South African Class 12B 4-8-2

South African Class 12B & 12R 4-8-2
Class 12R no. 1931 at Port Elizabeth sheds, with Belpaire firebox, c. 1930
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: ​  • Whyte 4-8-2 (Mountain)  • UIC ♠ 2′D1’n2 - ♥ 2′D1’h2 Driver 2nd coupled axle 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) Trailing dia. 33 in (838 mm) Tender wheels 34 in (864 mm) Wheelbase 58 ft 3+3⁄4 in (17,774 mm) ​  • Engine 31 ft 9+1⁄2 in (9,690 mm)  • 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) ♥ 12 ft 7+1⁄2 in (3,848 mm) Frame type Plate Axle load ♠ 16 LT 15 cwt (17,020 kg) ♥ 17 LT 9 cwt (17,730 kg) ​  • Leading ♠ 15 LT 13 cwt (15,900 kg) ♥ 16 LT 2 cwt (16,360 kg)  • 1st coupled ♠ 16 LT 13 cwt (16,920 kg) ♥ 16 LT 15 cwt (17,020 kg)  • 2nd coupled ♠ 16 LT 15 cwt (17,020 kg) ♥ 17 LT 9 cwt (17,730 kg)  • 3rd coupled ♠ 16 LT 14 cwt (16,970 kg) ♥ 16 LT 17 cwt (17,120 kg)  • 4th coupled ♠ 16 LT 15 cwt (17,020 kg) ♥ 16 LT 15 cwt (17,020 kg)  • Trailing ♠ 12 LT 4 cwt (12,400 kg) ♥ 11 LT 16 cwt (11,990 kg)  • Tender bogie Bogie 1: 27 LT 10 cwt (27,940 kg) Bogie 2: 23 LT 11 cwt (23,930 kg)  • Tender axle 13 LT 15 cwt (13,970 kg) Adhesive weight ♠ 66 LT 17 cwt (67,920 kg) ♥ 67 LT 16 cwt (68,890 kg) Loco weight ♠ 94 LT 14 cwt (96,220 kg) ♥ 95 LT 14 cwt (97,240 kg) Tender weight 51 LT 1 cwt (51,870 kg) Total weight ♠ 145 LT 15 cwt (148,100 kg) ♥ 146 LT 15 cwt (149,100 kg) Tender type MP1 (2-axle bogies) MP, MP1, MR, MS, MT, MT1, MT2, MX, MY, MY1 permitted Fuel type Coal Fuel capacity 10 LT (10,160 kg) Water cap. 4,250 imp gal (19,300 L) Firebox: ​  • Type ♠ Belpaire - ♥ Round-top  • Grate area ♠ 40 sq ft (3.7 m2) ♥ 37 sq ft (3.4 m2) Boiler: ​  • Model Watson Standard no. 2  • Pitch ♠ 7 ft 7 in (2,311 mm) ♥ 7 ft 8+1⁄4 in (2,343 mm)  • Diameter ♠♥ 5 ft 7+1⁄2 in (1,714 mm)  • Tube plates ♠ 20 ft (6,096 mm) ♥ 19 ft 4 in (5,893 mm) steel ♥ 19 ft 3+5⁄8 in (5,883 mm)  • Small tubes ♠ 139: 2+1⁄4 in (57 mm) ♥ 87: 2+1⁄2 in (64 mm)  • Large tubes ♠ 24: 5+1⁄2 in (140 mm) ♥ 30: 5+1⁄2 in (140 mm) Boiler pressure ♠♥ 190 psi (1,310 kPa) Safety valve ♠ Ramsbottom - ♥ Pop Heating surface: ​  • Firebox ♠ 160 sq ft (15 m2) ♥ 142 sq ft (13.2 m2)  • Tubes ♠ 2,328 sq ft (216.3 m2) ♥ 1,933 sq ft (179.6 m2)  • Total surface ♠ 2,488 sq ft (231.1 m2) ♥ 2,075 sq ft (192.8 m2) Superheater: ​  • Heating area ♠ 574 sq ft (53.3 m2) ♥ 492 sq ft (45.7 m2) Cylinders Two Cylinder size 22+1⁄2 in (572 mm) bore 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers Johnston link-and-pin AAR knuckle (1930s)
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 c. 1984
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.^[1][2]