A concrete mold form (10) is provided to form concrete products such as concrete bridge girder (12). The form (10) has first and second side forms (14, 16) which are supported on carriages (22) riding on tracks (24) for moving the side forms (14, 16) between a closed position to cast the product and an open position to allow the cast product to be removed. At least one of the carriages (22) is a powered carriage (22P, 22M) which rotates a roller (28, 70) engaging the track with a hydraulic motor (38) to move the side form between the closed and open positions.