South African Class B 0-6-4T

NZASM 46 Tonner 0-6-4T IMR 46 Tonner 0-6-4T CSAR Class B 0-6-4T South African Class B 0-6-4T
NZASM 46 Tonner no. 230 Jan Wintervogel at Witbank, Transvaal, April 1993
Type and origin Power type Steam Designer Maschinenfabrik Esslingen Builder 175 by Esslingen 20 by Werkspoor Serial number Esslingen: 2598-2617, 2624-2633, 2656-2665, 2703-2712, 2714-2733, 2745-2789, 2824-2843, 2854-2873, 2877-2886, 2941-2950 Werkspoor: 1-10, 29-38 Model NZASM 46 Tonner Build date 1893-1899 Total produced 195
Specifications Configuration: ​  • Whyte 0-6-4T  • UIC C2'n2t Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Coupled dia. 51 3⁄16 in (1,300 mm) Trailing dia. 31 7⁄8 in (810 mm) Wheelbase 19 ft 8 7⁄32 in (6,000 mm)  • Coupled 10 ft 2 1⁄32 in (3,100 mm)  • Trailing 5 ft 3 in (1,600 mm) Wheel spacing (Asymmetrical) 1-2: 5 ft 2 3⁄16 in (1,580 mm) 2-3: 4 ft 11 27⁄32 in (1,520 mm) Length: ​  • Over couplers 34 ft 8 in (10,566 mm) Height 12 ft 4 1⁄2 in (3,772 mm) Frame type Plate Axle load 10 LT 12 cwt (10,770 kg)  • Coupled 10 LT 12 cwt (10,770 kg)  • Trailing 13 LT 19 cwt 1 qtr (14,190 kg) Adhesive weight 31 LT 16 cwt (32,310 kg) Loco weight 45 LT 12 cwt (46,330 kg) Fuel type Coal Fuel capacity 4 LT (4.1 t) Water cap 1,503 imp gal (6,830 l) Firebox type Round-top  • Firegrate area 15.6 sq ft (1.45 m2) Boiler: ​  • Pitch 5 ft 9 1⁄2 in (1,765 mm)  • Diameter 3 ft 10 5⁄8 in (1,184 mm)  • Tube plates 12 ft 8 3⁄4 in (3,880 mm)  • Small tubes 144: 1 25⁄32 in (45 mm) Boiler pressure 160 psi (1,103 kPa) Heating surface 936.2 sq ft (86.98 m2)  • Tubes 845 sq ft (78.5 m2)  • Firebox 91.2 sq ft (8.47 m2) Cylinders Two Cylinder size 16 15⁄16 in (430 mm) bore 24 13⁄16 in (630 mm) stroke Valve gear Heusinger Valve type Slide Couplers Johnston link-and-pin
Performance figures Tractive effort 16,580 lbf (73.8 kN) @ 75%
Career Operators NZASM Pretoria-Pietersburg Railway CFM Imperial Military Railways Central South African Railways South African Railways Class NZASM 46 Tonner CSAR & SAR Class B Number in class NZASM 177, IMR 195, SAR 28 Numbers NZASM: 61-237 CFM: 20-49 IMR: 61-255 CSAR: 27-202 SAR: 1-2, 4-6, 8, 10-16, 18-22, 24-30, 33-43, 45-48, 50, 52, 54-55 Delivered 1893-1899 First run 1893 Withdrawn 1919

The South African Railways Class B 0-6-4T of 1893 was a steam locomotive from the pre-Union era in Transvaal.

Between 1893 and 1898, 175 46 Tonner 0-6-4 tank steam locomotives were placed in service by the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij in the Zuid-Afrikaansche Republiek.

In 1899, twenty more were ordered, of which only two were delivered by the time the Imperial Military Railways took over all railway operations in the two Boer Republics during the Second Boer War. The other eighteen locomotives in this order were intercepted by the Imperial Military Railways, who diverted two of them to Lourenço Marques.

At the end of the war, the survivors of these locomotives were taken onto the roster of the Central South African Railways, renumbered and designated Class B, while the two in Mozambique were taken onto the roster of the Caminhos de Ferro de Mocambique. In 1912, when the remaining locomotives were assimilated into the South African Railways, they were renumbered again, but retained their Class B designation.

In 1891, the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM, often shortened to ZASM) of the Zuid-Afrikaansche Republiek (ZAR) placed an order with Emil Kessler's firm, the Maschinenfabrik Esslingen in Germany, for twenty 40 Tonner 0-6-2 tank steam locomotives. While these locomotives were satisfactory in service, the trailing wheels initially proved troublesome owing to insufficient sideways freedom of movement when traversing sharp curves.

To overcome this problem, the next order from the same manufacturer was for 0-6-4T locomotives which were practically identical to the 40 Tonners in their main dimensions, but with a four-wheeled trailing bogie. Because of the resultant increase in weight, these locomotives became known as the 46 Tonners.