| Weight | 145t 7cwt |
| Driving Wheels | 4ft 9ins |
| Boiler Pressure | 185psi superheated |
| Cylinders | Outside – 22in x 28in |
| Tractive Effort | 32,990lbf |
| Valve Gear | Walschaerts |
Details above are as originally built.
Between 1914 and 1925 119 class 15A locomotives entered service with the South African Railways (SAR). They were the final development of the plate-framed 4-8-2 Mountain locomotive designed by D.A. Hendrie, Chief Mechanical Engineer (CME) of the SAR. Of the whole Hendrie Mountain family, the class 15A was the most numerous and proved to be his most useful.
The predecessor class 15 locomotives had one flaw, their excessively long fire tubes. When more locomotives of the type were ordered, Hendrie improved the boiler by adding a combustion chamber in the firebox, which shortened the distance between tube plates.
The locomotives were built in ten batches from three supplies with the slow delivery reflecting the effects of the First World War.
The first five were built by the North British Locomotive Company (NBL) and delivered in July 1914, numbered in the range from 1571 to 1575. A further eight were delivered by the NBL in 1914 and were numbered 1781-1788. Ten more were delivered by NBL in 1915, numbered in the range from 1789 to 1798.
Whilst the first two batches were delivered with all coupled wheels flanged, beginning with this third batch the leading coupled wheels were flangeless to cope with the sharp curves on the Hex River Pass. These and subsequent locomotives had rear end running boards which continued straight through underneath their cabs.
Further deliveries were made by the NBL.
- Six in 1916 numbered 1799-1804
- Four in 1917 numbered 1805-1808
- Twenty in 1917 numbered 1809-1828
Like the class 15 engines the early class 15A locomotives had narrow cabs but starting with thos delivered in 1917 the cab was wider.
Deliveries continued through until 1925.
- Twenty by Beyer, Peacock and Company (BP) in 1920 numbered 1839-1858
- Ten by Beyer, Peacock and Company (BP) in 1921 numbered 1961-1970
- Fifteen by the NBL in 1921 numbered 2011-2025
- Twenty one by J A Maffei, Munich in 1925 numbered 2080-2100
To reduce the weight on the trailing wheels, steel fireboxes were originally used instead of copper. Some locomotives in Natal had been fitted with steel fireboxes years previously and the results were fairly good, but wherever water supplies were of poor quality, steel fireboxes gave a lot of trouble and necessitated the introduction of water treatment plants to prevent corrosion. This reintroduction of steel fireboxes eventually led to its widespread use on all the larger locomotive types, but it also forced the SAR to adopt locomotive water treatment as a general policy.
The first five locomotives of 1914 were delivered with steel fireboxes. The majority of the rest of the class 15A fleet were originally fitted with copper fireboxes. Steel fireboxes were only fitted in large numbers by his successor and only the last batch of 1925, supplied by Maffei, were delivered with steel fireboxes.
During the 1930s, many serving locomotives were reboilered with a standard boiler type designed by A.G. Watson, CME of the SAR from 1929 to 1936, as part of his standardisation policy. Such Watson Standard reboilered locomotives were reclassified by adding an R suffix to their classification.
When class 15A locomotives were reboilered with Watson Standard no. 2A boilers, they were therefore reclassified to Class 15AR. Early conversions were equipped with copper and later conversions with steel fireboxes. In the process, they were also equipped with Watson cabs with their distinctive slanted fronts, compared to the conventional vertical fronts of their original cabs, while the cab platform was extended over the front end of the tender underframe. Many of the reboilered engines were later fitted with Type MR or Type MT tenders.
The reboilering replaced the combustion-chambered Belpaire boilers with less efficient Watson Standard boilers without combustion chambers and it was found that the rebuilds were inferior steamers compared with the non-rebuilt engines.
The class 15A was regarded as one of the best classes of mainline mixed traffic locomotives to see service in South Africa.
They were placed in service on the Cape mainline to Kimberley where they formed the mainstay of motive power for many years. The engine was a good utility type and gave a good account of itself on goods and passenger working alike. It is noted for reducing the running time of the Union Limited which ran between Johannesburg and Cape Town by 2½ hours in March 1922. When they were superseded on this section by more powerful types, they ended up working in all parts of the country and proved to be reliable, free-steaming locomotives which ran up high mileage figures between major overhauls.
As the reboilered class 15AR, many ended up working in the Eastern Transvaal around Waterval Boven, in the Western Transvaal, Eastern Cape and the Orange Free State. During the 1960s, many were transferred to the Cape Midland and used mainly on the section from Port Elizabeth to Klipplaat and in passenger service on the Uitenhage suburban.
Near the end of their service lives in the early 1980s, they were all relegated to shunting work at centres all around the country, except for some which were hired out to Swaziland and which were still employed in mainline service on the Swaziland Railway until they were eventually replaced by diesel traction and retired. By the time they were withdrawn after more than sixty years in service, many of these locomotives had completed three million miles of heavy-duty mainline work.
Preservation
Two locomotives have been preserved as class 15A locomotives
North British Locomotive Company Works No 21056 – SAR 1791
Beyer, Peacock and Company Works No 5987 – SAR 1970
There are ten class 15AR locomotives preserved including two (SAR 2093 & SAR 2100) built in Germany by Maffei in Munich. All of these engines were originally introduced as class 15A locomotives.
Beyer, Peacock and Company Works No 5956 – SAR 1840
Beyer, Peacock and Company Works No 5966 – SAR 1850
Beyer, Peacock and Company Works No 5980 – SAR 1963
Beyer, Peacock and Company Works No 5983 – SAR 1966
North British Locomotive Company Works No 21063 – SAR 1798
North British Locomotive Company Works No 21729 – SAR 1820
North British Locomotive Company Works No 22737 – SAR 2012
North British Locomotive Company Works No 22741 – SAR 2016
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