One on the popular techniques for controlling damping direction in our Rotary Viscous Damper is using a one way wrap spring clutch. This mechanism has 4 major advantages : zero back-lash, slimline, low cost and high strength. We implement a clutch when a products design needs damping in one direction and zero or decreased damping/friction in the other direction. For example a heavy lid that lifts easily and then needs damping when dropped or released. We can do the same motion for a friction hinge. Many applications need this sort of mechanism: garbage pail lids, protective screens, toy boxes, medical equipment, aerospace & marine products. Visit us at http://www.mmtech.us or give us a call at 203-406-7900. We would love to hear about your application.