Wheel - Wikipedia, The Free Encyclopedia

8/12/2019 Wheel - Wikipedia, The Free Encyclopedia

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29/3/2014 Wheel - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Wheel 1/11

Three wheels on an antique tricycle

WheelFrom Wikipedia, the free encyclopedia

A wheelisa circular component that is intended to rotate on anaxial bearing. The wheel is one of the main components of thewheel and axle which is one ofthe six simple machines. Wheels,in conjunction with axles, allow heavyobjects to be moved easilyfacilitating movement or transportation while supporting a load,or performing labor in machines. Wheels are also used for otherpurposes, such as a ship's wheel, steering wheel, potter's wheeland flywheel.

Common examplesare found in transport applications. A wheelgreatly reduces friction by facilitating motion by rolling togetherwith the use of axles. In order for wheels to rotate, a momentneeds to be applied tothe wheel about its axis, either by way of

gravity, or by the application of another external force or torque.

Contents

1 Etymology2 History

2.1 Images3 Mechanics and function

4 Construction4.1 Rim4.2 Hub4.3 Spokes

4.3.1 Wire4.4 Tire

5 Alternatives6 Symbolism7 Gallery8 See also9 References10 External links

Etymology

The English word wheelcomes from the Old English word hweol, hweogol, from Proto-Germanic*hwehwlan, *hwegwlan, from Proto-Indo-European *kwekwlo-,[1]an extended form of the root *kwel-"torevolve, move around". Cognates within Indo-European include Greek kklos, "wheel" and Sanskritchakra, both meaning "circle" or "wheel".[2]

History
http://en.wikipedia.org/wiki/Chakrahttp://en.wikipedia.org/wiki/Chakrahttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Proto-Indo-European_languagehttp://en.wiktionary.org/wiki/wheelhttp://en.wikipedia.org/wiki/Old_Englishhttp://en.wikipedia.org/wiki/Axlehttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Wheel_and_axlehttp://en.wikipedia.org/wiki/Chakrahttp://en.wikipedia.org/wiki/Sanskrithttp://en.wikipedia.org/wiki/Greek_languagehttp://en.wikipedia.org/wiki/Proto-Indo-European_languagehttp://en.wikipedia.org/wiki/Proto-Germanic_languagehttp://en.wikipedia.org/wiki/Old_Englishhttp://en.wiktionary.org/wiki/wheelhttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Moment_(physics)http://en.wikipedia.org/wiki/Axlehttp://en.wikipedia.org/wiki/Rollinghttp://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Transporthttp://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Potter%27s_wheelhttp://en.wikipedia.org/wiki/Steering_wheelhttp://en.wikipedia.org/wiki/Ship%27s_wheelhttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Wheel_and_axlehttp://en.wikipedia.org/wiki/Bearing_(mechanical)http://en.wikipedia.org/wiki/Tricyclehttp://en.wikipedia.org/wiki/File:TricycleAntique.jpg


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A depiction of an onager-drawn carton the Sumerian "battle standard ofUr" (c. 2500 BC)

A figurine featuring the New World'sindependently invented wheel

Evidence of wheeled vehicles appears from the second half of the 4thmillennium BC, near-simultaneously in Mesopotamia (Sumeriancivilization), the Northern Caucasus (Maykop culture) and CentralEurope, so that the question of which culture originally invented thewheeled vehicle remains unresolved and under debate.

The oldest securely dated wheel-axle combination, that from StareGmajne near Ljubljana in Slovenia (Ljubljana Marshes WoodenWheel) is now dated in 2-limits to 3340-3030 cal BC, the axle to3360-3045 cal BC [3]

The earliest well-dated depiction of a wheeled vehicle (here a wagonfour wheels, two axles) is on the Bronocice pot, a c. 3500 3350BC clay pot excavated in a Funnelbeaker culture settlement insouthern Poland.[4]

The wheeled vehicle spread from the area of its first occurrence

(Mesopotamia, Caucasus, Balkans, Central Europe) across Eurasia,reaching the Indus Valley by the 3rd millennium BC. During the 2ndmillennium BC, the spoke-wheeled chariot spread at an increasedpace, reaching both China and Scandinavia by 1200 BC.

In China, the wheel was certainly present with the adoption of thechariot in c. 1200 BC,[5]although Barbieri-Low[6]argues for earlierChinese wheeled vehicles, c. 2000 BC.

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 stones have been found on objects identified as children's toysdating to about 1500 BC.[7]It is thought that the primary obstacle to large-scale development of the wheel inthe Western hemisphere was the absence of domesticated large animals which could be used to pull wheeledcarriages. The closest relative of cattle present in Americas in pre-Columbian times, the American Bison, isdifficult to domesticate and was never domesticated by Native Americans; several horse species existed untilabout 12,000 years ago, but ultimately went extinct.[8]The only large animal that was domesticated in theWestern hemisphere, the llama, did not spread far beyond the Andes by the time of the arrival of Columbus.

Nubians from after about 400 BC used wheels for spinning pottery and as water wheels.[9]It is thought thatNubian waterwheels may have been ox-driven[10]It is also known that Nubians used horse-driven chariots

imported from Egypt.[11]

The wheel was barely used in Sub-Saharan Africa into the 19th century, only arriving with Europeans after theyexplored the region and then moved to exploit it.[12][13]

The invention of the wheel thus falls in the late Neolithic, and may be seen in conjunction with other technologicaladvances that gave rise to the early Bronze Age. Note that this implies the passage of several wheel-lessmillennia even after the invention of agriculture and of pottery:

95006500 BC: Aceramic Neolithic

65004500 BC: Ceramic Neolithic (Halafian), earliest wooden wheels (disks with a hole for the axle)c. 4500 BC: invention of the potter's wheel, beginning of the Chalcolithic (Ubaid period)45003300 BC: Chalcolithic, earliest wheeled vehicles, domestication of the horse33002200 BC: Early Bronze Age
http://en.wikipedia.org/wiki/Early_Bronze_Agehttp://en.wikipedia.org/wiki/Domestication_of_the_horsehttp://en.wikipedia.org/wiki/Chalcolithichttp://en.wikipedia.org/wiki/Ubaid_periodhttp://en.wikipedia.org/wiki/Chalcolithichttp://en.wikipedia.org/wiki/Potter%27s_wheelhttp://en.wikipedia.org/wiki/Halafianhttp://en.wikipedia.org/wiki/Neolithichttp://en.wikipedia.org/wiki/Aceramic_Neolithichttp://en.wikipedia.org/wiki/Neolithic_Revolutionhttp://en.wikipedia.org/wiki/Bronze_Agehttp://en.wikipedia.org/wiki/Neolithichttp://en.wikipedia.org/wiki/Sub-Saharan_Africahttp://en.wikipedia.org/wiki/Egypthttp://en.wikipedia.org/wiki/Water_wheelshttp://en.wikipedia.org/wiki/Potteryhttp://en.wikipedia.org/wiki/Nubiahttp://en.wikipedia.org/wiki/Andeshttp://en.wikipedia.org/wiki/Llamahttp://en.wikipedia.org/wiki/American_Bisonhttp://en.wikipedia.org/wiki/Cattlehttp://en.wikipedia.org/wiki/Cultureshttp://en.wikipedia.org/wiki/Olmechttp://en.wikipedia.org/wiki/Nordic_Bronze_Agehttp://en.wikipedia.org/wiki/Bronze_Age_Chinahttp://en.wikipedia.org/wiki/Chariothttp://en.wikipedia.org/wiki/Indus_Valley_Civilizationhttp://en.wikipedia.org/wiki/Funnelbeaker_culturehttp://en.wikipedia.org/wiki/Bronocice_pothttp://en.wikipedia.org/wiki/Ljubljana_Marshes_Wooden_Wheelhttp://en.wikipedia.org/wiki/Central_Europehttp://en.wikipedia.org/wiki/Maykop_culturehttp://en.wikipedia.org/wiki/Caucasushttp://en.wikipedia.org/wiki/Mesopotamiahttp://en.wikipedia.org/wiki/4th_millennium_BChttp://en.wikipedia.org/wiki/New_Worldhttp://en.wikipedia.org/wiki/File:Remojadas_Wheeled_Figurine.jpghttp://en.wikipedia.org/wiki/Urhttp://en.wikipedia.org/wiki/Sumerhttp://en.wikipedia.org/wiki/Onagerhttp://en.wikipedia.org/wiki/File:Ur_chariot.jpg


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22001550 BC: Middle Bronze Age, invention of the spoked wheel and the chariot

Wide usage of the wheel was probably delayed because smooth roads were needed for wheels to be effective.Carrying goods on the back would have been the preferred method of transportation over surfaces thatcontained many obstacles. The lack of developed roads prevented wide usage of the wheel for transportationuntil well into the 20th century in less developed areas.

Early wheels were simple wooden disks with a hole for the axle. Because of the structure of wood, a horizontalslice of a tree trunk is not suitable, as it does not have the structural strength to support relevant stresses withoutfailing; rounded pieces of longitudinal boards are required.

The spoked wheel was invented more recently, and allowed the construction of lighter and swifter vehicles. Inthe Harappan civilization of the Indus Valley and Northwestern India, we find toy-cart wheels made of clay withlines which have been interpreted as spokes painted or in relief, [14]and a symbol interpreted as a spoked wheelin the script of the seals,[15]already in the second half of the 3rd millennium BC. The earliest known examples owooden spoked wheels are in the context of the Andronovo culture, dating to c. 2000 BC. Soon after this,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 peoplesto give rise, eventually, to classical Greece after the breaking of Minoan dominance and consolidations led bypre-classical Sparta and Athens. Celtic chariots introduced an iron rim around the wheel in the 1st millenniumBC. The spoked wheel was in continued use without major modification until the 1870s, when wire wheels andpneumatic tires were invented.[16]

The invention of the wheel has also been important for technology in general, important applications including thewater wheel, the cogwheel (see also antikythera mechanism), the spinning wheel, and the astrolabe ortorquetum. More modern descendants of the wheel include the propeller, the jet engine, the flywheel(gyroscope) and the turbine.

Images

Bronze Age disk wheelas depicted on theStandard of Ur (c. 2500BC)

Classical Greek four-spoked chariot-wheel(the Linear B glyph),in use from c.1500 BC.Hittite and Egyptianchariots tended to havesix spokes, Iron AgeAssyrian ones eight.

Bronze Age "wheelpendants" of the Urnfieldculture (c. 1200 BC),found in Zrich (Swiss

National Museum)

An Early Iron Agespoked wheel fromChoqa Zanbil (c. 1000BC, National Museum ofIran)
http://en.wikipedia.org/wiki/Turbinehttp://en.wikipedia.org/wiki/Gyroscopehttp://en.wikipedia.org/wiki/Flywheelhttp://en.wikipedia.org/wiki/Jet_enginehttp://en.wikipedia.org/wiki/Propellerhttp://en.wikipedia.org/wiki/Torquetumhttp://en.wikipedia.org/wiki/Astrolabehttp://en.wikipedia.org/wiki/Spinning_wheelhttp://en.wikipedia.org/wiki/Antikythera_mechanismhttp://en.wikipedia.org/wiki/Cogwheelhttp://en.wikipedia.org/wiki/Water_wheelhttp://en.wikipedia.org/wiki/Technologyhttp://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Celthttp://en.wikipedia.org/wiki/Athenshttp://en.wikipedia.org/wiki/Spartahttp://en.wikipedia.org/wiki/Minoan_civilizationhttp://en.wikipedia.org/wiki/Chariotshttp://en.wikipedia.org/wiki/Caucasushttp://en.wikipedia.org/wiki/Andronovo_culturehttp://en.wikipedia.org/wiki/Indus_Valley_Civilizationhttp://en.wikipedia.org/wiki/Spokehttp://en.wikipedia.org/wiki/Woodhttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Spokehttp://en.wikipedia.org/wiki/Middle_Bronze_Agehttp://en.wikipedia.org/wiki/National_Museum_of_Iranhttp://en.wikipedia.org/wiki/Choqa_Zanbilhttp://en.wikipedia.org/wiki/Swiss_National_Museumhttp://en.wikipedia.org/wiki/Urnfield_culturehttp://en.wikipedia.org/wiki/Linear_Bhttp://en.wikipedia.org/wiki/Chariothttp://en.wikipedia.org/wiki/Standard_of_Ur


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Wheel of the Etruscanchariot (c. 530 BC)

The classic spokedwheel with hub and ironrim, in use from about500 BC (Iron AgeEurope) until the 20thcentury AD

Penny-farthing bicycle(1882)

Modern motorcycle alloywheel with pneumatictire, suspension andhydraulic disc brake

Mechanics and function

Main article: wheel and axle

The wheel is a device that enables efficient movement of an object across a surface where there is a forcepressing the object to the surface. Common examples are a cart pulled by a horse, and the rollers on an aircraftflap mechanism.

Wheels are used in conjunction with axles; either the wheel turns on the axle, or the axle turns in the objectbody. 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.

Bearings are used to help reduce friction at the interface. In the simplest and oldest case the bearing is just around hole through which the axle passes (a "plain bearing").

Example:

If a 100 kg object is dragged for 10 m along a surface with the coefficient of friction = 0.5, the normalforce is 981 N and the work done (required energy) is (work=force x distance) 981 0.5 10 = 4905joules.Now give the object 4 wheels. The normal force between the 4 wheels and axles is the same (in total)981 N. Assume, for wood,= 0.25, and say the wheel diameter is 1000 mm and axle diameter is50 mm. So while the object still moves 10 m the sliding frictional surfaces only slide over each other adistance of 0.5 m. The work done is 981 0.25 0.5 = 123 joules; the work done has reduced to 1/40of that of dragging.

Additional energy is lost from the wheel-to-road interface. This is termed rolling resistance which ispredominantly a deformation loss. This energy is also lowered by the use of a wheel (in comparison to dragging)because the net force on the contact point between the road and the wheel is almost perpendicular to the
http://en.wikipedia.org/wiki/Rolling_resistancehttp://en.wikipedia.org/wiki/Diameterhttp://en.wikipedia.org/wiki/Joulehttp://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Mechanical_workhttp://en.wikipedia.org/wiki/Newton_(unit)http://en.wikipedia.org/wiki/Normal_forcehttp://en.wikipedia.org/wiki/Coefficient_of_frictionhttp://en.wikipedia.org/wiki/Metrehttp://en.wikipedia.org/wiki/Kilogramhttp://en.wikipedia.org/wiki/Plain_bearinghttp://en.wikipedia.org/wiki/Bearing_(mechanical)http://en.wikipedia.org/wiki/Frictionhttp://en.wikipedia.org/wiki/Axlehttp://en.wikipedia.org/wiki/Wheel_and_axlehttp://en.wikipedia.org/wiki/Disc_brakehttp://en.wikipedia.org/wiki/Hydraulichttp://en.wikipedia.org/wiki/Suspension_(vehicle)http://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Pneumatichttp://en.wikipedia.org/wiki/Alloy_wheelhttp://en.wikipedia.org/wiki/Penny-farthinghttp://en.wikipedia.org/wiki/Iron_Age_Europehttp://en.wikipedia.org/wiki/Etruscan_chariot


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An aluminium alloy wheel

ground, and hence, generates an almost zero net work. This depends on the nature of the ground, of the materialof the wheel, its inflation in the case of a tire, the net torque exerted by the eventual engine, and many otherfactors.

A wheel can also offer advantages in traversing irregular surfaces if the wheel radius is sufficiently largecompared to the irregularities.

The wheel alone is not a machine, but when attached to an axle in conjunction with bearing, it forms the wheeland axle, one of the simple machines. A driven wheel is an example of a wheel and axle. Note that wheels pre-date driven wheels by about 6000 years.

Construction

Rim

Main article: Rim (wheel)

The rimis the "outer edge of a wheel, holding the tire."[17]It makesup the outer circular design of the wheel on which the inside edge ofthe tire is mounted on vehicles such as automobiles. For example, ona bicycle wheel the rim is a large hoop attached to the outer ends ofthe spokes of the wheel that holds the tire and tube.

In the 1st millennium BC an iron rim was introduced around thewooden wheels of chariots.

Hub

The hub is the center of the wheel, and typically houses a bearing, andis where the spokes meet.

A hubless wheel (also known as a rim-rider or centerless wheel) is a type of wheel with no center hub. Morespecifically, the hub is actually almost as big as the wheel itself. The axle is hollow, following the wheel at veryclose tolerances.

Spokes

Main article: spoke

A spokeis one of some number of rods radiating from the center of a wheel (the hub where the axle connects),connecting the hub with the round traction surface. The term originally referred to portions of a log which hadbeen split lengthwise into four or six sections. The radial members of a wagon wheel were made by carving aspoke (from a log) into their finished shape. A spokeshave is a tool originally developed for this purpose.Eventually, the term spoke was more commonly applied to the finished product of the wheelwright's work, thanto the materials he used.

Wire

Main article: wire wheel
http://en.wikipedia.org/wiki/Wire_wheelhttp://en.wikipedia.org/wiki/Wheelwrighthttp://en.wikipedia.org/wiki/Toolhttp://en.wikipedia.org/wiki/Spokeshavehttp://en.wikipedia.org/wiki/Axlehttp://en.wikipedia.org/wiki/Bicycle_hubhttp://en.wikipedia.org/wiki/Spokehttp://en.wikipedia.org/wiki/Engineering_tolerancehttp://en.wikipedia.org/wiki/Axlehttp://en.wiktionary.org/wiki/hubhttp://en.wikipedia.org/wiki/Hubless_wheelhttp://en.wikipedia.org/wiki/Bearing_(mechanical)http://en.wikipedia.org/wiki/Chariothttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Bicycle_wheelhttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Rim_(wheel)http://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Wheel_and_axlehttp://en.wikipedia.org/wiki/Axlehttp://en.wikipedia.org/wiki/Alloy_wheelhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/File:AluminumWheel_spoke_design.jpg


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A spoked wheel ondisplay at The NationalMuseum of Iran, inTehran. The wheel is

dated to the late 2ndmillennium BC and wasexcavated at ChoqaZanbil.

A 1957 MGA Automobile withwire wheels

Stacked and standing car tires

The rims of wire wheels(or "wire spoked wheels") are connected to their hubsby wire spokes. Although these wires are generally stiffer than a typical wirerope, they function mechanically the same as tensioned flexible wires, keeping therim true while supporting applied loads.

Wire wheels are used on most bicycles and still used on many motorcycles. Theywere invented by aeronautical engineer George Cayley and first used in bicyclesby James Starley. A process of assembling wire wheels is described aswheelbuilding.

Tire

Main article: tire

A tire(in American English and Canadian English) or tyre(in someCommonwealth Nations such as UK, and Australia) is a ring-shaped coveringthat fits around a wheel rim to protect it and enable better vehicle performance by

providing a flexible cushion that absorbs shock while keeping the wheel in closecontact with the ground. The word itself may be derived from the word"tie," which refers to the outer steel ring part of a wooden cart wheel thatties the wood segments together (see Etymology below).

The fundamental materials of modern tires are synthetic rubber, naturalrubber, fabric and wire, along with other compound chemicals. Theyconsist of a tread and a body. The tread provides traction while the bodyensures support. Before rubber was invented, the first versions of tireswere simply bands of metal that fitted around wooden wheels to prevent

wear and tear. Today, the vast majority of tires are pneumatic inflatablestructures, comprising a doughnut-shaped body of cords and wiresencased in rubber and generally filled with compressed air to form aninflatable cushion. Pneumatic tires are used on many types of vehicles,such as cars, bicycles, motorcycles, trucks, earthmovers, and aircraft.

Alternatives

While wheels are very widely used for ground transport, there are

alternatives, some of which are suitable for terrain where wheels areineffective. Alternative methods for ground transport without wheels(wheel-less transport) include:

Being raised by electromagnetic energy (maglev train and othervehicles)Dragging with runners (sled) or without (travois)Being raised by air pressure (hovercraft)Riding an animal such as a horseHuman powered:

Walking on one's own legsBeing carried (litter/sedan chair or stretcher)

A walking machineCaterpillar tracks (although it is still operated by wheels)
http://en.wikipedia.org/wiki/Caterpillar_trackshttp://en.wikipedia.org/wiki/Walker_(machine)http://en.wikipedia.org/wiki/Stretcherhttp://en.wikipedia.org/wiki/Litter_(vehicle)http://en.wikipedia.org/wiki/Legshttp://en.wikipedia.org/wiki/Walkhttp://en.wikipedia.org/wiki/Horsehttp://en.wikipedia.org/wiki/Working_animalhttp://en.wikipedia.org/wiki/Equestrianismhttp://en.wikipedia.org/wiki/Hovercrafthttp://en.wikipedia.org/wiki/Travoishttp://en.wikipedia.org/wiki/Sledhttp://en.wikipedia.org/wiki/Maglev_trainhttp://en.wikipedia.org/wiki/Electromagnetic_forcehttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Heavy_equipment_(construction)http://en.wikipedia.org/wiki/Truckhttp://en.wikipedia.org/wiki/Motorcycleshttp://en.wikipedia.org/wiki/Bicyclehttp://en.wikipedia.org/wiki/Carshttp://en.wikipedia.org/wiki/Inflatable_structurehttp://en.wikipedia.org/wiki/Pneumatichttp://en.wikipedia.org/wiki/Traction_(engineering)http://en.wikipedia.org/wiki/Natural_rubberhttp://en.wikipedia.org/wiki/Synthetic_rubberhttp://en.wikipedia.org/wiki/Rim_(wheel)http://en.wikipedia.org/wiki/English_in_the_Commonwealth_of_Nationshttp://en.wikipedia.org/wiki/Canadian_Englishhttp://en.wikipedia.org/wiki/American_Englishhttp://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Wheelbuildinghttp://en.wikipedia.org/wiki/James_Starleyhttp://en.wikipedia.org/wiki/George_Cayleyhttp://en.wikipedia.org/wiki/Motorcycleshttp://en.wikipedia.org/wiki/Bicyclehttp://en.wikipedia.org/wiki/Tension_(physics)http://en.wikipedia.org/wiki/Wire_ropehttp://en.wikipedia.org/wiki/Wirehttp://en.wikipedia.org/wiki/Spokehttp://en.wikipedia.org/wiki/Rim_(wheel)http://en.wikipedia.org/wiki/File:Car_tires.jpghttp://en.wikipedia.org/wiki/File:1957_mga.jpeghttp://en.wikipedia.org/wiki/Choqa_Zanbilhttp://en.wikipedia.org/wiki/Tehranhttp://en.wikipedia.org/wiki/National_Museum_of_Iranhttp://en.wikipedia.org/wiki/File:Wheel_Iran.jpg


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Pedrail wheels, using aspects of both wheel and caterpillar trackSpheres, as used by Dyson vacuum cleaners and hamster balls

Symbolism

The wheel has also become a strong cultural and spiritual metaphor for a cycle or regular repetition (see chakra,reincarnation, Yin and Yang among others). As such and because of the difficult terrain, wheeled vehicles were

forbidden in old Tibet.

The winged wheel is a symbol of progress, seen in many contexts including the coat of arms of Panama and thelogo of the Ohio State Highway Patrol.

The introduction of spoked (chariot) wheels in the Middle Bronze Age appears to have carried somewhat of aprestige. The sun cross appears to have a significance in Bronze Age religion, replacing the earlier concept of aSolar barge with the more "modern" and technologically advanced solar chariot.

The wheel was also a solar symbol for the Ancient Egyptians.[18]

The wheel is also the prominent figure on the flag of India. The wheel in this case represents law (dharma). Italso appears in the flag of the Romani people, hinting to their nomadic history and their Indian origins.

The flag of India

The Romani flag

The flag of MahlKshatriyas

Gallery
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A driving wheel on a steam

locomotive

0 Series Shinkansen wheel

Flanged railway wheel

Wheels on a track panel at DonegalRailway Centre
http://en.wikipedia.org/wiki/Donegal_Railway_Centrehttp://en.wikipedia.org/wiki/Flangehttp://en.wikipedia.org/wiki/0_Series_Shinkansenhttp://en.wikipedia.org/wiki/Steam_locomotive


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A pair of wheels on a cart

Bicycle wheel

Training wheels are used to help thelearner cope with instability of thetwo-wheel vehicle at low speeds.

Automobiles started with spokedwheels
http://en.wikipedia.org/wiki/Training_wheels


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A modern automobile wheel

See also

Alloy wheelArtillery wheelAxleBicycle wheel

BigwheelBreaking wheel, a form of tortureCasterCompact discColor wheelPressed Steel wheelDriving wheelFerris wheelTheHorse, The Wheel and Language

(book)

Hubless wheelMagnetic levitationMansell wheelMecanum wheelOmni wheel

Reinventing the wheelRimRolling resistance, r. friction, r. dragRotating locomotion in living systems

Ship's wheelSimple machineSquare wheelSteering wheelTerrestrial locomotion in animals: RollingTireTweelWagon-wheel effectWheelbarrowWheel and axle

Wheel sizingWire wheelsWheel of FortuneWheelset (rail transport)

References

1. ^"wheel" (http://www.etymonline.com/index.php?term=wheel). Online Etymology Dictionary.2. ^The American Heritage Dictionary of the English Language: Fourth Edition. 2000

(http://www.ahdictionary.com/word/search.html?q=wheel&submit.x=42&submit.y=19)3. ^A. Veluek, K. ufar, M. Zupani, Prazgodovinsko leseno kolo z osjo s kolia Stare gmajne na

Ljubljanskem barju. In: A. Veluek (Hrsg.). Koliarska naselbina Stare gmajne in njen as. Ljubljansko barje v
http://www.ahdictionary.com/word/search.html?q=wheel&submit.x=42&submit.y=19http://www.etymonline.com/index.php?term=wheelhttp://en.wikipedia.org/wiki/Wheelset_(rail_transport)http://en.wikipedia.org/wiki/Wheel_of_Fortune_(disambiguation)http://en.wikipedia.org/wiki/Wire_wheelshttp://en.wikipedia.org/wiki/Wheel_sizinghttp://en.wikipedia.org/wiki/Wheel_and_axlehttp://en.wikipedia.org/wiki/Wheelbarrowhttp://en.wikipedia.org/wiki/Wagon-wheel_effecthttp://en.wikipedia.org/wiki/Tweelhttp://en.wikipedia.org/wiki/Tirehttp://en.wikipedia.org/wiki/Terrestrial_locomotion_in_animals#Rollinghttp://en.wikipedia.org/wiki/Steering_wheelhttp://en.wikipedia.org/wiki/Square_wheelhttp://en.wikipedia.org/wiki/Simple_machinehttp://en.wikipedia.org/wiki/Ship%27s_wheelhttp://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systemshttp://en.wikipedia.org/wiki/Rolling_resistancehttp://en.wikipedia.org/wiki/Rim_(wheel)http://en.wikipedia.org/wiki/Reinventing_the_wheelhttp://en.wikipedia.org/wiki/Omni_wheelhttp://en.wikipedia.org/wiki/Mecanum_wheelhttp://en.wikipedia.org/wiki/Mansell_wheelhttp://en.wikipedia.org/wiki/Magnetic_levitationhttp://en.wikipedia.org/wiki/Hubless_wheelhttp://en.wikipedia.org/wiki/The_Horse,_The_Wheel_and_Languagehttp://en.wikipedia.org/wiki/Ferris_wheelhttp://en.wikipedia.org/wiki/Driving_wheelhttp://en.wikipedia.org/wiki/Disteelhttp://en.wikipedia.org/wiki/Color_wheelhttp://en.wikipedia.org/wiki/Compact_dischttp://en.wikipedia.org/wiki/Casterhttp://en.wikipedia.org/wiki/Torturehttp://en.wikipedia.org/wiki/Breaking_wheelhttp://en.wikipedia.org/wiki/Big_wheel_(disambiguation)http://en.wikipedia.org/wiki/Bicycle_wheelhttp://en.wikipedia.org/wiki/Axlehttp://en.wikipedia.org/wiki/Artillery_wheelhttp://en.wikipedia.org/wiki/Alloy_wheelhttp://en.wikipedia.org/wiki/Automobile


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2. polovici 4. tisoletja pr. Kr. Opera Instituti Archaeologici Sloveniae 16 (Ljubljana 2009)197-222.4. ^Anthony, David A. (2007). The horse, the wheel, and language: how Bronze-Age riders from the Eurasian

steppes shaped the modern world. Princeton, N.J: Princeton University Press. p. 67. ISBN 0-691-05887-3.5. ^Dyer, Gwynne, War: the new edition, p. 159: Vintage Canada Edition, Randomhouse of Canada, Toronto, ON6. ^Barbieri-Low, Anthony, "Wheeled Vehicles in the Chinese Bronze Age (c. 2000-741 B.C.)", Sino-Platonic

Papers, February 20007. ^Ekholm, Gordon F (1945). "Wheeled Toys in Mexico".American Antiquity11.8. ^Singer, Ben (May 2005).A brief history of the horse in America

(http://www.canadiangeographic.ca/Magazine/ma05/indepth/#cnd). Canadian Geographic Magazine.9. ^CRAFTS; Uncovering Treasures of Ancient Nubia; New York Times

(http://query.nytimes.com/gst/fullpage.html?res=9C00E5D71E3BF934A15751C0A962958260)10. ^What the Nubians Ate (http://discovermagazine.com/1994/jun/whatthenubiansat393)11. ^The Cambridge History of Africa (http://books.google.com/books?

id=JAca1F3qG34C&pg=PA278&lpg=PA278&dq=Nubian+horse+chariots&source=web&ots=wWVGBxkwJD&sig=4wS7bIPBseMDkQJxC_7iT3oYyZo&hl=en&ei=fbmMSe2mKY60yQWF8a2_Bg&sa=X&oi=book_result&resnum=2&ct=result)

12. ^Chaves, Isaas; Engerman, Stanley L.; Robinson, James A. (2012).Reinventing the Wheel: The EconomicBenefits of Wheeled Transportation in Early Colonial British West Africa

(http://scholar.harvard.edu/files/jrobinson/files/the_wheel_in_africa_february_2012.pdf). Weatherhead Center

for International Affairs. p. 1. Retrieved 5 January 2014. "One of the great technological puzzles of Sub-Saharan African economic history is that wheeled transportation was barely used prior to the colonial period.Instead, head porterage was the main method of transportation."

13. ^Law, Robin C. (1980). "Wheeled Transportation in Pre-Colonial West Africa".Africa50: 24962.14. ^Ghosh, A. (1989). An Encyclopedia of Indian Archaeology (http://books.google.com/books?id=Wba-

EZhZcfgC&printsec=frontcover&hl=it#v=onepage&q=wheel&f=false). New Delhi: Munshiram Manoharlal.p.337; Rao, L.S. (2005-06). The Harappan Spoked Wheels Rattled Down the Streets of Bhirrana, DistrictFatehabad, Haryana. Puratattva 36. pp.59-67.

15. ^See e.g. http://www.harappa.com/indus/90.html and http://www.harappa.com/indus/27.html16. ^bookrags.com (http://www.bookrags.com/research/wheel-and-axle-woi/) Wheel and axle

17. ^Jewel, Elizabeth (2006). The Pocket Oxford Dictionary and Thesaurus(http://books.google.com/books?id=fUE0bazkcxAC&pg=PA722&lpg=PA722&dq=rim+3+outer+edge+of+a+wheel,+holding+the+tire+722).Oxford University Press. p. 722. ISBN 978-0-19-530715-3. Retrieved 2012-01-04.

18. ^Hall, Adelaide S. (2005).A Glossary of Important Symbols in Their Hebrew: Pagan and Christian Forms(http://books.google.es/books?id=OxcOmjiAWXAC&printsec=frontcover#v=onepage&q&f=false). p. 56.ISBN9781596055933.

External links

TheOldest Wooden Wheel (http://www.koliscar.si/en/virtual-exhibition/). Virtual exhibition. City

Museum of Ljubljana. Accessed 31 January 2012.

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