The 4-8-2 locomotive of the class 12A was the last design by D.A. Hendrie for the South African Railways. It was based on the class 12 that had been introduced before World War I. The biggest change was that the area of the firebox was enlarged by 30 percent. All in all, they had the maximum size that was possible for a Mountain locomotive on cape gauge.

Between 1919 and 1929, North British built 48 and Henschel built 19 more. At the beginning, they were used for coal trains on the line between Witbank and Germiston. Later they were also used for passenger trains and spread over all South Africa. Starting in 1943, a total of 44 were rebuilt to class 12AR. Since there was no Watson standard boiler in a suitable size, they got a completely new boiler.

All in all, both the unrebuilt class 12A and the rebuilt class 12AR were reported to be very free steaming and powerful for a cape gauge Mountain. Between 1947 and 1953, North British built eight similar locomotives without superheater for industrial operators. In SAR service, the remaining class 12A and 12AR locomotives had all been moved to shunting service by 1977. The last ones were withdrawn in the eighties.

Since the axle load of the SAR class 19 was still too high for some branch lines, Col F.R. Collins designed the lighter class 19A. Changes included a smaller boiler, a cylinder diameter of 19.5 instead of 21 inches and a driver diameter of 51 instead of 54 inches. In total, this made a weight saving of four tons. Additionally, the axle load could be changed by setting of a pin in the suspension of the trailing axle. 

36 were built in 1929 by the Swiss SLM. As early as in the middle of the thirties, five got a standard boiler developed by A.G. Watson and were designated class 19AR. Two of these got domeless boilers. The SAR used the classes 19A and 19AR until 1977. After this, a few were sold for industrial service. Three 19 and two 19A have been preserved.

The class 24 were the only 2-8-4 “Berkshire” locomotives in South Africa. They were designed by M.M. Loubser for use on branch lines with light rails of not much more than 40 pounds per yard or 20 kg per metre. There they had to replace the classes 6, 7 and 8 while still having a low axle load. 100 locomotives were built by North British in Scotland.

As a first for any locomotive in South Africa, they had integrally cast frames and cylinders. These, and the bogies of the tenders, were supplied by General Steel Castings of Eddystone, Pennsylvania. In the result, these locomotives had a maximum axle load of only eleven and a half tons. The tenders were of the Vanderbuilt type and had six axles, so that they also had an axle load of less than ten tons. Roller bearings were only present on the leading and trailing axles. 

55 of the 100 locomotives were used in the South West Africa region. When this region was dieselized in the early sixties, these locomotives came to other regions. Later others became surplus due to the electrification of lines. Their general withdrawals came in the eighties and 20 were preserved. Nine of these are now owned by the Transnet Heritage Foundation. No. 3620 was shipped to New Zealand in 1997 and went to Australia in 2001. Since 2021 it operates on the Bellarine Peninsular Railway in Victoria.

In the desert areas of the Karoo and Kalahari, the large water requirements of powerful steam locomotives posed a major problem for the SAR. The contract for the development of a 4-8-4 locomotive and a condensation tender went to Henschel in Kassel. At the same time, the class 25NC was developed without a condenser. The prototype was built by Henschel and taken to North British in Scotland, where the rest was built. For the conditions of the Cape Gauge, these locomotives were very large and powerful.

In order to provide sufficient draft for the fire, the blower had to be particularly powerful. This did not work with a steam jet as usual, but with a fan driven by a turbine. When running under load, no exhaust beats could be heard, but instead the whine of the turbine.

In order to protect the fan from damage caused by solid objects in the smokebox, it was provided with a banjo-shaped extension. The fan still had to be changed later because it wore out very quickly. Instead of an injector, a turbo pump had to be used to feed the boiler because the condensed water was still at a very high temperature.

Timken roller bearings were installed everywhere, which caused problems in the early days. Oil was thrown from the bearings on the coupling rods against the underside of the boiler, which then dripped onto the wheel tires and made the locomotive more prone to slipping. This could only be remedied after the bearings on a large part of the locomotives had been replaced with ones from SKF and after Timken had repaired the remaining bearings.

The operations took place on the non-electrified lines in the desert areas in front of all types of trains. All in all, the locomotives achieved a range of around 500 miles or 800 km with one water filling, but at the expense of extensive maintenance. The fans in the smokebox and on the tender were particularly important here.

Therefore, between 1973 and 1980, 87 of the 90 class 25 locomotives were rebuilt into Class 25NC. The long tenders with a round water tank and no condenser were now called “Worshond Tender” because of their appearance, which stands for “Dachshund” and literally means “sausage dog”. They were retired around 1990 when all remaining steam locomotives were replaced by diesel and electric locomotives.

Based on the 4-6-2 Karoo class locomotives, the Cape Government Railways ordered four “Enlarged Karoo” locomotives also designed by H.M. Beatty shortly before the founding of the South African Railways. In comparison to the original Karoo, they had a higher pitched boiler, larger wheels and larger cylinders. In contrast to earlier CGR locomotives, they had a Belpaire firebox and no round-topped one. They were only delivered in 1912 directly to the SAR and called class 5, while the original Karoo locomotives were called class 5A and 5B.

In 1935, in a time when many SAR locomotives got superheated A.G. Watson standard boilers, only one Enlarged Karoo got this boiler. In this process it was renamed class 5R it also got larger drivers, larger cylinders and a lower boiler pressure. While the unrebuilt locomotives were relegated to secondary services in 1928 and withdrawn in 1942, the single class 5R locomotive survived until 1969. For a long time it had been in use in suburban services around Cape Town and was regularly operated at 60 mph (97 km/h) until the mid-sixties.

After the single 2-6-2+2-6-2 Modified Fairlie of class FC of the South African Railways, Colonel F.R. Collins specified a somewhat heavier variant that was again to be built by North British. The four locomotives were delivered in 1925 and were called class FD. They had direct competition from the class GD Garratt that had the same wheel arrangement.

In service it was found that the long rigid frame produced some problems. These included huge side overhangs when running through curves and oscillations of the water and coal tanks at speed. Also the pivot bearings had to support considerably higher weights due to the supplies being on the main frame. So ultimately the GD Garratts were more successful with 14 built. All FD locomotives were scrapped in 1949.

The class GEA was a 4-8-2+2-8-4 “Double Mountain” Garratt designed by M.M. Loubser for freight traffic on light branch lines directly after World War II. It was a successor of the class GE 2-8-2+2-8-2 “Double Mikado” where the leading axles had been replaced by two-axle bogies, mainly to carry the weight of larger supplies. Another prominent difference were the streamlined water tank and coal bunker of the GEA. Other differences included bar frames and Timken roller bearings on the leading and trailing axles. 

The boiler of the GEA had the same external dimensions as the one of the GE. But it had a round-topped firebox, a larger superheater and a higher pressure. Although the grate had an area of 51.3 square feet or 4.8 square metres, it was the last Garratt in South Africa without a stoker. With a diameter of 18.5 inches and a stroke of 26 inches, the cylinders were larger than those of the predecessor. With 50 locomotives, this was the largest Garratt order that Beyer, Peacock had received.

After some years in service, the front water tanks of some class members were modified without changing the capacity. This reduced the adhesive weight by more than three tons, but did not reduce the maximum axle load of 15 tons. Some had their coal bunkers extended at the top and were designated GEAM. The last ones were withdrawn in 1976 and after that, six were used by industrial operators. Three have been preserved, all of which are being owned by the Transnet Heritage Foundation.

The South African Railways were looking for a powerful locomotive that could also be used on branch lines and that would be suitable for mixed service at a higher speed. Since at that time only articulated locomotives were to be procured and the required speed required leading bogies, the choice of wheel arrangement fell on the “Double Pacific” for the first time for the SAR, i.e. 4-6-2+2-6-4T.

The specifications were drawn up by Colonel F. R. Collins and sent to Hanomag in Germany, where 37 engines were made in 1927. In 1928, 18 more followed from Henschel and ten from Maffei. This made it the largest number of Garratts built for the SAR until 1953 when the GMA was introduced.

The origin of the locomotive could be seen from the sloped side walls of the driver's cab at the height of the windows. As the first South African Garratt, it had a bar frame that was now established in Germany. The chassis allowed a speed of 80 km/h, but the bearings of the trailing axles often overheated. The solution was to no longer store these axles in an inside but in an outside frame.

As planned, the locomotives were used in front of passenger and freight trains and on branch and main lines. The operational area of most locomotives was in Natal. A higher axle load was permitted on the line from Johannesburg to Mafeking, so that the quantity of coal was increased from 10 long tons to 11 long tons 10 cwt.

Four locomotives were sold to Mozambique as early as 1950, but the remaining machines remained in the SAR's inventory until 1972. At this point, however, not all of them were actively used and it only took until 1979 for the last remaining ones to be scrapped. In the meantime some had been sold to mine operators, most of them to the Enyati Railway. Some of these had received an air brake powered by a diesel-powered compressor. Two examples survive today and a third is being restored.

The sole member of the SAR class GG was a Double Prairie Garratt built for fast passenger service in the Touws River area. For this task it had the largest drivers yet seen on a Garratt in South Africa with 57 inches. A coal pusher was installed in the tender to ease the work of the fireman or 1,448 mm. It could reach a speed of 57 mph or 92 km/h, but at speed its running was somewhat unsteady due to the single leading axle. So it had to give way to 4-8-2 locomotives and was usually only used for slower passenger and freight trains. On an incline of 1 in 80 (1.25%) it could haul 1,245 tons, what was reduced to 340 tons on 1 in 40 (2.5%). It was withdrawn from active service in 1938 and scrapped nine years later.

The class HF was a 2-8-2+2-8-2 Modified Fairlie that did not only have two driving axles more than the preceding classes FC and FD, but also a higher axle loading. The class designation should have been “FE”, but obviously “HF” was chosen to denote it as a “Henschel Fairlie” in contrast to the other Fairlies built by North British. It had a direct competitor in the class GE Garratt with the same wheel arrangement that was introduced two years earlier.

When put into service, they had some problems with steam production which had to be addressed in the Durban Workshops. A general problem of Modified Fairlies were the overly long frames which did not only have to carry the boiler, but also the supplies. So there were often cracks in the frames and also the pivot bearings were subject to a huge amount of wear and tear. So all in all, they were not as successful as the Garratts and no further Modified Fairlies were ordered by the SAR. The eleven class HF locomotives were withdrawn by 1951.