The Mechanics of the Spiral Spring

Abstract

When working with the English watch master Thomas Thompin in 1678, Robert Hook (1635-1703) observed that when an elastic body is subjected to stress, its dimension or shape changes in proportion to the applied stress over a range of stresses. On the basis of his experiments with springs, stretching wires and coils, he discovered a relationship between the force and the extension of the spring. This is the so-called Hooke's law, which we learnt in high school. Using the Hooke's law, in this chapter, we studied the hairspring of the mechanical watch movement. The study also extends to include the case of Tourbillon.