Designing a Visual Effect to Replace the Needle Indicator of an Advanced Mechanical Stopwatch Function

Abstract

This thesis describes the process of designing a visual effect to replace the needle indicator of a rattrapante complication. The mechanisms of the chronograph and rattrapante are explained as well as the importance of aesthetics in the luxury watchmaking industry. After establishing a method to determine a feasible design, the criteria that need to be fulfilled for the final design are quantified. Extra attention is given to: the minimum part size with respect to human visibility; assessing the aesthetic value of different visual effects based on a survey; and quantifying the maximum rotational inertia by means of a friction study. From the aesthetically pleasing ideas from the survey feasible concepts are generated as well as weighted with respect to each other. The best concept is turned into a working mechanism by establishing a production method and calculating stresses in compliant flexures. A torsion hinge that can be produced from a double-BOX-layered silicon wafer is also designed. The actuation by a discrete vertical clutch gripper is designed as well as the extra parts needed for a fully functioning mechanism that fits the design space. As a result, a demonstrator at scale 15:1 is build to show the working mechanisms of the design as well as the visual effect itself. It concludes with a successful mechanism which probably also has relevance in other watches.