South African Class 19C 4 8 2

Manufacturer

When the need for more branchline locomotives became apparent in 1934, tenders were invited by the South African Railways (SAR) for another fifty Class 19B locomotives with Walschaerts valve gear, but redesigned by Chief Mechanical Engineer (CME) A.G. Watson with his Watson Standard no. 1A boilers. When the tenders were received, it was found that the North British Locomotive Company (NBL) of Glasgow, Scotland, had also tendered for a locomotive with Rotary Cam Poppet valve gear as an alternative to Walschaerts valve gear.

Even though this would increase the cost per locomotive by £200, Watson decided to accept this tender, in view of the good reports he had received concerning poppet valve gear. This variation on the design led to these locomotives being designated Class 19C when they were delivered in 1935.

Tenders

All fifty Class 19C loco­motives were erected at the Salt River shops and numbered in the range from 2435 to 2484, and many remained stationed at Cape Town while being subjected to exhaustive testing. As built, the Class 19C was delivered with Type MT tenders with a 12 long tons (12.2 tonnes) coal and a 6,000 imperial gallons (27,300 litres) water capacity, even though the axle load of 16 long tons 11 hundredweight (16,820 kilograms) of these tenders exceeded the permissible limits on the branchlines for which the Class 19B 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 had a lighter axle load of 13 long tons 15 hundredweight (13,970 kilograms) and was therefore more suitable for branchline work. This policy was followed with all the Classes 19B, 19C and 19D, except the last batch of Class 19D which was delivered with Type MX torpedo tenders.

Watson Standard boilers

Soon after A.G. Watson was appointment as CME in 1929, he set out on a program of standardisation of locomotive boilers and engine parts, which ultimately led to a considerable reduction in the time taken for locomotive repairs. At the time, 88 different types of locomotive were in service, for which some fifty types of replacement boiler were still being ordered prior to 1929.

The Class 19C was the first to be built new with Watson Standard boilers. The no. 1A boiler had a larger superheater than the Class 19B and, in a break with prior custom, the ash pan and running boards were affixed to the locomotive frame instead of to the boiler to facilitate easier removal of the boiler for repairs. The Class 19C was also built with Watson's altered cab with an inclined front to facilitate access to the firebox stays on the sides ahead of the cab. The Watson cab, like the Watson Standard boiler, was to become standard on later SAR steam locomotive classes.

The first five Watson Standard boilers to be designed were the numbers 1, 1A, 2, 2A and 2B. The no. 1 boiler was suitable for the Classes 5, 5B, 10A, 10B and 10C. The no. 1A boiler was similar to the no. 1, but with the boiler barrel lengthened by 2 feet 5 inches (737 millimetres), and was suitable for the Classes 19, 19A and 19B. Like the Class 19C, the Class 19D would also be built new with no. 1A boilers.

The no. 2 boiler was suitable for the Classes 3, 3B, 4A, 12, 12B, 14, 14A and 14C. The no. 2A boiler was similar to the no. 2, but with the boiler barrel lengthened by 2 feet 4 inches (711 millimetres), and was suitable for the Classes 15, 15A and 15B. The no. 2B boiler was also similar to the no. 2, but with the boiler barrel shortened by 1 foot (305 millimetres), and was suitable for the Classes 16, 16B and 16C.

These were later followed by the numbers 3A and 3B boilers. The no. 3A boiler was suitable for the Class 16E, while the no. 3B boiler was 3 feet 5 ¹⁄₂ inches (1,054 millimetres) longer and suitable for the Classes 15E, 15F, 21 and 23.

Copper and steel fireboxes

Some of the locomotives were built with steel fireboxes for use in those areas where good or treated water was readily available, while others were still equipped with copper or composite fireboxes for use in areas with poor water quality.

Copper or composite fireboxes are considerably more expensive to manufacture and repair than steel ones. It was only by the late 1960s, when severe corrosion was no longer a big problem as a result of the availability of water treatment facilities throughout the country, that copper and composite fireboxes were no longer considered necessary.

Rotary Cam Poppet valve gear

The Rotary Cam Poppet valve gear consists of two admission valves and two exhaust valves per cylinder, operated by a camshaft arranged in a box, fixed to each cylinder between the valve chambers. The cam boxes are self-contained and detachable, and replacement cam boxes can be fitted at running sheds in a few hours. The camshafts are driven from the return cranks on the driving wheels through worm wheels and universal propeller shafts, arranged so that the camshafts and the coupled wheels revolve at the same speeds.

There were originally eight cams for forward motion and three for reverse, which gave a range of cut-offs from 15% to 85% in forward gear. The hand reversing screw spindle carried a disk, suitably notched with a locking device to ensure that the cam rollers would be in the centre of the selected cams under working conditions. During drifting, the reversing gear is placed in the neutral position, where the exhaust valves are held fully open. These conditions were ideal for drifting and superior to any Walschaerts valve gear in admitting steam to the steam chests, even with cylinders equipped with by-pass valves, snifting valves and drifting valves.

In service, some trouble was experienced with transmission shaft joints and with worn cams and rollers. If the valves were set with the engine cold, there appeared to be some distortion under working conditions due to the high temperature of superheated steam, which caused deterioration of the valve events. Drivers also reported that, when the engines were standing or moving at very slow speed, it was difficult to reverse, since the cam rollers were not readily able to climb over the inclined surfaces leading from one cam to another. Trouble was also experienced with steam leaking past the tappet spindles into the cam boxes, where it boiled up the oil and caused it to overflow from the cam boxes. This was overcome by serrating the collars of the spindle bushes to allow the steam to escape and prevent entry into the cam boxes.

The photograph alongside shows a Class 19C loco­motive after a record speed test run, during which the engine achieved a speed of 67 miles per hour (108 kilometres per hour). A.G. Watson is standing sixth from left in the group in front of the locomotive, with hat in hand.

An official test was conducted in 1938 to compare the steam consumption of the poppet valve Class 19C with the piston valve Class 19D. The Class 19D performed slightly better. However, the valve travel of the Class 19D is 7 ¹⁄₂ inches (191 millimetres), compared to a valve travel of about 4 ³⁄₄ inches (121 millimetres) in all previous engines fitted with piston or slide valves. It was concluded that, had the valve travel of the Class 19D been retained at 4 ³⁄₄ inches (121 millimetres), the test would have shown an advantage for the poppet valves.

Balancing

The balancing of these locomotives represented another advance on former practices. Until then, locomotives had been balanced to an extent of 50% to 75% of their reciprocating parts, and fully as regards their revolving parts.

On the Class 19C, the proportion of reciprocating parts balanced was reduced to 20%, which resulted in a big decrease of vertical hammer blow to not more than 18 long hundredweight (914 kilograms) on any wheel at 50 miles per hour (80 kilometres per hour). Similar balancing metods on subsequent new locomotives enabled the SAR to adopt axle loads exceeding those permitted on many other railways of the world for comparable weight of rail.

Service

The Class 19C was designed for mainline as well as branchline service. They initially worked in the Witwatersrand area, the Eastern Cape and Western Cape. The Poppet valves made the Class 19C a very free-running locomotive, although it required special maintenance techniques.

As a result, the whole class was allocated to the Western Cape during the Second World War and based at the Paardeneiland shed in Cape Town. From here, they worked on branchlines such as those from Cape Town to Saldanha, along the long branchline via Klawer to Bitterfontein, and across Sir Lowry's Pass to Caledon and Protem in the Overberg.

In later years, around 1970, a few were stationed at Bloemfontein, from where they worked the line to Aliwal North. They were withdrawn from service in 1978.

One, no. 2439, was preserved, but none of them were sold into industry, firstly because of the special maintenance required for the Poppet valves, and secondly because Cape Town was a long distance away from any potential industrial operators, which would increase the cost of relocation after purchase.