For a rectangular growing area, a linear lamp moving system is preferable. The self-propelled Light Rail 3.5 Intelli-Drive is without question the finest linear lamp mover available. It uses no pulleys, chains or gears. Simply mount the standard 6 foot track over the desired area and place the lamp-moving drive motor onto the track. The Light Rail 3.5 Intelli Drive is supplied with adjustable switch stops, so lamp travel can be any length you wish. This is perfect for a start-up size garden through to a full growth garden. The standard 6 foot track may also be extended.
Light Rail 3.5 is rated to 35 lbs
Motor is 10 RPM
Usage instructions can be found here