A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, as opposed to quartz watches which function using the vibration modes of a piezoelectric quartz tuning fork. A mechanical watch is driven by a mainspring which must be wound either periodically by hand or via a self-winding mechanism. Its force is transmitted through a series of gears to power the balance wheel, a weighted wheel which oscillates back and forth at a constant rate. A device called an escapement releases the watch's wheels to move forward a small amount with each swing of the balance wheel, moving the watch's hands forward at a constant rate. The escapement is what makes the 'ticking' sound which is heard in an operating mechanical watch. Mechanical watches evolved in Europe in the 17th century from spring powered clocks, which appeared in the 15th century.
Mechanical watches are typically not as accurate as quartz watches, and they eventually require periodic cleaning, lubrication and calibration by a skilled watchmaker. Since the 1970s and 1980s, as a result of the quartz crisis, quartz watches have taken over most of the watch market, and mechanical watches (especially Swiss-made watches) are now mostly marketed as luxury goods, purchased for their aesthetic and luxury values, for appreciation of their fine craftsmanship, or as a status symbol.
Components
The internal mechanism of a watch, excluding the face and hands, is called the movement. All mechanical watches have these five parts: A mainspring,Hand-winding Mechanical Watch Movement Mainspring which stores mechanical energy to power the watch. A gear train, called the wheel train,Mechanical Clock / Watch Movement Gear Train Photos which has the dual function of transmitting the force of the mainspring to the balance wheel and adding up the swings of the balance wheel to get units of seconds, minutes, and hours. A separate part of the gear train, called the keyless work, allows the user to wind the mainspring and enables the hands to be moved to set the time. A balance wheel, which oscillates back and forth. This is the timekeeping element in the watch. Its timekeeping accuracy is due to the fact that it is a harmonic oscillator, with a period of oscillation which is very constant, dependent on the inertia of the wheel and the elasticity of the balance spring. An escapement mechanism, which has the dual function of keeping the balance wheel vibrating by giving it a push with each swing, and allowing the watch's gears to advance or 'escape' by a set amount with each swing. The periodic stopping of the gear train by the escapement makes the 'ticking' sound of the mechanical watch. An indicating dial, usually a traditional clock face with rotating hands, to display the time in human-readable form.
Additional functions on a watch besides the basic timekeeping ones are traditionally called complications. Mechanical watches may have these complications: Automatic winding or self-winding—in order to eliminate the need to wind the watch, this device winds the watch's mainspring automatically using the natural motions of the wrist, with a rotating-weight mechanism. Calendar—displays the date, and often the weekday, month, and year. Simple calendar watches do not account for the different lengths of the months, requiring the user to reset the date five times a year, but perpetual calendar watches account for this, and even leap years. An annual calendar does not make the leap year adjustment, and treats February as a 30-day month, so the date must be reset on March 1 every year when it incorrectly says February 29 or 30. Alarm—a bell or buzzer that can be set to go on at a given time. Chronograph—a watch with additional stopwatch functions. Buttons on the case start and stop the second hand and reset it to zero, and usually several subdials display the elapsed time in larger units. Hacking feature—found on military watches, a mechanism that stops the second hand while the watch is being set. This enables watches to be synchronized to the precise second. This is now a very common feature on many watches. Moon phase dial—shows the phase of the moon with a moon face on a rotating disk. Wind indicator or power reserve indicator—mostly found on automatic watches, a subdial that shows how much power is left in the mainspring, usually in terms of hours left to run. Repeater—a watch that chimes the hours audibly at the press of a button. This rare complication was originally used before artificial lighting to check what time it was in the dark. These complex mechanisms are now only found as novelties in extremely expensive luxury watches. Tourbillon—this expensive feature was originally designed to make pocket watch more accurate, Nowadays it has limited utility for wristwatches, but it remains among the most virtuous demonstrations. In an ordinary watch the balance wheel oscillates at different rates, because of gravitational bias, when the watch is in different positions, causing inaccuracy. In a tourbillon, the balance wheel is mounted in a rotating cage so that it will experience all positions equally. The mechanism is usually exposed on the face to show it off. The FHH (Fondation de la Haute Horlogerie) definition is: "Any function other than the indication of hours, minutes and seconds, regardless of whether the mechanism is hand-wound or self-winding, mechanical or electronic, and of movement height . The tourbillon is considered complication even if it do not fall within the generic definition." Its function is not to provide additional information, but to adjust the timekeeping even more precisely. It is an adjustment device that is not essentially necessary for the operation of the watch.
Mechanism
The mechanical watch is a mature technology, with watch hands movements consists of similar parts and works the same way.The parts are shown in detail in
Mainspring and motion work
The mainspring that powers the watch, a spiral ribbon of spring steel, is inside a cylindrical barrel, with the outer end of the mainspring attached to the barrel. The force of the mainspring turns the barrel. The barrel has gear teeth around the outside that turn the center wheel once per hour — this wheel has a shaft that goes through the dial. On the dial side the cannon pinion is attached with a friction fit (allowing it to slide when setting the hands) and the minute hand is attached to the cannon pinion. The cannon pinion drives a small 12-to-1 reduction gearing called the motion work that turns the hour wheel and hand once for every 12 revolutions of the minute hand.
For the same rate of oscillation, the duration of run, runtime or power reserve of a mechanical watch is mainly a question of what size of mainspring is used, which is, in turn, a question of how much power is needed and how much room is available. If the movement is dirty or worn, the power may not transfer from the mainspring efficiently to the escapement. Service can help restore a degraded runtime. Most mechanical watch movements have a duration of run between 36 and 72 hours. Some mechanical watch movements are able to run for a week. The exact duration of run for a mechanical movement is calculated with the formula "The Theory of Horology", Charles-Andre Reymondin, et al., Swiss Federation of Technical Colleges, 1999, where is the number of barrel teeth, is the number of center pinion leaves, is the number of revolutions of the barrel, and is the number of revolutions of the center pinion — the run duration.
Wheel train The center wheel drives the pinion of the third wheel, and the third wheel drives the pinion of the fourth wheel. In watches with the seconds hand in a subsidiary seconds dial, usually located above the 6 o'clock position, the fourth wheel is geared to rotate once per minute, and the second hand is attached directly to the arbour of this wheel.
Escapement The fourth wheel also drives the escape wheel of the lever escapement. The escape wheel teeth alternately catch on two fingers called pallets on the arms of the pallet lever, which rocks back and forth. The other end of the lever has a fork which engages with an upright impulse pin on the balance wheel shaft. Each time the balance wheel swings through its center position, it unlocks the lever, which releases one tooth of the escape wheel, allowing the watch's wheels to advance by a fixed amount, moving the hands forward. As the escape wheel turns, its tooth pushes against the lever, which gives the balance wheel a brief push, keeping it swinging back and forth.
Balance wheel The balance wheel keeps time for the watch. It consists of a weighted wheel which rotates back and forth, which is returned toward its center position by a fine spiral spring, the balance spring or "hair spring". The wheel and spring together constitute a harmonic oscillator. The mass of the balance wheel combines with the stiffness of the spring to precisely control the period of each swing or 'beat' of the wheel. A balance wheel's period of oscillation T in seconds, the time required for one complete cycle (two beats), is
where is the wheel's moment of inertia in kilogram-meter2 and is the stiffness (spring constant) of its balance spring in newton-meters per radian. Most watch balance wheels oscillate at 5, 6, 8, or 10 beats per second. This translates into 2.5, 3, 4, and 5 Hz respectively, or 18000, 21,600, 28,800, and 36,000 beats per hour (BPH). In most watches there is a regulator lever on the balance spring which is used to adjust the rate of the watch. It has two curb pins which embrace the last turn of the spring, holding the part behind the pins motionless, so the position of the curb pins determines the length of the spring. Moving the regulator lever slides the curb pins up or down the spring to control its effective length. Sliding the pins up the spring, shortening the spring's length, makes it stiffer, increasing in the equation above, decreasing the wheel's period so it swings back and forth faster, causing the watch to run faster.
Keyless work A separate set of gears called the keyless work winds the mainspring when the crown is rotated, and when the crown is pulled out a short distance allow the hands to be turned to set the watch. The stem attached to the crown has a gear called the clutch or castle wheel, with two rings of teeth that project axially from the ends. When the stem is pushed in, the outer teeth turn the ratchet wheel on top of the mainspring barrel, which turns the shaft that the inner end of the mainspring is attached to, winding the mainspring tighter around the shaft. A spring-loaded pawl or click presses against the ratchet teeth, preventing the mainspring from unwinding. When the stem is pulled out, the inner teeth of the castle wheel engage with a gear which turns the minute wheel. When the crown is turned, the friction coupling of the cannon pinion allows the hands to be rotated.
Center seconds If the seconds hand is co-axial with the minute and hour hand, that is it is pivoted at the center of the dial, this arrangement is called "center seconds" or "sweep seconds", because the seconds hand sweeps around the minute track on the dial.
Initially center seconds hands were driven off the third wheel, sometimes via an intermediate wheel, with the gearing on the outside of the top plate. This method of driving the seconds hand is called indirect center seconds. Because the gearing was outside the plates, it added to the thickness of the movement, and because the rotation of the third wheel had to be geared up to turn the seconds hand once a minute, the seconds hand had a fluttering motion.THE PURSUIT OF CENTER SECONDS BY WALT ODETS