Abstract: A vehicle body including an outer shell including side walls, end walls and a floor. The floor has a discharge recess located at one end thereof inside the shell. A plurality of vertically positioned and spaced apart bulkhead members are mounted inside the shell to provide a plurality of separate, material containing, storage compartments therein. A bulkhead drive including a plurality of power screws is provided for successively driving the bulkhead members along the floor of the shell and over at least a portion of the discharge recess. The power screws each have an unthreaded portion and a threaded portion with the threaded portion normally in threaded engagement with the bulkhead members. The unthreaded portions of the power screws are located the discharge recess so that as each bulkhead member moves over the discharge recess it will become disengaged from the threaded portions of the power screws so that the lead bulkhead members can become nested over the discharge recess.