A mechanism and method for operating a track-mounted door is disclosed. The mechanism includes a pair of side drums that are connected by first cables to the bottom of the door. The side drums are coaxially mounted on a shaft for simultaneous rotation with a pair of cable drums. The cable drums are connected to high pressure gas struts by second cables. Each second cable is carried around a shiv wheel that slides along a guide track as the second cable moves. Each shiv wheel is operatively connected to one of the gas struts. As the shiv wheel moves along the guide track toward the cable drum, the gas strut is charged. As the shiv wheel moves away from the cable drum, the gas strut is discharged. A standard electric motor and screw driven lift-arm is used to initiate the opening and closing of the door. The charged gas strut stores sufficient energy to overcome friction and gravity to assist the electric motor and lift-arm to open the door.