Design of a bracket mechanism for the Competr outboard motor

This thesis presents the design of a two-degree-of-freedom mechanical system for the integration of an outboard motor onto the transom of a boat. The developed bracket mechanism plays a fundamental role in controlling the relative position of the outboard motor with respect to the hull, enabling precise management of the boat’s behaviour and ensuring high performance in terms of speed, manoeuvrability and overall efficiency. The system is designed for the proprietary Competr electric outboard motor, characterized by an unconventional propulsion arrangement with front-facing contrarotating propellers to achieve superb efficiency and pristine performances. The study is focused on kinematic optimization to obtain the best trim and height ranges of the outboard, by acting on two hydraulic actuators. Force analysis has been carried out both in static and dynamic case and a control architecture has been hypothesized and then tested in a MATLAB simulator. The starting point is an existing one-degree-of-freedom four-bar trim mechanism. Its main limitation is that trim angle and vertical position are coupled by the geometry. The proposed solution preserves most of the original architecture but replaces one fixed link with a second linear actuator. The result is a planar mechanism able to successfully control the outboard position and motion, to extract the best performance from the engine. Moreover, with this study some new interesting possibilities have been unlocked such as surface piercing propeller usage.