South African type FT tender

South African type FT tender

Type FT tender on Class 21, c. 1937

Type and origin Locomotive Class 21 Designer South African Railways (A.G. Watson) Builder North British Locomotive Company In service 1937

Specifications Configuration 2-8-2 Gauge 3 ft 6 in (1,067 mm) Cape gauge Length 32 ft 7 7⁄16 in (9,943 mm) Wheel dia. 34 in (864 mm) Wheelbase 22 ft 3 in (6,782 mm)  • Rigid 12 ft 3 in (3,734 mm) Axle load 12 LT 10 cwt (12,700 kg)  • 1st axle 7 LT 18 cwt (8,027 kg)  • 2nd axle 12 LT 10 cwt (12,700 kg)  • 3rd axle 12 LT 10 cwt (12,700 kg)  • 4th axle 12 LT 10 cwt (12,700 kg)  • 5th axle 12 LT 10 cwt (12,700 kg)  • 6th axle 7 LT 18 cwt (8,027 kg) Weight empty 69,122 lb (31,353 kg) Weight w/o 65 LT 16 cwt (66,860 kg) Fuel type Coal Fuel cap. 10 LT (10.2 t) Water cap. 5,587 imp gal (25,400 l) Stoking Mechanical Couplers Drawbar & AAR knuckle

Career Operators South African Railways Numbers SAR 2551

The South African type FT tender was a steam locomotive tender.

A single Type FT tender entered service in 1937, as tender to the sole Class 21 2-10-4 steam locomotive which was placed in service by the South African Railways in that year.

The Type FT tender was built in 1937 by North British Locomotive Company in Glasgow.

The South African Railways (SAR) placed a single Class 21 steam locomotive in service in 1937. The engine and tender were built to the design of A.G. Watson, Chief Mechanical Engineer of the SAR from 1929 to 1936. After trials, the locomotive was placed in service on the Oosterlijn line from Pretoria to the Eastern Transvaal.

The tender had a coal capacity of 10 long tons (10.2 tonnes), a water capacity of 5,587 imperial gallons (25,400 litres) and a maximum axle load of 12 long tons 10 hundredweight (12,700 kilograms). It had an unusual wheel structure of six pairs of wheels in a 2-8-2 wheel arrangement, with the leading and trailing wheels in Bissel-type pony trucks and the rest of the axles mounted with a rigid wheelbase. Like the leading and trailing wheels of its engine, all tender wheels were fitted with roller bearings. The rationale behind the design was that, if the tender frame could be carried on more points, represented by the rigidly mounted and Bissel wheels, instead of on only two bogie pivot centres, the frame could be made lighter.

The tender was equipped with a mechanical stoker. The water tank was of welded construction and the coal bunker was of the self-trimming design. Each Bissel truck was compensated with its neighbouring two pairs of rigidly mounted wheels. The eight rigidly mounted wheels were fitted with overhead laminated bearing springs, while the spring gear for each pony truck and two adjacent axles were compensated throughout the springing system, constituting two equal groups. Vacuum cylinders, mounted on top of the tank, actuated brake blocks on the rigidly mounted wheels.

The tender's wheel arrangement did not prove to be very successful and, with the exception of the Type JV tender, a similar experimental tender which had been built in the Salt River shops as a prototype test-model of the Type FT in 1936 during the design phase of the Class 21, it was not used again on the SAR. Comparison, in working order, with the Type MR tender showed that the Type FT tender weighed 30,128 pounds (13,666 kilograms) more than the Type MR, while it carried the same amount of coal and only 987 imperial gallons (4,490 litres) more water, a payload difference representing a weight of 9,870 pounds (4,477 kilograms).