Development of SPRING DRIVE Sonnerie

Abstract

This paper describes an air-viscous slow governor used in Spring Drive Sonnerie. Spring Drive movement makes no noise during hand movement. This is an ideal condition for installing mechanism for striking a bell. Japanese Buddhists' prayer bell "orin" was chosen for the sound source. Our objective was to create a sonnerie that offered the resonance and the clear tone of an orin. The reverberation resonance of an orin is produced by a hammer that strikes the bell at approximately 3-second interval. Along with the smoothly flowing second hand, the sound imparts a sense of slow and tranquil flow of time. To achieve the ringing tone of an orin amid a tranquil stillness, we developed a non-contact slow governor that made virtually no noise. The key to the "silent" slow governor is the wings around the rotor that produce resistance caused by viscosity of the air. This rotor turns at a constant speed at which the reactive force of the main spring and the viscous resistance caused by the air are balanced.