South African Class 15CA 4 8 2

Class 15C redesign

After the twelve Class 15C 4-8-2 Mountain type locomotives, which were delivered by Baldwin Locomotive Works in 1925, had been in service a short while, it was discovered that the frames under the front of the firebox had a tendency to crack, necessitating heavy repairs.

To overcome this, a new modified design was prepared by Col F.R. Collins DSO, the Chief Mechanical Engineer (CME) of the South African Railways (SAR), for an almost identical locomotive, but with the frames shortened to the front of the firebox and widened under the firebox by means of a bridle casting.

Manufacturers

The first batch of 23 of these redesigned locomotives were built for the SAR by the American Locomotive Company (ALCO). They were delivered in 1926, numbered in the range from 2039 to 2059, 2072 and 2073, and designated Class 15CA, with the "A" supposedly indicating the manufacturer ALCO rather than, as was usual SAR practice, a different version of an existing locomotive type.

The earlier Baldwin-built Class 15C was then reclassified to Class 15CB for no good reason, since the "B" merely indicated the manufacturer Baldwin and not, as was usual practice, a branchline locomotive.

Another 61 Class 15CA locomotives were acquired in four batches from three other manufacturers in 1929 and 1930. Like the 23 ALCO-builts, all except the last batch were built with 23 inches (584 millimetres) bore cylinders.

Characteristics

Apart from the redesigned frame under the firebox, these locomotives were very similar to the Class 15C in proportions and appearance. They also had Coale pop type safety valves, a Schmidt type superheater and a combustion chamber in the firebox, which was equipped with flexible side stays and water siphon arch tubes. Their coupled wheel axleboxes, crank pins and connecting rod big ends were grease lubricated. These engines used the same Type KT tenders with a coal capacity of 14 long tons (14.2 tonnes) and a water capacity of 6,000 imperial gallons (27,300 litres).

Retyring

The locomotives were delivered with 57 inches (1,448 millimetres) diameter coupled wheels and their boilers were set at an operating pressure of 200 pounds per square inch (1,379 kilopascals). All their coupled wheels were eventually retyred to a 60 inches (1,524 millimetres) diameter and, to compensate for the loss of tractive effort due to the larger diameter wheels, their operating boiler pressure was increased from 200 to 210 pounds per square inch (1,379 to 1,448 kilopascals) by an adjustment of the setting of their safety valves. This modification enabled these mixed traffic locomotives to handle the fastest mainline passenger trains.

In addition, all those locomotives which had been built with 23 inches (584 millimetres) bore cylinders, had their cylinders reamed to a 24 inches (610 millimetres) bore.

When larger tyres were fitted to their coupled wheels, the old tyres were left in position and turned down on the wheel centres to serve as liners, and the new tyres were then shrunk on over the liners. The leading coupled wheels, which had been flangeless, as built, were flanged during the retyring. The practice of increasing the diameter of coupled wheels, wheel spacing and other considerations permitting, was begun by A.G. Watson during his term in office as CME and was continued by his successors. The reduction of tractive effort caused by the larger wheels, was made up by increasing boiler pressure or by fitting larger cylinders or both, as required. This policy resulted in more mileage between heavy repairs, less cost-per-mile on repairs and locomotives capable of higher speeds.

Reboilering

Three of the Class 15CB and Class 15CA locomotives were reboilered during the early 1940s, with new boiler numbers in the range from 9504 to 9506. These boilers were of similar dimensions as the originals, but with a different tube arrangement, and were designed by Dr. M.M. Loubser, CME at the time. The reboilered locomotives were not reclassified.

South African Railways

The Class 15CA locomotives were placed in service on the mainline between Cape Town and Kimberley, but like the Class 15CB, they were later transferred to Bloemfontein. From here, they worked throughout the Free State, until they were eventually relocated to the Eastern Transvaal system. Here they worked out of Pretoria to Pietersburg in the north and, from there, to Tzaneen in the east and Messina on the Rhodesian border in the north. Some also worked out of Witbank and Breyten.

In the mid-1960s, a few joined the Class 15CB on the Natal North Coast line. In 1983, they all went from there to the Cape Northern system, for use on the lines from Beaconsfield in Kimberley, working north to Mafeking and south to De Aar. Eventually nearly forty of them ended up as heavy shunters at Kaserne and Germiston in Johannesburg, where they replaced the Class 12AR and Class S1.

Industry

Three Class 15CA locomotives were sold into industrial service. Numbers 2807 and 2839 went to Dunn's Locomotive Works and were eventually sold to Rustenburg Platinum Mines. No. 2811 went to South Witbank Colliery as their no. 4.

Works numbers

The table lists the Class 15CA engine numbers, builders, years built and the builders' works numbers. The colour coding following the engine numbers refer to the three axle loadings of the different batches of the Class 15CA, as shown in the table of specifications.

Illustration

The main picture shows Breda-built no. 2802, serving as school guard at Esselen Park, the Transnet School of Rail in Kaalfontein, Gauteng, on 21 September 2009.