A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle bearing. The wheel is one of the key components of the wheel and axle which is one of the six 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 a ship's wheel, steering wheel, potter's wheel, and flywheel.
Common examples can be found in transport applications. A wheel reduces friction by facilitating motion by rolling together with the use of axles. 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 the application of another external force or torque.
The English word wheel comes from the Old English word hwēol, from Proto-Germanic *hwehwlaz, from Proto-Indo-European *kwékwlos, [1] an extended form of the root *kwel-'to revolve, move around'. Cognates within Indo-European include Icelandic hjól'wheel, tyre', Greek κύκλοςkúklos, and Sanskrit chakra , the last two both meaning 'circle' or 'wheel'. [2]
Mesopotamian civilization was credited with the invention of the wheel by several, mainly old sources. [3] [4] [5] Research in the 2000s suggests that the wheel was invented independently in Eastern Europe, [6] [7] [8] with the oldest potter's wheel and oldest wheels for vehicles found in the Cucuteni–Trypillia culture, which predates Mesopotamia finds by several hundred years. [9] [10] In 2024, a team of researchers reported what may be the earliest evidence of wheel-like stones in what is now Israel, being 12,000 years old. [11] [12]
The invention of the solid wooden disk wheel falls into the late Neolithic, and may be seen in conjunction with other technological advances that gave rise to the early Bronze Age. This implies the passage of several wheel-less millennia after the invention of agriculture and of pottery, during the Aceramic Neolithic.
The Halaf 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. [13] Potter's wheels are thought to have been used in the 4th millennium BCE in the Middle East. [14] The oldest surviving example of a potter's wheel was thought to be one found in Ur (modern day Iraq) dating to approximately 3100 BCE. [15] However, a potter's wheel found in western Ukraine, of the Cucuteni–Trypillia culture, dates to the middle of the 5th millennium BCE which pre-dates the earliest use of the potter's wheel in Mesopotamia. [10] [16] [8] [17] [7] [18] Wheels of uncertain dates have been found in the Indus Valley civilization of the late 4th millennium BCE covering areas of present-day India and Pakistan. [19]
The oldest indirect evidence of wheeled movement was found in the form of miniature clay wheels north of the Black Sea before 4000 BCE. From the middle of the 4th millennium BCE onward, the evidence is condensed throughout Europe in the form of toy cars, depictions, or ruts, with the oldest find in Northern Germany dating back to around 3400 BCE. [20] [21] [22] In Mesopotamia, depictions of wheeled wagons found on clay tablet pictographs at the Eanna district of Uruk, in the Sumerian civilization are dated to c. 3500–3350 BCE. [23] In the second half of the 4th millennium BCE, evidence of wheeled vehicles appeared near-simultaneously in the Northern (Maykop culture) and South Caucasus and Eastern Europe (Cucuteni-Trypillian culture).
Depictions of a wheeled vehicle appeared between 3631 and 3380 BCE in the Bronocice clay pot excavated in a Funnelbeaker culture settlement in southern Poland. [24] In nearby Olszanica, a 2.2 m wide door was constructed for wagon entry; this barn was 40 m long with three doors, dated to 5000 BCE, and belonged to the neolithic Linear 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 two standard deviations to 3340–3030 BCE, the axle to 3360–3045 BCE. [25] Two types of early Neolithic European wheel and axle are known: a circumalpine type of wagon construction (the wheel and axle rotate together, as in Ljubljana Marshes Wheel), and that of the Baden culture in Hungary (axle does not rotate). They both are dated to c. 3200–3000 BCE. [26] Some historians believe that there was a diffusion of the wheeled vehicle from the Near East to Europe around the mid-4th millennium BCE. [27]
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 of wood, 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.
The spoked 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 the Sintashta culture, dating to c. 2000 BCE (Krivoye Lake). 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 peoples to give rise, eventually, to classical Greece after the breaking of Minoan dominance and consolidations led by pre-classical Sparta and Athens. Celtic chariots introduced an iron rim around the wheel in the 1st millennium BCE.
In China, wheel tracks dating to around 2200 BCE have been found at Pingliangtai, a site of the Longshan Culture. [28] Similar tracks were also found at Yanshi, a city of the Erlitou culture, dating to around 1700 BCE. The earliest evidence of spoked wheels in China comes from Qinghai, in the form of two wheel hubs from a site dated between 2000 and 1500 BCE. [29] Wheeled vehicles were introduced to China from the west. [30] [31] [32]
In Britain, a large wooden wheel, measuring about 1 m (3.3 ft) in diameter, was uncovered at the Must 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. [33]
Although large-scale use of wheels did not occur in the 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. [34] 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. [35] The closest relative of cattle present in Americas in pre-Columbian times, the American 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. [36] The only large animal that was domesticated in the Western hemisphere, the llama, a pack animal, was not physically suited to use as a draft animal to pull wheeled vehicles, [37] and use of the llama did not spread far beyond the Andes by the time of the arrival of Europeans.
On the other hand, Mesoamericans never developed the wheelbarrow, the potter's wheel, nor any other practical object with a wheel or wheels. [38] [39] Although present in a number of toys, very similar to those found throughout the world and still made for children today ("pull toys"), [38] [39] the wheel was never put into practical use in Mesoamerica before the 16th century. [38] [39] Possibly the closest the Mayas came to the utilitarian wheel is the spindle whorl, and some scholars believe that these toys were originally made with spindle whorls and spindle sticks as "wheels" and "axes". [39]
Aboriginal Australians traditionally used circular discs rolled along the ground for target practice. [40]
Nubians from after about 400 BCE used wheels for spinning pottery and as water wheels. [41] It is thought that Nubian waterwheels may have been ox-driven. [42] It is also known that Nubians used horse-drawn chariots imported from Egypt. [43]
Starting from the 18th century in West Africa, wheeled vehicles were mostly used for ceremonial purposes in places like Dahomey. [44] The wheel was barely used for transportation, with the exception of Ethiopia and Somalia in Sub-Saharan Africa well into the 19th century. [45] [44]
The spoked wheel was in continued use without major modification until the 1870s, when wire-spoked wheels and pneumatic tires were invented. [46] 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. Cast alloy wheels are now more commonly used; forged alloy wheels are used when weight is critical.
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.
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 the frictional work done is no longer at the surface that the vehicle is traversing, but in the bearings. 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:
Example:
Additional energy is lost from the wheel-to-road interface. This is termed rolling 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 an axle in conjunction with bearing, it forms the wheel and axle, one of the simple 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.
The rim is the "outer edge of a wheel, holding the tire". [47] It makes up the outer circular design of the wheel on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim 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 an iron rim was introduced around the wooden wheels of chariots.
The hub is the center of the wheel, and typically houses a bearing, and is 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. More specifically, the hub is actually almost as big as the wheel itself. The axle is hollow, following the wheel at very close tolerances.
A spoke is 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 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. 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, than to the materials used.
The rims of wire wheels (or "wire spoked wheels") are connected to their hubs by wire spokes. Although these wires are generally stiffer than a typical wire rope, they function mechanically the same as tensioned flexible wires, keeping the rim true while supporting applied loads.
Wire wheels are used on most bicycles and still used on many motorcycles. They were invented by aeronautical engineer George Cayley and first used in bicycles by James Starley. A process of assembling wire wheels is described as wheelbuilding.
A tire (American English and Canadian English) or tyre (Commonwealth English) is a ring-shaped covering that 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 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 (see Etymology above).
The fundamental materials of modern tires are synthetic rubber, natural rubber, fabric, and wire, along with other compound chemicals. They consist of a tread and a body. The tread provides traction 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 are pneumatic inflatable 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 as cars, bicycles, motorcycles, trucks, earthmovers, and aircraft.
Extreme off-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:
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 the side-view mirrors. These devices were invented and patented in 1998 by a Canadian truck shop owner. [51]
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 (see chakra, reincarnation, Yin and Yang among others). As such and because of the difficult terrain, wheeled vehicles were forbidden in old Tibet. The wheel in ancient China is seen as a symbol of health and strength and used by some villages as a tool to predict future health and success. The diameter of the wheel is indicator of one's future health. The Kalachakra or wheel of time is also a subject in some forms of Buddhism, along with the dharmachakra. [52] [53]
The winged wheel is a symbol of progress, seen in many contexts including the coat of arms of Panama, the logo of the Ohio State Highway Patrol and the State Railway of Thailand. 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.
The introduction of spoked (chariot) wheels in the Middle Bronze Age appears to have carried somewhat of a prestige. The sun cross 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 was also a solar symbol for the Ancient Egyptians. [54]
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 ]
Some Neopagans such as Wiccans have adopted the Wheel of the Year into their religious practices. [55]
A chariot is a type of cart driven by a charioteer, usually using horses to provide rapid motive power. The oldest known chariots have been found in burials of the Sintashta culture in modern-day Chelyabinsk Oblast, Russia, dated to c. 1950–1880 BC and are depicted on cylinder seals from Central Anatolia in Kültepe dated to c. 1900 BC. The critical invention that allowed the construction of light, horse-drawn chariots was the spoked wheel.
A spoke is one of some number of rods radiating from the center of a wheel, connecting the hub with the round traction surface.
A bicycle wheel is a wheel, most commonly a wire wheel, designed for a bicycle. A pair is often called a wheelset, especially in the context of ready built "off the shelf" performance-oriented wheels.
A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analogue computers. Differentials can also provide a gear ratio between the input and output shafts. For example, many differentials in motor vehicles provide a gearing reduction by having fewer teeth on the pinion than the ring gear.
A carriage is a two- or four-wheeled horse-drawn vehicle for passengers. In Europe they were a common mode of transport for the wealthy during the Roman Empire, and then again from around 1600 until they were replaced by the motor car around 1900. They were generally owned by the rich, but second-hand private carriages became common public transport, the equivalent of modern cars used as taxis. Carriage suspensions are by leather strapping or, on those made in recent centuries, steel springs. There are numerous names for different types. Two-wheeled carriages are usually owner-driven.
A wheelwright is a craftsman who builds or repairs wooden wheels. The word is the combination of "wheel" and the word "wright" as in shipwright and arkwright. This occupational name became the English surname Wright. It also appears in surnames like Cartwright and Wainwright. It corresponds with skilful metal workers being called Smith.
The Funnel(-neck-)beaker culture, in short TRB or TBK, was an archaeological culture in north-central Europe. It developed as a technological merger of local neolithic and mesolithic techno-complexes between the lower Elbe and middle Vistula rivers. These predecessors were the (Danubian) Lengyel-influenced Stroke-ornamented ware culture (STK) groups/Late Lengyel and Baden-Boleráz in the southeast, Rössen groups in the southwest and the Ertebølle-Ellerbek groups in the north. The TRB introduced farming and husbandry as major food sources to the pottery-using hunter-gatherers north of this line.
A velocipede is a human-powered land vehicle with one or more wheels. The most common type of velocipede today is the bicycle.
The Nordic Bronze Age is a period of Scandinavian prehistory from c. 2000/1750–500 BC.
The Karasuk culture describes a group of late Bronze Age societies who ranged from the Aral Sea to the upper Yenisei in the east and south to the Altai Mountains and the Tian Shan in ca. 1500–800 BC.
The wheel and axle is a simple machine, consisting of a wheel attached to a smaller axle so that these two parts rotate together, in which a force is transferred from one to the other. The wheel and axle can be viewed as a version of the Lever, with a drive force applied tangentially to the perimeter of the wheel, and a load force applied to the axle supported in a bearing, which serves as a fulcrum.
Chariot burials are tombs in which the deceased was buried together with their chariot, usually including their horses and other possessions. An instance of a person being buried with their horse is called horse burial.
The rim is the "outer edge of a wheel, holding the tire". It makes up the outer circular design of the wheel on which the inside edge of the tire is mounted on vehicles such as automobiles. For example, on a bicycle wheel the rim is a large hoop attached to the outer ends of the spokes of the wheel that holds the tire and tube. In cross-section, the rim is deep in the center and shallow at the outer edges, thus forming a "U" shape that supports the bead of the tire casing.
Wire wheels, wire-spoked wheels, tension-spoked wheels, or "suspension" wheels are wheels whose rims connect to their hubs by wire spokes. Although these wires are considerably stiffer than a similar diameter wire rope, they function mechanically the same as tensioned flexible wires, keeping the rim true while supporting applied loads. The term suspension wheel should not be confused with vehicle suspension.
The Bronocice pot is a ceramic vase incised with one of the earliest known depictions of a wheeled vehicle. It was discovered in the village of Bronocice near the Nidzica River in Poland. Attributed to the Funnelbeaker archaeological culture, radiocarbon tests dated the pot to the mid-fourth millennium BCE. Today it is housed at the Archaeological Museum of Kraków in southern Poland.
Ratha is the Indo-Iranian term for a spoked-wheel chariot. The term has been used since antiquity for both fast chariots and other wheeled vehicles pulled by animals or humans, in particular the large temple cars or processional carts still used in Indian religious processions to carry images of a deity.
The ancient Chinese chariot was used as an attack and pursuit vehicle on the open fields and plains of ancient China from around 1200 BCE. Chariots also allowed military commanders a mobile platform from which to control troops while providing archers and soldiers armed with dagger-axes increased mobility. They reached a peak of importance during the Spring and Autumn period, but were largely superseded by cavalry during the Han dynasty.
Sinauli is an archaeological site in western Uttar Pradesh, India, at the Ganga-Yamuna Doab. The site gained attention for its Bronze Age solid-disk wheel carts, found in 2018, which were interpreted by some as horse-pulled "chariots".
Wheel construction refers to the making of wheels. Construction of wire-spoked wheels is generally termed as wheelbuilding, so wheel construction refers to construction of non-wire wheels, e.g. wheels of cars and other heavier vehicles. Wheels are constructed in a wide variety of designs using different materials, but in the early 21st century, aluminum and steel are most often used, with steel-made wheels being heavier and more durable than aluminum wheels. The performance of a wheel depends on the alloy and technique used to construct it. A wheel is usually made up of a rim, which connects with the tire, and a central disc, also known as the disc or spider, which connects the wheel to the vehicle. Wheels are usually of two types: semi-drop center (SDC), used in trucks, and drop center (DC), used in other vehicles.
The wheel in Africa was used, to various extents, throughout the history of Africa. While it may have been common for Africans to manually carry their goods or use pack animals to transport economic goods in Africa, there was broad awareness, knowledge, and use of wheeled transports in Africa. However, the environment in some parts of tropical Africa, as well as alternative forms of travel and transport, such as via canoe and beasts of burden/riding animals, may have resulted in decreased use of animal-drawn wheeled transport in Africa. The wheel was also given other technical applications in Africa, such as a water wheel and a potter's wheel.
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.
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.