The K class was a branch line steam locomotive that ran on Victorian Railways from 1922 to 1979. Although its design was entirely conventional and its specifications unremarkable, the K class was in practice a remarkably versatile and dependable locomotive. It went on to outlast every other class of steam locomotive in regular service on the VR, and no fewer than 21 examples of the 53 originally built have survived into preservation.
The K class is credited with working virtually every line in the VR system and hauling almost every kind of train.
A total of ten were built from 1922-23. They were put to work on goods services on steeply graded branch lines where their superior tractive effort and high factor of adhesion were put to good use.
The design was modified in 1925 into the N class 2-8-2, in response to a new Victorian Railways policy that all new locomotives be capable of conversion from broad to standard gauge in the event of the Victorian Railways network being standardised. (The K, with its firebox mounted between the frames, was unsuitable for standard gauge conversion.)
The K class proved to be such a successful locomotive than during World War II when the VR faced a shortage of motive power on the branchline network, it built a further 43 K class locomotives even though the K was not gauge convertible. The decision to build more Ks reflected their greater versatility: they had the same tractive effort as the N class but unlike the longer wheelbase N class the K could be turned on the smallest (53 ft) turntables.
Although originally designed as a goods locomotive, their maximum permissible speed was raised in the 1950s from 45 to 50 mph (72 to 80 km/h) for branchline passenger service, further increasing their versatility.
The success of the K class was such that even in 1953, when dieselisation was already underway on Victorian Railways, the basic design of the K class was updated into the J class 2-8-0, the final class of steam locomotives to be introduced to the Victorian Railways.