South African Class 12B 4-8-2

South African Class 12B & 12R 4-8-2

300px Class 12R no. 1931 at Port Elizabeth sheds, with Belpaire firebox, c. 1945

Type and origin ♠ Class 12B as built with a Belpaire firebox ♥ Class 12R rebuilt with a Watson Standard boiler Power type Steam Designer South African Railways (D.A. Hendrie) Builder Baldwin Locomotive Works Serial number 52476, 52558-52559, 52583-52584, 52649-52651, 52690-52693, 52712-52713, 52723-52724, 52754-52767 Model Class 12B Build date 1920 Total produced 30

Specifications Configuration 4-8-2 (Mountain) Driver axle 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia Coupled dia 51 in (1,295 mm) Trailing dia 33 in (838 mm) Tender wheels 34 in (864 mm) Wheelbase  • Engine  • Leading 6 ft 2 in (1,880 mm)  • Coupled 13 ft 6 in (4,115 mm)  • Tender 16 ft 9 in (5,105 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Length:  • Over couplers 66 ft 8 in (20,320 mm) Height ♠ 12 ft 10 in (3,912 mm) ♥ Frame type Plate Axle load ♠ ♥  • Leading ♠ ♥  • 1st coupled ♠ ♥  • 2nd coupled ♠ ♥  • 3rd coupled ♠ ♥  • 4th coupled ♠ ♥  • Trailing ♠ ♥  • Tender bogie Bogie 1: Bogie 2:  • Tender axle Adhesive weight ♠ ♥ Loco weight ♠ ♥ Tender weight Loco & tender weight ♠ ♥ Tender type MP1 (2-axle bogies) MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted Fuel type Coal Fuel capacity Water cap Boiler Watson Standard no. 2  • Pitch ♠ 7 ft 7 in (2,311 mm) ♥  • Diameter ♠♥  • Tube plates ♠ 20 ft (6,096 mm) ♥ 19 ft 4 in (5,893 mm) steel ♥  • Small tubes ♠ 139: ♥ 87:  • large tubes ♠ 24: ♥ 30:  • Firebox type ♠ Belpaire - ♥ Round-top Boiler pressure ♠♥ 190 psi (1,310 kPa) Safety valve ♠ Ramsbottom - ♥ Pop Firegrate area ♠ 40 sq ft (3.7 m2) ♥ 37 sq ft (3.4 m2) Heating surface ♠ 2,488 sq ft (231.1 m2) ♥ 2,075 sq ft (192.8 m2)  • Tubes ♠ 2,328 sq ft (216.3 m2) ♥ 1,933 sq ft (179.6 m2)  • Firebox ♠ 160 sq ft (15 m2) ♥ 142 sq ft (13.2 m2) Superheater:  • Heating area ♠ 574 sq ft (53.3 m2) ♥ 492 sq ft (45.7 m2) Cylinders Two Cylinder size bore 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Bell link-and-pin AAR knuckle (1950s)

Performance figures Tractive effort ♠♥ 36,780 lbf (163.6 kN) @ 75%

Career Operators South African Railways Class Class 12B & 12R Number in class 30 Numbers 1931-1960 Delivered 1920 First run 1920 Withdrawn 1980s

The leading coupled axle had flangeless wheels

The South African Railways Class 12B 4-8-2 of 1920 was a steam locomotive.

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

Manufacturer

In May 1920, an additional thirty locomotives, built to the Class 12 design of SAR Chief Mechanical Engineer (CME) D.A. Hendrie, were delivered to the South African Railways (SAR) from Baldwin Locomotive Works in the United States of America. Most of them were erected in the SAR workshops, but a few were contracted to James Brown and Company at Durban for erection. Even though they were very similar to the second and subsequent orders of the Class 12, they were classified separately as Class 12B and numbered in the range from 1931 to 1960. They were also built with plate frames, Walschaerts valve gear and Belpaire fireboxes.

Classification

File:D.A. Hendrie.jpg

D.A. Hendrie

The separate classification has been ascribed to the fact that the wheelbase of the leading bogie was 2 inches (51 millimetres) longer than on the original Class 12 locomotives. This was probably not the reason, bearing in mind that only the first eight out of altogether 46 Class 12 locomotives were built with leading bogies with a 6 feet (1,829 millimetres) wheelbase, while the other thirty-eight all had leading bogies with a 6 feet 2 inches (1,880 millimetres) 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.

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.

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.

Their original Belpaire boilers were fitted with Ramsbottom safety valves, while the Watson Standard boiler was fitted with Pop safety valves. Other obvious differences between an original and a Watson Standard reboilered locomotive are usually a rectangular regulator cover, just to the rear of the chimney on the reboilered locomotive and, in the case of the Classes 12B and 12R locomotives, the Watson cab and the absence of the Belpaire firebox hump between the cab and boiler on the reboilered locomotives.

Service

South African Railways

They were placed in service on the Cape Midland, working on the mainline 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.

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 no. 1936 was sold to Enyati Colliery and later became Western Holdings Gold Mine's no. 8.

Works numbers

The Baldwin works numbers did not run consecutively for the whole order and are shown in the table.

Class 12B 4-8-2
Works numbers

SAR no.	Works no.
1931	52476
1932	52558
1933	52559
1934	52583
1935	52584
1936	52649
1937	52650
1938	52651
1939	52690
1940	52691
1941	52692
1942	52693
1943	52712
1944	52713
1945	52723
1946	52724
1947	52754
1948	52755
1949	52756
1950	52757
1951	52758
1952	52759
1953	52760
1954	52761
1955	52762
1956	52763
1957	52764
1958	52765
1959	52766
1960	52767

Illustration

The main picture shows Class 12B no. 1931 at the Port Elizabeth sheds on 31 March 1979.

• SAR Class 12R 1939 New Brighton 310379.jpg

  12R no. 1939 at New Brighton, 31 March 1979