An unloading conveyor system for unloading grain through the floor of a grain bin. A removeable cover is vertically supported by the plurality of ribs to cover the span of the midpan to allow maintenance. The midpan comprises a plurality of slots and ledges to receive and support the ribs to allow easy installation and maintenance. A central pit having an internal portion and an access support wall also provides easy installation and maintenance. The first bearing mount, second bearing mount, and roller are all accessible for service through the internal portion of the central pit.