South African Class MA 2-6-6-0

NGR Mallet 2-6-6-0 1909
South African Class MA 2-6-6-0

NGR Mallet no. 336, SAR Class MA no. 1601, c. 1909

Type and origin
Power type	Steam
Designer	American Locomotive Company
Builder	American Locomotive Company
Serial number	46044
Model	NGR Mallet
Build date	1909
Total produced	1

Specifications
Configuration	2-6-6-0 (Denver)
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.	45 ¹⁄₂ in (1,156 mm)
Tender wheels	30 in (762 mm)
Wheelbase	60 ft 2 ³⁄₄ in (18,358 mm)
• Engine	33 ft 2 in (10,109 mm)
• Coupled	8 ft 4 in (2,540 mm) per unit
• Tender	17 ft 10 in (5,436 mm)
• Tender bogie	5 ft 10 in (1,778 mm)
Length:
• Over couplers	68 ft 2 ³⁄₈ in (20,787 mm)
Height	12 ft 5 ¹⁄₈ in (3,788 mm)
Frame type	Bar
Axle load	13 LT 18 cwt (14,120 kg)
• Leading	6 LT 17 cwt (6,960 kg)
• 1st coupled	12 LT 14 cwt (12,900 kg)
• 2nd coupled	13 LT 18 cwt (14,120 kg)
• 3rd coupled	13 LT 6 cwt 2 qtr (13,540 kg)
• 4th coupled	13 LT 2 cwt (13,310 kg)
• 5th coupled	12 LT 18 cwt (13,110 kg)
• 6th coupled	13 LT 16 cwt (14,020 kg)
• Tender bogie	Bogie 1: 20 LT 7 cwt (20,680 kg) Bogie 2: 22 LT 10 cwt (22,860 kg)
Adhesive weight	79 LT 14 cwt 2 qtr (81,000 kg)
Loco weight	86 LT 11 cwt 2 qtr (87,960 kg)
Tender weight	42 LT 17 cwt (43,540 kg)
Total weight	129 LT 8 cwt 2 qtr (131,500 kg)
Tender type	2-axle bogies
Fuel type	Coal
Fuel capacity	8 LT 5 cwt (8.4 t)
Water cap	4,000 imp gal (18,000 l)
Firebox type	Round-top & combustion chamber
• Firegrate area	40 sq ft (3.7 m²)
Boiler:
• Pitch	7 ft 4 in (2,235 mm)
• Diameter	5 ft 4 in (1,626 mm)
• Tube plates	17 ft 10 ¹⁄₂ in (5,448 mm)
• Small tubes	230: 2 ¹⁄₄ in (57 mm)
Boiler pressure	200 psi (1,379 kPa)
Safety valve	Ramsbottom
Heating surface	2,574 sq ft (239.1 m²)
• Tubes	2,422 sq ft (225.0 m²)
• Firebox	125 sq ft (11.6 m²)
Cylinders	Four
High-pressure cylinder	17 ¹⁄₂ in (444 mm) bore 26 in (660 mm) stroke
Low-pressure cylinder	28 in (711 mm) bore 26 in (660 mm) stroke
Valve gear	Walschaerts
Valve type	HP: piston valves LP: Slide valves
Valve travel	HP: 5 in (127 mm) LP: 5 ¹⁄₂ in (140 mm)
Valve lap	HP: 1 in (25 mm) LP: ⁷⁄₈ in (22 mm)
Valve lead	HP & LP: ³⁄₁₆ in (5 mm)
Couplers	Bell link-and-pin

Performance figures
Tractive effort	44,810 lbf (199.3 kN) @ 50%

Career
Operators	Natal Government Railways South African Railways
Class	NGR Mallet SAR Class MA
Number in class	1
Numbers	NGR 336, SAR 1601
Delivered	1909
First run	1909
Withdrawn	1927

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

1 2 3 4 5 6 7 8 9 Holland, D.F. (1971). Steam Locomotives of the South African Railways, Volume 1: 1859-1910 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 103–105. ISBN 978-0-7153-5382-0.
1 2 3 4 5 6 7 8 9 Espitalier, T.J.; Day, W.A.J. (1944). The Locomotive in South Africa - A Brief History of Railway Development. Chapter III - Natal Government Railways (Continued). South African Railways and Harbours Magazine, August 1944. pp. 592-593.
1 2 3 Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer’s Office, Pretoria, January 1912, pp. 9, 12, 15, 46 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)
1 2 3 4 5 6 7 Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 84–85. ISBN 0869772112.
↑ Powerful Freight and Passenger Locomotives for a Narrow Gauge Railway (1910). American Engineer and Railroad Journal, May 1910, pp. 192-193
↑ The South African Railways - Historical Survey. Editor George Hart, Publisher Bill Hart, Sponsored by Dorbyl Ltd., Published c. 1978, p. 25.
↑ Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. p. 140. ISBN 978-0-7153-5427-8.

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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 Harbour 0-4-0 Table Bay Harbour 0-4-0ST Table Bay Harbour 0-4-0T Table Bay Harbour 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 Coffee Pot CGR 0-6-0ST 1902 CGR 0-6-0T 1876 Back-to-Back 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 1876 CGR 1st Class 4-4-0T 1875 CGR 2nd Class 4-4-0T 1882 CGR 3rd Class 2-6-0T CGR Railmotor CSAR Class C CSAR Class E CSAR Rack CSAR Railmotor DSWA Eight-Coupled Tank 2-8-0T Durban's Congella Durban's Edward Innes Durban's John Milne Durban's Sir Albert Port Elizabeth Harbour 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 0-4-0ST 1903 SAR 0-4-0T no. 69 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 Clayton Railmotor

3' 6" gauge Tender engines	CGR 1st Class 2-6-0 1876 Beyer, Peacock 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 1879 CGR 1st Class 4-4-0TT 1881 CGR 2nd Class 2-6-2TT 1875 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 1884 CGR 5th Class 4-6-0 1890 CGR 5th Class 4-6-0 1891 DSWA Eight-Coupled Tender 2-8-0 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 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 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 Red Devil

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 0-6-0T 1871 Cape Copper Britannia Cape Copper Caledonia Cape Copper Clara Class Cape Copper Condenser Cape Copper Scotia Class Namaqua Copper Pioneer

2' & 600mm gauges	ACR Class NG-G16A CGR NG 0-6-0T CGR NG 4-6-2T CGR Type A 2-6-4T CGR Type C 0-4-0T DSWA Class Ha DSWA Class Hb DSWA Class Hc DSWA Class Hd DSWA Jung DSWA Zwillinge NGR Class N 4-6-2T SAR NG 0-4-0T 1899 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

Electric

Amcoal Class E38

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 SAR Class 36-000 SAR Class 36-200 SAR Class 37-000 Spoornet Class 39-000 TFR Class 35-800 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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