South African Class 23 4-8-2

In 1938 and 1939 the South African Railways placed one hundred and thirty-six Class 23 steam locomotives in service. The Class 23 was the last and the largest 4-8-2 Mountain locomotive to be designed by the South African Railways.^[4][5]

Manufacturers

The Class 23 4-8-2 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, numbers 2552 to 2558, and Henschel thirteen, numbers 2559 to 2571.^[1][3]

The urgency brought about by the rapidly deteriorating political climate in Europe at the time led to a further one hundred and sixteen locomotives being ordered even before the first batch could be delivered and tested. Of these, Henschel built eighty-five, numbers 3201 to 3285, and Berliner thirty-one, numbers 3286 to 3316. The last locomotive of this second order was delivered in August 1939, just one month before the outbreak of World War II.^[1][3][6]

Locomotive number 3301 received an out of sequence works number, Berliner 10816 instead of 11000, since works number 11000 was reserved for a new 4-6-2 Pacific type locomotive for the German State Railways. The table shows the Class 23 running numbers, builders and works numbers. On the builders’ works lists all the locomotives are recorded as having been built in 1938.^[1][2][4]

Design considerations

Watson Standard boiler

As originally intended, the locomotive would have had 66 inches (1,680 millimetres) driving wheels, which would have required a newly designed boiler to accommodate the extra length. 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 to partially compensate for the shorter boiler. This boiler was one of the range of standard type boilers designed by Day’s predecessor as CME, A.G. Watson, as part of the latter’s standardisation policy.^[1]

Driving wheel diameter

In order to enable them to negotiate 300 feet (91.4 metres) radius curves, the leading driving wheels were given a 1 inch (25.4 millimetres) side-play. In addition, largely also as a result of the decision to use the shorter Watson Standard boiler, it was decided to reduce the driving wheel diameter from 66 inches (1,680 millimetres) to 63 inches (1,600 millimetres), which shortened the coupled wheelbase and would further ease passage on sharp curves.^[1][3]

These decisions appear to have been taken at quite a late stage, since the cylinders were cast to suit the larger wheel diameter. To compensate for the decreased wheel diameter, the maximum boiler pressure was raised to 225 pounds per square inch (1,550 kilopascals), at the time the highest yet used on the SAR.^[5]

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 tenders with a high water capacity that rode on six wheeled bogies. They were the largest tenders to have been used in South Africa up to that time and as designed, they would have had a water capacity of 10,000 imperial gallons (45,000 litres).^[1][3]

Axle load restrictions, however, led to the water capacity being reduced to 9,200 imperial gallons (42,000 litres) for the first order of twenty locomotives. This was increased to 9,500 imperial gallons (43,000 litres) for the second order of one hundred and sixteen. Four vacuum cylinders operated clasp brakes on all tender wheels.^[1][3]

Streamlining

During the 1930s the streamlining of locomotives was fashionable in Europe and the United States. It was proposed to adopt streamlining on some of the Class 23 locomotives, but investigation showed that it would increase the cost by £500 per locomotive and increase the weight by approximately 2 long tons (2.0 tonnes). Those factors, coupled to the negligible performance benefit of streamlining at normal goods train speeds as well as the reduced accessibilty of working parts on a streamlined locomotive, led to this idea being abandoned.^[1][3]

Service

In general appearance and power the Class 23 locomotive is very similar to the Class 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 Klerksdorp via Kimberley.^[3]

Electrification of the section between Kimberley and Klerksdorp and, almost simultaneously, the arrival of the new Class 25 and Class 25NC in 1953 caused them to be transferred to Bloemfontein, to work from there to Kimberley to the west and Kroonstad to the north.^[3]

Due to metal fatigue cracks that developed in their 5 inches (127 millimetres) thick rolled steel bar frames, they were withdrawn from main line service considerably earlier than the similar 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 number 3209, was later rebuilt to a water only tender.^[3][5]

Gallery

The main picture shows Berliner built number 2556, which was plinthed next door 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 by SAR chief executive Dr. Kobus Loubser on 24 September 1977.^[7]

See also

• Tender locomotive numbering and classification
• Watson Standard boilers
• The 4-8-2 "Mountain"
• List of South African locomotive classes

References

1. ^ ^{a b c d e f g h i} Holland, D.F. (1972). Steam Locomotives of the South African Railways, Volume 2: 1910-1955 (1st ed.). Newton Abbott, Devon: David & Charles. pp. 98–100. ISBN 0715354272. 
2. ^ ^{a b} Henschel & Son works list, compiled by Dietmar Stresow
3. ^ ^{a b c d e f g h i j} Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 10-11, 75-76. ISBN 0869772112. 
4. ^ ^{a b c} South African Railways and Harbours Locomotive Diagram Book, 2’0” & 3’6” Gauge Steam Locomotives, 15 August 1941, as amended
5. ^ ^{a b c} Durrant, A E (1989). Twilight of South African Steam (1st ed.). Newton Abbott, London: David & Charles. p. 105. ISBN 0715386387. 
6. ^ Touws River, Municipality - SAR Class 23 No 2556
7. ^ Touwsrivier – Daos Ab – 1877-1977 (J.H. Stassen, 1977), pp79, 83-85