South African Class 12B 4-8-2

South African Class 12B 4-8-2
& South African Class 12R 4-8-2
Class 12R 1939 at New Brighton, Port Elizabeth, Cape Province, 31 March 1979
Power type Steam
Designer South African Railways
Builder Baldwin Locomotive Works
Serial number 52476, 52558-52559, 52583-52584, 52649-52651, 52690-52693, 52712-52713, 52723-52724, 52754-52767[1]
Model Class 12B
Build date 1920
Total produced 30
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: 61 ft 3.875 in (18.691 m)
Engine:
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
Tender:
6 ft 2 in (1.880 m) bogie
20 ft 5 in (6.223 m) total
Length 69 ft 3.5 in (21.120 m)
Height 12 ft 10 in (3.912 m) as built
12 ft 7.5 in (3.848 m) reboilered
Frame Plate frame
Axle load 16.75 long tons (17.02 t) on 2nd & 4th drivers as built
16.7 long tons (17.0 t) on 2nd driver reboilered
Weight on drivers 66.85 long tons (67.92 t) as built
64.9 long tons (65.9 t) reboilered
Locomotive weight 94.7 long tons (96.2 t) as built
91.6 long tons (93.1 t) reboilered
Tender weight 61,520 lb (27.91 t) empty
66 long tons (67 t) w/o
Locomotive & tender
combined weight		 160.7 long tons (163.3 t) w/o
Tender type MT - MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted
* 2 axle bogies
* Wheels 34 in (864 mm) dia
* Length 28 ft 5.375 in (8.671 m)
Fuel type Coal
Fuel capacity 12 long tons (12 t)
Water capacity 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 3.625 in (5.883 m) int length
7 ft 8.25 in (2.343 m) pitch
Boiler pressure 190 psi (1,310 kPa)
Firegrate area 46 sq ft (4.274 m2) as built
37 sq ft (3.437 m2) reboilered
Heating surface:
Tubes		 As built:
139 tubes 2.25 in (57.2 mm) ext dia
24 tubes 5.5 in (140 mm) ext dia
2,328 sq ft (216.278 m2)
Reboilered:
87 tubes 2.5 in (63.5 mm) ext dia
30 tubes 5.5 in (140 mm) ext 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[2]
Career South African Railways
Class Class 12B, Class 12R
Number in class 30
Number 1931-1960
Delivered 1920
First run 1920
Disposition Retired

In 1920 the South African Railways placed thirty Class 12B steam locomotives with a 4-8-2 Mountain wheel arrangement in service.[3]

Contents

Manufacturer

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 SAR Chief Mechanical Engineer (CME) D.A. Hendrie’s already successful Class 3B, also built with plate frames, Walschaerts valve gear and Belpaire fireboxes.[3]

In May 1920 an additional thirty locomotives, built to the Class 12 design, were delivered from Baldwin Locomotive Works in the United States. Even though they were very similar to the second and subsequent orders of the Class 12, they were classified separately as Class 12B.[1]

Classification

The separate classification has been ascribed to the fact that the wheelbase of the leading bogie was 2 inches (50.8 millimetres) longer than on the original Class 12 locomotives, but this was probably not the reason, keeping in mind that only the first eight out of altogether forty-six Class 12 locomotives were built with leading bogies with a 6 feet (1.829 metres) wheelbase while the other thirty-eight all had leading bogies with a 6 feet 2 inches (1.880 metres) wheelbase, the same as the Class 12B. More likely the separate classification was simply based on the fact that the Class 12 was British built while the Class 12B was American built.[1][3]

The Baldwin works numbers did not run consecutively for the whole order and are set out in the table.[1][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.[2][3]

All thirty Class 12B locomotives were eventually reboilered with Watson Standard no. 2 boilers. In the process they were also equipped with Watson cabs, with their distinctive slanted fronts, compared to the conventional vertical fronts of their original cabs. Upon reboilering the original reason for the separate classification was ignored and, instead of becoming Class 12BR, the reboilered locomotives were reclassified to Class 12R along with the reboilered Class 12 locomotives.[2][4]

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 12B 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.[2]

Service

South African Railways

They were placed in service on the Cape Midlands, working on the main line out of Port Elizabeth, where they largely remained until being withdrawn from service. Even though they were not designed to be mixed traffic locomotives, they saw service on both passenger and goods working.[1][3]

Industrial

For some reason few Class 12Rs ended up in industrial service, despite their evident suitability for such work. Of the ex Class 12B locomotives, only number 1936 ended up in private service, first sold to Enyati Colliery and later becoming Western Holdings Gold Mine’s number 8.[4]

Gallery

The main picture shows Class 12R 1939 at New Brighton, Port Elizabeth, on 31 March 1979.

See also

References

  1. ^ a b c d e Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 38-41. ISBN 0715354272. 
  2. ^ a b c d South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
  3. ^ a b c d e f Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10-11, 54-56. ISBN 0869772112. 
  4. ^ a b Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 59. ISBN 0715386387.