The South African Railways Class 19D 4-8-2 of 1937 was a steam locomotive.

Between 1937 and 1949, the South African Railways placed 235 Class 19D steam locomotives with a 4-8-2 Mountain type wheel arrangement in service. Between 1951 and 1955, 33 more were built for other operators like the Rhodesia and Angolan railways and the Nkana and Wankie mines, which makes the Class 19D the most numerous South African steam locomotive type ever built.Espitalier, T.J.; Day, W.A.J. (1946). The Locomotive in South Africa – A Brief History of Railway Development. Chapter VII – South African Railways (Continued). South African Railways and Harbours Magazine, November 1946. pp. 893-894.

Manufacturers

The Class 19D 4-8-2 steam locomotive was the final development of the Class 19 family of locomotives. At the request of Colonel F.R. Collins, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1922 to 1929, the original basic design of the Class 19 was done in the late 1920s by Test Engineer M.M. Loubser, who was himself later to serve as the CME from 1939 to 1949.Espitalier, T.J.; Day, W.A.J. (1946). The Locomotive in South Africa – A Brief History of Railway Development. Chapter VII – South African Railways (Continued). South African Railways and Harbours Magazine, Jul 1946. pp. 541-543.Information supplied by R.S. Loubser, son of M.M. Loubser

The final development of the Class was done in 1937 by W.A.J. Day, CME from 1936 to 1939. The Class 19D was a revised version of the Class 19C with piston valves and Walschaerts valve gear instead of rotary cam poppet valve gear.

Between 1937 and 1955, 268 Class 19D locomotives were built in seven batches by six locomotive manufacturers in Czechoslovakia, Germany and the United Kingdom and delivered to the SAR and several other operators in Southern Africa. The first forty were built in Germany in 1937, twenty with domeless boilers by Friedrich Krupp in Essen and numbered in the range from 2506 to 2525, and twenty by the Borsig Lokomotiv Werke in Hennigsdorf, Berlin and numbered in the range from 2526 to 2545.Friedrich Krupp AG, Essen Listen-Verwaltung: Stw – works list as supplied by Piotr Staszewski In 1938, a further 95 locomotives were ordered, built by three manufacturers. Škoda Works in Czechoslovakia built fifteen numbered in the range from 2626 to 2640, Krupp built forty, this time with domed boilers and numbered in the range from 2641 to 2680, and Borsig built forty numbered in the range from 2681 to 2720.Škoda Works, Plzeň, Czechoslovakia works list, as supplied by Piotr Staszewski Locomotive building was interrupted by World War II and post-war locomotive procurement saw European suppliers being replaced by British ones. In 1947, the first fifty post-war Class 19D locomotives were delivered by Robert Stephenson & Hawthorns (RSH) of Darlington, England and numbered in the range from 2721 to 2770. Of this order, engine no. 2734, RSH works no. 7247, was lost at sea off the east coast of England. Its replacement with RSH works number 7360 was paid for by insurance and it was given the number 2734 of the lost locomotive. The final batch of fifty Class 19D locomotives for the SAR were delivered in 1949 by the North British Locomotive Company (NBL) of Glasgow, Scotland and numbered in the range from 3321 to 3370. These engines were delivered with Type MX Torpedo tenders.North British Locomotive Company works list, compiled by Austrian locomotive historian Bernhard SchmeiserSouth African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 August 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 3'6" Gauge/Spoorwydte. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. VIII, 45-46.South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 August 1941). Locomotive Diagram Book/Lokomotiefdiagramboek, 2'0" & 3'6" Gauge/Spoorwydte, Steam Locomotives/Stoomlokomotiewe. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. VIII, 6a-7a, 20-21, 28-28A, 45-46. In 1951, six were built by NBL for the Caminho de Ferro de Benguela (CFB) in Angola. Between 1951 and 1953, Henschel & Son built 21 more for the Rhodesia Railways (RR) and the Nkana copper mine in Northern Rhodesia.Henschel & Son works list, compiled by Dietmar Stresow In 1955, four more were built by NBL for the Wankie coal mine in Southern Rhodesia.

Characteristics The Class 19D, nicknamed Dolly, was very similar to its predecessor Class 19C, but Day specified piston valves and Walschaerts valve gear instead of rotary cam poppet valve gear. The cylinders were redesigned with straighter steam ports while the valve gear itself was revamped with a longer steam lap and greater valve travel. In all other respects they were identical to the Class 19C. The last five locomotives of the first batch from Krupp, numbers 2521 to 2525, were fitted with exhaust steam injectors.

The cylinders were of the combined type, being cast in two identical and interchangeable sections, each made up of one cylinder and half of the smokebox saddle. They were of cast iron and had liners fitted. The design of the steam passages provided for a large cross-sectional area for both live and exhaust steam.

All coupled wheels were flanged. The axle boxes of the leading and trailing wheels were equipped with roller bearings while the solid bronze coupled wheel axle boxes were soft grease-lubricated. Soft grease lubrication was used throughout for the motion gear, except the piston rods, valve spindles and main crossheads which were oil-lubricated. Two four-feed sight lubricators, arranged in the cab, supplied oil to the steam chests and cylinders.

Watson Standard boilers The Class 19D was delivered with a Watson Standard no. 1A boiler, fitted with Ross Pop safety valves and set at pressure. The regulator was of the multiple-valve type, with the valves arranged on the saturated steam side of the superheater header in accordance with SAR practice. The boiler was one of the range of standard type boilers which were designed by Day's predecessor as CME, A.G. Watson, as part of his standardisation policy. The locomotive was also equipped with a Watson cab with its distinctive inclined front.

Despite the specifications, the first batch of Class 19D locomotives, built by Krupp and Borsig and delivered in 1937 and 1938, came in two variations. The Krupp-built locomotives were delivered with domeless boilers, while the Borsig-built locomotives conformed to the specifications with domed boilers.

While the domeless boilers did not conform to the specified Watson Standard no. 1A boiler as far as the dome was concerned, they were accepted nevertheless, probably since all their other dimensions were identical to that of the Watson Standard boiler. It appears that Krupp had decided on their own accord that a dome was not necessary since there was no regulator in the dome, but merely a standpipe. Krupp substituted the dome with a manhole cover on which the two Pop safety valves were mounted, while the steam was collected through a battery of collecting pipes, situated high up in the boiler in a similar manner to that which was used in the Class 16E.

All the subsequent Class 19D orders were delivered with domed Watson Standard no. 1A boilers with the usual standpipe steam collector high up in the dome, from where steam was led to the multi-valve regulator in the smokebox. Technically, whenever the loading gauge permitted the use of domes, their use was preferable to the domeless system which resulted in crowding multiple pipes into the boiler and other complications better left out of boilers. Operationally, according to drivers, there was no apparent difference in locomotive performance between the two boiler types.Soul of A Railway, System 7, Western Transvaal, based in Johannesburg, Part 16: Eastwards from Germiston Part 4: Leven to Breyten and Bethal to Volksrust by Peter Micenko. Introduction. (Retrieved 27 April 2017)

The Watson Standard boilers are interchangeable between locomotives. In the process of locomotives undergoing major overhauls, these twenty Krupp-built domeless boilers migrated between engines during subsequent years. As a result, locomotives from the other builders and even some Classes 19A and 19C locomotives eventually ended up with some of these domeless boilers.

Tenders As a result of having been built over such a long time span by so many different manufacturers, the six main groups of the Class 19D all had different all-up weights and axle loadings, as shown in the table and the specifications in the infobox. Over the eleven years during which the Class 19D was being produced for the SAR, some alterations occurred. As built, the Class 19D was delivered with Type MT tenders with a coal and a water capacity, even though the axle load of of these tenders exceeded the permissible limits on the branch lines for which the Class 19D was intended. Upon delivery, their new Type MT tenders were exchanged for the smaller modified Type MP1 tenders from some of the reboilered mainline locomotives. The Type MP1, many of which were later rebuilt to Type MR tenders, had a lighter axle load of and was therefore more suitable for branch line work. This policy was followed with all the Classes 19B, 19C and 19D, except the last batch of Class 19D for the SAR, numbers 3321 to 3370. During 1944 Dr. M.M. Loubser, then CME, who had been involved with the design of the Class 19 family from the very beginning in the late 1920s, made further improvements to the Class 19D. All the post-war locomotives came equipped with vacuum brake systems in addition to the steam brakes. The two vacuum cylinders were fitted under the running boards on either side at a point about midway between the leading and driving coupled wheels, while the vacuum chamber was arranged in line with the intermediate coupled wheels. The final batch from NBL, numbers 3321 to 3370, had Type MX tank wagon type tenders with cylindrical water tanks, similar in appearance to the American Vanderbilt type tenders. They were built to the design of Dr. M.M. Loubser, ran on three-axle Buckeye bogies and became commonly known as Torpedo tenders.

Service South African Railways During the service life of the Class 19D, several tender exchanges occurred to best equip a locomotive for the region it was allocated to and the type of service it was to be employed in. In line service, type MX Torpedo tenders were usually preferred for their larger coal and water capacities. The result was that by the time the Class 19D was withdrawn from service in the late 1980s, many had exchanged their Type MP1 or Type MR tenders for Type MX Torpedo tenders and vice versa. Type MX Torpedo tenders also ended up attached to Class 19B and Class 19C locomotives.Soul of A Railway, System 1, Part 11: Cape Town-Kraaifontein-Malmesbury-Bitterfontein by C P Lewis. Caption 27. (Retrieved 2 December 2016)

The Class 19D was the most numerous South African branch line locomotive and, at 235 built for the SAR, was only twenty less in number than the Class 15F mainline locomotive, the most numerous South African steam class. The Class 19D was very versatile and saw main- and branch line service all over South Africa with the exception of the Western Cape, where the Class 19C was used.

Tasks varied from mainline local and international passenger trains on the section between Warrenton and Mafeking en route between South Africa and Northern Rhodesia via Bechuanaland and Southern Rhodesia, to secondary and branch line duties and in later years as shunting engines. On occasion, South African Class 19D locomotives worked through from Mafikeng in South Africa via Botswana all the way to Bulawayo in Zimbabwe. SAR Class 19D locomotives were also hired out for shunting work to the Rhodesia Railways for use at Beit Bridge and to Mozambique for use at Lourenco Marques.