In mechanical clocks, the energy released by restoring deformation using a spring (spring) or the gravity of a heavy object falling as the energy source is used, and the mechanical vibration system is used as the time benchmark to achieve the mechanical mechanism of measuring time and time period. There are various types of mechanical clock mechanisms, but they are generally composed of a primary drive system, a transmission system, an escapement speed control system, an upper needle system, and a pointer system, and their working principles are basically the same. In addition, the calendar watch also includes a calendar (or double calendar) mechanism, and the automatic watch also includes an automatic winding mechanism.

The mechanism for storing and transmitting working energy in the primary system. It can be divided into two types: heavy hammer primary system and spring primary system.

The primary system of the heavy hammer utilizes the gravity of the heavy hammer as its energy source. Mainly used for simple wall clocks and floor mounted pendulum clocks. The original drive system of the heavy hammer has a simple structure and stable torque, but when the heavy hammer is lifted, the transmission system and the original drive system detach, and the clock mechanism stops working.

The spring primary system uses the energy released by the spring (spring) that is coiled into a spiral shape to restore deformation as energy. One end of the spring is connected to the shaft, and the other end is connected to a stationary part or the shell of the spring box. The spring primary system is used as the energy source for portable clocks and also for pendulum clocks. There are three types of spring drive systems: fixed strip box type, non strip box type, and movable strip box type.

The transmission system transmits the energy of the primary drive system to a set of transmission gears in the escapement speed control system. Usually composed of a series of wheel discs and gear shafts (Figure 3), in the main transmission, the wheel discs are the driving gear and the gear shaft is the driven gear. The transmission ratio is calculated according to the following formula: i=Z1/Z2, where Z1 is the number of teeth on the driving gear and Z2 is the number of teeth on the driven gear. For clocks with a second hand device, the transmission ratio from the center wheel to the second wheel must be equal to 60. The tooth shape of the clock transmission system is mostly specially designed.