South African Class A 4-8-2T

NGR Class D1 & D2 4-8-2T
South African Class A 4-8-2T

SAR Class A Belpaire no. 196, ex NGR no 133, at Masons Mill, Pietermaritzburg, 10 December 2010

Type and origin ♠ - Round-top firebox ♥ - Belpaire firebox Power type Steam Designer Natal Government Railways (William Milne) Builder Dübs and Company South African Railways Serial number 2446-2451, 2499-2504, 2604-2628, 2965-2967, 3317-3322, 3363-3368, 3477-3486, 3604-3605, 3556-3567, 3811-3834 Build date 1888-1915 Total produced 102 Rebuilder South African Railways Rebuild date 1926 Number rebuilt 21 to Class 17 4-8-0TT (Mastodon)

Specifications Configuration 4-8-2T (Mountain) Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 25 3⁄4 in (654 mm) Coupled dia. 39 in (991 mm) Trailing dia. 25 3⁄4 in (654 mm) Wheelbase 24 ft 9 in (7,544 mm)  • Leading 5 ft (1,524 mm)  • Coupled 11 ft (3,353 mm) Length: ​  • Over couplers 32 ft 6 1⁄2 in (9,919 mm) Height ♠ 12 ft 1⁄2 in (3,670 mm) ♥ 12 ft 2 1⁄2 in (3,721 mm) Frame type Plate Axle load ♠ 8 LT 9 cwt (8,586 kg) ♥ 9 LT 4 cwt (9,348 kg)  • Leading ♠ 7 LT 18 cwt (8,027 kg) ♥ 7 LT (7,112 kg)  • 1st coupled ♠ 8 LT 2 cwt (8,230 kg) ♥ 8 LT 9 cwt (8,586 kg)  • 2nd coupled ♠ 8 LT 9 cwt (8,586 kg) ♥ 9 LT 4 cwt (9,348 kg)  • 3rd coupled ♠ 8 LT 2 cwt (8,230 kg) ♥ 8 LT 14 cwt (8,840 kg)  • 4th coupled ♠ 8 LT 2 cwt (8,230 kg) ♥ 8 LT 17 cwt (8,992 kg)  • Trailing ♠ 6 LT 10 cwt (6,604 kg) ♥ 6 LT 8 cwt (6,503 kg) Adhesive weight ♠ 32 LT 15 cwt (33,280 kg) ♥ 35 LT 4 cwt (35,760 kg) Loco weight ♠ 47 LT 3 cwt (47,910 kg) ♥ 48 LT 12 cwt (49,380 kg) Fuel type Coal Fuel capacity ♠♥ 2 LT 5 cwt (2.3 t) Water cap ♠ 1,062 imp gal (4,830 l) ♥ 1,358 imp gal (6,170 l) Firebox type ♠ Round-top ♥ Belpaire  • Firegrate area ♠ 15.7 sq ft (1.46 m2) ♥ 23.5 sq ft (2.18 m2) Boiler: ​  • Pitch ♠ 6 ft 7 1⁄2 in (2,019 mm) ♥ 7 ft (2,134 mm)  • Diameter ♠ 3 ft 11 in (1,194 mm) ♥ 3 ft 10 3⁄4 in (1,187 mm)  • Tube plates ♠♥ 10 ft 10 1⁄8 in (3,305 mm)  • Small tubes ♠ 178: 1 3⁄4 in (44 mm) ♥ 187: 1 3⁄4 in (44 mm) Boiler pressure ♠ 140 psi (965 kPa) ♥ 160 psi (1,103 kPa) Safety valve ♠ Salter & Ramsbottom ♥ Ramsbottom Heating surface ♠ 978.38 sq ft (90.894 m2) ♥ 991.5 sq ft (92.11 m2)  • Tubes ♠ 888.20 sq ft (82.516 m2) ♥ 929.5 sq ft (86.35 m2)  • Firebox ♠ 90.18 sq ft (8.378 m2) ♥ 62 sq ft (5.8 m2) Cylinders Two Cylinder size 17 in (432 mm) bore 21 in (533 mm) stroke Valve gear Stephenson Valve type Slide Couplers Johnston link-and-pin AAR knuckle (1930s)

Performance figures Tractive effort ♠ 16,340 lbf (72.7 kN) @ 75% ♥ 18,660 lbf (83.0 kN) @ 75% Factor of adh. 3.99

Career Operators Natal Government Railways South African Railways Class ♠ NGR Class D1, SAR Class A ♥ NGR Class D2, SAR Class A Belpaire Number in class 102 Numbers NGR 49-148 SAR 97-196, 332-333 Delivered 1888-1915 First run 1888 Withdrawn 1962

The leading coupled axle had flangeless wheels

The South African Railways Class A 4-8-2T of 1888 was a steam locomotive from the pre-Union era in the Colony of Natal.

In 1888, the Natal Government Railways placed the first five of its eventual one hundred Class D 4-8-2T steam locomotives in service. The last was delivered in 1899. They were the first locomotives in the world to be built with a 4-8-2 wheel arrangement, later to become known as the Mountain type. In 1912, when these locomotives were assimilated into the South African Railways, they were renumbered and designated Class A. In 1915, another two Class A locomotives were built from spare parts.

The Natal Government Railways (NGR) Class D 4-8-2 tank locomotive was designed by William Milne, the Locomotive Superintendent of the NGR from 1877 to 1896, and was built by Dübs and Company. The first 46 locomotives, with an operating boiler pressure of 140 pounds per square inch (965 kilopascals) and numbered in the range from 49 to 94, were placed in service during Milne's term. They proved to be such good engines that, when G.W. Reid took over as Locomotive Superintendent in 1896, he continued to place further orders for another 58, numbered in the range from 91 to 148, but with the boiler pressure increased to 160 pounds per square inch (1,103 kilopascals). These 100 locomotives, initially known on the NGR as the Dübs A, were delivered in ten batches by Dübs between 1888 and 1899.

As far as is known, the Dübs A locomotives were the first in the world to be designed and built with a 4-8-2 wheel arrangement, later to become known as the Mountain type.

The performance in service of the Dübs A was gradually improved by various modifications. New boilers were fitted as and when the originals needed replacement, with a working pressure of 160 pounds per square inch (1,103 kilopascals) instead of the as-delivered 140 pounds per square inch (965 kilopascals) of the first few batches. This increased their tractive effort at 75% boiler pressure from 16,340 pounds-force (72.7 kilonewtons) to 18,670 pounds-force (83.0 kilonewtons). The coal bunkers were also enlarged and the connecting rod big-ends were changed to the marine type to increase ground clearance.

Another modification was an extended smokebox on most locomotives, such as on NGR no. 87 depicted below. In the 1890s, some improvements to smokebox design took place. Extending the smokebox forward increased its volume. The increased amount of exhaust gases present in the smokebox had the effect of stabilising and improving the draught. The date of this improvement can be pinned to 1891 when the second batch of Michael Stephens’ Cape Government Railways (CGR) 5th Class 4-6-0 locomotives with their lengthened smokeboxes entered service. This had such a profound effect on the boiler’s steaming ability that virtually every locomotive on the CGR and NGR had their smokeboxes extended.