56 ACF Center Flow Hopper - CHICAGO & NORTH WESTERN - HO Scale. American Car and Foundry (ACF) manufactured a variety of railroad cars, including Center-Flow Hopper Cars. Hopper cars are used to transport bulk commodities like coal, grain and iron ore. A Center-Flow Hopper can be distinguished from gondola cars as it has doors underneath for the discharge of its cargo. Bachmann Center-Flow Hoppers, come in a variety of colors and road names. Each car is fully assembled and features; Highly Detailed Painted Bodies with Precision Graphics (where applicable), Blackened Machined Metal Wheels with RP 25 Contours, Magnetically Operated E-Z Mate Couplers, Non-magnetic Blackened Brass Axles with Needle-point Bearings, Celcon Trucks, and Added Weight for Optimum Tracking Performance.