WAGR P and Pr classes

The WAGR P and Pr classes are two classes of 4-6-2 "Pacific" type steam locomotives designed for express passenger service on the Western Australian Government Railways 3 ft 6 in (1,067 mm) narrow gauge mainline network. The initial designs were prepared by E.S. Race^[2] 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 West Australian stage of the Trans-Australian Railway, the 'Westland Express'.^[3]

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.^[4] The Great Depression of the 1930s, coupled with the effects of The Great War, thwarted the WAGRs 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 the Second World War. The new locomotives became the first WAGR engines to be given names, each bearing that of a prominent West 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.^[5] All eighteen locomotives were officially classified as the 'Pr Class' in 1946.^[6]

The initial ten P class locomotives were built for the WAGR by the North British Locomotive Company in Glasgow while the remainder, including the new ten Pr class locomotives, were built locally by the WAGRs Midland Government Railway Workshops in Midland near Perth.^[4] One example of the P class (P 508) and one example of the Pr class (class leader Pr 521 Ashburton) are preserved in non-working order at the Australian Railway Historical Society's Rail Transport Museum in Bassendean, Perth.^[7]

Background

By the early 1920s the WAGR had obtained only a handful of new locomotive designs since the beginning of the twentieth century and there was a particular lack of large passenger locomotives.^[8] The Annual Report of 1920 pointed out the large numbers of obsolete locomotives in service and steadily growing rail traffic, stressing the need for more powerful engines.^[2] The most substantial design then in service was the E class 4-6-2s of 1902, of which 65 locomotives had been built for operation in Western Australia and served on a variety of services. Likewise the 20 D class 4-6-4T tank locomotives had helped alleviate pressure on suburban services while the 57 F class 4-8-0s did the same for goods. However, all had been introduced (and subsequently superheated) prior to the First World War, meaning that by the 1920s they were becoming inadequate. At this time the most significant operation requiring new locomotives were the long distance passenger services, particularly on the Perth - Kalgoorlie and Perth - Albany expresses, both of which covered distances in excess of 350 kilometres.^[8]

In 1923 approval was given for the construction of ten new superheated pacific type locomotives for operation on heavier mainline rails, suitable for the hauling of the expresses. The locomotives were based on plans drawn up in 1920 under Chief Mechanical Engineer of the WAGR Ernest A. Evans which called for a new design with large diameter driving wheels, a large firebox and a two-wheel trailing wheel for stable operation at speed.^[2] The final outline drawings were prepared by E.S. Race in the Midland Railway Workshops and completed in December 1923. Influence for the new P class designs were drawn from both the New Zealand Railways Ab and the Tasmanian R class pacifics.^[2]

Details of design

While initial plans called for a round-top firebox (such as featured on the New Zealand Ab class), the P class was eventually designed and delivered with Belpaire fireboxes, which improve steam production over the more traditional round-top types, but are harder to fit. The P class locomotives featured a wide firebox located behind the coupled wheels and supported by a trailing-wheel.^[2] The large firebox aided with the use of poor-grade local coal from the Collie coalfields, south of Perth. This low quality coal had frequently resulted in poor steaming in earlier locomotives,^[9] but the P class design largely avoided this problem, resulting in a locomotive 30% more economical than the earlier F class engines of similar tractive effort.^[2] The P and Pr class also featured innovations to alter the weight-distribution between the driving and trailing wheels, improving adhesive traction.

Two types of tender were used by the P and Pr class locomotives. The original tender (as designed) had a water capacity of 2,800 imperial gallons and a coal capacity of 8 tons. These were built with the initial builds of the 10 P and 10 Pr class locomotives. The remaining 15 P class locomotives (all locally constructed) were fitted with modified R Class tenders which were shorter, and had been upgraded to have a water capacity of 2,440 gallons and 7 tons of coal.^[6] These short tenders were distinctive and referred to as the 'bob-tailed' tenders.

Construction history

It was the North British Locomotive Company of Glasgow, Scotland which secured the order for the P class locomotives in 1924, ahead of several other companies including the Victorian Thompson & Co of Australia. North British was to supply ten locomotives with delivery inside of 33-weeks, which would be in time for the 1924/1925 wheat harvest when the introduction of the P class locomotives would free up other locomotives for use on wheat trains.^[10] Accordingly, six locomotives entered traffic in December 1924, followed by an additional four in the February 1925.^[2]

The next batch of ten P class locomotives were constructed locally in Western Australia in 1927, at the Midland Railway Workshops. They were identical to the North British locomotives excepting the short tenders rebuilt from those of the obsolete R class engines. This order was extended by an additional five locomotives which were delivered in 1929, giving the total-build for the class at twenty-five locomotives.^[4] Several exchanges of tenders occurred throughout the service life of the P and Pr class locomotives, such as exchanging the long tender of an unconverted P class locomotive for the short tender of a later Pr class engine.^[11]

The P class locomotives were given the numbers P441-P465 in order of delivery, with 451-465 being delivered with short tenders.

Pr class modifications

By the late 1930s, with even more engines requiring urgent maintenance and repairs, orders were placed for an additional ten P class locomotives which would be improved through modifications to the boilers, bogies, headlights and valve gear. These new locomotives were constructed at the Midland Railway Workshops.^[10] The boilers featured an increase in pressure from 160 to 175psi, which provided more power, and the bogies were constructed in cast steel.^[6] These improved locomotives were delivered to the same operating specifications as the original P class, with the same weight distribution and boiler pressure limited to 160 psi, though improvements to the track and bridges on the Perth-Kalgoorlie railway in 1940 meant that they could be altered to use their designed power^[6] through the increasing of the axle load from 12.8 to 14.2 tons^[12] and the resetting of the boiler-top safety valves to 175 psi. The result was a 9% increase in tractive effort with the same economical running of the P class.^[5]

The Pr class were numbered 138-147 and were further distinguished from other classes by the placement of running-board nameplates; each locomotive bearing the name of a prominent West Australian river, such as Ashburton, Avon and Chapman. For this reason the class was initially known as the 'River class'.^[8] They were the first W.A.G.R. locomotives to be given names.

The Pr class proved such a success that it was decided to convert eight of the locally-constructed P class locomotives to Pr standard. Numbers 453-457, 459,461 and 464 were rebuilt in this way and the naming practise was continued. These conversions retained their short tenders, and were completed between June 1941 and June 1944, when the demands of wartime traffic required more powerful locomotives.^[5]

Following the war ten of the class were converted to oil burners in 1947 and again in 1949 due to industrial trouble on the Collie coalfields, where the WAGR obtained its coal fuel. These conversions were temporary, lasting only as long as the lack of fuel prevailed.^[11] In later years the boilers were modified to be interchangeable with the Pm and Pmr class locomotives, which were introduced in 1949.^[6]

Service history

The P class locomotives proved to be an excellent design, being free steaming and easy to operate.^[4] They quickly reduced the need for bank engines which were normally need to provide extra power up the steep gradients across the Darling Scarp. In addition to saving time and resources, this freed up additional badly needed locomotives.^[2] Better economy also allowed for higher running distances without stops for resupply and higher speeds made for more efficient running of the expresses on which the P class served, primarily on the Great Southern Railway and Eastern Goldfields railways to Albany and Kalgoorlie respectively. Experiments into engine pooling with the P class on the GSR in 1932 led to the adoption of this practice across the system, freeing up further locomotives for other duties.^[6]

The introduction of the Pr class revolutionised passenger travel, and as part of a national commitment to shaving a day off the transcontinental express the WAGR introduced the Westland Express in 1938.^[3] The use of Pr class locomotives helped to reduce travel times across the West Australian stage of the journey by more than two hours, accompanied by an increase in the permissible load of 300tons by additional 20.

During the 1940s both P and Pr class locomotives were used extensively on troop trains, while civilian patronage also increased during this time.^[13] The increased war traffic was so great that it necessitated the conversion of the 8 P class locomotives to Pr standard at a time when lack of available resources and labour had stalled the production of new locomotives, such as the S class until 1943.^[10] Both during and following the war the Pr class remained the premier express locomotive, while the P class continued on secondary passenger services, concentrated in the states' South West around Albany,^[8] particularly on the GSR.

The introduction in 1949 of thirty-five Pm and Pmr class Pacifics was originally intended to oust the Pr locomotives from express services the later designs proved unstable at speed and were transferred instead to fast goods workings, leaving the Pr class as the only express locomotive in the WAGR.^[14] The introduction of X class Diesels in 1954, however, ended their long tenure in this position and both P and Pr class locomotives were gradually relegated to goods and shunting duties.^[4] Their adequate tractive effort and economy, however, ensured their survival until the very end of steam.^[11]

The P class were withdrawn between January 1968 and October 1969. With the exception of Pr 528 Murray, which was destroyed by a fire while on-shed at Kalgoorlie in 1950 following an oil leak while operating as an oil-burner, the Pr class were withdrawn between September 1967 and 1970 when class leader Pr 521 Ashburton became the last to be withdrawn on 10 September.^[11]

Livery and numbering

When introduced the P class locomotives were painted in overall black with red buffer beams, in keeping with WAGR livery policies of the time. The Pr class wore both the overall black livery and a paint scheme with black smoke boxes, tenders and cabs with grey boilers lined in black.^[11] The W class of 1951 introduced the Larch Green with black smoke boxes and red buffer beams livery to Western Australia and this was applied to the majority of tender locomotives, including the P and Pr classes.^[8]

The twenty-five P class locomotives originally bore the numbers P 441-P 465, but the surviving class members were renumbered P 501-P 517 in 1947. The initial batch of 10 Pr class engines were numbered Pr 138-Pr 147, while the eight later conversion retained their P class numbers. The 'Pr class' designation was only adopted officially on locomotive registers in 1946, and accordingly saw the class renumbered Pr 521-Pr 538.^[11]

Preservation

Two locomotives of the P/Pr class have been preserved. Neither is in working condition.^[7]

• P 508 (originally P 448) was delivered to the Australian Railway Historical Society museum in October, 1971, after being withdrawn from service in February 1969. It was the only P class locomotive to survive, and remains in original livery in non-working condition at the Bassendean Rail Transport Museum as of early 2009.

• Pr class leader, Pr 521 Ashburton. was similarly given to the ARHS museum in October, 1971, just under one year after being withdrawn. Ashburton had served with distinction, being (along with Pr 522 Avon) one of the two Pr class locomotives in service at the time of the launching of the Westland express in 1938, and was thus the flagship of sorts of the W.A.G.R. fleet at the time. It remains in larch-green livery in non-working condition at the Bassendean Rail Transport Museum as of early 2009.

Class lists

P class lists

The numbers and periods in service of each member of the P class were as follows:^[15]

Pr class list

The numbers, names and periods in service of each member of the Pr class were as follows:^[16]

See also

• History of rail transport in Western Australia
• List of Western Australian locomotive classes

References

Notes

Bibliography

External links

Media related to WAGR P and Pr classes at Wikimedia Commons

• Rail Heritage WA Page with preserved examples

Classes of locomotives of the Western Australian Government Railways (WAGR/Westrail) Tender (3 ft 6 in (1,067 mm)) A C/Ca E/Es Ec F/Fs G I J L M O Oa P (1896) P/Pr Pm/Pmr Q R/Ra S T U V W Tank (narrow gauge) B C (1880) D (1884) D/Ds Dm Dd E F (1892) H I K (1891) K N Q (1895) S (1888) U (1903) Ut Garratt (narrow gauge) ASG M/Ms Msa Diesel-hydraulic (narrow gauge) B E (ex MRWA) M/MA Diesel-mechanical (narrow gauge) Z Diesel-electric (narrow gauge) A/AA/AB C D/DA DB F (ex MRWA) G (ex MRWA) N/NA P R/RA S T/TA X Y Diesel-electric (standard gauge) H J K KA L NB Q Rail transport in Western Australia Transperth trains Western Australian Government Railways Westrail