Chapter 4.4, Problem 22P

Old clocks were constructed using a fusee B to drive the gears and watch hands. The purpose of the fusee is to increase the leverage developed by the mainspring A as it uncoils and thereby loses some of its tension. The mainspring can develop a torque (moment) T_s = kθ, where k = 0.015 N · m/rad is the torsional stiffness and θ is the angle of twist of the spring in radians If the torque Tf developed by the fusee is to remain constant as the mainspring winds down, and x = 10 mm when θ = 4 rad, determine the required radius of the fusee when θ = 3 rad.

Prob.4-22