South African Class 12 4-8-2

South African Class 12 4-8-2
& South African Class 12R 4-8-2
Class 12R 1505 crossing the Great Fish River near Nelland, between Cradock and Cookhouse, 22 April 1981
Power type Steam
Designer South African Railways
Builder North British Locomotive Company
Beyer, Peacock and Company
Order number BP 01830[1]
Serial number NBL 19593-19596, 19684-19687, 20173-20180, 20812-20821[2]
BP 5988-5997, 6003-6012[1][3]
Model Class 12
Build date 1912-1921
Total produced 46
Configuration 4-8-2 "Mountain"
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Leading wheel
diameter		 28.5 in (724 mm)
Driver diameter 51 in (1,300 mm)
Trailing wheel
diameter		 33 in (838 mm)
Wheelbase Total (1494-1501):
58 ft 1.375 in (17.713 m) with MP1 tender
61 ft 1.875 in (18.640 m) with MT tender
Engine (1494-1501):
6 ft (1.829 m) pilot
13 ft 6 in (4.115 m) coupled
31 ft 7.5 in (9.639 m) total
Total (1502-1519, 1859-1878): 58 ft 3.375 in (17.764 m) with MP1 tender
61 ft 3.875 in (18.691 m) with MT tender
Engine (1502-1519, 1859-1878):
6 ft 2 in (1.880 m) pilot
13 ft 6 in (4.115 m) coupled
31 ft 9.5 in (9.690 m) total
MP1 Tender:
4 ft 7 in (1.397 m) bogie
16 ft 9 in (5.105 m) total
MT Tender:
6 ft 2 in (1.880 m) bogie
20 ft 5 in (6.223 m) total
Length 1494-1501:
66 ft 5.75 in (20.263 m) with MP1 tender
69 ft 1.5 in (21.069 m) with MT tender
1502-1519, 1859-1878:
66 ft 7.75 in (20.314 m) with MP1 tender
69 ft 3.5 in (21.120 m) with MT tender
Height 12 ft 10 in (3.912 m) as built
12 ft 7.5 in (3.848 m) reboilered
Frame Plate frame
Axle load 16.9 long tons (17.2 t) on 4th driver as built
16.7 long tons (17.0 t) on 2nd driver reboilered
Weight on drivers 66.65 long tons (67.7 t) as built
64.9 long tons (65.9 t) reboilered
Locomotive weight 94.85 long tons (96.4 t) as built
91.6 long tons (93.1 t) reboilered
Tender weight MP1: 49,452 lb (22.4 t) empty
51.05 long tons (51.9 t) w/o
MT: 61,520 lb (27.9 t) empty
66 long tons (67.1 t) w/o
Locomotive & tender
combined weight		 With MP1: 194,300 lb (88.1 t) empty
145.9 long tons (148.2 t) w/o
With MT: 197,200 lb (89.4 t) empty
157.6 long tons (160.1 t) w/o
Tender type MP1 & MT - MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted
* 2 axle bogies
* Wheels 34 in (864 mm) dia
* MP1 length 25 ft 10.75 in (7.893 m)
* MT length 28 ft 5.375 in (8.671 m)
Fuel type Coal
Fuel capacity MP1 10 long tons (10.2 t)
MT 12 long tons (12.2 t)
Water capacity MP1 4,250 imp gal (19,300 l)
MT 6,000 imp gal (27,000 l)
Boiler As built:
5 ft 7.5 in (1.715 m) int dia
20 ft (6.096 m) int length
7 ft 7 in (2.311 m) pitch
Reboilered:
5 ft 7.5 in (1.715 m) int dia
19 ft 4 in (5.893 m) int length, steel firebox
19 ft 3.625 in (5.883 m) int length, copper firebox
7 ft 8.25 in (2.343 m) pitch
Boiler pressure 190 psi (1,310 kPa)
Firegrate area 40 sq ft (3.716 m2) as built
37 sq ft (3.437 m2) reboilered
Heating surface:
Tubes		 As built:
139 tubes 2.25 in (57.2 mm) dia
24 tubes 5.5 in (140 mm) dia
2,328 sq ft (216.278 m2)
Reboilered:
87 tubes 2.5 in (63.5 mm) dia
30 tubes 5.5 in (140 mm) dia
1,933 sq ft (179.582 m2)
Heating surface:
Firebox		 160 sq ft (14.864 m2) as built
142 sq ft (13.192 m2) reboilered
Heating surface:
Total		 2,488 sq ft (231.143 m2) as built
2,075 sq ft (192.774 m2) reboilered
Superheater area 574 sq ft (53.326 m2) as built
492 sq ft (45.708 m2) reboilered
Cylinders Two
Cylinder size 22.5 in (572 mm) bore
26 in (660 mm) stroke
Valve gear Walschaerts
Tractive effort 36,780 lbf (163.6 kN) at 75% boiler pressure[4]
Career South African Railways
Class Class 12, Class 12R
Number in class 46
Number 1494-1519, 1859-1878[5]
Delivered 1912-1922
First run 1912
Disposition Retired

Between April 1912 and 1922 the South African Railways placed altogether forty-six Class 12 steam locomotives with a 4-8-2 Mountain wheel arrangement in goods train service.[6]

Contents

Manufacturers

The Class 12 was the first locomotive design to originate from the newly established South African Railways (SAR) in 1912. It was in effect an enlarged version of the already successful Class 3B, also designed by SAR Chief Mechanical Engineer (CME) D.A. Hendrie during his years on the Natal Government Railways, and was also built with plate frames, Walschaerts valve gear, superheaters and Belpaire fireboxes.[6][7]

Orders for the first eight locomotives in the Class were placed on 22 March 1911. They were built in two batches of four, the first of which was delivered from North British Locomotive Company (NBL) in April 1912, numbered 1494 to 1497. The second batch, numbered 1498 to 1501, followed shortly thereafter. These first eight locomotives had pilot bogies with a 6 feet (1.829 metres) wheelbase.[3][4][5][6]

These were followed by another eight in 1913, numbered 1502 to 1509, and ten more in 1915, numbered 1510 to 1519, all built by NBL. These and all subsequent Class 12 locomotives had pilot bogies with a 6 feet 2 inches (1.880 metres) wheelbase.[3][4][6]

In 1922 Beyer, Peacock and Company (BP) delivered the final twenty Class 12 locomotives, built in two batches of ten and numbered 1859 to 1878.[6]

The builders, years built and works numbers are set out in the table.[1][2]

Distinguishing features

The original Class 12 locomotives were equipped with a new Type MP1 tender, which marked the introduction of a standard type that, with few modifications, was eventually to be used on all the Hendrie-designed locomotives. During the 1920s many of the Class 12 locomotives had their original Type MP1 tenders replaced with Type MT tenders with a larger coal and water capacity.[3]

The North British built locomotives were very similar in appearance to the Class 3B, with running boards that curved down below the cab, while the Beyer, Peacock built locomotives had larger and more spacious cabs and running boards that ran straight through to the rear buffer beams.[3]

Watson standard boilers

During the 1930s many serving locomotives were reboilered with a standard boiler type designed by then CME A.G. Watson as part of his standardisation policy. Such Watson Standard reboilered locomotives were reclassified by adding an "R" suffix to their classification.[4][6]

All forty-six Class 12 locomotives were eventually reboilered with Watson Standard no. 2 boilers and reclassified to Class 12R. In the process they were also equipped with Watson cabs, with their distinctive slanted fronts compared to the vertical fronts of the original cabs and, in the case of the NBL built locomotives, with running boards that continued straight through underneath their cabs.[3][4][7]

An obvious visual difference between an original and a Watson Standard reboilered locomotive is usually a rectangular regulator cover just to the rear of the chimney on the reboilered locomotive. In the case of the Class 12 locomotives two even more obvious visual differences are the Watson cab and the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.[4]

Service

South African Railways

The Class 12 was designed for use in coal traffic on the line from Witbank to Germiston. At the time they were introduced, they were the largest non-articulated locomotives in South Africa and, on railways of less than 1,435 millimetres (4 feet 8½ inches) Standard gauge, probably in the world.[3]

They proved to be most successful in the service they had been designed for, handling loads of 1,400 tons and doing the return trip in one day. This compared favourably with the 2-6-6-0 and 2-6-6-2 Mallet locomotives which, while able to handle 1,600 tons, could not make a round trip in one day.[3]

They were also used around Ladysmith in Natal. In the 1940s the Natal locomotives were relocated to the Orange Free State.[6]

By the 1970s some were allocated to the Cape Midlands system, stationed at Sydenham in Port Elizabeth for use as dock shunters and for yard work in the New Brighton marshalling yards. In the Orange Free State some were shedded at Bloemfontein and at Bethlehem, all in shunting service. The Transvaal had a large contingent, stationed at Springs, Germiston and Krugersdorp, also mainly used for shunting.[7]

International

Ten Class 12R locomotives were briefly hired to the Zambian Railways during a peak in that country’s perpetual diesel motive power crisis in 1980, but were soon returned since the Zambian knowledge base on steam maintenance had virtually disappeared by then.[7]

Industrial

For some reason few Class 12 locomotives ended up in industrial service, despite their evident suitability for such work. Only five were sold into private service.

Gallery

The main picture shows NBL built Class 12R 1505 with a Type MP1 tender.

See also

References

  1. ^ a b c Beyer, Peacock and Company production list, excluding Garratts, Customer List V1 04.08.02
  2. ^ a b North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard Schmeiser
  3. ^ a b c d e f g h Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 20-21. ISBN 0715354272. 
  4. ^ a b c d e f South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
  5. ^ a b 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)
  6. ^ a b c d e f g Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10-11, 54-56. ISBN 0869772112. 
  7. ^ a b c d e Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. pp. 59, 137. ISBN 0715386387.