South African Class H 4-10-2T

NGR Class C 4-10-2T
South African Class H 4-10-2T

NGR Class C no. 171 c. 1903, SAR Class H no. 253

Type and origin Power type Steam Designer Natal Government Railways (G.W. Reid) Builder Dübs and Company North British Locomotive Company Serial number Dübs 3835, 4040-4064, 4118-4141, 4254-4278, 4310-4329 NBL 15723-15727 Build date 1899-1903 Total produced 102 Rebuilder Natal Government Railways South African Railways Rebuild date c. 1910 onward Number rebuilt 98 to 4-8-2T (Mountain)

Specifications Configuration 4-10-2T (Reid Tenwheeler) Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 25 3⁄4 in (654 mm) Coupled dia. 45 in (1,143 mm) Trailing dia. 25 3⁄4 in (654 mm) Minimum curve 300 ft (91 m) Wheelbase 30 ft 6 in (9,296 mm)  • Leading 5 ft 4 in (1,626 mm)  • Coupled 16 ft 8 in (5,080 mm) Length: ​  • Over couplers 37 ft 6 in (11,430 mm) Height 12 ft 6 in (3,810 mm) Frame type Plate Axle load 12 LT 5 cwt (12,450 kg)  • Leading 9 LT 17 cwt (10,010 kg)  • 1st coupled 10 LT 18 cwt (11,070 kg)  • 2nd coupled 12 LT 5 cwt (12,450 kg)  • 3rd coupled 10 LT 13 cwt (10,820 kg)  • 4th coupled 10 LT 10 cwt (10,670 kg)  • 5th coupled 10 LT 10 cwt (10,670 kg)  • Trailing 4 LT 4 cwt (4,267 kg) Adhesive weight 54 LT 16 cwt (55,680 kg) Loco weight 68 LT 17 cwt (69,950 kg) Fuel type Coal Fuel capacity 4 LT (4.1 t) Water cap 1,880 imp gal (8,550 l) Firebox type Round-top  • Firegrate area 21.15 sq ft (1.965 m2) Boiler: ​  • Pitch 6 ft 10 in (2,083 mm)  • Diameter 4 ft 7 7⁄8 in (1,419 mm)  • Tube plates 10 ft 4 in (3,150 mm)  • Small tubes 287: 1 3⁄4 in (44 mm) Boiler pressure 175 psi (1,207 kPa) Safety valve Salter & Ramsbottom Heating surface 1,493.50 sq ft (138.751 m2)  • Tubes 1,358.71 sq ft (126.228 m2)  • Firebox 134.79 sq ft (12.522 m2) Cylinders Two Cylinder size 19 in (483 mm) bore 27 in (686 mm) stroke Valve gear Allan Valve type Richardson balanced slide Couplers Johnston link-and-pin

Performance figures Tractive effort 28,440 lbf (126.5 kN) @ 75%

Career Operators Natal Government Railways South African Railways Witbank Collieries Class NGR Class C SAR Class H Number in class NGR 101, SAR 93 Numbers NGR 149-249, SAR 232-324 Official name Reid Tenwheeler Nicknames Walloper Delivered 1899-1903 First run 1899 Withdrawn 1977

The leading and trailing coupled axles had flangeless wheels

The South African Railways Class H 4-10-2T of 1899 was a steam locomotive from the pre-Union era in the Colony of Natal.

Between 1899 and 1903, the Natal Government Railways placed 101 tank steam locomotives with a 4-10-2 wheel arrangement in service. In 1912, after the establishment of the South African Railways, 93 of these Class C Reid Tenwheelers survived unmodified and were designated Class H.

By 1898, increasing traffic on the new Natal Government Railways (NGR) mainline into the interior, with its sharp curves and severe 1 in 30 (3⅓%) gradients, necessitated double-heading of the NGR's Dübs A 4-8-2T locomotives on the heavier section of the Natal mainline between Estcourt and Mooirivier as a means to run longer trains to reduce occupation of the line. The requirement therefore arose for a tank locomotive which could haul at least one-and-a-half times as much as a Dübs A locomotive.

The limitations within which G.W. Reid, Locomotive Superintendent of the NGR at the time, had to meet this requirement were rather severe. The maximum axle load was not to exceed 14 long tons (14,220 kilograms) within the construction loading gauge of 13 feet (3,962 millimetres) high by 9 feet (2,743 millimetres) wide, while the locomotive had to be able to negotiate gradients of 1 in 30 (3⅓%), compensated for curves of 300 feet (91 metres) radius. The result was Reid's design of a 4-10-2 tank engine, the first locomotive in the world to use this wheel arrangement.

Since there was no precedent for such an enormous Cape gauge tank locomotive, the design was the subject of some severe criticism and various objections were put forward against its introduction. It was therefore decided to order only one experimental locomotive from Dübs and Company. It was delivered in 1899 and numbered 149.

In 1900, the General Manager of the NGR reported that the trials of the 4-10-2T Reid locomo­tive had proven successful beyond anticipation and that the engine could haul a gross load of 200 long tons (203.2 tonnes) over the worst section of line with ease, 50% in excess of that taken by a Dübs A locomotive. As a result, orders were placed for another 100 of these locomo­tives between 1901 and 1903. The first 95 of these locomotives were built in four batches by Dübs and were numbered in the range from 150 to 244.