What is the working principle of a mechanical watch?

　　What is the working principle of a mechanical watch? Mechanical watches can usually be divided into the following two types: hand-wound and self-winding watches. The power source for both types of mechanical watches relies on the mainspring within the movement to drive the gear train and subsequently move the hands, only the method of power source differs.

　　Working principle of mechanical watches

　　The mainspring is the component that provides energy for the watch and is coiled inside the barrel. The mainspring is wound using the square milling slot on the arbor. The square slot of the arbor is driven by the winding mechanism. Without rewinding, the watch can run for about 36 to 50 hours. Because the mainspring is subjected to significant stress, it can frequently lead to breakage; therefore, alloy materials are currently used so that the mainspring almost never breaks. The mainspring stores a certain amount of energy, which is distributed evenly and in small amounts to the oscillator. To achieve this, the supplied energy passes through the gear train, which reduces the transmission force by the same proportion while increasing the number of turns. This gear train includes 4 wheels and 4 pinions, with the last 3 wheels riveted onto the first 3 pinions.

　　Diagonal lines indicate meshing between moving parts, while horizontal lines indicate that moving parts are riveted to the same shaft. The first wheel is the barrel wheel with teeth milled on its circumference. The last wheel is the escapement gear, with the escape wheel riveted to this gear. The escape wheel belongs to the distribution mechanism and counter. The barrel wheel completes one revolution in approximately 6 hours, during which time the escapement gear and escape wheel rotate about 3600 revolutions. This figure represents the rotational frequency ratio between the first wheel and the last wheel. This ratio always remains within this numerical range. Efforts are generally made to position the gear train and minute wheel at the centre of the watch, completing one revolution per hour.

　　Hand-wound mechanical watches rely on manual winding, and the thickness of the movement is relatively thinner than that of average self-winding watches, making the overall weight of the watch relatively lighter. On the other hand, self-winding watches utilise the power generated by the swinging back and forth of the oscillating weight at the bottom of the movement to drive the mainspring and generate energy, but the thickness of the watch itself is relatively thicker than that of average hand-wound watches. The advantages of mechanical watches are that through regular servicing and cleaning, they can be used for a very long time; the disadvantages are that their margin of error is larger than that of quartz watches, due to variations in manufacturing quality and the internal movement being susceptible to the influence of gravity. The error of mechanical watches is usually calculated in terms of seconds gained or lost per day, whereas the error of quartz watches is calculated in terms of seconds gained or lost per month.