South African Class MB 2-6-6-0

The South African Class MB 2-6-6-0 of 1910 is a South African steam locomotive from the pre-Union era in the Natal Colony.

In 1910 the Natal Government Railways placed five 2-6-6-0 Mallet articulated compound steam locomotives in service. In 1912, when they were assimilated into the South African Railways, they were renumbered and classified as Class MB.^[1][2][3]

Manufacturer

Following on the satisfactory performance of the experimental Mallet compound steam locomotive that had been acquired by the Natal Government Railways (NGR) in 1909, a further five similar locomotives were ordered from the American Locomotive Company (ALCO) in 1910. They were delivered later that same year and numbered in the range from 337 to 341.^[1][3]

Characteristics

Like the previous Mallet locomotive, these five had Walschaerts valve gear, bar frames and used saturated steam. They differed little from the previous Mallet, basically only in respect of their larger boilers, which made them slightly heavier, and their tenders with a larger coal capacity.^[1][3]

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.^[4]

In the compound Mallet locomotive, the rear set of coupled wheels are driven by the smaller high pressure cylinders which are fed steam from the steam dome. Their spent steam is then fed to the larger low pressure cylinders that drive the front set of coupled wheels. 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.^[1][3]

Service

The five locomotives joined the first Mallet in banking service, working heavy coal trains between Estcourt and Highlands on the Natal mainline. To relieve coupler strain, they were used in three-locomotive trains and in this manner were able to haul 750 long tons (762.0 tonnes) up the one in thirty gradients on that line.^[1][3]

Railway network of the Natal Government Railways in 1910 upon the establishment of the Union of South Africa and the South African Railways

The Union of South Africa was established on 31 May 1910, in terms of the South Africa Act, enacted by the Parliament of the United Kingdom. One of the clauses in the Act required that the three Colonial Government railways, the Cape Government Railways, the NGR and the Central South African Railways, also be united under one single administration to control and administer the railways, ports and harbours of the Union. While the South African Railways (SAR) 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.^[2][5]

In 1912 these five locomotives were renumbered in the range from 1602 to 1606 and classified as Class MB on the SAR. They were withdrawn from service by 1924.^[1][2][3]

See also

• Articulated locomotive numbering and classification
• List of South African locomotive classes
• Mallet locomotive
• South African Class MA 2-6-6-0
• South African Class MC 2-6-6-0
• South African Class MC1 2-6-6-0
• South African Class MJ 2-6-6-0
• South African Class MJ1 2-6-6-0
• South African locomotive history
• The 2-6-6-0 Mallet

References

Wikimedia Commons has media related to: South African Class MB (2-6-6-0)

Locomotives of South Africa Steam Brunel gauge HBEL 0-4-0 HBTB 0-4-0T HBTB 0-4-0WT HBTB 0-4-0ST Broad gauge CGR Aid CGR Blackie CGR 0-4-2 CGR 2-4-0T NRC Durban NRC Natal NRC Perseverance Cape gauge Tank CGR Coffee Pot CGR 040 1873 CGR 040 1874 CGR 060 1876 CGR 060 1902 CGR 260 1900 CGR 260 1902 CGR 1st 040 1875 CGR 1st 440 1875 CGR 1st 040 1876 CGR 1st 260 1876 CGR 2nd 1882 CGR 3rd 1900 CGR RM CSAR C CSAR E CSAR Rack CSAR RM Dbn Congella Dbn Edward Innes Dbn John Milne Dbn Sir Albert HBPE 040 Kowie 060 Kowie 440 M&S 462 NGR Dbn & Pmb NGR I 262 NGR K 040 NGR K 060 NGR K 260 NZASM 10T NZASM 14T NZASM 18T NZASM 19T NZASM 32T NZASM 40T PPR 26T PPR 35T SAR RM SAR 0-4-0ST SAR 040 69 SAR A SAR B SAR C SAR C1 SAR C2 SAR D SAR E SAR F SAR G SAR H SAR H1 SAR H2 SAR J SAR K SWA 2-8-0T Cape gauge Tender CGR 1st 260 1876 BP CGR 1st 260 1876 K CGR 1st 260 1879 CGR 1st 440 1879 CGR 1st 1881 CGR 1st 1891 CGR 2nd 1875 CGR 3rd 1883 CGR 3rd 1884 CGR 3rd 1889 CGR 3rd 1898 CGR 3rd 1901 CGR 3rd 1903 CGR 4th 1880 CGR 4th 1882 CGR 4th 1884 CGR 4th 1897 CGR 5th 1890 CGR 5th 1891 NGR Havelock NGR I 260 Exp-1 Exp-2 Exp-3 Exp-4 Exp-5 Exp-6 SAR S SAR S1 SAR S2 SAR 1 SAR 1A SAR 1B SAR 2 SAR 2C SAR 3 SAR 3A SAR 3B SAR 4 SAR 4A SAR 5 SAR 5A SAR 5B SAR 6 SAR 6A SAR 6B SAR 6C SAR 6D SAR 6E SAR 6F SAR 6G SAR 6H SAR 6J SAR 6K SAR 6L SAR 6Y SAR 6Z SAR 7 SAR 7A SAR 7B SAR 7C SAR 7D SAR 7E SAR 7F SAR 8 SAR 8A SAR 8B SAR 8C SAR 8D SAR 8E SAR 8F SAR 8X SAR 8Y SAR 8Z SAR 9 SAR 10 SAR 10A SAR 10B SAR 10C SAR 10D SAR 11 SAR 12 SAR 12A SAR 12B SAR 13 SAR 14 SAR 14A SAR 14B SAR 14C SAR 15 SAR 15A SAR 15B SAR 15C SAR 15CA SAR 15E SAR 15F SAR 16 SAR 16A SAR 16B SAR 16C SAR 16D SAR 16DA SAR 16E SAR 17 SAR 18 SAR 19 SAR 19A SAR 19B SAR 19C SAR 19D SAR 20 SAR 21 SAR 23 SAR 24 SAR 25 SAR 25NC SAR 26 SWA 2-8-0 Cape gauge Articulated CGR Fairlie CGR Kitson-Meyer SAR FC SAR FD SAR GA SAR GB SAR GC SAR GCA SAR GD SAR GDA SAR GE SAR GEA SAR GF SAR GG SAR GH SAR GK SAR GL SAR GM SAR GMA SAR GO SAR HF SAR KM SAR MA SAR MB SAR MC SAR MC1 SAR MD SAR ME SAR MF SAR MG SAR MH SAR MJ SAR MJ1 SAR U 2ft 6in gauge CCC 1871 CCC Britannia CCC Caledonia CCC Clara CCC Condenser CCC Scotia NCC Pioneer 2ft & 600mm gauges ACR NG-G16A CGR NG 060 CGR NG 462 CGR A CGR C NGR N SAR 040 1899 SAR NG1 SAR NG2 SAR NG3 SAR NG4 SAR NG5 SAR NG6 SAR NG7 SAR NG8 SAR NG9 SAR NG10 SAR NG-G11 SAR NG-G12 SAR NG-G13 SAR NG-G14 SAR NG15 SAR NG-G16 SWA Ha SWA Hb SWA Hc SWA Hd SWA Jung SWA Zwillinge Diesel -electric SAR DS SAR DS1 SAR 31-000 SAR 32-000 SAR 32-200 SAR 33-000 SAR 33-200 SAR 33-400 SAR 34-000 SAR 34-200 SAR 34-400 SAR 34-500 SAR 34-600 SAR 34-800 SAR 34-900 SAR 35-000 SAR 35-200 SAR 35-400 SAR 35-600 SAR 36-000 SAR 36-200 SAR 37-000 SN 39-000 TFR 39-200 TFR 43-000 SAR 91-000 Afro4000 -hydraulic SAR 61-000 Electro-diesel SN 38-000 Electric SAR ES SAR ES1 Exp-AC SAR 1E SAR 2E SAR 3E SAR 4E SAR 5E-S1 SAR 5E-S2 SAR 5E-S3 SAR 5E1-S1 SAR 5E1-S2 SAR 5E1-S3 SAR 5E1-S4 SAR 5E1-S5 SAR 6E SAR 6E1-S1 SAR 6E1-S2 SAR 6E1-S3 SAR 6E1-S4 SAR 6E1-S5 SAR 6E1-S6 SAR 6E1-S7 SAR 6E1-S8 SAR 6E1-S9 SAR 6E1-S10 SAR 6E1-S11 SAR 7E SAR 7E1 SAR 7E2-S1 SAR 7E2-S2 SAR 7E3-S1 SAR 7E3-S2 SN 7E4 SAR 8E SAR 9E-S1 SAR 9E-S2 SAR 10E SAR 10E1-S1 SAR 10E1-S2 SAR 10E2 SAR 11E SAR 12E SN 14E SN 14E1 TFR 15E SN 16E SN 17E SN 18E-S1 TFR 18E-S2 TFR 19E TFR 20E TFR 21E E38 List of South African locomotive classes Rail transport in South Africa