Victorian Railways AA class
Encyclopedia
The AA class was an express passenger locomotive that ran on the Victorian Railways
between 1900 and 1932. The largest, heaviest and most powerful 4-4-0
steam locomotive
to run in Australia, it was the final development of this locomotive type in Australia.
2-4-0
which dated back to 1862. The 'New A' class 4-4-0
of 1889 had proven to be a successful design, as had its close cousin and exact contemporary the X class 0-6-0
. With traffic needs continuing to grow, the VR drafting office decided to take the best features of the New A and X class, but enlarge the locomotive with a larger, higher pressure boiler and larger cylinders.
s, horizontal grid spark arrestors, steam for auxiliaries supplied directly from the dome
, and a sloped ashpan to provide easier cleaning.
With a comparatively high 185 pound per square inches (1.3 MPa) boiler, later increased to 200 pound per square inches (1.4 MPa), it was considered impractical to use traditional slide valve
s. A trial installation of overhead piston valve
s on New A class locomotive No. 422 demonstrated considerably greater efficiency and reduced maintenance, and the AA became the first of many subsequent VR locomotive classes to be built with piston valves.
With an axle load
of 16.85 long tons (17.1 t), the AA had reached the design limits of size and power possible with a two coupled axle locomotive type with Victoria's relatively light track infrastructure. Its high tractive effort
and limited adhesive weight (due to axle load constraints and only two powered axles) combined to produce a less than ideal factor of adhesion
of 3.5. Future VR locomotive designs were based on three or four coupled axles.
Upon introduction in 1900, the AA went into service on mainline passenger service, hauling key express services such as the Sydney Express. They were chosen to haul the Royal Train
of the Duke
and Duchess of Cornwall
in 1901.
With the introduction of larger, heavier express passenger rolling stock in the form of the E type carriage
s of 1906, the VR introduced the considerably more powerful A2 class
4-6-0
in 1907, which superseded the AA class on premier services. However, the AA continued in service in assistant duties, as well as hauling show
and race
train specials.
mixed traffic locomotives which were introduced in 1902.
The second batch of AA locomotives utilised a bogie tender design based on that of the Dd in place of the original six wheel design, offering a far greater water capacity.
During 1923-24, Nos. 542, 544, 566 and 570 were fitted with Robinson superheater
s, based on the successful trial of Schmidt pattern superheaters on Dd 882. As was common VR practice at the time for locomotives converted to superheating, the boiler pressure was reduced - in this case to 175 pound per square inches (1.2 MPa) - to reduce maintenance and prolong boiler life. Nominal tractive effort was reduced to a quoted 19131 lbf (85.1 kN) at 85% boiler pressure, with total weight rising to 92.95 LT (94.4 t).
Another key improvement was the fitting of tablet exchangers to No. 552 and 570 for non-stop running on single-track sections of the North-eastern line, a portent of improvements on this line that would eventually lead to the non-stop Melbourne
-Albury
Spirit of Progress
service of 1937.
Bendigo service hauled by AA 564 and 544 crashed into the rear of an Up Ballarat
excursion service hauled by AA 534 and 'Old A' 202, resulting in the deaths of 44 people and the injury of over 400.
Withdrawals commenced in 1919 and by 1926 only the superheated AA locomotives remained on the register. A number of the boilers of the withdrawn locomotives saw further use powering river boats, while AA 532 served at Newport Workshops after withdrawal as a mobile stationary boiler.
By January 1932, the entire class had been recorded as withdrawn. They were all scrapped shortly after withdrawal, with the exception of Newport Workshops boiler locomotive AA 532, which lasted until 1940.
Victorian Railways
The Victorian Railways operated railways in the Australian state of Victoria from 1859 to 1983. The first railways in Victoria were private companies, but when these companies failed or defaulted, the Victorian Railways was established to take over their operations...
between 1900 and 1932. The largest, heaviest and most powerful 4-4-0
4-4-0
Under the Whyte notation for the classification of steam locomotives, 4-4-0 represents the wheel arrangement of four leading wheels on two axles , four powered and coupled driving wheels on two axles, and no trailing wheels...
steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
to run in Australia, it was the final development of this locomotive type in Australia.
History
In 1900, Victorian Railways still ran express passenger trains with the successful but ageing B classVictorian Railways B class
The B class was the first mainline diesel-electric locomotives in Victoria, Australia. The design was based on the successful General Motors EMD F-unit locomotives with the distinctive bulldog nose. They are a double ended streamliner locomotive, in contrast to North American practice...
2-4-0
2-4-0
Under the Whyte notation for the classification of steam locomotives, 2-4-0 represents the wheel arrangement of two leading wheels on one axle, four powered and coupled driving wheels on two axles, and no trailing wheels....
which dated back to 1862. The 'New A' class 4-4-0
4-4-0
Under the Whyte notation for the classification of steam locomotives, 4-4-0 represents the wheel arrangement of four leading wheels on two axles , four powered and coupled driving wheels on two axles, and no trailing wheels...
of 1889 had proven to be a successful design, as had its close cousin and exact contemporary the X class 0-6-0
0-6-0
Under the Whyte notation for the classification of steam locomotives, 0-6-0 represents the wheel arrangement of no leading wheels, six powered and coupled driving wheels on three axles, and no trailing wheels...
. With traffic needs continuing to grow, the VR drafting office decided to take the best features of the New A and X class, but enlarge the locomotive with a larger, higher pressure boiler and larger cylinders.
Design features
Innovative design features of the AA class included air sanding equipment, improved Gresham No. 9 injectorInjector
ʎ̩An injector, ejector, steam ejector, steam injector, eductor-jet pump or thermocompressor is a pump-like device that uses the Venturi effect of a converging-diverging nozzle to convert the pressure energy of a motive fluid to velocity energy which creates a low pressure zone that dɯaws in and...
s, horizontal grid spark arrestors, steam for auxiliaries supplied directly from the dome
Steam dome
A Steam dome is a vessel fitted to the top of the boiler of a steam locomotive. It contains the opening to the main steam pipe and its purpose is to allow this opening to be kept well above the water level in the boiler...
, and a sloped ashpan to provide easier cleaning.
With a comparatively high 185 pound per square inches (1.3 MPa) boiler, later increased to 200 pound per square inches (1.4 MPa), it was considered impractical to use traditional slide valve
D slide valve
The slide valve is a rectilinear valve used to control the admission of steam into, and emission of exhaust from, the cylinder of a steam engine.-Use:...
s. A trial installation of overhead piston valve
Piston valve
A piston valve is a device used to control the motion of a fluid along a tube or pipe by means of the linear motion of a piston within a chamber or cylinder.Examples of piston valves are:...
s on New A class locomotive No. 422 demonstrated considerably greater efficiency and reduced maintenance, and the AA became the first of many subsequent VR locomotive classes to be built with piston valves.
With an axle load
Axle load
The axle load of a wheeled vehicle is the total weight felt by the roadway for all wheels connected to a given axle. Viewed another way, it is the fraction of total vehicle weight resting on a given axle...
of 16.85 long tons (17.1 t), the AA had reached the design limits of size and power possible with a two coupled axle locomotive type with Victoria's relatively light track infrastructure. Its high tractive effort
Tractive effort
As used in mechanical engineering, the term tractive force is the pulling or pushing force exerted by a vehicle on another vehicle or object. The term tractive effort is synonymous with tractive force, and is often used in railway engineering to describe the pulling or pushing capability of a...
and limited adhesive weight (due to axle load constraints and only two powered axles) combined to produce a less than ideal factor of adhesion
Factor of adhesion
In railroad engineering, the factor of adhesion of a locomotive is the weight on the driving wheels divided by the starting tractive effort.A common rule is that for a steam locomotive a good factor of adhesion equals or exceeds 4, but not by too much...
of 3.5. Future VR locomotive designs were based on three or four coupled axles.
Production
Twenty of the class were built by the Phoenix Foundry in Ballarat, entering service between 1900 and 1903. The first batch of ten, delivered in 1900-01, were delivered with a traditional three-axle tender. The second batch had a slightly larger firebox and grate, a 200 psi boiler pressure and larger four-axle tenders.Service life
Victorian Railways Royal Train
The Victorian Railways operated Royal Trains to transport members of the Monarchy of Australia on their Royal visits to Australia. The same carriages were also used for a number of vice-regal trains for the Governor-General of Australia and the Governor of Victoria...
of the Duke
George V of the United Kingdom
George V was King of the United Kingdom and the British Dominions, and Emperor of India, from 6 May 1910 through the First World War until his death in 1936....
and Duchess of Cornwall
Mary of Teck
Mary of Teck was the queen consort of the United Kingdom and the British Dominions, and Empress of India, as the wife of King-Emperor George V....
in 1901.
With the introduction of larger, heavier express passenger rolling stock in the form of the E type carriage
E type carriage
The E type carriages were wooden express passenger carriage used on the railways of Victoria, Australia. Introduced by Victorian Railways Chairman of Commissioners Thomas James Tait and based on Canadian carriage design, the class remained in regular service for 85 years.-Design:Carriages on...
s of 1906, the VR introduced the considerably more powerful A2 class
Victorian Railways A2 class
The A2 class was an express passenger locomotive that ran on Victorian Railways from 1907 to 1963. A highly successful design entirely the work of Victorian Railways' own design office, its long service life was repeatedly extended as economic depression and war delayed the introduction of more...
4-6-0
4-6-0
Under the Whyte notation for the classification of steam locomotives, 4-6-0 represents the wheel arrangement of four leading wheels on two axles in a leading truck, six powered and coupled driving wheels on three axles, and no trailing wheels. This wheel arrangement became the second-most popular...
in 1907, which superseded the AA class on premier services. However, the AA continued in service in assistant duties, as well as hauling show
Agricultural show
An agricultural show is a public event showcasing the equipment, animals, sports and recreation associated with agriculture and animal husbandry. The largest comprise a livestock show , a trade fair, competitions, and entertainment...
and race
Horse racing
Horse racing is an equestrian sport that has a long history. Archaeological records indicate that horse racing occurred in ancient Babylon, Syria, and Egypt. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 648 BC...
train specials.
Design improvements
The AA class inherited a number of design improvements from the Dd classVictorian Railways Dd class
The Dd class was a passenger and mixed traffic steam locomotive that ran on Victorian Railways from 1902 to 1974...
mixed traffic locomotives which were introduced in 1902.
The second batch of AA locomotives utilised a bogie tender design based on that of the Dd in place of the original six wheel design, offering a far greater water capacity.
During 1923-24, Nos. 542, 544, 566 and 570 were fitted with Robinson superheater
Superheater
A superheater is a device used to convert saturated steam or wet steam into dry steam used for power generation or processes. There are three types of superheaters namely: radiant, convection, and separately fired...
s, based on the successful trial of Schmidt pattern superheaters on Dd 882. As was common VR practice at the time for locomotives converted to superheating, the boiler pressure was reduced - in this case to 175 pound per square inches (1.2 MPa) - to reduce maintenance and prolong boiler life. Nominal tractive effort was reduced to a quoted 19131 lbf (85.1 kN) at 85% boiler pressure, with total weight rising to 92.95 LT (94.4 t).
Another key improvement was the fitting of tablet exchangers to No. 552 and 570 for non-stop running on single-track sections of the North-eastern line, a portent of improvements on this line that would eventually lead to the non-stop Melbourne
Melbourne
Melbourne is the capital and most populous city in the state of Victoria, and the second most populous city in Australia. The Melbourne City Centre is the hub of the greater metropolitan area and the Census statistical division—of which "Melbourne" is the common name. As of June 2009, the greater...
-Albury
Albury, New South Wales
Albury is a major regional city in New South Wales, Australia, located on the Hume Highway on the northern side of the Murray River. It is located wholly within the boundaries of the City of Albury Local Government Area...
Spirit of Progress
Spirit of Progress
The Spirit of Progress was the premier express train passenger service on the Victorian Railways in Australia, running from Melbourne to the Victorian border, and later through to Sydney.-Route:...
service of 1937.
Accidents
Three AA class locomotives were involved in the Sunshine rail disaster of 1908, when an UpRailroad directions
Railroad directions are used to describe train directions on railroad systems. The terms used may be derived from such sources as compass directions, altitude directions, or other directions...
Bendigo service hauled by AA 564 and 544 crashed into the rear of an Up Ballarat
Ballarat railway line, Victoria
The Serviceton railway line is a railway serving the west of Victoria, Australia. The line links the state capital of Melbourne to the cities of Ballarat and Ararat, and once extended to the South Australian border as part of the Melbourne-Adelaide railway...
excursion service hauled by AA 534 and 'Old A' 202, resulting in the deaths of 44 people and the injury of over 400.
Withdrawal and scrapping
The AA class was gradually made redundant by the delivery of large numbers of 4-6-0 locomotives of the new Dd and A2 classes between 1902 and 1922, which eventually totalled 446 locomotives. The A2 offered considerably more power, while the Dd offered similar tractive effort to the AA but much greater route availability due to its lower axle load.Withdrawals commenced in 1919 and by 1926 only the superheated AA locomotives remained on the register. A number of the boilers of the withdrawn locomotives saw further use powering river boats, while AA 532 served at Newport Workshops after withdrawal as a mobile stationary boiler.
By January 1932, the entire class had been recorded as withdrawn. They were all scrapped shortly after withdrawal, with the exception of Newport Workshops boiler locomotive AA 532, which lasted until 1940.
External links
- VPRS 12903/P1 Box 299/04 Drawing of original series AA class steam locomotive with three axle tender
- VPRS 12903/P1 Box 299/05 Drawing of later series AA class steam locomotive with four axle tender
- VPRS 12800/P1 H 3750 Sydney Express at Wodonga, comprising E class cars, hauled by the later series AA No.556 with four axle tender.
- VPRS 12800/P1 H 1137 Original series AA class steam locomotive No.544, with three axle tender and original livery with polished brasswork, hauling Sydney Express (possibly at Broadmeadows) circa 1900.