| Weight | 47t 3cwt |
| Driving Wheels | 3ft 3ins |
| Boiler Pressure | 140psi |
| Cylinders | Two Outside – 17in x 21in |
| Tractive Effort | 16340lbf |
| Valve Gear | Stephenson |
Details above are as originally built.
The Natal Government Railways (NGR) class D 4-8-2T locomotive was designed by William Milne, the Locomotive Superintendent of the NGR and was built by Dübs and Company.
The first 46 locomotives had an operating boiler pressure of 140 psi. They were numbered in the range from 49 to 94. 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 psi. 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. This increased their tractive effort from 16,340 lbf to 18,670 lbf. The coal bunkers were also enlarged and the connecting rod big-ends were changed to the marine type to increase ground clearance.
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.
A Hendrie became the Locomotive Superintendent in 1905 and he gradually fitted the locomotives Belpaire fireboxes with wider firegrates. The cabs were also improved to offer the engine crew better protection, and new brass-capped chimneys replaced the original straight flared chimneys. These modified locomotives were known as the Improved Dübs A.
When a locomotive classification system was introduced on the NGR, the Dübs A locomotive family was designated class D. The unmodified locomotives became the class D1 while the modified locomotives with Belpaire fireboxes became the class D2.
When the Union of South Africa was established on 31 May 1910, the three Colonial government railways (CGR, NGR and Central South African Railways) were united under a single administration to control and administer the railways, ports and harbours of the Union. Although the South African Railways and Harbours came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways was only implemented with effect from 1 January 1912.
In 1912, these engines were designated class A and were renumbered in the range from 97 to 196. The unmodified class D1 locomotives receiving the numbers in the range from 97 to 186 and the ten, at the time, already reboilered class D2 locomotives receiving the numbers in the range from 187 to 196. In South African Railways (SAR) service, the Improved Dübs A locomotives became known as the class A Belpaire.
In 1915, to help counter wartime motive power shortages brought about by the diminished ability to order new locomotives from European builders due to hostilities, another two class A locomotives were built from spare parts by the SAR in their Durban shops. These two locomotives were numbered 332 and 333.
In the NGR era, the class D fleet remained in service on the Natal mainline until they were eventually displaced by more modern locomotives. They continued to serve well into the SAR era on the Dundee-Hlobane branchline, the Harrismith-Ladysmith section and on the north coast line to Empangeni.
In 1915, shortly after the outbreak of the First World War, the German South West Africa colony was occupied by the Union Defence Forces. Since a large part of the territory’s railway infrastructure and rolling stock was destroyed or damaged by retreating German forces, an urgent need arose for locomotives for use on the Cape gauge lines in that territory. In 1917, numbers 98 and 183 were transferred to the Defence Department for service in South West Africa. Both locomotives are believed to have returned to South Africa after the war.
When a shortage of suitable shunting locomotives developed in 1926, the SAR modified 21 class A and class A Belpaire 4-8-2T locomotives by removing the trailing bissel bogie and coal bunker, shortening the main frame and adding a tender to increase their coal and water capacity. Tenders from various scrapped locomotive types were used.
These 21 rebuilt locomotives became the SAR class 17 4-8-0 tank-and-tender locomotives, numbered in the range from 1415 to 1435. They were used as shunting locomotives around Durban and Port Elizabeth, until they were withdrawn from service by 1961.
The last of the class A was withdrawn from service in 1962. Several locomotives continued to serve in industrial use for many years.
Preservation
Dübs and Company Works No 2499 – NGR 55 & SAR 103
Dübs and Company Works No 2627 – NGR 84 & SAR 130 Patrys
Dübs and Company Works No 3318 – NGR 90 & SAR 136 & 1426 Umbilo
Dübs and Company Works No 3819 – NGR 133 & SAR 196 & 1418
Dübs and Company Works No 3823 – NGR 137 & SAR 176
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