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Jewel Bearing
A jewel bearing is a plain bearing in which a metal spindle turns in a jewel-lined pivot hole. The hole is typically shaped like a torus and is slightly larger than the shaft diameter. The jewels are typically made from the mineral corundum, usually either synthetic sapphire or synthetic ruby. Jewel bearings are used in precision instruments where low friction, long life, and dimensional accuracy are important. Their largest use is in mechanical watches. History Jewel bearings were invented in 1704 for use in watches by Nicolas Fatio de Duillier, Peter Debaufre, and Jacob Debaufre, who received an English patent for the idea. Originally natural jewels were used, such as diamond, sapphire, ruby, and garnet. In 1902, Verneuil process, a process to make synthetic sapphire and ruby (crystalline aluminium oxide, also known as corundum) was invented by Auguste Verneuil, making jewelled bearings much cheaper. Today most jewelled bearings are synthetic ruby or sapphire. Historica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chinese Movement Escapement And Jewels
Chinese can refer to: * Something related to China * Chinese people, people of Chinese nationality, citizenship, and/or ethnicity **''Zhonghua minzu'', the supra-ethnic concept of the Chinese nation ** List of ethnic groups in China, people of various ethnicities in contemporary China ** Han Chinese, the largest ethnic group in the world and the majority ethnic group in Mainland China, Hong Kong, Macau, Taiwan, and Singapore ** Ethnic minorities in China, people of non-Han Chinese ethnicities in modern China ** Ethnic groups in Chinese history, people of various ethnicities in historical China ** Nationals of the People's Republic of China ** Nationals of the Republic of China ** Overseas Chinese, Chinese people residing outside the territories of Mainland China, Hong Kong, Macau, and Taiwan * Sinitic languages, the major branch of the Sino-Tibetan language family ** Chinese language, a group of related languages spoken predominantly in China, sharing a written script (Chinese c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stepper Motor
A stepper motor, also known as step motor or stepping motor, is a brushless DC electric motor that divides a full rotation into a number of equal steps. The motor's position can be commanded to move and hold at one of these steps without any position sensor for feedback (an open-loop controller), as long as the motor is correctly sized to the application in respect to torque and speed. Switched reluctance motors are very large stepping motors with a reduced pole count, and generally are closed-loop commutated. Mechanism Brushed DC motors rotate continuously when DC voltage is applied to their terminals. The stepper motor is known for its property of converting a train of input pulses (typically square waves) into a precisely defined increment in the shaft’s rotational position. Each pulse rotates the shaft through a fixed angle. Stepper motors effectively have multiple "toothed" electromagnets arranged as a stator around a central rotor, a gear-shaped piece of iron. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystal Oscillator
A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is a quartz crystal, so oscillator circuits incorporating them became known as crystal oscillators. However, other piezoelectricity materials including polycrystalline ceramics are used in similar circuits. A crystal oscillator relies on the slight change in shape of a quartz crystal under an electric field, a property known as inverse piezoelectricity. A voltage applied to the electrodes on the crystal causes it to change shape; when the voltage is removed, the crystal generates a small voltage as it elastically returns to its original shape. The quartz oscillates at a stable ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pallet Fork
The pallet fork is a component of the lever escapement of a mechanical watch. The pallet fork and the lever form one component that sits between the escape wheel and the balance wheel. Its purpose is to lock the escape wheel, and release it one tooth at a time at each swing of the balance wheel, and also give the balance wheel small pushes to keep it going. In early watches the pallet fork and the lever were made as separate components and joined together. In later watches they were made as a single component as shown in the picture. The combined component is often referred to simply as the "lever". In a straight line Swiss lever type escapement, the lever is shaped like a 'T' or an anchor, which gives this escapement its alternative name of anchor escapement. The lever is pivoted in the center; in operation it rocks back and forth.{{cite web , last = Odets , first = Walt , author-link = , title = The Escapement , work = Illustrated Glossary of Watch Parts , pub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balance Wheel
A balance wheel, or balance, is the timekeeping device used in mechanical watches and small 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, known as 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 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Knoop Hardness Test
The Knoop hardness test is a microhardness test – a test for mechanical hardness used particularly for very brittle materials or thin sheets, where only a small indentation may be made for testing purposes. A pyramidal diamond point is pressed into the polished surface of the test material with a known (often 100g) load, for a specified dwell time, and the resulting indentation is measured using a microscope. The geometry of this indenter is an extended pyramid with the length to width ratio being 7:1 and respective face angles are 172 degrees for the long edge and 130 degrees for the short edge. The depth of the indentation can be approximated as 1/30 of the long dimension. The Knoop hardness ''HK'' or ''KHN'' is then given by the formula: :HK where: :''L'' = length of indentation along its long axis :''C''p = correction factor related to the shape of the indenter, ideally 0.070279 :''P'' = load HK values are typically in the range from 100 to 1000, when specified in the co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mohs Scale Of Mineral Hardness
The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by the German geologist and mineralogist Friedrich Mohs, in his book ''"Versuch einer Elementar-Methode zur naturhistorischen Bestimmung und Erkennung der Fossilien"''; it is one of several definitions of hardness in materials science, some of which are more quantitative. The method of comparing hardness by observing which minerals can scratch others is of great antiquity, having been mentioned by Theophrastus in his treatise ''On Stones'', , followed by Pliny the Elder in his ''Naturalis Historia'', . The Mohs scale is useful for identification of minerals in the field, but is not an accurate predictor of how well materials endure in an industrial setting – ''toughness''. Minerals The Mohs scale of mineral hardness is based on the ability ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stiction
Stiction is the static friction that needs to be overcome to enable relative motion of stationary objects in contact. The term is a portmanteau of the words ''static'' and ''friction'', and is perhaps also influenced by the verb '' to stick''. Any solid objects pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact in order to overcome static adhesion. Stiction is a ''threshold'', not a continuous force. However, stiction might also be an illusion made by the rotation of kinetic friction. In situations where two surfaces with areas below the micrometer scale come into close proximity (as in an accelerometer), they may adhere together. At this scale, electrostatic and/or Van der Waals and hydrogen bonding forces become significant. The phenomenon of two such surfaces being adhered together in this manner is also called stiction. Stiction may be related to hydrogen bonding or residual contamination. Automobiles Sticti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact. Dry friction is subdivided into ''static friction'' ("stiction") between non-moving surfaces, and ''kinetic friction'' between moving surfaces. With the exception of atomic or molecular friction, dry friction generally arises from the interaction of surface features, known as asperities (see Figure 1). *Fluid friction describes the friction between layers of a viscous fluid that are moving relative to each other. *Lubricated friction is a case of fluid friction where a lubricant fluid separates two solid surfaces. *Skin friction is a component of drag, the force resisting the motion of a fluid across the surface of a body. *Internal friction is the force resisting motion between the elements making up a so ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
War Production Board
The War Production Board (WPB) was an agency of the United States government that supervised war production during World War II. President Franklin D. Roosevelt established it in January 1942, with Executive Order 9024. The WPB replaced the Supply Priorities and Allocations Board and the Office of Production Management. The WPB directed conversion of companies engaged in activities relevant to war from peacetime work to war needs, allocated scarce materials, established priorities in the distribution of materials and services, and prohibited nonessential production. It rationed such commodities as gasoline, heating oil, metals, rubber, paper, and plastics. It was dissolved shortly after the Surrender of Japan, defeat of Japan in 1945 and was replaced by the Civilian Production Administration in late 1945. In 1942–1945, WPB supervised the production of $183 billion (equivalent to $ in ) worth of weapons and supplies, about 40 percent of the world output of munitions. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing military alliances: the Allies and the Axis powers. World War II was a total war that directly involved more than 100 million personnel from more than 30 countries. The major participants in the war threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. Aircraft played a major role in the conflict, enabling the strategic bombing of population centres and deploying the only two nuclear weapons ever used in war. World War II was by far the deadliest conflict in human history; it resulted in 70 to 85 million fatalities, mostly among civilians. Tens of millions died due to genocides (including the Holocaust), starvation, ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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