Bottom Discharge Hopper Cars - The hopper of a bottom (or side) discharge hopper car can be opened on one or both sides. The car tilts with the help of a curved discharge track at the unloading point, and the side door is opened by a pull rod for side unloading, or the bottom plate opens backward or to one side by gravity for bottom unloading. Bottom Discharge Hopper Cars and Unloading Pits consist of the hopper, side plates, and movable undercarriage, featuring whole bottom plate bottom discharge, two-section longitudinal bottom discharge, and two-section transverse bottom discharge. During unloading, the hopper car moves while the winged hopper runs on the support wheel assembly, the movable undercarriage opens along the unloading curved track, and then closes again while in motion. Common capacities range from 3.3 to 5.5 m³.