Abstract: The present invention relates to a mechanical seat apparatus for simulating motion which includes a novel spherical bearing located below each seat for providing realistic simulation of motion in the yaw, pitch and roll directions. The spherical bearing includes means for preventing movement of the spherical bearing in the event of a power failure or other similar event to avoid injury to the viewers. The mechanical seat apparatus of the present invention also includes supporting structure which enables movement of each seat in the backward and forward, side to side and upward and downward directions, for a total of six degrees of freedom. Common hydraulics are provided to simultaneously impart motion to a plurality of seats.