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An automatic watch, also known as a self-winding watch or simply an automatic, is a mechanical watch where the natural motion of the wearer provides energy to wind the mainspring, making manual winding unnecessary if worn enough. It is distinguished from a manual watch in that a manual watch must have its mainspring wound by hand at regular intervals. Operation 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. Then the energy from the mainspring powers the watch movement until it runs down, requiring the spring to be wound again. A self-winding watch movement has a mechanism which winds the mainspring using the natural motions of the wearer's body. The watch contains an oscillating weight that turns on a pivot. The normal movements of the watch in the user's pocket (for a pocketwatch) or on the user's arm (for a wristwatch) cause the rotor to pivot on its staff, which is attached to a ratcheted winding mechanism. The motion of the watch is thereby translated into circular motion of the weight which, through a series of reverser and reducing gears, eventually winds the mainspring. There are many different designs for modern self-winding mechanisms. Some designs allow winding of the watch to take place while the weight swings in only one direction while other, more advanced, mechanisms have two ratchets and wind the mainspring during both clockwise and anti-clockwise weight motions. The fully wound mainspring in a typical watch can store enough energy reserve for roughly two days, allowing the watch to keep running through the night while stationary. In many cases automatic wristwatches can also be wound manually by turning the crown, so the watch can be kept running when not worn, and in case the wearer's wrist motions are not sufficient to keep it wound automatically. Preventing overwinding Self-winding mechanisms continue working even after the mainspring is fully wound up. If a simple mainspring was used, this would put excessive tension on the mainspring. This could break the mainspring, and even if it did not, it can cause a problem called "knocking" or "banking". The excessive drive force applied to the watch movement gear train can make the balance wheel rotate with excessive amplitude, causing the impulse pin to hit the back of the pallet fork horns. This will make the watch run fast, and could break the impulse pin. To prevent this, a slipping clutch device is used on the mainspring so it cannot be overwound. Slipping spring or "bridle" The "slipping mainspring" device was patented by Adrien Philippe, one of the founders of Patek Philippe, on 16 June 1863, long before self-winding wristwatches. In an ordinary watch mainspring barrel, the outer end of the spiral mainspring is attached to the inside of the barrel. In the slipping barrel, the mainspring is attached to a circular steel expansion spring, often called the 'bridle', which presses against the inside wall of the barrel, which has serrations or notches to hold it. As long as the mainspring is less than fully wound, the bridle holds the mainspring by friction to the barrel wall, allowing the mainspring to be wound. When the mainspring reaches full wind, its force is stronger than the bridle spring, and further winding pulls the bridle loose from the notches and it simply slides along the wall, preventing the mainspring from being wound further. The bridle must grip the barrel wall with just the right force to allow the mainspring to wind fully but not overwind. If it grips too loosely, the bridle will begin to slip before the mainspring is fully wound, a defect known as 'mainspring creep' which results in a shortened reserve power time. A further advantage of this device is that the mainspring cannot be broken by excessive manual winding. This feature is often described in watch company advertising as an "unbreakable mainspring". History Pocket watches The earliest reference to self-winding watches is at the end of 1773 when a newspaper reported that Joseph Tlustos had invented a watch that did not need to be wound. But his idea was probably based on the myth of perpetual motion, and it is unlikely that it was a practical solution to the problem of self-winding watches. In 1776 Joseph Gallmayr also stated that he had made a self-winding watch, but there is no evidence to support this claim. The earliest credible evidence for a successful design is the watch made by the Swiss watchmaker Abraham-Louis Perrelet, who lived in Le Locle. In late 1776 or early 1777, he invented a self-winding mechanism for pocket watches but the original reports make no mention of the mechanism used, although later evidence could point to a side weight type. The Geneva Society of Arts, reporting on this watch in 1777, stated that 15 minutes walking was necessary to fully wind the watch. In 1777 Abraham-Louis Breguet also became interested in the idea, and his first attempts led him to make a self-winding mechanism with a barrel remontoire. Although a successful design, it was too complex and expensive for it to be manufactured and sold. About the end of 1777 or early 1778, Hubert Sarton designed a watch with a rotor mechanism. Towards the end of 1778 he sent a watch to the French Academy of Sciences and a report was written which, together with a drawing, gave a detailed description of the mechanism. Sarton's design is similar to those used in modern wrist watches, although there is no evidence linking the 18th-century design to 20th-century developments. About the beginning of 1779, Abraham-Louis Breguet became aware of Perrelet's watches, probably through Louis Recordon, who travelled from Geneva to London via Le Locle and Paris. Breguet studied and improved the design, and made many self-winding watches from then to about 1810. Although a few self-winding watches and patents for them were made from 1780 on, for more than one hundred years these watches were rare, until the advent of the wrist watch. During the years 1776 to 1810 four different types of weight were used: Side-weight The weight pivots at the edge of the movement and can oscillate up and down. The movement of the weight is limited to about 40°. This is the most common design produced by many makers including Breguet. These watches were called jerking watches because, even with buffers, when the weight hit the case the whole watch would jerk. Center-weight The weight pivots in the center of the movement and rotates clockwise and anti-clockwise. The weight is supported by a bridge that blocks the rotation and it is limited to about 180°. A few movements were made by different makers. Rotor-weight Again the weight pivots in the center of the movement and rotates clockwise and anti-clockwise. However, there is no bridge and it can rotate 360°. Very few of these movements were made. Movement-weight Here t.... Discover the Harold C Kelly popular books. Find the top 100 most popular Harold C Kelly books.