Theoretical and experimental determination of capstan drive stiffness

Cable or metal band capstan drives are used as rotary transmission elements for their very low (nominally zero) backlash and high stiffness properties. Cable drives, in particular, are found in many types of equipment, and to obtain high stiffness, the cable is typically wrapped around the input and output drum in a figure-eight pattern. This paper develops analytical methods for predicting the torsional stiffness of capstan drives to enable designers to better assess machine performance in the design study phase. Experiments validated the analysis.