South African Class 23 4 8 2

Manufacturers

The Class 23 4-8-2 Mountain type steam locomotive was designed by W.A.J. Day, Chief Mechanical Engineer (CME) of the South African Railways (SAR) from 1936 to 1939. It was intended as a general utility locomotive, capable of operating on 80 pounds per yard (40 kilograms per metre) rail, and was built in two batches by Berliner Maschinenbau and Henschel and Son in Germany. The original order in 1938 was for twenty locomotives, of which Berliner built seven, numbered in the range from 2552 to 2558, and Henschel thirteen, numbered in the range from 2559 to 2571.

At the time, the urgency brought about by the rapidly deteriorating political climate in Europe led to a further 116 locomotives being ordered, even before the first batch could be delivered and tested. Ordering this quantity of a new class of engine before any had been tried out, constituted a record for the SAR. Of this second batch, Henschel built 85, numbered in the range from 3201 to 3285, and Berliner 31, numbered in the range from 3286 to 3316. The last locomotive of this second order was delivered in August 1939, just one month before the outbreak of the Second World War.

Berliner-built locomotive no. 3301 received an out-of-sequence works number, Berliner no. 10816 instead of no. 11000, since works number 11000 was reserved for the new Class 01.10 4-6-2 Pacific type locomotive for the German State Railways.

Characteristics

As originally designed, the locomotive would have had 66 inches (1,676 millimetres) coupled wheels, which would have required a newly designed boiler to accommodate the extra length brought about by the long coupled wheelbase. The increasing political turmoil in Europe and the resulting urgency, however, prohibited time being spent on designing a new boiler. As a result, the existing Watson Standard no. 3B boiler was incorporated in the design, with an extra long smokebox which was extended by 1 foot 6 inches (457 millimetres) to partially compensate for the shorter boiler. This boiler was one of the range of standard type boilers which was designed by Day's predecessor as CME, A.G. Watson, as part of the latter's standardisation policy. To maintain approximately the same tractive effort as the Class 15E, the boiler pressure was raised to 225 pounds per square inch (1,551 kilopascals), at the time the highest yet used on the SAR, since the existing SAR loading gauge did not permit horizontal cylinders of greater bore diameter than 24 inches (610 millimetres) with normal cylinder spacing.

The inner firebox was of steel and was fitted with five 3 inches (76 millimetres) diameter arch tubes, which supported the brick arch. The rocking grate, with two drop-grates, was actuated by a steam shaker. As was the practice with Watson Standard boilers, the hopper type ashpan was secured to the main frames instead of to the boiler foundation ring, with a 4 inches (102 millimetres) air gap all round. Drench pipes were fitted to facilitate cleaning and the bottom of the ashpan was fitted with a hand-operated sliding door.

To enable them to negotiate 300 feet (91 metres) radius curves, the leading coupled wheels were given a 1 inch (25 millimetres) total side-play in their horn blocks, while the tyre flanges of the intermediate coupled wheels were of reduced thickness and the leading coupling rods were provided with spherical bearings at the knuckle joints and crank pins. In addition, largely also as a result of the decision to use the shorter Watson Standard boiler, it was decided to reduce the coupled wheel diameter from the originally intended 66 inches (1,676 millimetres) to 63 inches (1,600 millimetres), which shortened the coupled wheelbase and would further ease passage on sharp curves.

Tender

Since these locomotives were intended for working in the Karoo, where good quality water is a scarce resource, they were equipped with very large Type EW tenders which rode on six-wheeled bogies, to enable longer runs to be undertaken between watering stops or to skip bad watering places. They were the largest tenders to have been used in South Africa up to that time and, as originally designed, would have had a water capacity of 10,000 imperial gallons (45,500 litres) and a coal capacity of 18 long tons (18.3 tonnes). Owing to axle load restrictions, however, it was necessary to reduce the water capacity to 9,200 imperial gallons (41,800 litres). The first batch of twenty locomotives were delivered with such tenders.

The second batch of 116 locomotives were delivered with a modification to the tender's underframe. To improve the weight distribution, both tender pivot centres were relocated 6 inches (152 millimetres) towards the rear. This enabled the water capacity to be increased to 9,500 imperial gallons (43,200 litres) on these 116 tenders. While the locomotive-and-tender's length over couplers was not affected, the total wheelbase of the second batch was 6 inches (152 millimetres) longer, since the distance between the engine's trailing wheel and the first tender wheel was increased from 10 feet (3,048 millimetres) to 10 feet 6 inches (3,200 millimetres).

Four vacuum cylinders operated clasp brakes on all tender wheels and a hand brake was included. Since experience showed that a firegrate of 63 square feet (5.9 square metres) cannot be served effectively under all conditions by manual stoking, particularly on long runs, a type H.T-1 mechanical stoker was fitted, supplied by the Standard Stoker Company of America. The mechanical stoker engine was mounted on the tender.

Streamlining

During the 1930s, the streamlining of locomotives was fashionable in Europe and the United States of America. It was proposed to adopt streamlining on some of the Class 23 locomotives which were intended for the Cape mainline and the manufacturers were requested to submit estimates to that effect. Since streamlining would increase the cost by £500 per locomotive and increase the weight by approximately 2 long tons (2.0 tonnes), however, the idea was abandoned, especially in light of the negligible performance benefit of streamlining at the official maximum 55 miles per hour (89 kilometres per hour) goods train speeds on Cape gauge and the reduced accessibility of working parts on a streamlined locomotive.

Locomotive naming

Although the naming of locomotives in South Africa dates back to the Cape Town Railway and Dock Company's 0-4-2 locomotives of 20 March 1860 and the Natal Railway's 0-4-0WT Natal of 13 May 1860, it was rarely done. In 1945, the Minister of Transport at the time, the Honourable F.C. Sturrock MP, instructed that a number of Classes 15F and 23 engines should be named after various South African cities and towns and fitted with suitable nameplates in both official languages. The decorative plates were fitted to the sides of the smokebox, or to the elephant ears smoke deflectors of engines which were so equipped. Thirteen Class 23 locomotives were named.

In later years, some of these name plates migrated to other engines and classes, with several eventually ending up on Class 25NC locomotives.

Service

In general appearance and power, the Class 23 locomotive is very similar to the Classes 15E and 15F. In their first few years of service, the Class 23 fleet formed the bulk of the motive power on the lines from Touws River to Beaufort West and from De Aar to Welverdiend via Kimberley and Klerksdorp.

Upon the arrival of the new Classes 25 and 25NC in 1953, the Class 23 was transferred to Bloemfontein, to work from there to Kimberley to the west and Kroonstad to the north.

Due to metal fatigue cracks which developed in their 5 inches (127 millimetres) thick rolled steel bar frames, they were withdrawn from mainline service considerably earlier than the similar and contemporary Class 15F. They were all retired by 1983, many of them in the process donating their large Type EW tenders to increase the range of the Class 15F. At least one of these tenders, that of no. 3209, was later rebuilt to a water-only tender.

Works numbers

The table shows the Class 23 engine numbers, builders and works numbers. On the builders' works lists, all the locomotives are recorded as having been built in 1938.

Illustration

The main picture shows Berliner-built no. 2556, which was plinthed next to the High School in Gideon Joubert Park in Touws River on occasion of that Railway town's centenary in 1977. It was officially presented to the town on 24 September 1977 by SAR chief executive, Dr. Kobus Loubser.