Victorian Railways class A²

With the class A², the Victorian Railways introduced the first class of steam locomotives from 1907, which they had developed themselves and which were also built in their own workshops. The first series of 125 locomotives had Stephenson valve gear and were powered by saturated steam. Between 1915 and 1922, 60 more followed with Walschaerts valve gear and a larger cylinder diameter. Soon they were built with superheaters and the earlier ones were rebuilt.

They were designed for the main line of the VR, which had many steep gradients and tight curves. Although they were express locomotives, they had the highest starting tractive effort of all VR steam locomotives until 1918. Nevertheless, they were approved for speeds of up to 70 mph or 113 km/h and could also go faster if necessary. This made it possible to shorten travel times to times that have only been bettered in modern times.

The machines were also used in front of freight trains. This primarily happened when the axle boxes were worn in the time before the next maintenance. In the 1930s, with the collaboration of Richard Paul Wagner of the Reichsbahn, a new exhaust system was developed that increased drawbar horsepower by more than 40 percent and was retrofitted not only in this class, but also in many other classes.

Due to the great depression and the Second World War, the construction of newer express locomotives was delayed, so that the A² was the VR's primary express locomotive for over 40 years. After the introduction of the R class, they were increasingly used on branch lines that had since been upgraded to accommodate higher axle loads. In the 1950s there was an increasing number of withdrawals, and the last one disappeared in 1963.