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Tensioner
A tensioner is a device that applies a force to create or maintain tension. The force may be applied parallel to, as in the case of a hydraulic bolt tensioner, or perpendicular to, as in the case of a spring-loaded bicycle chain tensioner, the tension it creates. The force may be generated by a fixed displacement, as in the case of an eccentric bicycle bottom bracket, which must be adjusted as parts wear, or by stretching or compressing a spring, as in the case of a spring-loaded bicycle chain tensioner; by changing the volume of a gas, as in the case of a marine riser tensioner; by hydraulic pressure, as in the case of a hydraulic bolt tensioner; or by gravity acting on a suspended mass, as in the case of a chair lift cable tensioner. In the power sector, thtensioneris a machine for maintaining constant tension of the conductors during work of hanging the transmission network.. Applications *Bolt tensioners are devices designed to apply a specific tension to a bolt. The devi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Riser Tensioner
A marine riser tensioner is a device used on an offshore drilling vessel which provides a near constant upward force on the drilling riser independent of the movement of the floating drill vessel. The marine riser is connected to the wellhead on the sea bed and therefore the tensioner must manage the differential movements between the riser and the rig. If there were no tensioner and the rig moves downward, the riser would buckle; if the rig rises then high forces would be transmitted to the riser and it would stretch and be damaged. Tensioners have historically been composed of hydraulic actuated cylinders with wire sheaves. More recently, active electrical motors have been used for compensation purposes. Hydraulic Tensioner A hydraulic riser tensioner consists of a hydraulic cylinder with sheaves at both sides. The cylinder is connected to a number of high-pressure gas bottles via a medium separator. A wire rope is rigged in the cylinder; one end is connected to the fixed par ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guideline Tensioner
A guideline tensioner is a hydropneumatic device used on an offshore drilling rig that keeps a positive pulling force on the guidelines from the platform to a template on the seabed. The guidelines act as a guidance for equipment and tools that must be lowered to the template. If there was no tensioner and the platform moved, the guidelines would become slack and could be broken. For this reason a number of guideline tensioners are mounted between the platform and riser. Each of these guideline tensioners consists of a hydraulic cylinder with sheaves at both sides. The cylinder is connected to one or more high pressure gas bottles via a medium separator. A wire rope is rigged in the cylinder; one end is connected to the fixed part of the tensioner, the other end to the template. References See also *Conductor tensioner * Drill string compensator *Riser tensioner *Hydraulic jigger A hydraulic jigger is a hydraulically-powered mechanical winch. From the mid-19th century, hydra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Single-speed Bicycle
A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle. There are many types of modern single speed bicycles; BMX bicycles, most bicycles designed for children, cruiser type bicycles, classic commuter bicycles, unicycles, bicycles designed for track racing, fixed-gear road bicycles, and single-speed mountain and cyclocross bikes. Although most fixed-gear bicycles (fixies) are technically single speed, the term single-speed generally refers to a single gear ratio bicycle with a freewheel mechanism to allow it to coast. Vis-à-vis multi-speed bicycles Advantages A single-speed bicycle is generally cheaper, lighter, and mechanically simpler than its multi-geared equivalent. Without derailleurs or other gearing systems, there are fewer parts on the bicycle that require maintenance, making this type of cycle useful for city commuting in all weath ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timing Belt (camshaft)
In a piston engine, either a timing belt (also called a ''cambelt'') or timing chain or set of timing gears is used to synchronize the rotation of the crankshaft and the camshaft. This synchronisation ensures that the engine's valves open and close at the correct times in relation to the position of the pistons. Design In most piston engines, the camshaft(s) are mechanically connected to the crankshaft. The crankshaft drives the camshaft (via a timing belt, timing chain or pushrods), which in turn actuates the intake and exhaust valves. These valves allow the engine to inhale air (or an air/fuel mixture) and exhale the exhaust gasses. The most common devices to transfer the drive are toothed rubber belts, metal timing chains or a set of gears. The teeth of the belt/chain/gears mesh with both the crankshaft and camshaft(s), thereby synchronising their motion. In many older overhead valve engines, the camshaft is located in the block near the crankshaft, therefore a simple gear ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chainsaw
A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, cutting firebreaks in wildland fire suppression, and harvesting of firewood. Chainsaws with specially designed bar-and-chain combinations have been developed as tools for use in chainsaw art and chainsaw mills. Specialized chainsaws are used for cutting concrete during construction developments. Chainsaws are sometimes used for cutting ice; for example, ice sculpture and winter swimming in Finland. History In surgery The origin of chain saws in surgery is debated. A "flexible saw", consisting of a fine serrated link chain held between two wooden handles, was pioneered in the late 18th century (c. 1783–1785) by two Scottish doctors, John Aitken and James Jeffray, for symphysiotomy and excision of diseased bone, respectively. It was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serpentine Belt
A serpentine belt (or drive belt) is a single, continuous belt used to drive multiple peripheral devices in an automotive engine, such as an alternator, power steering pump, water pump, air conditioning compressor, air pump, etc. The belt may also be guided by an idler pulley and/or a belt tensioner (which may be spring-loaded, hydraulic, or manual). To allow the belt to pass over more than three pulleys with a large enough wrap angle to avoid slipping, idler pulleys which press against the back of the belt are included, forcing the belt into a serpentine shape. To accommodate this bidirectional flexing while remaining strong enough to transfer the total force required by multiple loads, a serpentine belt is almost always of multi-groove (multi-vee, poly-v, or multi-rib) construction. Variations On some engine designs, the "back" (smooth side) of the belt may drive some accessories. This is typically limited to components requiring less torque or where a large angle of wrap i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Belt-driven Bicycle
A belt-driven bicycle is a chainless bicycle that uses a toothed synchronous belt to transmit power from the pedals to the wheel. The application of belt drives to bicycles is growing, especially in the commuter bicycle market, due to the low maintenance and lubrication-free benefits. Belt drives are also available for stationary and fitness bicycles. Benefits * Belts do not rust. * Lubrication is not required. ** Cleanliness due to lack of lubrication. ** Little to no maintenance. * Smoother operation. * Quieter than chain. * Longer life than metal bicycle chains. * Some belt systems are lighter than conventional chain-driven system. Drawbacks * Derailleurs cannot be used, so a hub gear is used if multiple gear ratios are required. * Most belts cannot be taken apart as a chain can, so a frame must be able to accommodate the belt by having an opening in the rear triangle or an elevated chain stay. There is only one option where the belt can be spliced and joined th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Barbed-wire
A close-up view of a barbed wire Roll of modern agricultural barbed wire Barbed wire, also known as barb wire, is a type of steel fencing wire constructed with sharp edges or points arranged at intervals along the strands. Its primary use is the construction of inexpensive fences, and it is also used as a security measure atop walls surrounding property. As a wire obstacle, it is a major feature of the fortifications in trench warfare. A person or animal trying to pass through or over barbed wire will suffer discomfort and possibly injury. Barbed wire fencing requires only fence posts, wire, and fixing devices such as staples. It is simple to construct and quick to erect, even by an unskilled person. The first patent in the United States for barbed wire was issued in 1867 to Lucien B. Smith of Kent, Ohio, who is regarded as the inventor. Joseph F. Glidden of DeKalb, Illinois, received a patent for the modern invention in 1874 after he made his own modifications to previous v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Overhead Electrical Wire
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as: * Overhead catenary * Overhead contact system (OCS) * Overhead equipment (OHE) * Overhead line equipment (OLE or OHLE) * Overhead lines (OHL) * Overhead wiring (OHW) * Traction wire * Trolley wire This article follows the International Union of Railways in using the generic term ''overhead line''. An overhead line consists of one or more wires (or Overhead conductor rail, rails, particularly in tunnels) situated over rail tracks, raised to a high electrical potential by connection to feeder stations at regular intervals. The feeder stations are usually fed from a High voltage, high-voltage Electricity distribution, electrical grid. Overview Electric trains that collect their current from overhead lines use a device such as a Pantograph (transport), pantograph, bow collector or trolley pole. It presses ag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Churchill Tank
The Tank, Infantry, Mk IV (A22) Churchill was a British infantry tank used in the Second World War, best known for its heavy armour, large longitudinal chassis with all-around tracks with multiple bogies, its ability to climb steep slopes, and its use as the basis of many specialist vehicles. It was one of the heaviest Allied tanks of the war. The origins of the Churchill's design lay in the expectation that war in Europe might be fought in conditions similar to those of the First World War, and thus emphasised the ability to cross difficult ground. The Churchill was hurried into production in order to build up British defences against a possible German invasion. The first vehicles had flaws that had to be overcome before the Churchill was accepted for wide use. After several Marks (versions) had been built, a better-armoured specification, the Mark VII, entered service with the British Army. The improved versions performed well in the later stages of the war. The Churchil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chainlink Fence
A chain-link fence (also referred to as wire netting, wire-mesh fence, chain-wire fence, cyclone fence, hurricane fence, or diamond-mesh fence) is a type of woven fence usually made from galvanized or linear low-density polyethylene-coated steel wire. The wires run vertically and are bent into a zigzag pattern so that each "zig" hooks with the wire immediately on one side and each "zag" with the wire immediately on the other. This forms the characteristic diamond pattern seen in this type of fence. Development of chain-link fencing In the United Kingdom, the firm of Barnard, Bishop & Barnards was established in Norwich to produce chain-link fencing by machine. The process was developed by Charles Barnard in 1844 based on cloth weaving machines (up until that time, Norwich had a long history of cloth manufacture). The Anchor Post Fence Co. bought the rights to the wire-weaving machine and was the first company to manufacture chain-link fencing in the United States. Anchor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Fence
An electric fence is a barrier that uses electric shocks to deter people or animals from crossing a boundary. The voltage of the shock may have effects ranging from discomfort to death. Most electric fences are used for agricultural fencing and other forms of non-human animal control, although they are also used to protect high-security areas such as military installations or prisons, where potentially-lethal voltages may be used. Virtual electric fences for livestock using GPS technology have also been developed. Design and function Electric fences are designed to complete an electrical circuit when touched by an animal. A component called a power energizer converts power into a brief high voltage pulse. One terminal of the power energizer releases an electrical pulse along a connected bare wire about once per second. Another terminal is connected to a metal rod implanted in the earth, called a ground or earth rod. An animal touching both the wire and the earth during a pu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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