Wheel 33555 225035314 2008-07-11T15:58:55Z NawlinWiki 301395 Changed protection level for "[[Wheel]]": no reason to move this page w/o discussion [edit=autoconfirmed:move=sysop] {{otheruses}} {{semiprotected|small=yes}} [[Image:TricycleAntique.jpg|thumb|Three wheels on an antique tricycle]] A '''wheel''' is a circular device that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load ([[mass]]), or performing labour in machines. A wheel, together with an [[axle]] overcomes [[friction]] by facilitating motion by [[rolling]]. In order for wheels to rotate, a moment needs to be applied to the wheel about its axis, either by way of gravity, or by application of another external force. Common examples are found in [[transport]] applications. More generally the term is also used for other circular objects that rotate or turn, such as a [[Ship's wheel]], [[steering wheel]] and [[flywheel]]. ==Etymology== The English word ''[[:wikt:wheel|wheel]]'' comes from the [[Proto-Indo-European language|Proto-Indo-European]] *''k<sup>w</sup>ek<sup>w</sup>lo-'',<ref>{{cite encyclopedia|title=wheel|encyclopedia=Online Etymology Dictionary|url=http://www.etymonline.com/index.php?term=wheel}}</ref> which was an extended form of the root *''k<sup>w</sup>el-'' meaning "to revolve, move around". This is also the root of the [[Greek language|Greek]] κυκλος ''kuklos'', the [[Sanskrit]] ''[[chakra]]'', and [[Persian language|Persian]] ''charkh'', all meaning "circle" or "wheel",<ref>[http://www.bartleby.com/61/roots/IE250.html kwel-1. The American Heritage® Dictionary of the English Language: Fourth Edition. 2000<!-- Bot generated title -->]</ref> and also in [[Lithuanian language|Lithuanian]], ''sukti'' means "to rotate". The Latin word ''[[:wikt:rota|rota]]'' is from the Proto-Indo-European *''rotā-'', the extended o-grade form of the root *''ret-'' meaning "to roll, revolve".<ref>[http://www.bartleby.com/61/roots/IE432.html ret- The American Heritage® Dictionary of the English Language: Fourth Edition. 2000<!-- Bot generated title -->]</ref> ==History== {{Expert-verify|date=May 2008}} [[Image:Standard of Ur chariots.jpg|frame|right|A depiction of [[onager]]-drawn carts on the [[Sumer]]ian "battle standard of [[Ur]]" (circa 3200 BC)]] [[Image:Wheel Iran.jpg|thumb|right|250px|A spoked wheel on display at The [[National Museum of Iran]], in [[Tehran]]. The wheel is dated late 2nd millennium BC and was excavated at [[Choqa Zanbil]].]] Most authorities regard the wheel as one of the oldest and most important [[invention]]s, which originated in ancient [[Mesopotamia]] in the [[5th millennium BC]] ([[Ubaid period]]), originally in the function of [[potter's wheel]]s. Near the northern side of the [[Caucasus]] several graves were found, in which since 3700 BC people had been buried on wagons or carts (both types). The earliest depiction of what may be a wheeled vehicle (here a wagon—four wheels, two axles), is on the [[Bronocice pot]], a ca. 3500 BC clay pot excavated in southern Poland.<ref>[http://www.neolit.prv.pl Waza z Bronocic (in Polish)]</ref> The wheel reached [[Europe]] and [[Western Asia]] in the 4th millennium BC, and the [[Indus Valley Civilization|Indus Valley]] by the 3rd millennium BC. In [[China]], the wheel is certainly present with the adoption of the [[chariot]] in ca. 1200 BC,<ref>Dyer, Gwynne, War: the new edition, p. 159: Vintage Canada Edition, Randomhouse of Canada, Toronto, ON</ref> although Barbieri-Low (2000) argues for earlier Chinese wheeled vehicles, circa 2000 BC. Whether there was an independent "invention of the wheel" in East Asia or whether the concept made its way there after jumping the Himalayan barrier remains an open question. Although they did not develop the wheel proper, the [[Olmec]] and certain other [[western hemisphere]] [[cultures]] seem to have approached it, as wheel-like worked [[rock (geology)|stone]]s have been found on objects identified as [[children]]'s [[toys]] dating to about 1500 BC. The invention of the wheel thus falls in the late [[Neolithic]], and may be seen in conjunction with the other technological advances that gave rise to the early [[Bronze Age]]. Note that this implies the passage of several wheel-less millennia even after the invention of [[agriculture]]. Looking back even further, it is of some interest that although [[Paleoanthropology|paleoanthropologists]] now date the emergence of anatomically modern humans to ca.150,000 years ago, 143,000 of those years were "wheel-less". That people with capacities fully equal to our own walked the earth for so long before conceiving of the wheel may be initially surprising, but populations were extremely small through most of this period and the wheel, which requires an axle and socket to actually be useful, is not as simple a device as it may seem. Making and balancing a wheel requires a [[Skill (labor)|skilled]] [[wheelwright]]. Early wheels were simple wooden disks with a hole for the axle. Because of the structure of [[wood]] a horizontal slice of a trunk is not suitable, as it does not have the structural strength to support weight without collapsing; rounded pieces of longitudinal boards are required. The [[spoke]]d wheel was invented more recently, and allowed the construction of lighter and swifter vehicles. The earliest known examples are in the context of the [[Andronovo culture]], dating to ca 2000 BC. Shortly later, horse cultures of the [[Caucasus]] region used horse-drawn spoked-wheel war [[chariots]] for the greater part of three centuries. They moved deep into the Greek peninsula where they joined with the existing Mediterranean peoples to give rise, eventually, to classical Greece after the breaking of [[Minoan civilization|Minoan]] dominance and consolidations led by pre-classical [[Sparta]] and [[Athens]]. [[Celt]]ic chariots introduced an [[iron]] rim around the wheel in the 1st millennium BC. The spoked wheel had been in continued use without major modification until the 1870s CE, when wire wheels and pneumatic [[tire]]s were invented.<ref>[http://www.bookrags.com/research/wheel-and-axle-woi/ bookrags.com] - Wheel and axle</ref> The invention of the wheel has also been important for [[technology]] in general, important applications including the [[water wheel]], the [[cogwheel]] (see also [[antikythera mechanism]]), the [[spinning wheel]], and the [[astrolabe]] or [[torquetum]]. More modern descendants of the wheel include the [[propeller]], the [[jet engine]], the [[flywheel]] ([[gyroscope]]) and the [[turbine]]. ==Mechanics and function== The wheel is a device that enables efficient movement of an object across a surface where there is a force pressing the object to the surface. Common examples are a cart drawn by a horse, and the rollers on an aircraft flap mechanism. The wheel is not a machine, and should not be confused with the [[wheel and axle]], one of the [[simple machine]]s. A driven wheel is a special case, that is a [[wheel and axle]]. Note that wheels predate driven wheels by about 6000 years. Wheels are used in conjunction with [[axle]]s, either the wheel turns on the axle, or the axle turns in the object body. The mechanics are the same in either case. The low resistance to motion (compared to dragging) is explained as follows (refer to [[friction]]): *the normal force at the sliding interface is the same. *the sliding distance is reduced for a given distance of travel. *the coefficient of friction at the interface is usually lower. [[bearing (mechanical)|Bearings]] are used to reduce friction at the interface. Example: * If dragging a 100 [[kilogram|kg]] object for 10 [[metre|m]] along a surface with ''μ''&nbsp;= 0.5, the [[normal force]] is 981 [[newton|N]] and the [[Mechanical work|work]] done (required [[energy]]) is (work=force x distance) 981 &times; 0.5 &times; 10&nbsp;= 4905 [[joule]]s. * Now give the object 4 wheels. The normal force between the 4 wheels and axles is the same (in total) 981 N, assume ''μ''&nbsp;= 0.1, and say the wheel [[diameter]] is 1000 mm and axle diameter is 50 mm. So while the object still moves 10 m the sliding frictional surfaces only slide over each other a distance of 0.5 m. The work done is 981 x 0.1 x 0.5&nbsp;= 49 joules. Additional energy is lost at the wheel to road interface. This is termed [[rolling resistance]] which is predominantly a deformation loss. ==Alternatives to wheels== While wheels are used for ground transport very widely, there are alternatives, some of which are suitable for terrain where wheels are ineffective. Alternative methods for ground transport without wheels (wheel-less transport) include: * Being raised by [[electromagnetic]] energy ([[maglev train]] and other vehicles) * Dragging with runners ([[sled]]) or without ([[travois]]) * Being raised by air pressure ([[hovercraft]]) * [[Equestrianism|Riding]] an [[Working animal|animal]] such as a [[horse]] * Human powered: ** [[Walk]]ing on one's own [[legs]] ** Being carried ([[Litter (vehicle)|litter/sedan chair]] or [[stretcher]]) * A [[Walker (machine)|walking machine]] * [[Caterpillar tracks]] (although it is still operated by wheels) * [[Sphere]]s, as used by the [[Audi RSQ]] concept car, and [[Dyson (company)|Dyson]] vacuum cleaners ==Wheels as symbols== [[Image:Roma flag.svg|thumb|150px|right|The Romani flag]] [[Image:Dharmacakra.svg|thumb|left|90px|In the [[Unicode]] computer standard, the [[Dharmacakra]] is called the "Wheel of [[Dharma]]" and found in the eight-spoked form. It is represented as U+2638 (☸)]] The wheel has also become a strong [[cultural]] and spiritual metaphor for a cycle or regular repetition (see [[chakra]], [[reincarnation]], [[Yin and yang|Yin and Yang]] among others). As such and because of the difficult terrain, wheeled vehicles were forbidden in [[history of Tibet|old Tibet]]. The [[winged wheel]] is a symbol of progress, seen in many contexts including the [[coat of arms of Panama]] and the logo of the [[Ohio State Highway Patrol]]. The introduction of spoked ([[chariot]]) wheels in the Middle Bronze Age appear to have carried somewhat of a prestige. The [[solar wheel]] appears to have a significance in [[Bronze Age religion]], replacing the earlier concept of a [[Solar barge]] with the more "modern" and technologically advanced [[solar chariot]]. The wheel is also the prominent figure on the [[flag of India]]. The wheel in this case represents law ([[dharma]]). It also appears in the [[flag of the Romani people]], hinting to their nomadic history and their Indian origins. In recent times, the [[customization|custom]] [[aftermarket (automotive)|aftermarket]] [[automobile|car/automobile]] roadwheel has become a [[status symbol]]. These wheels are often incorrectly referred to as "[[Rim (wheel)|rims]]". The term "rim" is incorrect because the rim is only the outer portion of a wheel (where the tire is mounted), just as with a coffee cup or meteor crater. These "rims" have a great deal of variation, and are often highly polished and very shiny. Some custom "rims" include a bearing-mounted, free-spinning disc which continues to rotate by [[inertia]] after the automobile is stopped. In slang, these are referred to as "[[Spinner (wheel)|Spinners]]". {{clr}} ==See also== {{Wiktionary|wheel}} * [[Alloy wheel]] * [[Artillery wheel]] * [[Axle]] * [[Bicycle wheel]] * [[Big Wheel|Big wheel]] * [[Breaking wheel]], a form of [[torture]] * [[Caster]] * [[Color wheel]] * [[Disteel|Pressed Steel wheel]] * [[Driving wheel]] * [[Ferris wheel]] * [[Hubcap]] * [[Magnetic levitation]] and [[wheel-less]] * [[Mecanum wheel]] * [[Reinventing the wheel]] * [[Rim (wheel)|Rim]] * [[Rolling friction]] * [[Ship's wheel]] * [[Simple machine]] * [[Square wheel]] * [[Steering wheel]] * [[Tire]] * [[Tweel]] * [[Wagon-wheel effect]] * [[Wheel and axle]] * [[Wheel sizing]] * [[Wire wheels]] * [[Wheel of Fortune]] * [[Wheelset (railroad)]] * [[Terrestrial locomotion in animals#Rolling|Terrestrial locomotion in animals: Rolling]] ==Gallery of images== {{commonscat|Wheels}} {{commonscat|Automobile wheels}} <gallery> Image:Steam locomotive driving wheel.jpg|A driving wheel on a [[steam locomotive]] Image:0 Series Shinkansen Wheel-06.jpg|[[0 Series Shinkansen]] wheel Image:Aprilia disc brake.jpg|Modern motorcycle [[alloy wheel]] with [[disc brake]] Image:Australian cart.jpg|A pair of wheels on a cart Image:Training wheel.jpg|[[Training wheels]] are used to help the learner cope with gravity </gallery> ==References== <!-- Dead note "p-1": Casson, Lionel, "Travel in the Ancient World", The Johns Hopkins University Press, Baltimore, 1994. --> {{reflist}} [[Category:Wheels| ]] [[af:Wiel]] [[ar:دولاب]] [[ast:Rueda]] [[bs:Točak]] [[br:Rod]] [[ca:Roda]] [[ceb:Ligid]] [[cs:Kolo]] [[cy:Olwyn]] [[da:Hjul]] [[pdc:Raad]] [[de:Rad]] [[et:Ratas]] [[es:Rueda]] [[eo:Rado]] [[eu:Gurpil]] [[fa:چرخ]] [[fr:Roue]] [[fur:Ruede]] [[gd:Cuibhle]] [[gl:Roda]] [[hak:Lin-é]] [[ko:바퀴]] [[hy:Անիվ]] [[hi:चक्र]] [[hr:Kotač]] [[io:Roto]] [[id:Roda]] [[is:Hjól]] [[it:Ruota]] [[he:גלגל]] [[ka:ბორბალი]] [[la:Rota]] [[lv:Ritenis]] [[lt:Ratas]] [[hu:Kerék]] [[ms:Roda]] [[nl:Wiel (voortbeweging)]] [[ja:車輪]] [[no:Hjul]] [[nn:Hjul]] [[nrm:Reue]] [[uz:Gʻildirak]] [[nds:Rad]] [[pl:Koło (technika)]] [[pt:Roda]] [[ro:Roată]] [[qu:Qalla]] [[ru:Колесо]] [[sq:Rrota]] [[scn:Rota]] [[simple:Wheel]] [[sk:Koleso]] [[sl:Kolo]] [[sr:Точак]] [[sh:Kotač]] [[fi:Pyörä]] [[sv:Hjul]] [[ta:சில்லு]] [[te:చక్రం]] [[th:ล้อ]] [[tr:Tekerlek]] [[uk:Колесо]] [[vec:Rua]] [[wa:Rowe (mecanike)]] [[yi:ראד]] [[zh-yue:轆]] [[zh:輪]]