BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică „Gheorghe Asachi” din Iaşi Tomul LVII (LXI), Fasc. 5, 2011 Secţia CONSTRUCŢII DE MAŞINI SOLID MODELING AND MOTION STUDY OF CHRONOMETER DETENT ESCAPEMENT MECHANISM BY BRANISLAV POPKONSTANTINOVIC 1 , MARIJA OBRADOVIC 2 , BRANKO MALESEVIC 3 and ZORANA JELI 1 Abstract. Theory of clock, watch and chronometer escapements is important and interesting part of theory of mechanisms and kinematics. Despite the fact that chronometer escapements are invented in past times, from the viewpoint of kinematics and machine theory, these mechanisms represent the jewel treasuries of knowledge and engineering wisdom. This paper considers and discloses operational principles and constructive geometry of Thomas Earnshaw‟s chronometer detent escapement. Moreover, process of 3D solid modeling, and assembling of all escapement parts, as well as the motion study and simulation of escapement operational cycle are presented and explained. This analysis and considerations enlighten not just the kinematical properties and characteristic of one particular chronometer escapement type, but also clarify and illuminate the process of computer aided mechanism design, construction and motion analysis. Key words: chronometer, detent escapement, kinematics, mechanism, motion simulation, solid modeling. 1. Introduction Escapement is the clock or watch mechanism that executes the following two different and equally important functions: a) Regulative: it regulates the speed of the watch main movement. The escapement, controlled by the oscillations of the balance wheel (oscillator), allows the gears of the watch mechanism to advance or 'escape' a fixed amount with each periodic balance wheel‟s swing and thus to move the timepiece's hands forward and at a steady rate. b) Impulsive: it maintains the balance wheel oscillations and keeps its amplitude constant. Since the oscillatory motion of the balance wheel (coupled with the hair-spring) is dumped, the escapement retrieves and compensates the