 1912.^[3][6]

In 1912, the NGR 2-6-6-0 Mallet was renumbered 1601 and classified as the sole Class MA locomotive on the SAR. It was withdrawn from service in 1927.^[1][3][4][7]

References

Wikimedia Commons has media related to South African Class MA (2-6-6-0).

Locomotives of Natal
4' 8½" gauge	Natal 0-4-0ST Durban Natal 0-4-0WT Natal Natal 4-4-0T Perseverance
3' 6" gauge	Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert NGR Class A 1905 NGR Class A 1910 NGR Class B 4-8-0 1904 NGR Class B 4-8-0 1910 NGR Class B 4-8-2 1906 NGR Class B 4-8-2 1909 NGR Class B 4-8-2 1910 NGR Class C 4-8-2T NGR Class C 4-10-2T NGR Class D NGR Class E NGR Class F NGR Class G NGR Class H 4-6-2T NGR Class H 4-6-4T NGR Class I 2-6-0 NGR Class I 2-6-2T NGR Class K 0-4-0ST NGR Class K 0-6-0ST NGR Class K 2-6-0T NGR Class L 4-8-0 NGR Durban & Pietermaritzburg NGR Havelock NGR Mallet 1909 NGR Mallet 1910
2' gauge	NGR Class N 1906 NGR Class N 1907 NGR Class N 1911
List of South African locomotive classes South African locomotive history

Locomotives of South Africa
Steam	7' ¼" gauge East London 0-4-0VB Table Bay 0-4-0ST Table Bay 0-4-0T Table Bay 0-4-0WT 4' 8½" gauge Cape 0-4-0T Blackie Cape 0-4-2 Cape 2-4-0T CGR 0-4-0ST Aid Natal 0-4-0ST Durban Natal 0-4-0WT Natal Natal 4-4-0T Perseverance 3' 6" gauge Tank engines CGR 0-4-0ST 1873 CGR 0-4-0ST 1874 CGR 0-4-0ST 1881 CGR 0-4-0ST 1881 Coffee Pot CGR 0-6-0ST CGR 0-6-0T CGR 2-6-0ST 1900 CGR 2-6-0ST 1902 CGR 1st Class 0-4-0ST 1875 CGR 1st Class 0-4-0ST 1876 CGR 1st Class 2-6-0ST CGR 1st Class 4-4-0T CGR 2nd Class 4-4-0T CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack 4-6-4RT CSAR Railmotor Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth 0-4-0ST Kowie Railway 0-6-0T Kowie Railway 4-4-0T Metropolitan & Suburban 4-6-2T NGR 2-6-0T Durban & Pietermaritzburg NGR Class I 2-6-2T NGR Class K 0-4-0ST NGR Class K 0-6-0ST NGR Class K 2-6-0T NZASM 10 Tonner NZASM 13 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner PPR 26 Tonner PPR 35 Tonner Portuguese SAR Class A SAR Class B SAR Class C SAR Class C1 SAR Class C2 SAR Class D SAR Class E SAR Class F SAR Class G SAR Class H SAR Class H1 SAR Class H2 SAR Class J SAR Class K SAR Railmotor SAR Dock 0-4-0ST SAR Dock 0-4-0T SWA 2-8-0T 3' 6" gauge Tender engines CGR 1st Class 2-6-0 1876 BP CGR 1st Class 2-6-0 1876 Kitson CGR 1st Class 2-6-0 1879 CGR 1st Class 2-6-0 1891 CGR 1st Class 4-4-0 CGR 1st Class 4-4-0TT CGR 2nd Class 2-6-2TT CGR 3rd Class 4-4-0 1883 CGR 3rd Class 4-4-0 1884 CGR 3rd Class 4-4-0 1889 CGR 3rd Class 4-4-0 1898 CGR 3rd Class 4-4-0 1901 CGR 3rd Class 4-4-0 1903 CGR 4th Class 4-4-2 CGR 4th Class 4-6-0TT 1880 CGR 4th Class 4-6-0TT 1882 CGR 4th Class 4-6-0TT 1882 Joy CGR 4th Class 4-6-0TT 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 NGR Havelock NGR Class I SAR Class Exp 1 SAR Class Exp 2 SAR Class Exp 3 SAR Class Exp 4 SAR Class Exp 5 SAR Class Exp 6 SAR Class S SAR Class S1 SAR Class S2 SAR Class 1 SAR Class 1A SAR Class 1B SAR Class 2 SAR Class 2C SAR Class 3 SAR Class 3A SAR Class 3B SAR Class 4 SAR Class 4A SAR Class 5 SAR Class 5A SAR Class 5B SAR Class 6 SAR Class 6A SAR Class 6B SAR Class 6C SAR Class 6D SAR Class 6E SAR Class 6F SAR Class 6G SAR Class 6H SAR Class 6J SAR Class 6K SAR Class 6L SAR Class 6Y SAR Class 6Z SAR Class 7 SAR Class 7A SAR Class 7B SAR Class 7C SAR Class 7D SAR Class 7E SAR Class 7F SAR Class 8 SAR Class 8A SAR Class 8B SAR Class 8C SAR Class 8D SAR Class 8E SAR Class 8F SAR Class 8R SAR Class 8X SAR Class 8Y SAR Class 8Z SAR Class 9 SAR Class 10 SAR Class 10A SAR Class 10B SAR Class 10C SAR Class 10D SAR Class 11 SAR Class 12 SAR Class 12A SAR Class 12B SAR Class 13 SAR Class 14 SAR Class 14A SAR Class 14B SAR Class 14C 1st SAR Class 14C 2nd SAR Class 14C 3rd SAR Class 14C 4th SAR Class 15 SAR Class 15A SAR Class 15B SAR Class 15C SAR Class 15CA SAR Class 15E SAR Class 15F SAR Class 16 SAR Class 16A SAR Class 16B SAR Class 16C SAR Class 16D SAR Class 16DA 1928 SAR Class 16DA 1930 SAR Class 16E SAR Class 17 SAR Class 18 SAR Class 19 SAR Class 19A SAR Class 19B SAR Class 19C SAR Class 19D SAR Class 20 SAR Class 21 SAR Class 23 SAR Class 24 SAR Class 25 SAR Class 25NC SAR Class 26 SAR Katanga SWA 2-8-0 3' 6" gauge Articulated engines CGR Fairlie CGR Kitson-Meyer SAR Class FC SAR Class FD SAR Class GA SAR Class GB SAR Class GC SAR Class GCA SAR Class GD SAR Class GDA SAR Class GE SAR Class GEA SAR Class GF SAR Class GG SAR Class GH SAR Class GK SAR Class GL SAR Class GM SAR Class GMA SAR Class GO SAR Class HF SAR Class KM SAR Class MA SAR Class MB SAR Class MC SAR Class MC1 SAR Class MD SAR Class ME SAR Class MF SAR Class MG SAR Class MH SAR Class MJ SAR Class MJ1 SAR Class U 2' 6" gauge Cape Copper John King & Miner Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Cape Copper Condenser Cape Copper Scotia Namaqua Copper Pioneer Walvis Bay 2-4-2T Hope 2' & 600mm gauges ACR Class NG-G16A CGR NG 0-4-0T CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T NGR Class N 4-6-2T SAR Dutton SAR NG 0-4-0T SAR Class NG1 SAR Class NG2 SAR Class NG3 SAR Class NG4 SAR Class NG5 SAR Class NG6 SAR Class NG7 SAR Class NG8 SAR Class NG9 SAR Class NG10 SAR Class NG-G11 SAR Class NG-G12 SAR Class NG-G13 SAR Class NG-G14 SAR Class NG15 SAR Class NG-G16 SWA Class Ha SWA Class Hb SWA Class Hc SWA Class Hd SWA Jung SWA Zwillinge
Electric	Amcoal Class E38 SAR Class ES SAR Class ES1 SAR Class Exp-AC SAR Class 1E SAR Class 2E SAR Class 3E SAR Class 4E SAR Class 5E s1 SAR Class 5E s2 SAR Class 5E s3 SAR Class 5E1 s1 SAR Class 5E1 s2 SAR Class 5E1 s3 SAR Class 5E1 s4 SAR Class 5E1 s5 SAR Class 6E SAR Class 6E1 s1 SAR Class 6E1 s2 SAR Class 6E1 s3 SAR Class 6E1 s4 SAR Class 6E1 s5 SAR Class 6E1 s6 SAR Class 6E1 s7 SAR Class 6E1 s8 SAR Class 6E1 s9 SAR Class 6E1 s10 SAR Class 6E1 s11 SAR Class 7E SAR Class 7E1 SAR Class 7E2 s1 SAR Class 7E2 s2 SAR Class 7E3 s1 SAR Class 7E3 s2 Spoornet Class 7E4 SAR Class 8E SAR Class 9E s1 SAR Class 9E s2 SAR Class 10E SAR Class 10E1 s1 Spoornet Class 10E1 s2 SAR Class 10E2 SAR Class 11E SAR Class 12E Spoornet Class 14E Spoornet Class 14E1 TFR Class 15E Spoornet Class 16E Spoornet Class 17E Spoornet Class 18E s1 TFR Class 18E s2 TFR Class 19E TFR Class 20E TFR Class 21E TFR Class 22E
Gas-electric	SAR Gas-electric
Diesel	3' 6" gauge Diesel-electric PRASA Class Afro 4000 SAR Class DS SAR Class DS1 SAR Class 31-000 SAR Class 32-000 SAR Class 32-200 SAR Class 33-000 SAR Class 33-200 SAR Class 33-400 SAR Class 34-000 SAR Class 34-200 SAR Class 34-400 SAR Class 34-500 SAR Class 34-600 SAR Class 34-800 SAR Class 34-900 SAR Class 35-000 SAR Class 35-200 SAR Class 35-400 SAR Class 35-600 TFR Class 35-800 SAR Class 36-000 SAR Class 36-200 SAR Class 37-000 Spoornet Class 39-000 TFR Class 39-200 TFR Class 43-000 TFR Class 44-000 2' gauge Diesel-electric SAR Class 91-000 3' 6" gauge Diesel-hydraulic SAR Class 61-000 3' 6" gauge Electro-diesel Spoornet Class 38-000
List of South African locomotive classes South African locomotive numbering and classification