The Pacific-type locomotive evolved as the need for power and speed increased. First, the four-wheel leading truck delivered stability at the faster speeds. Second, six tall drivers provided pulling power and speed. Last, a two-wheel trailing truck provided support for a larger firebox. The sum of this design was the 4-6-2 USRA Pacific. The USRA designation for light and heavy locomotives was a function of the track's ability to withstand weight. Excessive axle weight could damage the rails, loosen fastenings, and also cause damage to the locomotive. The USRA deemed a maximum of 54,000 pounds per axle as a light locomotive. The USRA Light Pacific weighed in at 277,000 lbs, with a 73 inch driver diameter and a boiler pressure of 200 lb/in. BLI's models follow the original designs closely. Railroad specific variations are not modeled on these locomotives. In most instances we offer two locomotive numbers for each railroad, and we are offering a painted model (black) with no lettering. NOTICE: Due to insufficient boiler diameter in the USRA Heavy and Light Pacifics, these units will not have smoke units. FEATURES - NEW Paragon3 Sound & Operation System FEATURING ROLLING THUNDERTM with Authentic Sounds and Prototypical Operation in both DC and DCC environments - Locomotive Composition: ABS Body with Die Cast Chassis - Tender Composition: ABS Body with Die Cast Chassis - Couplers: (2) Operating Kadee or Compatible - Compatible Tracks: Code 70, 83, 100 Rail - Equipped with Traction Tires - Minimum Operating Radius: 18 in or greater