Superpower steam

"Superpower steam" was a term coined by Lima Locomotive Works in the mid-1920s, referring to steam locomotives with booster-equipped four-wheel trailing trucks supporting large fireboxes, as well as enlarged superheaters.

The design was invented by Lima for the New York Central's Boston and Albany Railroad.

The design was invented by Lima's Vice President of Engineering, William Woodard, who had experimented with a New York Central 2-8-2 Mikado in 1922.

The new design called for double the firebox size than the earlier Mikados, thus giving it more grate area leading to the development of the 2-8-4.

To accommodate the larger firebox, Woodard gave the new locomotive a two axle trailing truck instead of the common single axle trailing trucks previously used, and tests of the new design were done on the Boston and Albany Railroad.