Abstract: Two carriages are roller mounted to allow relative motion between them while maintaining precise relative positioning. Rollers engage precision ground spaced surfaces of a C-shaped hangar configuration, and wear compensation is provided by a spring bias arrangement maintaining conformity between the rollers and guide grooves in the underside of the rails.

Abstract: An improved drive for a scanning optical system in a photocopier is disclosed. The drive incorporates an adjustable capstan and precision tapes as well as cables. The precision tapes are used between the two carriages which mount the optics because precise control of length in this portion of the system is critical. Cables are used in the remainder of the drive where flexibility in all directions is important. There is also a single drive embodiment. Also disclosed is a method for proper alignment of the carriages after field replacement of a broken cable.