When EMD first offered a "road switcher" configuration, on the GP-7, the high short hood design was used in order to provide room for a steam generator. It was perceived by EMD's design team that the GP-7, being a "General Purpose" locomotive, might indeed haul local passenger and mixed trains. For this service, a steam generator was necessary. In fact, the locomotive which EMD made before the GP-7 for the same kind of service, the BL-2, could be ordered with a steam generator. Other makers had used similar designs, so this was not at all unusual.
EMD continued with this kind of design until some locomotives were ordered with shortened front hoods. Without a steam generator, there was no need for the extra height of the front hood. Much better visibility could be had by reducing the hood height and adding windshield glass across the front of the cab. On roads such as the Southern Pacific, with heavy winter snows and lots of curving track, increased visibility could be very important indeed! But, there was one small problem with the view. It was blocked.
The locomotive controls had originally been arranged without the worry of blocking a front view out of such windshields. In fact, the front windows on early Geeps were rather small. There was lots of room inside the cab to spread out controls. so there was no need to crowd them. In order to take advantage of the new visibility, a re-design was needed.
Some types, like the GP-20, were made available with either configuration. The basic controller itself remained unchanged, just minor components and control breakers had to be moved down out of the way. This re-arrangement took full advantage of the new windshield. Later locomotive types would not be available with high short hoods, and the lower controler shown above would be EMD's standard controller for many years to come. |
