In 1915, the South African Railways placed five Class MH Mallet articulated compound steam locomotives with a 2-6-6-2 wheel arrangement in coal hauling service.[1][2][3]
During 1914, the requirement for locomotives with a high tractive effort to cope with the increasing volume of coal traffic between Witbank and Germiston led to the introduction of a heavy Mallet compound superheated engine with a 2-6-6-2 wheel arrangement.[2]
D.A. Hendrie
The Class MH Mallet articulated locomotive was designed in detail in the locomotive drawing office in Pretoria under the personal direction of D.A. Hendrie, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1910 to 1922. The draughtsman, specially detached for the work, was J.R. Boyer who was later to become the Chief Locomotive Draughtsman of the SAR. Five of these very large locomotives were ordered from North British Locomotive Company and delivered in 1915, numbered in the range from 1661 to 1665. They were erected in the Salvokop shops in Pretoria and were placed in service in September 1915.[1][2][3][4]
CharacteristicsEdit
The main bar frames, 4+1⁄2 inches (114 millimetres) thick, were machined from a 2 ft 2+1⁄2 in (673 mm) wide solid. The hind part of this frame was rigidly secured to the boiler through the high-pressure cylinder saddle castings and terminated just in front of the firebox outer throat plate. From this point rearwards, the frame was of the plate type and arranged to carry the spring gear and other fittings for the trailing Bissel truck.[1][2][3]
The locomotives were superheated and had Walschaerts valve gear, controlled by steam reversing gear. The cylinders and steam chests were formed in three separate castings. The high-pressure cylinders were arranged with piston valves, while the low-pressure cylinders were arranged with Richardson balanced type slide valves, arranged above the cylinders. The steam chest covers of the low-pressure cylinders were designed with inclined joint faces to facilitate the handling of the valve and refacing of the ports during servicing.[2]
As built, the boiler pressure was set to blow off at 200 pounds per square inch (1,379 kilopascals), which gave the engine a tractive effort of 53,750 pounds-force (239.1 kilonewtons) at 50% of boiler pressure. The setting was later reduced to 180 pounds per square inch (1,241 kilopascals), which reduced the tractive effort to 48,370 pounds-force (215.2 kilonewtons) at 50% of boiler pressure.[1][2]
At the time of their introduction, the Class MH was the largest and most powerful locomotive in the world on Cape gauge. It attracted the attention of locomotive engineers throughout the world as an outstanding achievement for locomotive power on 3 feet 6 inches (1,067 millimetres) gauge.[1][2]
Its 105 long tons 13 hundredweight (107,300 kilograms) adhesive weight and the SAR's ultra-conservative practice of reporting a Mallet's tractive effort at only 50% of boiler pressure resulted in a much lower than actual starting tractive effort of 48,370 pounds-force (215.2 kilonewtons). The Class MH was almost certainly capable of exerting more than 60,000 pounds-force (270 kilonewtons) tractive effort at starting.[5]
ServiceEdit
They were initially placed in service on the coal line between Witbank and Germiston as intended to supplement the other Mallets already working on that line. In the 1930s they were transferred to Natal to work on the line between Vryheid and Glencoe, also hauling coal. They were outstanding in their performance and remained in Natal for the rest of their service lives until they were all retired and scrapped by 1940.[1][3][5]
IllustrationEdit
Class MH 2-6-6-2 Mallet no. 1661, c. 1915
ReferencesEdit
Wikimedia Commons has media related to South African Class MH 2-6-6-2.
^ abcdefHolland, D. F. (1972). Steam Locomotives of the South African Railways. Vol. 2: 1910-1955 (1st ed.). Newton Abbott, England: David & Charles. pp. 30–32. ISBN978-0-7153-5427-8.
^ abcdefgEspitalier, T.J.; Day, W.A.J. (1945). The Locomotive in South Africa – A Brief History of Railway Development. Chapter VII – South African Railways (Continued). South African Railways and Harbours Magazine, May 1945. pp. 350, 356.
^ abcdPaxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 87. ISBN0869772112.
^North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
^ abSoul of A Railway, System 7, Western Transvaal, based in Johannesburg, Part 21: Witbank Line by Les Pivnic, Eugene Armer, Peter Stow and Peter Micenko. Captions 3–4. (Accessed on 4 May 2017)
August 27, 2023
south, african, class, south, african, railways, class, 1915, articulated, mallet, design, steam, locomotive, class, 1661, 1915type, originpower, typesteamdesignersouth, african, railways, hendrie, buildernorth, british, locomotive, companyserial, number20958,. The South African Railways Class MH 2 6 6 2 of 1915 was an articulated Mallet design steam locomotive South African Class MH 2 6 6 2SAR Class MH no 1661 c 1915Type and originPower typeSteamDesignerSouth African Railways D A Hendrie BuilderNorth British Locomotive CompanySerial number20958 20962ModelSAR Class MHBuild date1915Total produced5SpecificationsConfiguration Whyte2 6 6 2 Prairie Mallet UIC 1 C C1 hv4Driver3rd amp 6th coupled axlesGauge3 ft 6 in 1 067 mm Cape gaugeLeading dia 28 1 2 in 724 mm Coupled dia 48 in 1 219 mm Trailing dia 33 1 2 in 851 mm Tender wheels34 in 864 mm Wheelbase70 ft 10 1 4 in 21 596 mm Engine43 ft 7 in 13 284 mm Coupled8 ft 8 in 2 642 mm per unit Tender16 ft 9 in 5 105 mm Tender bogie4 ft 7 in 1 397 mm Length Over couplers79 ft 5 in 24 206 mm Height12 ft 10 in 3 912 mm Frame typeBar amp PlateAxle load18 LT 4 cwt 18 490 kg Leading7 LT 9 cwt 7 570 kg 1st coupled16 LT 16 cwt 17 070 kg 2nd coupled16 LT 19 cwt 17 220 kg 3rd coupled17 LT 6 cwt 17 580 kg 4th coupled18 LT 4 cwt 18 490 kg 5th coupled18 LT 4 cwt 18 490 kg 6th coupled18 LT 4 cwt 18 490 kg Trailing15 LT 3 cwt 15 390 kg Tender bogieBogie 1 27 LT 10 cwt 27 940 kg Bogie 2 23 LT 11 cwt 23 930 kg Tender axle13 LT 15 cwt 13 970 kg Adhesive weight105 LT 13 cwt 107 300 kg Loco weight128 LT 5 cwt 130 300 kg Tender weight51 LT 1 cwt 51 870 kg Total weight179 LT 6 cwt 182 200 kg Tender typeMP1 2 axle bogies Fuel typeCoalFuel capacity10 LT 10 2 t Water cap 4 250 imp gal 19 300 L Firebox typeRound top Firegrate area53 sq ft 4 9 m2 Boiler Pitch7 ft 10 1 2 in 2 400 mm Diameter5 ft 11 in 1 803 mm Tube plates22 ft 6 706 mm Small tubes168 2 1 4 in 57 mm Large tubes25 5 1 2 in 140 mm Boiler pressure180 psi 1 241 kPa Safety valveRamsbottomHeating surface3 211 sq ft 298 3 m2 Tubes2 961 sq ft 275 1 m2 Firebox250 sq ft 23 m2 Superheater Heating area634 sq ft 58 9 m2 CylindersFourHigh pressure cylinder20 in 508 mm bore26 in 660 mm strokeLow pressure cylinder31 1 2 in 800 mm bore26 in 660 mm strokeValve gearWalschaertsValve typeHP PistonLP Richardson balanced slideCouplersJohnston link and pinAAR knuckle 1930s Performance figuresTractive effort48 370 lbf 215 2 kN 50 CareerOperatorsSouth African RailwaysClassClass MHNumber in class5Numbers1661 1665Delivered1915First run1915Withdrawn1940In 1915 the South African Railways placed five Class MH Mallet articulated compound steam locomotives with a 2 6 6 2 wheel arrangement in coal hauling service 1 2 3 Contents 1 Manufacturer 2 Characteristics 3 Service 4 Illustration 5 ReferencesManufacturer EditDuring 1914 the requirement for locomotives with a high tractive effort to cope with the increasing volume of coal traffic between Witbank and Germiston led to the introduction of a heavy Mallet compound superheated engine with a 2 6 6 2 wheel arrangement 2 D A HendrieThe Class MH Mallet articulated locomotive was designed in detail in the locomotive drawing office in Pretoria under the personal direction of D A Hendrie Chief Mechanical Engineer CME of the South African Railways SAR from 1910 to 1922 The draughtsman specially detached for the work was J R Boyer who was later to become the Chief Locomotive Draughtsman of the SAR Five of these very large locomotives were ordered from North British Locomotive Company and delivered in 1915 numbered in the range from 1661 to 1665 They were erected in the Salvokop shops in Pretoria and were placed in service in September 1915 1 2 3 4 Characteristics EditThe main bar frames 4 1 2 inches 114 millimetres thick were machined from a 2 ft 2 1 2 in 673 mm wide solid The hind part of this frame was rigidly secured to the boiler through the high pressure cylinder saddle castings and terminated just in front of the firebox outer throat plate From this point rearwards the frame was of the plate type and arranged to carry the spring gear and other fittings for the trailing Bissel truck 1 2 3 The locomotives were superheated and had Walschaerts valve gear controlled by steam reversing gear The cylinders and steam chests were formed in three separate castings The high pressure cylinders were arranged with piston valves while the low pressure cylinders were arranged with Richardson balanced type slide valves arranged above the cylinders The steam chest covers of the low pressure cylinders were designed with inclined joint faces to facilitate the handling of the valve and refacing of the ports during servicing 2 As built the boiler pressure was set to blow off at 200 pounds per square inch 1 379 kilopascals which gave the engine a tractive effort of 53 750 pounds force 239 1 kilonewtons at 50 of boiler pressure The setting was later reduced to 180 pounds per square inch 1 241 kilopascals which reduced the tractive effort to 48 370 pounds force 215 2 kilonewtons at 50 of boiler pressure 1 2 At the time of their introduction the Class MH was the largest and most powerful locomotive in the world on Cape gauge It attracted the attention of locomotive engineers throughout the world as an outstanding achievement for locomotive power on 3 feet 6 inches 1 067 millimetres gauge 1 2 Its 105 long tons 13 hundredweight 107 300 kilograms adhesive weight and the SAR s ultra conservative practice of reporting a Mallet s tractive effort at only 50 of boiler pressure resulted in a much lower than actual starting tractive effort of 48 370 pounds force 215 2 kilonewtons The Class MH was almost certainly capable of exerting more than 60 000 pounds force 270 kilonewtons tractive effort at starting 5 Service EditThey were initially placed in service on the coal line between Witbank and Germiston as intended to supplement the other Mallets already working on that line In the 1930s they were transferred to Natal to work on the line between Vryheid and Glencoe also hauling coal They were outstanding in their performance and remained in Natal for the rest of their service lives until they were all retired and scrapped by 1940 1 3 5 Illustration Edit Class MH 2 6 6 2 Mallet no 1661 c 1915References Edit Wikimedia Commons has media related to South African Class MH 2 6 6 2 a b c d e f Holland D F 1972 Steam Locomotives of the South African Railways Vol 2 1910 1955 1st ed Newton Abbott England David amp Charles pp 30 32 ISBN 978 0 7153 5427 8 a b c d e f g Espitalier T J Day W A J 1945 The Locomotive in South Africa A Brief History of Railway Development Chapter VII South African Railways Continued South African Railways and Harbours Magazine May 1945 pp 350 356 a b c d Paxton Leith Bourne David 1985 Locomotives of the South African Railways 1st ed Cape Town Struik p 87 ISBN 0869772112 North British Locomotive Company works list compiled by Austrian locomotive historian Bernhard Schmeiser a b Soul of A Railway System 7 Western Transvaal based in Johannesburg Part 21 Witbank Line by Les Pivnic Eugene Armer Peter Stow and Peter Micenko Captions 3 4 Accessed on 4 May 2017 Retrieved from https en wikipedia org w index php title South African Class MH 2 6 6 2 amp oldid 1126751006, wikipedia, wiki, book, books, library,
