| Weight | 123t 16cwt |
| Driving Wheels | 5ft 2ins |
| Boiler Pressure | 180psi |
| Cylinders | Outside – 20in x 28in |
| Tractive Effort | 24,390lbf |
| Valve Gear | Walschaert |
The details above are for the class 10B locomotives as originally built.
The South African Railways Class 10A 4-6-2 of 1910 was a steam locomotive from the pre-Union era in Transvaal.
In 1910, the Central South African Railways placed ten class 10-2 locomotives in service, of which five were built with and five without superheaters. In 1912, when the five saturated steam locomotives were assimilated into the South African Railways, they were renumbered and designated Class 10A.
The locomotives were designed by Central South African Railways (CSAR) Chief Mechanical Engineer G.G. Elliot and based on the class 10 design of his predecessor, CSAR Chief Locomotive Superintendent P.A. Hyde.
The first batch was ordered from the North British Locomotive Company and delivered in 1910 and entered service as CSAR numbers 665-674. Of these 665-669 were saturated 10A locomotives and 670-674 superheated engines of the 10B class.
A second batch was built by Beyer, Peacock and Company in 1911 and entered service with the SAR as numbers 757-761 of the 10B class.
When the Union of South Africa was established on 31 May 1910, the three Colonial government railways (Cape Government Railways, Natal Government Railways and CSAR) were united under a single administration to control and administer the railways, ports and harbours of the Union. Although the South African Railways and Harbours came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways were only implemented with effect from 1 January 1912.
When they were assimilated into the South African Railways (SAR) in 1912, the five saturated steam locomotives, numbered in the CSAR range from 665 to 669, were designated Class 10A and renumbered in the range from 747 to 751. The five superheated locomotives were designated Class 10B and numbered in the range 752 to 756.
All of the class 10A and five of the class 10B locomotives were eventually reboilered with Watson Standard no. 1 boilers. Since the original difference between the class 10A and class 10B lay only in the fact that their respective boilers were constructed without or with superheaters, distinction between the two types became unnecessary after this reboilering. The reboilered class 10A locomotives were therefore reclassified to class 10BR along with similarly reboilered class 10B locomotives.
The Belpaire boilers of the class 10B locomotives were originally fitted with Ramsbottom safety valves whereas the Watson Standard boilers were equipped with Pop safety valves.
The saturated locomotives (SAR 747-751) were placed in service to haul passenger trains out of Johannesburg. In service, it was found that their superheated sister locomotives could handle almost 25% more load, so much so that double-heading of passenger trains in the Orange Free State became unnecessary with the superheated locomotives.
The saturated locomotives were therefore soon taken off mainline passenger service and put to good use on suburban work. After reboilering and reclassification to class 10BR, most of the rest of their working lives were spent on the Cape Midland system where they were used on the mainline out of Port Elizabeth.
The superheated locomotives (SAR 752-761) were placed in service to haul passenger trains out of Johannesburg. On the fast trains running between Pretoria and Johannesburg, the scheduled time of 1 hour 15 minutes was maintained daily between Pretoria and Germiston they maintained an average speed of just over 37mph in both directions.
Following the fitting of the Watson boilers most of working lives of the class 10BR locomotives was spent on the Cape Midland system, where they were used on the mainline out of Port Elizabeth. Two of them worked as station pilots at Kimberley until 1960, when they joined the rest of the Class which were by then working the suburban between Port Elizabeth and Uitenhage.
They were all withdrawn from service in 1974.
Preservation
Three of the locomotives have been preserved.
North British Locomotive Company Works No 18974 – CSAR 668 & SAR 750
North British Locomotive Company Works No 18980 – CSAR 674 & SAR 756
Beyer, Peacock & Company Works No 5484 – SAR 758
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