The locomotives were among the heaviest of locomotives in Australia with a 24 tonne axle load and this along with their width restricted their sphere of operation to Thirroul on the Illawrra line, Wallerawang on the Main Western line and Junee on the Main South line.

They had the highest tractive effort of any conventional engines used in Australia and were of approximately equal capability to the 60 class Garratt locomotives. They were very reliable and had the nickname Lazy Lizzies because they made heavy workings seem effortless. Another nickname was bestowed on the class, Chuckling Charlies due to their syncopated exhaust beat. The three cylinder design fitted to the class gave it a distinctive off-beat exhaust sound when climbing upgrade. This design was also fitted to the 58 class. However, a couple of features, such as the Gresley conjugating valve gear fitted to these locomotives has been the source of debate as to its efficiency.

Source: Wikipedia