A bottom discharge open topped hopper car has a center sill with a bottom flange having laterally protruding edges. A shed plate assembly is provided to discourage accumulation of product on the exposed upwardly facing shelf otherwise presented by the bottom flange protrusions. The shed plate assembly may be mounted to the center sill in a manner that avoids impairment of the stress performance of the flanges of the center sill, whether by mechanical fastenings to other objects, or welding to objects that are not the center sill. The shed plate assembly may have walls having upper margins that are higher than the upper extremity of the hopper discharge opening such that the shelf of the center sill bottom flange is in the lee of, or sheltered by, the shed plate. The lading may thereby move under the influence of gravity past the shed plate to its desired unloading receptacle.