In a mechanical clock or watch, what mechanism ensures that the hands are driven at an even rate?
"manufacture. Water clocks are sometimes still used today, and can be examined in places such as ancient castles and museums. The Salisbury Cathedral clock, built in 1386, is considered to be the world's oldest surviving mechanical clock that strikes the hours. Clockmakers developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability. Clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock's accuracy, so many different mechanisms were tried. Spring-driven clocks appeared during"
"keep time. It consists of a small AC synchronous motor, which turns the clock's hands through a reduction gear train. The motor contains electromagnets which create a rotating magnetic field which turns an iron rotor. The rotation rate of the motor shaft is synchronized to the utility frequency; 60 cycles per second (Hz) in North America and parts of South America, 50 cycles per second in most other countries. The gear train scales this rotation so the minute hand rotates once per hour. Thus the synchronous clock can be regarded as not so much a timekeeper as a mechanical counter,"
"with the balance wheel's moment of inertia, formula_2 in kg*m, determines the wheel's oscillation period formula_3 in seconds: This period controls the rate of the timepiece. Balance spring A balance spring, or hairspring, is a spring attached to the balance wheel in mechanical timepieces. It causes the balance wheel to oscillate with a resonant frequency when the timepiece is running, which controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands. A regulator lever is often fitted, which can be used to alter the free length of the spring and"
"and a longer, rotating minute hand. Many watches also incorporate a third hand that shows the current second of the current minute. Watches powered by quartz usually have a second hand that snaps every second to the next marker. Watches powered by a mechanical movement appears to have a gliding second hand, although it is actually not gliding; the hand merely moves in smaller steps, typically 1/5 of a second, corresponding to the beat (half period) of the balance wheel. In some escapements (for example the ""duplex"" escapement), the hand advances every two beats (full period) of the balance wheel,"
"Balance spring A balance spring, or hairspring, is a spring attached to the balance wheel in mechanical timepieces. It causes the balance wheel to oscillate with a resonant frequency when the timepiece is running, which controls the speed at which the wheels of the timepiece turn, and thus the rate of movement of the hands. A regulator lever is often fitted, which can be used to alter the free length of the spring and thereby adjust the rate of the timepiece. The balance spring is a fine spiral or helical torsion spring used in mechanical watches, alarm clocks, kitchen timers,"
"rate. This makes the 'ticking' sound characteristic of all mechanical watches. 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 modern electronic quartz watches, and they require periodic cleaning by a skilled watchmaker. Since the 1970s, quartz watches have taken over most of the watch market, and mechanical watches are now mostly a high-end product, purchased for aesthetic reasons, for appreciation of their fine craftsmanship, or as a status symbol. The internal mechanism of a watch, excluding the face and hands, is"
"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, and can be slid 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 formula_3 in the equation above, decreasing the wheel's period formula_5 so it swings back and forth faster, causing the watch to run faster. A separate set of gears called the ""keyless work"" winds the"
"sometimes also called ""timers"". Mechanical timers use clockwork to measure time. Manual timers are typically set by turning a dial to the time interval desired; turning the dial stores energy in a mainspring to run the mechanism. They function similarly to a mechanical alarm clock; the energy in the mainspring causes a balance wheel to rotate back and forth. Each swing of the wheel releases the gear train to move forward by a small fixed amount, causing the dial to move steadily backward until it reaches zero when a lever arm strikes a bell. The mechanical kitchen timer was invented"
"screw that adjusts a capacitor for that purpose. Atomic clocks are primary standards, and their rate cannot be adjusted. Some clocks rely for their accuracy on an external oscillator; that is, they are automatically synchronized to a more accurate clock: This has the dual function of keeping the oscillator running by giving it 'pushes' to replace the energy lost to friction, and converting its vibrations into a series of pulses that serve to measure the time. In mechanical clocks, the low Q of the balance wheel or pendulum oscillator made them very sensitive to the disturbing effect of the impulses"
"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. 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"
"Balance wheel A balance wheel, or balance, is the timekeeping device used in mechanical watches and some clocks, analogous to the pendulum in a pendulum clock. It is a weighted wheel that rotates back and forth, being returned toward its center position by a spiral torsion spring, the balance spring or hairspring. It is driven by the escapement, which transforms the rotating motion of the watch gear train into impulses delivered to the balance wheel. Each swing of the wheel (called a 'tick' or 'beat') allows the gear train to advance a set amount, moving the hands forward. The balance"
"causes the wheel to turn, and a tooth presses against one of the pallets ""(h)"", giving the pendulum a short push. The clock's wheels, geared to the escape wheel, move forward a fixed amount with each pendulum swing, advancing the clock's hands at a steady rate. The pendulum always has a means of adjusting the period, usually by an adjustment nut ""(c)"" under the bob which moves it up or down on the rod. Moving the bob up decreases the pendulum's length, causing the pendulum to swing faster and the clock to gain time. Some precision clocks have a small"
"wheel and hairspring together form a harmonic oscillator, which due to resonance oscillates preferentially at a certain rate, its resonant frequency or 'beat', and resists oscillating at other rates. The combination of the mass of the balance wheel and the elasticity of the spring keep the time between each oscillation or ‘tick’ very constant, accounting for its nearly universal use as the timekeeper in mechanical watches to the present. From its invention in the 14th century until tuning fork and quartz movements became available in the 1960s, virtually every portable timekeeping device used some form of balance wheel. Until the"
"typically 1/2 second in those watches, or even every four beats (two periods, 1 second), in the ""double duplex"" escapement. A truly gliding second hand is achieved with the ""tri-synchro regulator"" of Spring Drive watches. All of the hands are normally mechanical, physically rotating on the dial, although a few watches have been produced with ""hands"" that are simulated by a liquid-crystal display. Analog display of the time is nearly universal in watches sold as jewelry or collectibles, and in these watches, the range of different styles of hands, numbers, and other aspects of the analog dial is very broad."
"was kept most of the time in a breast pocket, the exact position could still vary over 45°. Watchmakers can regulate a watch in up to eight positions: dial up, crown down, dial down, crown left, crown up, crown right, half-way position crown up, and half-way position crown down. A tourbillon quite neatly reduces this problem; it only needs to be regulated for three positions; the two horizontal positions, dial up & down, and one vertical position. Even with new materials and improved theories, it is impossible to regulate a mechanical watch so it keeps the same time in all"
"Automatic watch An automatic or self-winding watch is a mechanical watch in which the natural motion of the wearer provides energy to run the watch, making manual winding unnecessary. A mechanical watch which is neither self-winding nor electrically driven is called a ""manual watch"". In a mechanical watch the watch's gears are turned by a spiral spring called a mainspring. In a ""manual watch"" energy is stored in the mainspring by turning a knob, the ""crown"" on the side of the watch, winding the mainspring. Then the energy from the mainspring powers the watch movement until it runs down, requiring"
"to be ""isochronous"", and the period of oscillation is independent of the amplitude of oscillation. This is an essential property for accurate timekeeping, because no mechanical drive train can provide absolutely constant driving force. This is particularly true in watches and portable clocks which are powered by a mainspring, which provides a diminishing drive force as it unwinds. Another cause of varying driving force is friction, which varies as the lubricating oil ages. Early watchmakers empirically found approaches to make their balance springs isochronous. For example, John Arnold in 1776 patented a helical (cylindrical) form of the balance spring, in"
"whose hands display a running count of the number of cycles of alternating current. One of the gears turning the clock's hands has a shaft with a sliding friction fitting, so the clock's hands can be turned manually by a knob on the back, to set the clock. Synchronous motor clocks are rugged because they do not have a delicate pendulum or balance wheel. However, a temporary power outage will stop the clock, which will show the wrong time when power is restored. Some synchronous clocks have an indicator which shows if it has stopped and restarted. Some electric clocks"
"forward, re-compressing the maintaining spring ready for its next use. The whole mechanism is completely automatic in its operation and has remained one of Harrison's lasting contributions to horology. Maintaining power In horology, a maintaining power is a mechanism for keeping a clock or watch going while it is being wound. The weight drive used by Christiaan Huygens in his early clocks acts as a maintaining power. In this layout, the weight which drives the clock is carried on a pulley and the cord (or chain) supporting the weight is wrapped around the main driving wheel on one side and"
"the torsion pendulum oscillates slowly, clockwise and counterclockwise. The clock's gears apply a pulse of torque to the top of the torsion spring with each rotation to keep the wheel going. The wheel and torsion spring function similarly to a watch's balance wheel and hairspring, as a harmonic oscillator to control the rate of the clock's hands. Torsion clocks are usually delicate, ornamental, spring-wound mantel clocks. The polished clock mechanism is exposed under a glass case or dome, to allow people to watch the torsion pendulum turn. Clocks of this style, first made by Anton Harder around 1880, are also"
"over the course of each day creates approximately enough pressure to raise a one-pound weight by one inch (equivalent to 0.113 Joules or 31 μWh), which drives the clock mechanism. A similar mechanism in a commercially available clock which operates on the same principle is the Atmos clock, which is manufactured by the Swiss watchmaker Jaeger-LeCoultre. While the clock has not been wound since it was made by Arthur Beverly in 1864, it has stopped on a number of occasions, such as when its mechanism needed cleaning or there was a mechanical failure, and when the Physics Department moved to"
"became less popular and less favored in the 1970s, watch design and industrialists came out with the automatic watch. Whereas a mechanically-wound watch must be wound with the pendant or a levered setting, an automatic watch does not need to be wound by the pendant; simply rotating the watch winds the watch automatically. The interior of an automatic watch houses a swiveling metal or brass ""plate"" that swivels on its axis when the watch is shaken horizontally. Mechanical watch A mechanical watch is a watch that uses a clockwork mechanism to measure the passage of time, as opposed to quartz"
"all the clocks at a railway station have to run synchronously in order to show reliable time for both passengers and railway personnel anywhere on or around the station. The station clocks in Switzerland are synchronized by receiving an electrical impulse from a central master clock at each full minute, advancing the minute hand by one minute. The second hand is driven by an electrical motor independent of the master clock. It requires only about 58.5 seconds to circle the face, then the hand pauses briefly at the top of the clock. It starts a new rotation as soon as"
"type of mechanism, a shaft is driven by the clock so it rotates once a year, at constant speed. The shaft carries a cam, which is approximately ""kidney shaped"" such that its radius is essentially a graph of the annual variation of the equation of time. A follower and lever rest against the cam, so that as the cam rotates the lever moves in a way that represents the changing equation of time. This lever drives other components in the clock. To a close approximation, the equation of time can be represented as the sum of two sine waves, one"
"bph). The beats per minute depend on the balance spring's stiffness (spring constant); to keep time, the stiffness should not vary with temperature. Consequently, balance springs use sophisticated alloys; in this area, watchmaking is still advancing. As with the pendulum, the escapement must provide a small kick each cycle to keep the balance wheel oscillating. Also, the same lubrication problem occurs over time; the watch will lose accuracy (typically it will speed up) when the escapement lubrication starts failing. Pocket watches were the predecessor of modern wristwatches. Pocket watches, being in the pocket, were usually in a vertical orientation. Gravity"
"Regulator's"" innovations result in a watch where the hands glide instead of ticking as in a conventional mechanical or quartz watch. This is because the movement never stops as in a traditional escapement, it is slowed to the proper speed by the brake. The movement is specified to 1 second accuracy per day. However, 1–2s per week is commonly reported by owners. The movement is used on the Spring Drive International collection and in some watches of Grand Seiko, Credor, Galante, Izul, Ananta and Prospex series. Complications include moon phase, power reserve, chronograph, sonnerie, GMT and calendar functions. These watches"
"by pushing down on a lever at the side of the dial. This lever also engages the bolt. A similar type of mechanism is sometimes used on turret clocks. Because these take much longer to wind, and are usually wound by trained staff, the bolt carries a segment of a gear wheel rather than a single pawl and is engaged manually. John Harrison invented a form of maintaining power around the mid-1720s. His clocks of the period used a grasshopper escapement which malfunctioned if not driven continuously—even while the clock was being wound. In essence, the maintaining power consists of"
"In watches sold for timekeeping, analog display remains very popular, as many people find it easier to read than digital display; but in timekeeping watches the emphasis is on clarity and accurate reading of the time under all conditions (clearly marked digits, easily visible hands, large watch faces, etc.). They are specifically designed for the left wrist with the stem (the knob used for changing the time) on the right side of the watch; this makes it easy to change the time without removing the watch from the wrist. This is the case if one is right-handed and the watch"
"Maintaining power In horology, a maintaining power is a mechanism for keeping a clock or watch going while it is being wound. The weight drive used by Christiaan Huygens in his early clocks acts as a maintaining power. In this layout, the weight which drives the clock is carried on a pulley and the cord (or chain) supporting the weight is wrapped around the main driving wheel on one side and the rewinding wheel on the other. The chain then loops down from the rewinding wheel and up again to the main driving wheel via a second pulley carrying a"
"balance wheel. This crucial advance finally made accurate pocket watches possible. This resulted in a great advance in accuracy of pocket watches, from perhaps several hours per day to 10 minutes per day, similar to the effect of the pendulum upon mechanical clocks. The great English clockmaker, Thomas Tompion, was one of the first to use this mechanism successfully in his pocket watches, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern-day configuration. The Rev. Edward Barlow invented the rack and snail striking mechanism for striking clocks, which was a"
"causes some loss of accuracy as it magnifies over time any lack of symmetry in the weight of the balance . The ""tourbillon"" was invented to minimize this: the balance and spring is put in a cage which rotates (typically but not necessarily, once a minute), smoothing gravitational distortions. This very clever and sophisticated clock-work is a prized ""complication"" in watches, even though the natural movement of the wearer tends to smooth gravitational influences much more than for a pocket watch. The most accurate commercially produced mechanical clock was the electromechanical Shortt-Synchronome free pendulum clock invented by W. H. Shortt"
"in 1999. Early models, manual wind and 48h power reserve: Current calibers with standard features. Time accuracy: monthly rate within ±15 sec (equivalent to a daily rate of ±1 sec) and power reserve (72h) indicator. Spring Drive The Spring Drive is a watch movement that was developed by Seiko Epson through collaboration with Seiko Instruments and Seiko Holdings. One of its unique features is a true continuously sweeping second hand, instead of the traditional beats per time unit as seen with traditional mechanical and most quartz watches. Most quartz watches are electronically regulated to a single ""tick"" per second to"
"regulate. Gears drive a shaft at the desired rate, and turn the cam. The most common application of this timer now is in washers, driers and dishwashers. This type of timer often has a friction clutch between the gear train and the cam, so that the cam can be turned to reset the time. Electromechanical timers survive in these applications because mechanical switch contacts may still be less expensive than the semiconductor devices needed to control powerful lights, motors and heaters. In the past, these electromechanical timers were often combined with electrical relays to create electro-mechanical controllers. Electromechanical timers reached"