South African Class S2 0-8-0

South African Class S2 0-8-0
No. 3728 in the Table Bay yard, August 1973
Type and origin Power type Steam Designer South African Railways (L.C. Grubb) Builder Friedrich Krupp AG Serial number 2966-3065 Model Class S2 Build date 1952-1953 Total produced 100
Specifications Configuration: ​  • Whyte 0-8-0 (Eight-coupled)  • UIC Dh2 Driver 3rd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Coupled dia. 48 in (1,219 mm) Tender wheels 34 in (864 mm) Wheelbase 51 ft 2 5⁄8 in (15,611 mm)  • Engine 12 ft 9 in (3,886 mm)  • Tender 24 ft 7 1⁄4 in (7,499 mm)  • Tender bogie 8 ft 8 in (2,642 mm) Length: ​  • Over couplers 63 ft 3 3⁄4 in (19,298 mm) Height 12 ft 4 in (3,759 mm) Frame type Cast Axle load 13 LT (13,210 kg)  • 1st coupled 13 LT (13,210 kg)  • 2nd coupled 12 LT 6 cwt (12,500 kg)  • 3rd coupled 11 LT 4 cwt 3 qtr (11,420 kg)  • 4th coupled 11 LT 2 cwt 3 qtr (11,320 kg)  • Tender bogie Bogie 1: 26 LT 15 cwt 3 qtr (27,220 kg) Bogie 2: 26 LT 12 cwt 1 qtr (27,040 kg)  • Tender axle 8 LT 18 cwt 2 qtr (9,068 kg) Adhesive weight 47 LT 13 cwt 2 qtr (48,440 kg) Loco weight 47 LT 13 cwt 2 qtr (48,440 kg) Tender weight 54 LT 8 cwt (55,270 kg) Total weight 102 LT 1 cwt 2 qtr (103,700 kg) Tender type MY1 (Buckeye 3-axle bogies) Fuel type Coal Fuel capacity 8 LT (8.1 t) Water cap 4,200 imp gal (19,100 l) Firebox type Round-top  • Firegrate area 30 sq ft (2.8 m2) Boiler: ​  • Pitch 8 ft 4 in (2,540 mm)  • Diameter 4 ft 6 7⁄8 in (1,394 mm)  • Tube plates 13 ft 5 3⁄8 in (4,099 mm)  • Small tubes 91: 2 in (51 mm)  • Large tubes 18: 5 1⁄2 in (140 mm) Boiler pressure 195 psi (1,344 kPa) Safety valve Pop Heating surface 1,092 sq ft (101.5 m2)  • Tubes 979 sq ft (91.0 m2)  • Firebox 113 sq ft (10.5 m2) Superheater: ​  • Heating area 330 sq ft (31 m2) Cylinders Two Cylinder size 18 in (457 mm) bore 26 in (660 mm) stroke Valve gear Walschaerts Valve type Piston Couplers AAR knuckle
Performance figures Maximum speed 25 mph (40 km/h) Tractive effort 25,300 lbf (113 kN) @ 75%
Career Operators South African Railways Class Class S2 Number in class 100 Numbers 3701-3800 Delivered 1952-1953 First run 1952 Withdrawn 1985
The 3rd coupled axle had flangeless wheels

The South African Railways Class S2 0-8-0 of 1952 was a steam locomotive.

In 1952 and 1953, the South African Railways placed one hundred Class S2 shunting steam locomotives with a 0-8-0 wheel arrangement in service.

By 1952, the need arose for shunting locomotives with a light axle load for harbour work, where most of the trackwork was laid with light rail. Under the direction of L.C. Grubb, Chief Mechanical Engineer of the South African Railways (SAR) from 1949 to 1954, specifications were prepared for a light locomotive with the 0-8-0 wheel arrangement which had already been proven successful with the Classes S and S1 shunting engines. To keep the total weight of the engine and tender down to approximately 100 long tons (101.6 tonnes), it was to be equipped with the Watson Standard no. 1 boiler, the smallest of the standard boilers.

When tenders were called for, a number of firms responded, but all except one stated that it would not be possible to construct the locomotive within the stipulated weight. Only the firm of Friedrich Krupp AG of Essen in Germany undertook to build the locomotives to the required specifications.

When design work commenced after the signing of the contract, however, it was discovered that the other tendering firms had been correct and that the locomotives could not be built within the specified weight limit, if the specifications were to be adhered to. It was eventually agreed that Krupp should design a suitable smaller boiler which would bring the locomotive's weight down to a level which would be in line with the stipulated maximum. The end result was an engine which had the appearance of a Cape gauge locomotive with a narrow gauge boiler, particularly when viewed from the front.

One hundred Class S2 locomotives were subsequently built by Krupp and delivered in 1952 and 1953, numbered in the range from 3701 to 3800. Even with the smaller Krupp-designed boiler, the locomotive's eventual working order weight was still more than 2 long tons (2.0 tonnes) over the desired maximum.

The locomotive had Walschaerts valve gear and was superheated. Its cast steel frame was a single casting with separately attached cylinders. As built, the third coupled axle had flangeless wheels to negotiate the tight curves found in docks.