HO Scale - 1958 cu.ft. 2-Bay Covered Hopper - Great Northern -Description: The 2 bay covered hopper first entered service in the 1950s. The cars handle loads such as cement, sand and similar denser bulk commodities. In the 1960s, American Car and Foundry introduced the Centerflow design. The Centerflow relies on the car's rounded body to provide structural strength without the added weight of bracing, as well as making gravity unloading easier. This 2 bay car came in a 2,970 cubic foot capacity. The first ACF