The R3d Class is a class of Duplex Drive locomotives designed by Conan Diederich at the Eastern & Atlantic's Charlotte Works.
Late in the war, the Eastern & Atlantic Railroad began to research duplex locomotives, along with the Pennsylvania Railroad. The Eastern & Atlantic was a competitor to the Pennsy, and often acquired the same types of locomotives. It was no different in this instance.
The Pennsylvania Railroad was the first to use the 4-4-6-4 layout, in their unsuccessful Q1 locomotive. Conan Diederich, who had come to the states late in the war, found employment at the Charlotte works of the E&A. One of his first projects was the R3d Class.
The E&A used belpaire fireboxes almost universally on it's larger locomotives, and this was the case with the R3d Class. An Elesco feedwater heater was used on this locomotive, mounted behind the smokestack.
The E&A built 55 of this class in 1944-1946, and a further 20 in 1950-1952, the entire first production run going on fast freight services, along with the next 15, while the last 5 were semi-streamlined and put to work in Passenger services. These last 5 were re-designated R4da Class.