Awheel is a rotating component (typically circular in shape) that is intended to turn on anaxlebearing. The wheel is one of the key components of thewheel and axle which is one of thesix simple machines. Wheels, in conjunction with axles, allow heavy objects to be moved easily facilitating movement or transportation while supporting a load, or performing labor in machines. Wheels are also used for other purposes, such as aship's wheel,steering wheel,potter's wheel, andflywheel.
Common examples can be found intransport applications. A wheel reducesfriction by facilitating motion byrolling together with the use ofaxles. In order for wheels to rotate, amoment needs to be applied to the wheel about its axis, either by way of gravity or by the application of another external force ortorque.
Terminology
The English wordwheel comes from theOld English wordhwēol, fromProto-Germanic*hwehwlaz, fromProto-Indo-European*kwékwlos,[1] an extended form of the root*kwel-'to revolve, move around'. Cognates within Indo-European includeIcelandichjól'wheel, tyre',Greekκύκλοςkúklos, andSanskritchakra, the last two both meaning'circle' or'wheel'.[2]
History
The place and time of the invention of the wheel remains unclear, because the oldest hints do not guarantee the existence of real wheeled transport,[clarification needed] or are dated with too much scatter.
The invention of the solid wooden disk wheel falls into the lateNeolithic, and may be seen in conjunction with other technological advances that gave rise to the earlyBronze Age. This implies the passage of several wheel-less millennia even after theinvention of agriculture and ofpottery, during theAceramic Neolithic.
4500–3300 BCE (Copper Age): invention of thepotter's wheel; earliest solid wooden wheels (disks with a hole for the axle); earliest wheeled vehicles
TheHalaf culture of 6500–5100 BCE is sometimes credited with the earliest depiction of a wheeled vehicle, but there is no evidence of Halafians using either wheeled vehicles or pottery wheels.[3] Potter's wheels are thought to have been used in the 4th millennium BCE in the Middle East.[4] The oldest surviving example of a potter's wheel was thought to be one found inUr (modern dayIraq) dating to approximately 3100 BCE.[5] However, a potter's wheel found inwestern Ukraine, of theCucuteni–Trypillia culture, dates to the middle of the 5th millennium BCE which pre-dates the earliest use of the potter's wheel in Mesopotamia.[6][7][8][9][10][11] Wheels of uncertain dates have been found in theIndus Valley civilization of the late 4th millennium BCE covering areas of present-day India andPakistan.[12]
The oldest indirect evidence of wheeled movement was found in the form of miniature clay wheels north of the Black Sea before 4000BCE. From the middle of the4th millennium BCE onward, the evidence is condensed throughoutEurope in the form of toy cars, depictions, or ruts, with the oldest find in Northern Germany dating back to around 3400BCE.[13][14][15] InMesopotamia, depictions of wheeledwagons found onclay tabletpictographs at theEanna district ofUruk, in theSumerian civilization are dated to c.3500–3350BCE.[16] In the second half of the 4thmillennium BCE, evidence of wheeled vehicles appeared near-simultaneously in the Northern (Maykop culture) and SouthCaucasus andEastern Europe (Cucuteni-Trypillian culture).
Depictions of a wheeled vehicle appeared between 3631 and 3380 BCE in theBronocice clay pot excavated in aFunnelbeaker culture settlement in southernPoland.[17] In nearbyOlszanica, a 2.2m wide door was constructed for wagon entry; this barn was 40m long with three doors, dated to 5000 BCE, and belonged to theNeolithicLinear Pottery culture.[citation needed] Surviving evidence of a wheel-axle combination, from Stare Gmajne near Ljubljana in Slovenia (Ljubljana Marshes Wooden Wheel), is dated within twostandard deviations to 3340–3030 BCE, the axle to 3360–3045 BCE.[18] Two types of early Neolithic European wheel and axle are known: acircumalpine type of wagon construction (the wheel and axle rotate together, as in Ljubljana Marshes Wheel), and that of theBaden culture inHungary (axle does not rotate). They both are dated to c.3200–3000 BCE.[19] Some historians believe that there was a diffusion of the wheeled vehicle from theNear East to Europe around the mid-4th millennium BCE.[20]
Early wheels were simple wooden disks with a hole for the axle. Some of the earliest wheels were made from horizontal slices of tree trunks. Because of the uneven structure ofwood, a wheel made from a horizontal slice of a tree trunk will tend to be inferior to one made from rounded pieces of longitudinal boards.
Thespoked wheel was invented more recently and allowed the construction of lighter and swifter vehicles. The earliest known examples of wooden spoked wheels are in the context of theSintashta culture, dating to c.2000 BCE (Krivoye Lake). Soon after this, horse cultures of theCaucasus region used horse-drawn spoked-wheel warchariots 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 ofMinoan dominance and consolidations led by pre-classicalSparta andAthens.Celtic chariots introduced aniron rim around the wheel in the 1stmillennium BCE.
InChina, wheel tracks dating to around 2200BCE have been found at Pingliangtai, a site of theLongshan Culture.[21] Similar tracks were also found atYanshi, a city of theErlitou culture, dating to around 1700 BCE. The earliest evidence of spoked wheels inChina comes fromQinghai, in the form of two wheel hubs from a site dated between 2000 and 1500BCE.[22]Wheeled vehicles were introduced to China from the west.[23][24][25]
In Britain, a large wooden wheel, measuring about 1 m (3.3 ft) in diameter, was uncovered at theMust Farm site in East Anglia in 2016. The specimen, dating from 1,100 to 800 BCE, represents the most complete and earliest of its type found in Britain. The wheel's hub is also present. A horse's spine found nearby suggests the wheel may have been part of a horse-drawn cart. The wheel was found in a settlement built on stilts over wetland, indicating that the settlement had some sort of link to dry land.[26]
A figurine featuring theNew World's independently invented wheel. Among the places where wheeled toys were found,Mesoamerica is the only one where the wheel was never put to practical use before the 16th century.
Although large-scale use of wheels did not occur inthe Americas prior to European contact, numerous small wheeled artifacts, identified as children's toys, have been found in Mexican archeological sites, some dating to approximately 1500 BCE.[27] Some argue that the primary obstacle to large-scale development of the wheel in the Americas was the absence of domesticated large animals that could be used to pull wheeled carriages.[28] The closest relative ofcattle present in Americas in pre-Columbian times, theAmerican bison, is difficult to domesticate and was never domesticated by Native Americans; several horse species existed until about 12,000 years ago, but ultimately became extinct.[29] The only large animal that was domesticated in the Western hemisphere, thellama, a pack animal, was not physically suited to use as a draft animal to pull wheeled vehicles,[30] and use of the llama did not spread far beyond theAndes by the time of the arrival of Europeans.
On the other hand,Mesoamericans never developed thewheelbarrow, thepotter's wheel, nor any other practical object with a wheel or wheels.[31][32] Although present in a number of toys, very similar to those found throughout the world and still made for children today ("pull toys"),[31][32] the wheel was never put into practical use in Mesoamerica before the 16th century.[31][32] Possibly the closest the Mayas came to the utilitarian wheel is thespindle whorl, and some scholars believe that these toys were originally made with spindle whorls and spindle sticks as "wheels" and "axes".[32]
Aboriginal Australians traditionally used circular discs rolled along the ground for target practice.[33]
Nubians from after about 400BCE used wheels for spinningpottery and aswater wheels.[34] It is thought that Nubian waterwheels may have been ox-driven.[35] It is also known that Nubians used horse-drawn chariots imported fromEgypt.[36]
Starting from the 18th century in West Africa, wheeled vehicles were mostly used for ceremonial purposes in places likeDahomey.[37] The wheel was barely used for transportation, with the exception ofEthiopia andSomalia inSub-Saharan Africa well into the 19th century.[38][37]
The spoked wheel was in continued use without major modification until the 1870s, whenwire-spoked wheels andpneumatic tires were invented.[39] Pneumatic tires can greatly reduce rolling resistance and improve comfort. Wire spokes are under tension, not compression, making it possible for the wheel to be both stiff and light. Early radially-spoked wire wheels gave rise to tangentially-spoked wire wheels, which were widely used on cars into the late 20th century. Castalloy wheels are now more commonly used; forged alloy wheels are used when weight is critical.
This section is about the application to transport. For the simple machine, seeWheel and axle.
A wheeled vehicle requires much less work to move than simply dragging the same weight. The low resistance to motion is explained by the fact that thefrictional work done is no longer at the surface that the vehicle is traversing, but in thebearings. In the simplest and oldest case the bearing is just a round hole through which the axle passes (a "plain bearing"). Even with a plain bearing, the frictional work is greatly reduced because:
The normal force at the sliding interface is same as with simple dragging.
The sliding distance is reduced for a given distance of travel.
The coefficient of friction at the interface is usually lower.
Example:
If a 100 kg object is dragged for 10 m along a surface with thecoefficient of frictionμ = 0.5, thenormal force is 981N and thework done (requiredenergy) 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,μ = 0.25, and say the wheeldiameter 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 × 0.25 × 0.5 = 123 joules; the work done has reduced to 1/40 of that of dragging.
Additional energy is lost from the wheel-to-road interface. This is termedrolling resistance which is predominantly a deformation loss. It depends on the nature of the ground, of the material of the wheel, its inflation in the case of a tire, the net torque exerted by the eventual engine, and many other factors.
A wheel can also offer advantages in traversing irregular surfaces if the wheel radius is sufficiently large compared to the irregularities.
The wheel alone is not a machine, but when attached to anaxle in conjunction with bearing, it forms thewheel and axle, one of thesimple machines. A driven wheel is an example of a wheel and axle. Wheels pre-date driven wheels by about 6000 years, themselves an evolution of using round logs as rollers to move a heavy load—a practice going back in pre-history so far that it has not been dated.
Construction
This section is about the structure of a wheel. For the making of wire-spoked wheels, seeWheelbuilding. For the making of non-wire spoked wheels, seeWheel construction.
Therim is the "outer edge of a wheel, holding the tire".[40] It makes up the outer circular design of the wheel on which the inside edge of thetire is mounted on vehicles such asautomobiles. For example, on abicycle wheel therim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube.
In the 1st millennium BCE aniron rim was introduced around the wooden wheels ofchariots.
Hub
The hub is the center of the wheel, and typically houses abearing, and is where the spokes meet.
Ahubless wheel (also known as a rim-rider or centerless wheel) is a type of wheel with no centerhub. More specifically, the hub is actually almost as big as the wheel itself. Theaxle is hollow, following the wheel at very closetolerances.
Aspoke is one of some number of rods radiating from the center of a wheel (thehub where theaxle connects), connecting the hub with the round traction surface. The term originally referred to portions of a log which had been split lengthwise into four or six sections. The radial members of a wagon wheel were made by carving a spoke (from a log) into their finished shape. Aspokeshave is atool originally developed for this purpose. Eventually, the term spoke was more commonly applied to the finished product of thewheelwright's work, than to the materials used.
Therims ofwire wheels (or "wire spoked wheels") are connected to their hubs by wirespokes. Although thesewires are generally stiffer than a typicalwire rope, they function mechanically the same astensioned flexible wires, keeping the rim true while supporting applied loads.
Wire wheels are used on mostbicycles and still used on manymotorcycles. They were invented by aeronautical engineerGeorge Cayley and first used in bicycles byJames Starley. A process of assembling wire wheels is described aswheelbuilding.
Atire (inAmerican English andCanadian English) ortyre (in someCommonwealth Nations such as UK,India,South Africa,Australia andNew Zealand) is a ring-shaped covering that fits around a wheelrim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact 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 that ties the wood segments together (seeEtymology above).
The fundamental materials of modern tires aresynthetic rubber,natural rubber, fabric, and wire, along with other compound chemicals. They consist of a tread and a body. The tread providestraction while the body ensures support. Before rubber was invented, the first versions of tires were simply bands of metal that fitted around wooden wheels to prevent wear and tear. Today, the vast majority of tires arepneumaticinflatable structures, comprising a doughnut-shaped body of cords and wires encased in rubber and generally filled with compressed air to form an inflatable cushion. Pneumatic tires are used on many types of vehicles, such ascars,bicycles,motorcycles,trucks,earthmovers, andaircraft.
Protruding or covering attachments
Extremeoff-road conditions have resulted in the invention of several types of wheel cover, which may be constructed as removable attachments or as permanent covers. Wheels like this are no longer necessarily round, or have panels that make the ground-contact area flat.
Examples include:
Snow chains - Specially designed chain assemblies that wrap around the tire to provide increased grip, designed for deep snow.[41]
Dreadnaught wheel - A type of permanently attached hinged panels for general extreme off-road use. These are not connected directly to the wheels, but to each other.
Pedrail wheel - A system of rails that holds panels that hold the vehicle. These do not necessarily have to be built as a circle (wheel) and are thus also a form ofContinuous track.
A version of the above examples (name unknown to the writer) was commonly used on heavyartillery duringWorld War I. Specific examples:Cannone da 149/35 A and theBig Bertha. These were panels that were connected to each other by multiple hinges and could be installed over a contemporary wheel.
Continuous track - A system of linked and hinged chains/panels that cover multiple wheels in a way that allows the vehicles mass to be distributed across the space between wheels that are positioned in front of / behind other wheels.
"Tire totes" - A bag designed to cover a tire to improve traction in deep snow.[42][43]
Truck and bus wheels may block (stop rotating) under certain circumstances, such as brake system failure. To help detect this, they sometimes feature "wheel rotation indicators": colored strips of plastic attached to the rim and protruding out from it, such that they can be seen by the driver in theside-view mirrors. These devices were invented and patented in 1998 by a Canadian truck shop owner.[44]
Alternatives
While wheels are very widely used for ground transport, there are alternatives, some of which are suitable for terrain where wheels are ineffective. Alternative methods for ground transport without wheels include:
The wheel has also become a strong cultural and spiritual metaphor for a cycle or regular repetition (seechakra,reincarnation,Yin and Yang among others). As such and because of the difficult terrain, wheeled vehicles were forbidden inold Tibet. The wheel in ancientChina is seen as a symbol of health and strength and used by some villages as a tool to predict future health and success. Thediameter of the wheel is indicator of one's future health. TheKalachakra or wheel of time is also a subject in some forms ofBuddhism, along with thedharmachakra.[45][46]
The introduction of spoked (chariot) wheels in the Middle Bronze Age appears to have carried somewhat of a prestige. Thesun cross appears to have a significance inBronze Age religion, replacing the earlier concept of asolar barge with the more 'modern' and technologically advancedsolar chariot. The wheel was also a solar symbol for theAncient Egyptians.[47]
In modern usage, the 'invention of the wheel' can be considered as a symbol of one of the first technologies of early civilization, alongside farming and metalwork, and thus be used as a benchmark to grade the level of societal progress.[citation needed]
^Holm, Hans J. J. G.: The Earliest Wheel Finds, their Archaeology and Indo-European Terminology in Time and Space, and Early Migrations around the Caucasus. Series Minor 43. ARCHAEOLINGUA ALAPÍTVÁNY, Budapest, 2019.ISBN978-615-5766-30-5.
^John Marshall (1996).Mohenjo-Daro and the Indus Civilization: Being an Official Account of Archaeological Excavations at Mohenjo-Daro Carried Out by the Government of India Between the Years 1922 and 1927, Volume 1. Asian Education Services. p. 554.ISBN9788120611795.
^Holm, Hans J. J. G. "The Earliest Wheel Finds, Their Archeology and Indo-European Terminology in Time and Space, and Early Migrations around the Caucasus".Archaeolingua Alapítvány, Budapest, 2019,ISBN978-963-9911-34-5
^Anthony, David A. (2007).The horse, the wheel, and language: how Bronze-Age riders from the Eurasian steppes shaped the modern world. Princeton, NJ: Princeton University Press. p. 67.ISBN978-0-691-05887-0.
^Velušček, A.; Čufar, K. and Zupančič, M. (2009) "Prazgodovinsko leseno kolo z osjo s kolišča Stare gmajne na Ljubljanskem barju", pp. 197–222 in A. Velušček (ed.).Koliščarska naselbina Stare gmajne in njen as. Ljubljansko barje v 2. polovici 4. tisočletja pr. Kr. Opera Instituti Archaeologici Sloveniae 16. Ljubljana.
^abcChasin Calvo, Sherri."The Technology of the Incas and Aztecs".Encyclopedia.com.Archived from the original on 20 August 2021. Retrieved21 August 2021.There were no wheeled carts, or even wheelbarrows. Although wheeled toys and decorations have been found at Mesoamerican sites, the wheel was never put to practical use.
.jpg)
.jpg)
