Abstract: The specification discloses a hydrodynamic gravity motor for use in converting gravitational and buoyant forces into useful energy. A plurality of hollow vessels are attached between a pair of endless power chains. The power chains define a closed path of movement for the vessels moving by buoyant forces upward through a reservoir holding a column of liquid and returning downward outside of the reservoir from the gravitational forces on the vessels. A radial gate valve is disposed at the bottom of the reservoir for admitting each of the hollow vessels into the reservoir. The radial gate valve has a pair of lower panels operating in sequence with a pair of upper panels for defining a chamber for receiving each of the vessels. The radial gate valve has a plurality of buoyant lift tanks attached to the upper panels for reducing the force necessary to open the gate.