Application and Experience of the SSS (Synchro-Self-Shifting) Clutch for High Speed Gas Turbine Marine Propulsion Systems

Synchro-Self-Shifting (SSS) Overrunning Clutches are used in a myriad of propulsion system configurations for naval and commercial vessels powered by gas turbines and/or combined gas turbine and cruise engines worldwide. Of these, much has been written about high power gas turbine propulsion clutches for large naval vessels (frigates, destroyers, cruisers, etc.), whereas less has been published about the application and experience of the propulsion machinery with Synchro-Self-Shifting Clutches for hydrofoils, hovercraft, fast patrol boats, fast ferries, yachts, etc. Space, weight, and high-speed constraints can be different for high speed gas turbine propulsion systems used in these smaller types of vessels, and can therefore provide gearing challenges, including system design challenges for these clutches. A comparison between Synchro-Self-Shifting overrunning clutches and other types of freewheels will be given discussing the advantages and disadvantages of each, particularly as they relate to high speed gas turbine marine propulsion applications. Lastly, this paper will give some history of a number of high speed gas turbine driven marine propulsion applications with clutches from the early 1960’s until the present, describe various gearing arrangements that were used in particular vessels, articulate where these clutches are incorporated, and discuss the application experience of these clutch installations.