South African Class 4 4-8-2

CGR Mountain 4-8-2
South African Class 4 4-8-2

SAR Class 4 no. 1478 at Worcester, c. 1930

Type and origin Power type Steam Designer Cape Government Railways (H.M. Beatty) Builder North British Locomotive Company Serial number 19242-19243 Model CGR 4-8-2 Build date 1911 Total produced 2

Specifications Configuration 4-8-2 (Mountain) Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm) Cape gauge Leading dia. 28 1⁄2 in (724 mm) Coupled dia. 54 in (1,372 mm) Trailing dia. 33 in (838 mm) Tender wheels 33 1⁄2 in (851 mm) as built 34 in (864 mm) retyred Wheelbase 57 ft 8 3⁄8 in (17,586 mm)  • Engine 31 ft 11 in (9,728 mm)  • Leading 6 ft 2 in (1,880 mm)  • Coupled 14 ft 5 in (4,394 mm)  • Tender 16 ft 1 in (4,902 mm)  • Tender bogie 4 ft 7 in (1,397 mm) Wheel spacing (Asymmetrical) 1-2: 4 ft 10 in (1,473 mm) 2-3: 4 ft 9 in (1,448 mm) 3-4: 4 ft 10 in (1,473 mm) Length: ​  • Over couplers 65 ft 3⁄8 in (19,822 mm) Height 12 ft 10 in (3,912 mm) Frame type Bar Axle load 15 LT (15,240 kg)  • Leading 11 LT 3 cwt (11,330 kg)  • 1st coupled 14 LT 10 cwt (14,730 kg)  • 2nd coupled 14 LT 15 cwt (14,990 kg)  • 3rd coupled 14 LT 17 cwt (15,090 kg)  • 4th coupled 15 LT (15,240 kg)  • Tender bogie Bogie 1: 21 LT 11 cwt (21,900 kg) Bogie 2: 21 LT 18 cwt (22,250 kg)  • Tender axle 10 LT 19 cwt (11,130 kg) Adhesive weight 59 LT 2 cwt (60,050 kg) Loco weight 82 LT 2 cwt (83,420 kg) Tender weight 43 LT 9 cwt (44,150 kg) Total weight 125 LT 11 cwt (127,600 kg) Tender type XJ (2-axle bogies) Fuel type Coal Fuel capacity 6 LT 10 cwt (6.6 t) Water cap 3,500 imp gal (15,900 l) Firebox type Round-top, combustion chamber  • Firegrate area 37 sq ft (3.4 m2) Boiler: ​  • Pitch 7 ft 6 in (2,286 mm)  • Diameter 5 ft 6 3⁄8 in (1,686 mm)  • Tube plates 18 ft (5,486 mm)  • Small tubes 201: 2 1⁄4 in (57 mm) Boiler pressure 180 psi (1,241 kPa) Safety valve Ramsbottom (No. 850/1477) Cole's Pop (No. 851/1478) Heating surface 2,317 sq ft (215.3 m2)  • Tubes 2,131 sq ft (198.0 m2)  • Firebox 186 sq ft (17.3 m2) Cylinders Two Cylinder size 20 1⁄2 in (521 mm) bore 28 in (711 mm) stroke Valve gear Stephenson Valve type Murdoch's D slide Couplers Johnston link-and-pin

Performance figures Tractive effort 29,420 lbf (130.9 kN) @ 75%

Career Operators Cape Government Railways South African Railways Class SAR Class 4 Number in class 2 Numbers CGR 850-851 SAR 1477-1478 Delivered 1911 First run 1911 Withdrawn 1938

The leading coupled axle had flangeless wheels

The South African Railways Class 4 4-8-2 of 1911 was a steam locomotive from the pre-Union era in the Cape of Good Hope.

In 1911, the Cape Government Railways placed two steam locomotives with a 4-8-2 Mountain type wheel arrangement in service. They were renumbered and designated Class 4 when they were assimilated into the South African Railways a year later.

The first 4-8-2 Mountain type locomotive of the Cape Government Railways (CGR) was designed as a heavy mixed traffic engine at the Salt River shops by H.M. Beatty, the Chief Locomotive Superintendent of the CGR from 1896 to 1910. Two locomotives were built by the North British Locomotive Company (NBL) and delivered in March 1911.

The locomotives were a further development of the two experimental locomotives which had been placed in service by the CGR in 1906, the CGR Class 9 2-8-2 (SAR Class Experimental 5) and the CGR Class 10 4-8-0 (SAR Class Experimental 6), both built by Kitson and Company.

The Class 4 locomotives had 4 ¹⁄₂ inches (114 millimetres) thick bar frames, Stephenson valve gear with flat "D" slide valves arranged above the cylinders, and used saturated steam. The boiler was equipped with a combustion chamber which was carried forward 2 feet (610 millimetres) from the firebox into the boiler barrel, of which the diameter was increased at the hind course to suit. This reduced the distance between the tube plates to 18 feet (5,486 millimetres) and made them excellent steamers.

They were numbered 850 and 851 in the CGR numbering sequence, but were not designated a classification. The two engines were not identical, no. 850 being equipped with the usual Ramsbottom safety valves while no. 851 had Cole’s muffled type Pop safety valves, both set to open at 180 pounds per square inch (1,241 kilopascals) boiler pressure. They were delivered with Type XJ tenders with a 6 long tons 10 hundredweight (6.6 tonnes) coal and a 3,500 imperial gallons (15,900 litres) water capacity.