Class 24 3601-3700 2-8-4 South African Railways Gauge 3ft 6in

Weight	129t
Driving Wheels	4ft 3in
Boiler Pressure	200psi
Cylinders	Outside – 19in x 26in
Tractive Effort	27,600lbf
Valve Gear	Walschaerts

In 1948/50 the North British Locomotive Company in Glasgow built 100 locomotives which became the South African Railways (SAR) class 24. The cast engine main frames and the Buckeye bogies for the tenders were supplied by General Steel Castings of Eddystone, Pennsylvania.

The locomotives were designed by Dr. M.M. Loubser who was the Chief Mechanical Engineer of the SAR and were intended to replace older locomotives on branch line services on light rails.

The Class 24 had a one-piece cast-steel main frame which was cast integrally with the cylinders, including the cylinder hind covers, smokebox support frame, stays and various brackets, all of which would normally be separate items riveted or bolted onto the frames. They were the first South African steam locomotive to be built using this technique which aimed to reduce maintenance requirements and hence less time out of service.

They were built with Watson Standard boilers, while their double hopper type ashpans were specially designed to clear the four-wheeled trailing bogies. Their specially designed tenders, which rode on three-axle bogies to reduce the axle load, had cylindrical water tanks and were commonly known as torpedo tenders.

The locomotives were employed on branch line duties on light rails and 55 of them were based on the South West Africa System (now Namibia).

From some time between 1955 and 1959, they were also employed on the Keetmanshoop-Walvisbaai section. They remained in that territory until 1961, when strengthening of the track and the complete dieselisation of the South West Africa System made them available to be employed elsewhere.

Other branch lines to be served by the Class 24 include Breyten to Lothair, Nylstroom to Vaalwater, Port Elizabeth to Alexandra and George to Knysna. As a relatively powerful locomotive, they were also useful as suburban locomotives, a role they served in on the Springs-Nigel commuter line until electrification. Some eventually also worked on the Selati line in the Transvaal Lowveld. Heavy overhauls were done at Bloemfontein. The only province where they were unknown was Natal.

The locomotives were withdrawn from service in the 1980s.