MTH: 20-21805-1 MTH Premier Frisco #22 F-7 A-Unit Diesel Engine with ProtoSound 3.0 O Gauge Electro-Motive Division's F7 was the zenith of the “covered wagon,” or carbody-style diesel. With 3,849 units built between 1949 and 1953, the F7 was both the most popular carbody diesel and its last hurrah. By 1954 U.S. railroads had virtually stopped ordering F-units in favor of hood units like EMD’s GP9 and Alco’s RS-3. The side walkways of hood units offered better access for maintenance and better visibility for backup moves, making them truly universal locomotives useful for both mainline runs and road switching. Externally, the F7 was very similar to the earlier F3. The key spotting features that distinguished an F7 were its stainless steel upper body grilles that replaced the “chicken wire” worn by most F3s, and the rooftop dynamic brake fan that replaced the F3’s rectangular roof vents just behind the cab. Internally, the F7 was also an evolution of the F3. While horsepower was the same, new D27 traction motors allowed the F7 to handle a heavier load. Capture the excitement of the first-generation diesel era with this four-motored, full-scale model. Throttle down to speeds as low as 3 scale miles per hour with any load, or roll along at the prototype’s maximum speed of 102 mph with passenger gearing. Proto-Sound 3.0 offers authentic EMD 567 prime mover sounds, a first-generation diesel horn and bell, crew and station sounds, and adjustable smoke volume. The F7 features the same level of superb detailing that characterizes all Premier F-units, with added-on details that include legible builder’s plates, grab irons, multiple-unit hoses, rooftop lift rings, see-through side grilles and rooftop fan housings, steam generator exhaust stack (for passenger versions), windshield wipers, and our super-detailed Blomberg trucks with separately-applied spring hangers, brake cylinders, and air pipes.