The Victorian Railways H class was an express passenger steam locomotive operated by the Victorian Railways from 1941 to 1958. Intended to eliminate the use of double heading A2 class locomotives on The Overland services on the steeply graded Western line to Adelaide, wartime restrictions led to only one locomotive being built. Nicknamed Heavy Harry, H220 was the largest locomotive ever built in Australia and the largest non-articulated steam locomotive to run on Australian railways.
History
By 1923, the A2 class 4-6-0 locomotives, which dated back to 1907, were frequently double-heading on interstate expresses to Serviceton and Albury, because increasing traffic saw loads exceed the eight-car maximum of a single A2. The Victorian Railways Commissioners recommended considerably more powerful locomotives, that could haul trains of up to eleven cars unassisted over the ruling gradients on those lines. The S class 4-6-2 Pacifics displaced the A2s from North East line express services from 1928 onwards and allowed a faster timetable to be introduced. However, a Pacific-type locomotive was not well suited to the Western line. The section between Melbourne and Ballarat had sharply-curved, steep inclines, the most notorious of which was the , 1 in 48 (2.08%) ruling gradient of the Ingliston Bank. As early as 1923, VR locomotive designers were considering 4-8-2 Mountain-type locomotives for the purpose, along with the use of a third cylinder to provide increased power without exceeding the loading gauge.
Design brief
In 1936, the Victorian Railways Design Office finalised the major design requirements for a steam locomotive that was capable of hauling a load of at a minimum up the Ingliston Bank unassisted. In order to develop the power required, a very large grate and a very large boiler were needed, and the 4-8-4 wheel arrangement enabled that, because its four-wheeled trailing truck could support a large firebox, and four coupled axles would support a large boiler and ensure a good factor of adhesion.
VR designers wanted to improve on aspects of the earlier S class design. Those three-cylinder Pacifics, although capable of hauling heavy loads at high speed, had proved to be relatively maintenance-intensive, particularly with regard to servicing the valve gear and motion for the third (inside) cylinder. The Gresley conjugated valve gear, driven from the valve spindles of the outside cylinder piston valves, was prone to heat expansion and wear, causing timing difficulties, and it required dismantling and removal whenever the centre cylinder valve needed to be serviced.
To overcome those problems, the H class was provided with a significantly different arrangement for its third cylinder. Rather than the Gresley mechanism, it had German Henschel & Son conjugated valve gear apparatus, driven from the combination levers of the Walschaert valve gear for the outside cylinders. The inside cylinder was also positioned further forward of the outside cylinders, and it drove the leading coupled axle, with the outside cylinders driving the second coupled axle.
The H class also became the first VR locomotive to feature a mechanical stoker, and boasted many other modern features, such as roller bearings, hydrostatically controlled load compensating brake gear on the tender, power-operated reversing gear, American-style bar frame construction, thermic siphons, and duplex blast pipes.
Production
Construction of three H class locomotives at Newport Workshops commenced in 1939 and three sets of frames were manufactured. However, work was halted due to the outbreak of World War II. A shortage of motive power, caused by increased wartime traffic, led to the completion of class leader H220 being authorised and the locomotive entered service on 7 February 1941. Streamlining, similar to that on the S class locomotives, was originally planned, but wartime economies saw that abandoned.
The two additional, partly-built, H class locomotives remained incomplete while wartime production of armaments (and later postwar rebuilding of badly run-down infrastructure) took precedence over express passenger locomotive construction. They were never completed, and the parts were subsequently scrapped.