Modeling and analysis of a weight driven mechanical tower clock

The tower clock has served European communities beginning in the 14th century and American towns since the 18th century. Although the early clocks acted as audible alarms, they progressed to feature time dials and synchronized melodies from struck bells. The mechanical tower clock consists of gear trains, escapement, pendulum, driving weights, large dials with hour/minute hands, and bell(s) with striking mechanism. These clock components offer excellent examples of fundamental engineering concepts and control system principles. In this paper, a Seth Thomas Graham deadbeat escapement tower clock has been investigated. A brief survey of the societal impact of horology technology has been offered to motivate the study. The general operation of a weight driven tower clock has been reviewed and the governing mathematical equations discussed. Representative numerical and experimental results have been presented and discussed to validate the model.

I. Introduction

THE design of early mechanical clocks featured weight driven escapements that controlled the periodic gear motion which measured time in equal intervals. By 1280 AD, the available clock construction components included flywheels, cranks, differential gears, and a regulator [1]. In general, the main clock elements are the power source (weights, main spring), regulator (escapement - verge and foliot, anchor with pendulum), and display or bell. The escapement (or mechanical controller) maintains the power source by carefully releasing the stored energy, introduces oscillations to divide time into equal parts, and counts beats with metal pallets [2]. In other words, the escapement controls the periodic motion of mechanical clocks through the rhythmic behavior of an oscillating mechanism, which advances the gears in small increments to conserve energy. Lastly, the pendulum with bob offers a consistent swing (period) due to its length and center of mass.