Amtrak SDP40F (500-539) Locomotive Shell
Based on EMD's SD40-2 freight locomotive, 150 SDP40Fs were built over a period of two years. They were full-width body cowl unit locomotives, similar in appearance to the traditional cab units that many passenger locomotives at the time featured, but featuring a normal frame and superficial bodywork. They were identical structurally to the narrow-hood SD-40 road switcher freight locomotive, but with a "passenger-style" full width cab. One difference was that as a passenger locomotive, it featured a higher 57:20 gearing that allowed 100 mph (160 km/h). Two vapor steam generators and a 1,350 US gal water tank at the rear of the engine room made the steam needed for supplying heat (and sometimes cooling) and hot water for the train, as most of Amtrak's passenger cars were steam-heated at the time. They were designed for easy conversion to freight locomotives should Amtrak cease operation.