South Australian Railways 620 class

Infobox Locomotive
name = South Australian Railways 620 class
powertype = Steam


caption = The preserved example of the 620 class, the SteamRanger 621 "Duke of Edinburgh".
data for = 621
designer = P. J. Shea
builder = South Australian Railways, Islington Workshops
builddate = 1936–1938
totalproduction = 10
gauge = RailGauge|63|lk=on
whytetype = 4-6-2
uicclass = 2'C1'h
length = convert|69|ft|8|in|m|2|abbr=on
driversize = convert|5|ft|6|in|m|3|abbr=on
weight = convert|140.75|LT|t|lk=on
tenderc
Coal: convert|9|LT|t;
Water: convert|5200|impgal|l|abbr=on|lk=on
weightondrivers =
cylindercount = Two
cylindersize = 18½×28 in (470 × 710 mm)
valvegear = Baker
tractiveeffort = convert|25000|lbf|kN|abbr=on|lk=on at 85% BP
axleload = convert|15.9|LT|t
boilerpressure = convert|200|psi|MPa|abbr=on|lk=on
firearea = convert|33.4|sqft|m2|abbr=on
fireboxarea = convert|175|sqft|m2|abbr=on
superheaterarea = convert|421|sqft|m2|abbr=on
tubearea = convert|1560|sqft|m2|abbr=on
railroad = South Australian Railways
railroadclass = 620
roadnumber = 620–629
preservedunits = 621, 624
scrapdate =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.

Development of the 620 class

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 convert|200|LT|t|sing=on train up a 1-in-45 (2.2%) grade at convert|25|mi/h|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,cite web| url=http://www.nationalrailmuseum.org.au/exhibits/nrm_624.html| title= National Railway Museum - Port Adelaide (620-class 4-6-2 locomotive No.624)| publisher=www.nationalrailmuseum.org.au| |accessdate=2007-06-18] was the use of Baker valve gear in lieu of the more common Walschaerts valve gear.cite web| url=http://www.steamranger.org.au/enthusiast/steam.htm| title= SteamRanger Enthusiast Page - Steam Locos| publisher=www.steamranger.org.au| |accessdate=2007-06-18] The first locomotive (620) was completed at the SAR workshops at Islington 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. 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.

In 1994, 621 ran a special tour to Bacchus Marsh in Victoria, when the Melbourne-Adelaide line was still 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.

References

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External links

* [http://images.slsa.sa.gov.au/mpcimg/24040/B24028.htm State Library of South Australia] photograph of streamlined locomotive 620 "Sir Winston Duggan" travelling through the Mount Lofty Ranges, South Australia
* [http://www.csse.monash.edu.au/~ajh/trains/sa/620class/index.html 620class:SA:Trains:AJH] Photographs and further details of the 620 class courtesy John Hurst
* [http://www.steamranger.org.au/enthusiast/steam.htm SteamRanger website] steam locomotive information page