|South Australian Railways 520 Class|
|520 as preserved|
|V - E - T - D|
The 520 Class is a 4-8-4 "Northern" type steam locomotive, of the South Australian Railways that operated in regular revenue service from 1943 to 1967.
Designed and constructed during World War 2, the South Australian Railways 520 class 4-8-4s helped fill gaps in the motive power requirements of that railway caused by the additional traffic generated by the conflict. More powerful engines with greater route availability were required and thus the new locomotives were designed with a conservative axle loading, facilitating their use on secondary country routes in addition to the heavier rails of the main lines. They could haul heavy trains at the maximum lines speeds permissible and take all but the heaviest trains up the 1 in 45 gradients of the tortuous Adelaide Hills route unassisted. Combining the best features of the 620 Class 4-6-2's and 500B Class 4-8-4's that preceded them, the 520 class also featured many modern elements designed to improve performance, reduce maintenance and lower operating costs. They were also streamlined in a fashion similar to the T1 Duplex 4-4-4-4 locomotives of the Pennsylvania Rail Road (although most were partly de-streamlined during their service life)
During the late1940's-early1950's, many of the class were converted to a locally-designed Coal-Oil firing system to compensate for issues associated with the poor quality coal supplies at the time. The Class was eventually superseded by Diesel power in the 1950's and 60's, the last to be scrapped meeting it's end in 1971.
Two members of the class survive to the present day;
- The class leader, 520 (original streamlining style complete with front pilot cowling) is in the care of the South Australian division of the Australian Railway Historical Society (trading as SteamRanger Heritage Railway) and was returned to service for heritage train duties in 1971/2. Repainted to it's original Hawthorne Green livery in 1978, it operated with SteamRanger on mainline tours and on the Victor Harbour Tourist Railway until placed in storage at the end of the 1998 running season. It will require extensive and costly mechanical work (primarily associated with a reversion to coal firing and tender frame corrosion) before it is fit for service again. As of August 2017, privately funded work has been begun to reconstruct the locomotive's life-expired tender, but significant fundraising efforts will be required to facilitate the remainder of the work necessary for a return to operational status.
- 523 survives in static preservation at the National Rail Museum in Port Adelaide, South Australia. Withdrawn following a major mechanical failure on an enthusiasts tour in 1968, the locomotive spent many years in the open air at the Museum's original Mile End site, before being transferred to the current Museum complex at Port Adelaide in 1988. It is displayed in it's 1950's/60's guise with lined black livery and minus it's front pilot cowling. Due to display changes at the museum in recent years, the locomotive is currently sited in the historic Port Adelaide Goods Shed (part of the Museum precinct), rather than in the climate-controlled main pavilion, the only one of the museum's preserved 'big power' locomotives so relegated.
The 520 Class weighs 204 tonnes and has an axle load of 16.1 tonnes. The welded steel boiler operates at 215 psi for a maximum 36,600lbs of Tractive Effort (2,800 drawbar horsepower). The firebox possesses a grate area of 42 square feet (4.2 m^2). The cylinders are 20.5 inches (521 mm) in bore and 28 inches (711 mm) in stroke. The driving wheels are 66 inches (1.68 m) in diameter
Originally, the 520 class tenders (riding on six-wheel cast steel bogies) could carry 9 tons of coal and 9100 gallons (41,000 litres) of water, although they were limited to loads of 5 tons of coal and 8200 gallons of water (37,277 litres) when running on secondary lines constructed with 60lb rail.
- The 520 was the first engine class in South Australia (if not in Australia more broadly) to feature an all welded steel boiler and firebox.
- The 520's had several other modern features such as Timken roller bearings on all axles (the first locomotive in Australia so fitted), one piece cast steel bar frames, thermic siphons in the firebox, power reversing gear, a self cleaning smokebox and several other modern features.
- The design was built combining the best design features of the 620 class Light Pacifics (4-6-2) and the powerful 500B class Northerns (4-8-4) with a stated design intent of matching both the haulage capacity of the 600 class Heavy Pacifics and the route availability of the 620 class.
- The first three locomotives (520-522) were built with a less prominent streamlined front end compared to 523-532, which had a higher and more rakish design, more in keeping with style of the PRR T1 Duplexes which inspired their designer, F. J Harrison (Chief Mechanical Engineer of the SAR)
- As part of a commission by the Post-War Australian Government's Rail Standardiation Project, the SAR Engineering department used the design of the 520 Class as the basis for a proposed 4-8-4 express engine to supersede existing express passenger locomotives on the Trans-Australian Railway between Port Pirie, (South Australia) and Kalgoorlie (Western Australia). The proposed locomotives would run on standard gauge tracks (4' 8.5"/ 1,435 mm), have 72 inch (1.83 meter) diameter driving wheels and a 16-wheel high-capacity tender. However, political and budgetary pressures to use diesel power in the recapitalisation plans saw steam plans dumped in favour of internal combustion (Diesels were acquired to replace the legacy steam fleet from 1951).
- The South Australian Railways also had plans for further 4-8-4 construction in the late 1940's-early 1950's. Proposals were developed for additional members of the 520 class with minor modifications to keep abreast of current best practice in steam design. Other proposals proposed an entirely new class of locomotive (to be known as the 800 class) intended to supplement/supersede the existing 500B class 4-8-4s on the heaviest passenger and freight work. These locomotives, although un-streamlined, would incorporate many design features introduced on the 520 class and were to have exceeded the tractive effort of both the 500Bs and Victorian Railways H Class 4-8-4's, becoming the most powerful non-articulated steam locomotives in Australia. However, due to political and budgetary pressures to adopt diesel power these locomotives were never constructed. Their intended place on the motive power roster was filled by the locally-built 900 class Diesel Electrics, the first of which entered service in 1951.