WAGR S Class

WAGR S class
Preserved S549 Greenmount at Harvey following restoration to working condition
Type and origin Power type Steam Designer Frederick Mills Builder Midland Railway Workshops Build date 1943-1947 Total produced 10
Specifications Configuration: ​  • Whyte 4-8-2 Gauge 1,067 mm (3 ft 6 in) Total weight 119 long tons 6 cwt (267,200 lb or 121.2 t) Fuel type Coal Fuel capacity 7 long tons 0 cwt (15,700 lb or 7.1 t)/ 9 long tons 0 cwt (20,200 lb or 9.1 t) Water cap 5,000 and 3,500 imp gal (23,000 and 16,000 L; 6,000 and 4,200 US gal) Firebox:  • Firegrate area 40 sq ft (3.7 m2) Boiler pressure 200 lbf/in2 (1,379 kPa) Cylinder size 19 in × 24 in (483 mm × 610 mm) Loco brake Steam (locomotive) Vacuum (tender)
Performance figures Tractive effort 30,685 lbf (136.49 kN)
Career Operators Western Australian Government Railways Numbers S541-S550 Retired 1971-1972 Preserved S542, S547, S549 Disposition 3 preserved, 7 scrapped

The WAGR S class was a class of 4-8-2 steam locomotives built by the Midland Railway Workshops between 1943 and 1947 and operated by the Western Australian Government Railways (WAGR).

The S class locomotives were built with a 4-8-2 wheel arrangement, a configuration commonly used in Australia for heavy goods locomotives, smaller driving wheels giving increased tractive effort at the cost of reduced speed.

In the 1920s and 1930s the West Australian rail system was thoroughly run down. The vast majority of locomotives were well past their useful service life and many were badly in need of repairs. The P and Pr classes had helped alleviate pressure on aging passenger locomotives when introduced in 1924 and 1938 respectively, but more powerful machines were needed with an order for 10 authorised.

The first three were built in 1943, with the remaining seven deferred while Midland Railway Workshops completed its order for 10 Australian Standard Garratts for the Commonwealth Land Transport Board. A further two were completed in 1945, with the remaining five deferred again until 1947 while the Dm and Dd classes were built.

The class was initially intended for service on both passenger and goods services on the Eastern Goldfields Railway between Perth and Kalgoorlie, though following World War II they worked primarily on the South Western Railway. After suffering from a range of early problems (which led to controversy involving the designer Frederick Mills), the class became highly popular and was very successful.