A railroad hopper car body includes a set of hopper and hopper discharges. Egress of lading from the discharges is governed by movable doors that swing between a closed position and an open position. The motion is driven by a mechanical transmission that is itself driven by an actuator. Each pair of doors is driven by a single actuator. The actuator is mounted to act through the center sill. A portion, or substantially all, of the actuator may be mounted in a predominantly squat, vertical orientation within the center sill. In alternate embodiments, the transmission output may be bifurcated. The center sill bottom flange may be narrower adjacent to the doors. The mechanism may have a secondary lock. The mechanism may have an auxiliary manual release.