Analysis of the Mechanisms for Compensation in Clock B

Abstract This chapter assesses the design requirements of the grasshopper escapement, the pendulum and suspension spring to provide compensation for changing density and viscosity of the air surrounding the pendulum and changing escapement torque. It assesses the key components of the Harrison system: a pendulum bob of modest mass; a pendulum operating at a large running arc; and the grasshopper escapement’s increased torque delivery, ability to run without lubrication, its composers that allow fine adjustment to the torques delivered before and after the escaping arcs are reached and the importance of the thickness of the suspension spring that runs within circular cheeks. It also compares the system to the traditional pendulum clock design that traditionally employs a pendulum with a large mass and high-quality factor—high Q. Furthermore, it discusses Harrison’s stipulation that the pendulum needed to slightly reduce its length when warm.