South African Class 12 4-8-2

South African Class 12 & 12R 4-8-2
No. 1505 crossing the Great Fish River near Nelland, between Cradock and Cookhouse, 22 April 1981
Type and origin ♠ Class 12 as built with a Belpaire firebox ♥ Class 12R rebuilt with a Watson Standard boiler ♣ Steel firebox - ♦ Copper firebox ʘ No. 1494-1501 - ʘ All others Power type Steam Designer South African Railways (D.A. Hendrie) Builder North British Locomotive Company Beyer, Peacock and Company Order number BP 01830 Serial number NBL 19593-19596, 19684-19687, 20173-20180, 20812-20821 BP 5988-5997, 6003-6012 Model Class 12 Build date 1912-1921 Total produced 46
Specifications Configuration: ​  • Whyte 4-8-2 (Mountain)  • UIC 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 ʘ 58 ft 1 1⁄2 in (17,716 mm) ʘ 58 ft 3 3⁄8 in (17,764 mm)  • Engine ʘ 31 ft 7 1⁄2 in (9,639 mm) ʘ 31 ft 9 1⁄2 in (9,690 mm)  • Leading ʘ 6 ft (1,829 mm) ʘ 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 ʘ 66 ft 5 3⁄4 in (20,263 mm) ʘ 66 ft 7 3⁄4 in (20,314 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 19 cwt (17,220 kg) ♥♣ 17 LT 5 cwt (17,530 kg) ♥♦ 16 LT 14 cwt (16,970 kg)  • Leading ♠ 15 LT 18 cwt (16,160 kg) ♥♣ 16 LT 2 cwt (16,360 kg) ♥♦ 15 LT 8 cwt (15,650 kg)  • 1st coupled ♠ 16 LT 11 cwt (16,820 kg) ♥♣ 16 LT 15 cwt (17,020 kg) ♥♦ 16 LT 1 cwt (16,310 kg)  • 2nd coupled ♠ 16 LT 13 cwt (16,920 kg) ♥♣ 17 LT 5 cwt (17,530 kg) ♥♦ 16 LT 14 cwt (16,970 kg)  • 3rd coupled ♠ 16 LT 11 cwt (16,820 kg) ♥♣ 16 LT 17 cwt (17,120 kg) ♥♦ 16 LT 2 cwt (16,360 kg)  • 4th coupled ♠ 16 LT 19 cwt (17,220 kg) ♥♣ 16 LT 15 cwt (17,020 kg) ♥♦ 16 LT 1 cwt (16,310 kg)  • Trailing ♠ 12 LT 5 cwt (12,450 kg) ♥♣ 11 LT 16 cwt (11,990 kg) ♥♦ 11 LT 6 cwt (11,480 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 14 cwt (67,770 kg) ♥♣ 67 LT 12 cwt (68,680 kg) ♥♦ 64 LT 18 cwt (65,940 kg) Loco weight ♠ 94 LT 17 cwt (96,370 kg) ♥♣ 95 LT 14 cwt (97,240 kg) ♥♦ 91 LT 12 cwt (93,070 kg) Tender weight 51 LT 1 cwt (51,870 kg) Total weight ♠ 145 LT 18 cwt (148,200 kg) ♥♣ 146 LT 15 cwt (149,100 kg) ♥♦ 142 LT 13 cwt (144,900 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 (10.2 t) Water cap 4,250 imp gal (19,300 l) Firebox type ♠ Belpaire - ♥ Round-top  • Firegrate 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) ♥♦ 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 ♠ 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 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 12 & 12R Number in class 46 Numbers 1494-1519, 1859-1878 Delivered 1912-1921 First run 1912
The leading coupled axle had flangeless wheels

The South African Railways Class 12 4-8-2 of 1912 was a steam locomotive.

Between April 1912 and 1922, the South African Railways placed altogether 46 Class 12 steam locomotives with a 4-8-2 Mountain type wheel arrangement in goods train service.

Design work commenced in 1910 for a new heavy goods engine for use on the heavy coal service between Witbank and Germiston. The resulting 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 which had also been designed by SAR Chief Mechanical Engineer (CME) D.A. Hendrie during his years on the Natal Government Railways.

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 in the range from 1494 to 1497. The second batch, numbered in the range from 1498 to 1501, followed shortly thereafter. These first eight locomotives had bogies with a 6 feet (1,829 millimetres) wheelbase.

These engines were followed by another eight in August 1913, numbered in the range from 1502 to 1509, and ten more in January 1915, numbered in the range from 1510 to 1519, all built by NBL. These and all subsequent Class 12 locomotives had leading bogies with a 6 feet 2 inches (1,880 millimetres) wheelbase. These locomotives were also 2 inches (51 millimetres) longer between couplers than the first eight.

In June 1921, Beyer, Peacock and Company (BP) delivered the final twenty Class 12 locomotives, built in two batches of ten and numbered in the range from 1859 to 1878.

When the Class 12 was introduced, it was the largest non-articulated engine in South Africa and possibly in the world on railways of less than 4 feet 8 ¹⁄₂ inches (1,435 millimetres) gauge. The first eight locomotives had cast steel frames for the leading bogies with three-point suspension links, similar to those of the Class 3B. On subsequent engines, this arrangement was modified to the two-point swing-link type controlled by laminated side springs, a design Hendrie adhered to in all his later engines.