The Pennsylvania Railroad F1s were 2-6-0 steam locomotives that were built for the Pennsylvania Railroad by Altoona Works in 1895. On the Pittsburgh Division, these Moguls were rated at 375 tons light, 433 tons loaded. Fitted with Belpaire firebox. Of the development of the H6 class Consolidations that the F1 design was a definite improvement on the then-current H3s: tractive effort was up 16% and the weight showed a 10% increase. With 12" larger drivers, they were able to handle 2,700 ton trains and roll them faster than the H3s. Favorable grades, particularly along fairly level Eastern divisions helped make such performance possible. Atlhough dwarfed in numbers by the thousands of Pennsy Consolidations, the unusual and ambidextrous many-faceted F-series Mogul delivered good service in a variety of roles. F-series development came from an unexpected choice by Altoona's designers, a mamoth new 2-6-0 design tucked up their garter-banded shirtsleeves that had just about bigger everything cylinders, driving wheels, steam pressure, weight, and pulling power. A twelve-inch (305 mm ) increase in driver diameter marked the designers' intentions to have this class handle fast freight.
