An apparent almost binding rule in Chilean State Railways (EFE) locomotive policy was that no type of locomotive should have driving wheels of a diameter greater than 5´6”, which, by coincidence, was the gauge of the Southern Network (RS) main line and of many of its branches. There was not really much point in having bigger wheels, since most of the main lines were single tracked and occupied by both fast and slow passenger trains and even slower freight trains, all worked in both directions. There were two exceptions to the rule, one of which is the subject of this article and the other
