WAGR P and Pr classes

WAGR P class
P508 at the Western Australian Rail Transport Museum
Type and origin Power type Steam Designer E.S. Race Builder North British Locomotive Company & Midland Railway Workshops Build date 1924-1929 Total produced 25 Rebuilder Midland Railway Workshops Rebuild date 1941-1944 Number rebuilt 8 as Pr class
Specifications Configuration: ​  • Whyte 4-6-2 Gauge 3 ft 6 in (1,067 mm) Driver dia. 4 ft 0 in (1,219 mm) Length 62 ft 2 in (18.95 m) Total weight 102 long tons 5 cwt (229,000 lb or 103.9 t) Fuel type Coal Fuel capacity 7 long tons 0 cwt (15,700 lb or 7.1 t)/ 8 long tons 0 cwt (17,900 lb or 8.1 t) Water cap. 2,440 imp gal (11,100 L; 2,930 US gal)/ 2,800 imp gal (13,000 L; 3,400 US gal) Firebox: ​  • Grate area 35 sq ft (3.3 m2) Boiler pressure 160 lbf/in2 (1,100 kPa)
Performance figures Tractive effort 23,638 lbf (105.15 kN) Factor of adh. 3.6
Career Operators Western Australian Government Railways Numbers P441-P465 (as delivered), renumbered P501-P517 in 1947 Last run 1969 Preserved P508 Disposition 1 preserved, 24 scrapped

The WAGR P and Pr classes were two classes of 4-6-2 steam locomotives designed for express passenger service on the Western Australian Government Railways mainline network. The initial designs were prepared by E.S. Race^[1] and together the two classes had a total build number of thirty-five locomotives, the P and Pr classes entering service in 1924 and 1938 respectively. Both classes were used on express passenger services, greatly improving the economy and speed of long-distance passenger travel in Western Australia, the results of which were most visible on the Western Australian stage of the Trans-Australian Railway and Westland Express.^[2]

The need for more powerful locomotives in the 1920s resulted in the introduction of twenty-five P class locomotives which provided a significant improvement in power, speed and economy over previous WAGR locomotives, quickly proving to be a highly successful design.^[3] The Great Depression of the 1930s, coupled with the effects of the Great War, thwarted the WAGR's later expansion and acquisition plans resulting in many obsolete locomotives remaining in operation into this period. As a result ten new P class locomotives featuring detail improvements to boilers, valves and bogies were introduced in 1938, a year before the outbreak of World War II. The new locomotives became the first WAGR engines to be given names, each bearing that of a prominent Western Australian river. These 'River class' locomotives were very successful and proved so invaluable to the operation of the wartime WAGR that eight P class locomotives were modified to their standard.^[4] All eighteen locomotives were officially classified as the Pr class in 1946.^[5]

The initial ten P class locomotives were built by the North British Locomotive Company in Glasgow while the remainder, including the ten Pr class locomotives, were built locally by the Midland Railway Workshops.^[3]