| South Australian Railways 620 class | |
|---|---|
| The preserved example of the 620 class, the SteamRanger 621 Duke of Edinburgh. | |
| Power type | Steam |
| Designer | P. J. Shea |
| Builder | South Australian Railways, Islington Workshops |
| Build date | 1936–1938 |
| Total produced | 10 |
| Configuration | 4-6-2 |
| UIC classification | 2′C1′h |
| Gauge | 5 ft 3 in (1,600 mm) |
| Driver diameter | 5 ft 6 in (1.676 m) |
| Length | 69 ft 8 in (21.23 m) |
| Axle load | 15 tons 18 cwt (35,600 lb or 16.1 t) |
| Locomotive weight | 81 tons 10 cwt (182,600 lb or 82.8 t) |
| Locomotive & tender combined weight |
140 tons 15 cwt (315,300 lb or 143.0 t) |
| Fuel type | Coal |
| Fuel capacity | 9 tons 0 cwt (20,200 lb or 9.2 t) |
| Water capacity | 5,200 imp gal (24,000 l) |
| Boiler pressure | 200 psi (1.4 MPa) |
| Firegrate area | 33.4 sq ft (3.10 m2) |
| Heating surface: Tubes |
1,560 sq ft (145 m2) |
| Heating surface: Firebox |
175 sq ft (16.3 m2) |
| Superheater area | 421 sq ft (39.1 m2) |
| Cylinders | Two |
| Cylinder size | 18.5 × 28 in (470 × 711 mm) |
| Valve gear | Baker |
| Tractive effort | 25,239 lbf (112.27 kN) |
| Career | South Australian Railways |
| Class | 620 |
| Number | 620–629 |
| Preserved | 621, 624 |
| Scrapped | 1964–1969 |
| Disposition | Two preserved, eight scrapped |
The South Australian Railways 620 class is a class of 10 4-6-2 Pacific steam locomotives built in the late 1930s, designed to operate on lightly laid 60-pound lines.
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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 (29.8 kg/m) rail branch lines of the SAR. The specification included the ability to haul a 200-long-ton (200 t) train up a 1-in-45 (2.2%) grade at 25 miles per hour (40 km/h).
Mr P.J. Shea, Chief Mechanical Engineer of the SAR designed a 140 ton Pacific type. A notable feature of the design, unique to South Australian Railways,[1] was the use of Baker valve gear in lieu of the more common Walschaerts valve gear.[2] The first locomotive (620) was completed at the SAR workshops at the Islington Workshops in 1936, with the tenth and final locomotive of the class (629) completed in 1938.
Class leader No. 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.[1] The remainder of the class were unstreamlined.
In service, the 620 class replaced the Q and S 4-4-0 types 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 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.
The 620 class was phased out in favour of Bluebird Railcars, although a spate of railcar failures in 1954–55 saw the 620 class return to service on the Port Pirie line.[2]
In 1994, 621 ran a special tour to Bacchus Marsh in Victoria, when the Melbourne-Adelaide line was still broad gauge. This was the first ever time a South Australian Railways Steam Locomotive had worked east into Victoria. With the standard gauge conversion imminent the tour would be last steam special hauled by a South Australian Steam Locomotive running on the Broad Gauge.
All but two of the locomotives were scrapped by 1969. One is preserved in working condition by SteamRanger (621) with the second (624) held in the Port Dock Museum.
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