South African Class MG 2-6-6-2

CSAR Mallet 2-6-6-2 Stoker
South African Class MG 2-6-6-2

SAR no. 1628, ex CSAR no. 1024, c. 1912

Type and origin
Power type	Steam
Designer	American Locomotive Company Central South African Railways (G.G. Elliot)
Builder	American Locomotive Company
Serial number	49124
Model	CSAR Mallet
Build date	1911
Total produced	1

Specifications
Configuration	2-6-6-2 (Prairie Mallet)
Driver	3rd & 6th coupled axles
Gauge	3 ft 6 in (1,067 mm) Cape gauge
Leading dia.	28 ¹⁄₂ in (724 mm)
Coupled dia.	51 in (1,295 mm) front unit 46 in (1,168 mm) rear unit
Trailing dia.	28 ¹⁄₂ in (724 mm)
Tender wheels	34 in (864 mm)
Wheelbase	66 ft 9 in (20,345 mm)
• Engine	41 ft 6 in (12,649 mm)
• Coupled	9 ft 2 in (2,794 mm) front unit 8 ft 4 in (2,540 mm) rear unit
• Tender	17 ft 11 in (5,461 mm)
• Tender bogie	4 ft 7 in (1,397 mm)
Length:
• Over couplers	74 ft 10 ¹⁄₄ in (22,816 mm)
Height	12 ft 10 ⁷⁄₈ in (3,934 mm)
Frame type	Bar
Axle load	15 LT 3 cwt 2 qtr (15.42 t)
• Leading	7 LT 11 cwt 2 qtr (7.697 t)
• 1st coupled	14 LT 6 cwt (14.53 t)
• 2nd coupled	14 LT 14 cwt 2 qtr (14.96 t)
• 3rd coupled	14 LT 14 cwt 2 qtr (14.96 t)
• 4th coupled	14 LT 14 cwt 2 qtr (14.96 t)
• 5th coupled	14 LT 14 cwt 2 qtr (14.96 t)
• 6th coupled	15 LT 3 cwt 2 qtr (15.42 t)
• Tender bogie	25 LT 8 cwt 2 qtr (25,830 kg) each
• Tender axle	12 LT 14 cwt 1 qtr (12,920 kg) av.
Adhesive weight	88 LT 7 cwt 2 qtr (89.79 t)
Loco weight	103 LT 2 cwt (104.8 t)
Tender weight	50 LT 17 cwt (51.67 t)
Total weight	153 LT 19 cwt (156.4 t)
Tender type	2-axle bogies
Fuel type	Coal
Fuel capacity	10 LT (10.2 t)
Water cap	4,000 imp gal (18,200 l)
Firebox type	Round-top
• Firegrate area	49.5 sq ft (4.60 m²)
Boiler:
• Pitch	7 ft 11 ¹⁄₂ in (2,426 mm)
• Diameter	6 ft ¹⁄₈ in (1,832 mm)
• Tube plates	20 ft 4 ¹⁄₈ in (6,201 mm)
• Small tubes	269 2 ¹⁄₄ in (57 mm)
Boiler pressure	200 psi (1,379 kPa)
Safety valve	Ramsbottom
Heating surface	3,383.5 sq ft (314.34 m²)
• Tubes	3,223 sq ft (299.4 m²)
• Firebox	160.5 sq ft (14.91 m²)
Cylinders	Four
High-pressure cylinder	18 in (457 mm) bore 26 in (660 mm) stroke
Low-pressure cylinder	28 ¹⁄₂ in (724 mm) bore 28 in (711 mm) stroke
Valve gear	Walschaerts
Couplers	Bell link-and-pin

Performance figures
Tractive effort	45,200 lbf (201 kN) @ 50%

Career
Operators	Central South African Railways South African Railways
Class	Class MG
Number in class	1
Numbers	CSAR 1024, SAR 1628
Delivered	1911
First run	1911
Withdrawn	1927

The South African Railways Class MG 2-6-6-2 of 1911 was a steam locomotive from the pre-Union era in the Transvaal.

In 1911, the Central South African Railways placed an experimental Mallet articulated compound steam locomotive with a 2-6-6-2 wheel arrangement in service. In 1912, when it was assimilated into the South African Railways, it was renumbered and designated the sole Class MG.^[1]^[2]^[3]^[4]

Manufacturer

G.G. Elliot

A single experimental locomotive was included with the order for nine Class MF Mallet articulated compound steam locomotives which were delivered to the Central South African Railways (CSAR) by the American Locomotive Company (ALCO) in 1911.^[1]^[2]^[3]^[4]

It was similar to the other nine engines, but used saturated instead of superheated steam, had a mechanical stoker and the coupled wheels on the leading engine unit were of a 5 inches (127 millimetres) larger diameter than those of the trailing engine unit. It had Walschaerts valve gear and was numbered 1024.^[1]^[2]^[3]^[4]

Compound expansion

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. 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]^[5]

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, which drive the front set of coupled wheels.^[1]^[3]

Characteristics

Apart from having a different boiler, there were three major differences between this locomotive and the nine Class MF engines, which were built and delivered at the same time.^[3]

Saturated steam

It was not equipped with a superheater, although superheated locomotives had already been proven to be more economic and superior in performance.^[1]^[2]^[3]

Coupled wheels

The front set of coupled wheels was of a larger diameter than the rear set. In theory, this configuration was to result in improved acceleration, with the rear engine unit providing the traction. It was also believed that the difference in frequency between the front and rear cylinder exhaust beats would result in a more even pressure in the receiver pipe and therefore improved steam flow, although exactly how this was to come about was not clear. It was the only South African articulated locomotive to have coupled wheels of different diameters.^[1]^[2]^[3]

Owing to the larger diameter wheels of the rear engine unit, the boiler pitch had to be raised to 7 feet 11 ¹⁄₂ inches (2,426 millimetres), the highest pitched boiler in South Africa at the time.^[2]

The unorthodox driving wheel configuration did not have the expected results and, in comparison with the other nine superheated engines, the locomotive proved to be inferior in performance.^[1]

Mechanical stoker

This was the first South African locomotive to be equipped with a mechanical stoker. This device, of the Street type, consisted of a coal crusher, hand-fed by the fireman, which was fitted to the front left hand side of the tender footplate and driven by a small steam engine, which was mounted behind the hand brake column.^[1]^[2]^[3]

The crusher reduced the coal to a suitable size for the stoker. The crushed coal then fell by gravity into a chute, which led to a receiving bin which was fitted below the back buffer beam of the locomotive, from where it was picked up by a bucket elevator which worked in a large pipe. The full buckets were carried up in the left-hand-side tube, mounted on the back of the firebox, were discharged into a central receiver and then travelled empty down the right hand side tube.^[1]^[2]

The bucket belt was driven by another small steam engine, mounted on the left side of the firebox near the top. The main shaft of this engine had adjustable cams, which operated three steam cocks which supplied steam jets to the coal delivery orifices. From the central receiver, a cone-shaped tray directed the coal to the right, centre or left sides as required, while the cam-operated steam jets blew the coal into the firebox. When coal was only required at the back end of the firebox, the cams could be projected a short distance, thereby allowing steam jets of just sufficient power to project the coal to the required parts of the firebox.^[1]^[2]

It was a very complicated, cumbersome and extremely noisy arrangement, which required the fireman to attend to two auxiliary engines and feed the crusher, in addition to his normal duties. The noise created by this mechanism was stated to be deafening to the crew and was threefold, first the noise of the crusher, then the noisy circulation of the conveyor buckets, and finally the sharp reports of the steam jets which controlled the feeding.^[1]^[2]^[3]

The mechanical stoker was removed and the locomotive was converted to hand firing soon after being placed in service.^[1]^[2]^[3]

Service

When the Union of South Africa was established on 31 May 1910, the three Colonial government railways (Cape Government Railways, Natal Government Railways and CSAR) 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, with Sir William Hoy appointed as its first General Manager, 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.^[4]^[6]

In 1912, this locomotive was renumbered 1628 and classified as Class MG on the South African Railways (SAR). It joined the experimental Class MD and the Class MF on the coal traffic line between Witbank and Germiston, where it remained until it was withdrawn from service in 1927.^[1]^[3]^[4]

Illustration

The main picture shows Class MG number 1628 in its original lined SAR livery. It was later repainted in the more well-known plain black SAR livery.

No. 1628 in plain black SAR livery, c. 1920

References

1 2 3 4 5 6 7 8 9 10 11 12 13 14 Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 16–18, 140. ISBN 978-0-7153-5427-8.
1 2 3 4 5 6 7 8 9 10 11 Espitalier, T.J.; Day, W.A.J. (1945). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VII - South African Railways. South African Railways and Harbours Magazine, April 1945. pp. 275-276.
1 2 3 4 5 6 7 8 9 10 11 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. p. 87. ISBN 0869772112.
1 2 3 4 5 Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, pp. 9, 12, 16, 47 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
↑ Compounding Steam Engines
↑ The South African Railways - Historical Survey. Editor George Hart, Publisher Bill Hart, Sponsored by Dorbyl Ltd., Published c. 1978, p. 25.

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Locomotives of the Central South African Railways

3' 6" gauge	CSAR 0-6-0ST 1896 CSAR 4-6-0T 1887 CSAR Class 6-L1 CSAR Class 6-L2 CSAR Class 6-L3 CSAR Class 7 CSAR Class 8-L1 CSAR Class 8-L2 CSAR Class 8-L3 CSAR Class 9 CSAR Class 10 1904 CSAR Class 10 1910 CSAR Class 10-2 Saturated CSAR Class 10-2 Superheated CSAR Class 10-C CSAR Class 11 CSAR Class B 0-6-4T CSAR Class C 2-8-4T CSAR Class D CSAR Class E 4-8-0TT CSAR Class E 4-8-2T CSAR Class E 4-10-2T CSAR Class F CSAR Class M CSAR Mallet Saturated CSAR Mallet Stoker CSAR Mallet Superheated CSAR Rack 4-6-4RT CSAR Railmotor IMR 0-6-0ST 1896 IMR 4-6-0T 1887 IMR 46 Tonner 0-6-4T IMR 55 Tonner 2-6-4T IMR 7th Class 4-8-0 IMR 8th Class 4-8-0 IMR Reid Tenwheeler 4-10-2T IMR Western Australian 2-8-4T NZASM 10 Tonner NZASM 13 Tonner NZASM 14 Tonner NZASM 18 Tonner NZASM 19 Tonner NZASM 32 Tonner NZASM 40 Tonner NZASM 46 Tonner OVGS 1st Class 4-4-0TT OVGS 2nd Class 2-6-0 OVGS 2nd Class 2-6-0ST OVGS 3rd Class 4-4-0 OVGS 4th Class G 4-6-0 OVGS 5th Class K 4-6-0 1890 OVGS 5th Class K 4-6-0 1891 OVGS 6th Class L 4-6-0 OVGS 6th Class L2 4-6-0 OVGS 6th Class L3 4-6-0 PPR 0-4-0ST Natal PPR 26 Tonner PPR 35 Tonner Portuguese PPR 55 Tonner

2' gauge	CSAR Pankop

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

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

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