South Australian Railways 620 class

South Australian Railways 620 class

621 Duke of Edinburgh at Victor Harbor in June 2006

Type and origin Power type Steam Designer Fred Shea Builder Islington Railway Workshops Build date 1936-1938 Total produced 10

Specifications Configuration 4-6-2 Gauge 5 ft 3 in (1,600 mm) Driver dia. 5 ft 6 in (1.676 m) Length 69 ft 8 in (21.23 m) Axle load 15 long tons 18 cwt (35,600 lb or 16.2 t) Adhesive weight 47 long tons 5 cwt (105,800 lb or 48 t) Loco weight 81 long tons 10 cwt (182,600 lb or 82.8 t) Total weight 140 long tons 15 cwt (315,300 lb or 143 t) Fuel type Coal Fuel capacity 9 long tons 0 cwt (20,200 lb or 9.1 t) Water cap 5,200 imp gal (24,000 l) Firebox:  • Firegrate area 33.4 sq ft (3.10 m2) Boiler pressure 200 psi (1,379 kPa) Heating surface:  • Tubes 1,560 sq ft (145 m2)  • Firebox 175 sq ft (16.3 m2) Superheater: ​  • Heating area 421 sq ft (39.1 m2) Cylinders 2 Cylinder size 18.5 in × 28 in (470 mm × 711 mm) Valve gear Baker

Performance figures Tractive effort 25,239 lbf (112.27 kN)

Career Operators South Australian Railways Numbers 620-629 Preserved 621, 623 Scrapped 1964-1969 Disposition 2 preserved, 8 scrapped

The South Australian Railways 620 class was a class of 4-6-2 steam locomotives operated by the South Australian Railways.

The completion of the South Australian Railways (SAR) broad gauge route between Adelaide and Port Pirie created a need for a fast, light passenger locomotive to haul this service, as well as other traffic on the lightly laid 60 lb/yd (29.8 kg/m) rail branch lines of the SAR. The specification included the ability to haul a 200-long-ton (200 t; 220-short-ton) train up a 1-in-45 (2.2%) grade at 25 miles per hour (40 km/h).

Fred Shea, Chief Mechanical Engineer of the SAR designed a 140-ton Pacific type. A notable feature of the design, unique to South Australian Railways, was the use of Baker valve gear in lieu of the more common Walschaerts valve gear. The first locomotive was completed at the Islington Railway Workshops in 1936, with the last completed in 1938.

Class leader 620 was also notable for being Australia's first streamlined locomotive, the smokebox being covered with a chromed steel grille similar to those fitted to motor cars of the period, and painted Hawthorn green with yellow stripes. The press of the time described 620's appearance as 'a bit of fluff'. The remainder of the class was unstreamlined.

In service, the 620 class replaced the Q and S classes on branchline services, where they proved quite successful. With the introduction of the more powerful and modern 520 class from 1943, these locomotives were relegated to the Willunga, Bridgewater and Tailem Bend passenger services, as well as continued service on Murray Mallee line services (the locomotives' light axle loading providing good route ability plus the "get up and go" characteristics common to large wheeled Pacific type locomotives.