Eight factors affecting the timing accuracy of mechanical clocks and watches

- Apr 26, 2019-

The travel time accuracy of mechanical watches is affected by many factors. Generally speaking, the following eight factors are the main factors:






1. External impact


It is all kinds of influence from outside of the clock, depending on the working environment of the clock. The commonly adopted measures are: seismic design, waterproof design, magnetic design, additional protective shell and so on. Universal joints are often used on precise navigation clocks to keep them level in turbulence.






2. friction


Friction usually has both positive and negative effects. On the one hand, it has positive effects, such as friction wheel, friction between automatic spreader and barrel box, screw self-locking, etc. On the other hand, friction will lead to the reduction of transmission efficiency and friction loss of parts, thus affecting the timing. Commonly used solutions: improve lubrication conditions, according to different requirements, choose different lubricants; use gemstone bearings or gaskets; improve gear tooth surface conditions, including the use of scientific conjugate tooth shape and improve surface finish, but generally no lubrication (in this case, the resistance of lubricant viscous may be higher than friction).






3. fast and slow needles


Fast and slow needle is an economic structure which is convenient for school hours, but both theory and practice have proved that it will affect the isochronism of the system, and may also produce potential differences. These timing errors are random and can not be compensated or offset. Solutions include: minimizing the distance between internal and external fast and slow needles; but the best way is to adjust the speed by adjusting the inertia of the pendulum wheel, such as Rolex Mircro Stella regulating system.






4. escapement mechanism


The main influence of escaping mechanism is the influence of energy transfer on the pendulum-wheel yarn system. The pendulum-wheel yarn system can maintain a fixed oscillation frequency only in the case of free oscillation. Obviously, the energy transfer process of escaping mechanism will affect the oscillation frequency. The theory shows that when the transfer process is close to the balance point of the pendulum, the influence will be reduced. Solutions include: using precision escapement mechanism, such as claw escapement mechanism, its energy transfer process occurs near the equilibrium point, the angle of impulse transmission is very small, and the impact is relatively small. Moreover, its one-way impulse transmission makes the pendulum wheel and the yarn system have more free oscillation space (on this point, its relative error can be reduced by half!). Of course, Swiss leveraged escapement mechanism has the advantages of good workmanship and easy adjustment. It is the mainstream escapement mechanism of the international mechanical meter at present, but in the design, the angle of impulse transmission should be reduced as much as possible. In order to reduce the influence of escaping mechanism on timing benchmark, Omega Switzerland introduced coaxial escaping mechanism, which was invented by Dr. George Daniel of England. However, according to its working principle, it is a mixture of lever escaping mechanism and claw escaping mechanism.






5. Temperature effect


The influence of temperature is mainly manifested in two aspects: firstly, the change of temperature will affect the working length of the hairspring and the inertia of the pendulum wheel, which can directly affect the timing accuracy; secondly, the change of temperature will affect the viscosity of lubricating oil and transmission efficiency, thus affecting the timing. The following methods can be adopted: open bimetallic temperature compensation pendulum yarn system; special alloy material is used to make the pendulum yarn and the pendulum wheel, so that it has a certain temperature compensation in the working temperature range (8-38 degrees); and moving fast and slow needle temperature compensation. Standard lubricants are used for extreme temperature conditions, such as the Omega lunar landing surface, with no lubrication or solid lubrication.






6. magnetic field


The filament with the greatest influence of magnetic field can change its modulus of elasticity and deformation under the action of magnetic field, resulting in additional stress. In severe cases, magnetic field can cause filament adhesion and seriously affect travel time. The solution is to use antimagnetic materials.






7. hairspring balance


Generally, the center of gravity of framed hairspring varies with the swing angle of the pendulum wheel. Under the action of gravity, it will produce position error. Solutions are as follows: Baoji hairspring is used, the center of gravity shrinks, and the center of gravity does not change with the swing angle; Phillip's cylindrical hairspring with end curve is used symmetrically up and down; linear hairspring is used; some people have used spherical hairspring in history, which has superior performance but poor workmanship.