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A differential is a device, usually but not necessarily employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways. In one way, it receives one input and provides two outputs; this is found in most automobiles. In the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs. In automobiles and other wheeled vehicles, the differential allows each of the driving roadwheels to rotate at different speeds, while for most vehicles supplying equal torque to each of them. A vehicle's wheels rotate at different speeds, mainly when turning corners. The differential is designed to drive a pair of wheels with equal force, whilst allowing them to rotate at different speeds. In vehicles without a differential, such as karts, both driving wheels are forced to rotate at the same speed, usually on a common axle driven by a simple chain-drive mechanism. When cornering, the inner wheel needs to travel a shorter distance than the outer wheel, so with no differential, the result is the inner wheel spinning and/or the outer wheel dragging, and this results in difficult and unpredictable handling, damage to tires and roads, and strain on (or possible failure of) the entire drivetrain. In automotive applications, the differential housing is sometimes colloquially called a "pumpkin" as the differential housing typically resembles a pumpkin. A locking differential, such as ones using differential gears in normal use but using air or electrically controlled mechanical system, which when locked allow no difference in speed between the two wheels on the axle. They employ a mechanism for allowing the planetary gears to be locked relative to each other, causing both wheels to turn at the same speed regardless of which has more traction; this is equivalent to effectively bypassing the differential gears entirely. Other locking systems may not even use differential gears but instead drive one wheel or both depending on torque value and direction. [READ THE REST OF THIS ARTICLE]



Huntsman spiders is a family of spiders also known as the giant crab spiders, due to their size and appearance. Larger specimens of these spiders are also sometimes referred to as wood spiders, due to their preference for inhabiting woody places (forest, mine shafts, woodpiles, wooden shacks). They are known as rain spiders in southern Africa. They are are found in Australia, New Zealand, South Africa, Southeast Asia, the Mediterranean, Florida, and Hawaii, and possibly in many other tropical and semi-tropical regions. While frequently very large in Laos, Heteropoda maxima males can attain a legspan of 250300 mm (9.811.8 in) As with all spiders, they use venom to demobilise or digest prey, but they are not deadly to healthy humans. They do bite if provoked, but the victim will suffer only minor swelling and localised pain, and will recover in a day or two. Some larger types resemble tarantulas. Huntsman spiders can generally be identified by their legs, which, rather than being jointed vertically relative to the body, are twisted such that the legs extend forward in a crab-like fashion. Many huntsman spiders are dull shades of brown or grey. Their legs are covered with fairly prominent spines, but the rest of their bodies appear smooth. They are frequently found in sheds, garages and other infrequently-disturbed places. As adults, huntsman spiders do not build webs, but hunt and forage for food: their diet consists primarily of insects and other invertebrates, and occasionally small skinks and geckos. They live in the crevices of tree bark, but will frequently wander into homes and vehicles. They are able to travel extremely fast, often using a springing jump while running, and walk on walls and even on ceilings. They also tend to exhibit a "cling" reflex if picked up, making them difficult to shake off and much more likely to bite. The females are fierce defenders of their egg sacs and young. They will generally make a threat display if provoked, but if the warning is ignored they may attack and bite. The males anchor themselves firmly to the surface onto which they have crawled and then use their legs to transmit vibrations from their bodies to the surface. Most of the sound emitted is produced by strong vibrations of the abdomen. The characteristic frequency of vibration and the pattern of bursts of sound identify them to females of their species, who will approach if they are interested in mating. [READ THE REST OF THIS ARTICLE]





Kirov, the lead ship of her class of missile cruisers, is one of the major and biggest surface warships of the Russian Navy, though it was originally built for the Soviet Navy. It is one of the biggest warships of the world and is similar in size to a World War I battleship. Although commissioned as a missile cruiser Kirov's size and weapons complement have given her the unofficial designation of a battlecruiser throughout much of the world. The appearance of the Kirov class was a significant factor in the U.S. Navy recommissioning the Iowa class. She was named after Sergey Kirov, a Bolshevik hero. Kirov suffered a reactor accident in 1990 while serving in the Mediterranean Sea. Repairs were never carried out, due to lack of funds and the changing political situation in the Soviet Union. She may have been cannibalized as a spare parts cache for the other ships in her class. Admiral Ushakov at Severomorsk in 1992.In June 2004 the name Admiral Ushakov was transferred to the Sovremenny class destroyer Besstrashny. In September 2004 it was revealed that the Severodvinsk-based Design Bureau Onega had been tasked with developing the dismantlement project for the cruiser, currently moored at the Severdovinsk Zvezdochka plant. According to the Zvezdochka plant, dismantlement of the former Admiral Ushakov would cost $40 million, all of which was allocated by Norway. [READ THE REST OF THIS ARTICLE]



The IBM Selectric typewriter was a highly successful model line of electric typewriters introduced by IBM on July 31, 1961. Instead of the "basket" of individual typebars that swung up to strike the ribbon and page in a traditional typewriter, the Selectric had a type element that rotated and pivoted to the correct position before striking. The type element could be easily changed so as to print different fonts in the same document, resurrecting a capacity that had been pioneered by the Blickensderfer typewriter sixty years before. The Selectric also replaced the traditional typewriter's moving carriage with a paper roller that stayed in position while the typeball and ribbon mechanism moved from side to side. Mechanically, the Selectric borrowed some design elements from a toy typewriter produced earlier by Marx Toys. IBM bought the rights to the design. The typeball and carriage mechanism was similar to the design of the Teletype Model 26 and later, which used a rotating cylinder that moved along a fixed platen. The mechanism that positions the typing element is partly binary, and includes two mechanical digital-to-analog converters, which are basically "whiffletree" linkages of the type used for adding and subtracting in linkage-type mechanical analog computers. Every character has its own binary codes, one for tilt and one for rotate. When the typist presses a key, it unlatches a metal bar for that key. The bar is parallel to the side of the mechanism. This bar has several short projections . Only some of the fingers are present on any given code bar, those present corresponding to the binary code for the desired character. When the key's bar moves, its projections push against a second set of bars that extend all the way across the keyboard mechanism; each bar corresponds to one bit. All bars for the keys contact some of these crosswise bars. Those bars that move, of course, define the binary code. In addition to the "typeball" technology, Selectrics were also associated with a series of innovations in ribbon design. The original Selectric had to be ordered to use either cloth reusable ribbon or one-time carbon film ribbon; the same machine could not use both. The same was true of the original, non-correcting Selectric II. IBM had used a similar carbon film ribbon on their earlier "Executive" series of typewriters. As with these older machines, the carbon film ribbon presented a security issue in some environments: It was possible to read the text that had been typed from the ribbon, seen as light characters against the darker ribbon background. Selectrics and their descendants eventually captured 75 percent of the United States market for electric typewriters used in business. IBM replaced the Selectric line with the IBM Wheelwriter in 1984 and transferred its typewriter business to the newly-formed Lexmark in 1991. [READ THE REST OF THIS ARTICLE]



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