Wheel
A 100 kilogram object dragged for 10 metres across a rough surface demands 4905 joules of work. Give that same object four wheels and the figure collapses to 123 joules, roughly one fortieth of the effort. That single arithmetic gulf explains why the wheel sits among the six simple machines and why heavy loads, once immovable, suddenly travelled. A wheel is a rotating component, usually circular, that turns on an axle bearing. Paired with the axle, it forms the wheel and axle, one of those six machines. Yet the device took its time arriving. Several wheel-less millennia passed even after humans had learned farming and pottery. So where did it begin, and why did some civilisations never adopt it at all? The answers run from the riverbanks north of the Black Sea to the toy carts of ancient Mexico, and from a flooded settlement in East Anglia to the flag of a nation.
Miniature clay wheels found north of the Black Sea, dated to before 4000 BCE, offer the oldest indirect trace of wheeled movement. The solid wooden wheel, a disk with a hole bored for the axle, belongs to the late Neolithic, and its arrival sits beside the technological surge that opened the early Bronze Age. The Copper Age window of 4500 to 3300 BCE saw the potter's wheel invented, the first solid wooden wheels turned, and the earliest wheeled vehicles roll. Some of those first wheels were horizontal slices cut straight from a tree trunk. Because wood grows unevenly, such a slice tends to make an inferior wheel compared with one built from rounded longitudinal boards. Claims of priority scatter across the map. The Halaf culture of 6500 to 5100 BCE is sometimes credited with the earliest depiction of a wheeled vehicle, though no evidence shows Halafians used either wheeled carts or pottery wheels. A potter's wheel from Ur, in modern Iraq, was once thought the oldest at roughly 3100 BCE, until one of the Cucuteni-Trypillia culture surfaced in western Ukraine, dating to the middle of the 5th millennium BCE. That find predates the potter's wheel in Mesopotamia entirely.
On clay tablet pictographs at the Eanna district of Uruk, in the Sumerian civilisation, depictions of wheeled wagons appear dated to around 3500 to 3350 BCE. In southern Poland, the Bronocice clay pot from a Funnelbeaker settlement carries an image of a wheeled vehicle placed between 3631 and 3380 BCE. At nearby Olszanica, a barn 40 metres long with three doors, dated to 5000 BCE and belonging to the Linear Pottery culture, included a door 2.2 metres wide built for wagon entry. The most telling survival is the Ljubljana Marshes Wheel from Stare Gmajne near Ljubljana in Slovenia. Its wheel falls within 3340 to 3030 BCE and its axle within 3360 to 3045 BCE. Two early Neolithic European designs are known. In the circumalpine type, the wheel and axle rotate together, as in the Ljubljana example. In the Baden culture of Hungary, the axle stays fixed and does not turn. Both date to roughly 3200 to 3000 BCE. The radial members of a wagon wheel were carved into shape from a log, using a tool called the spokeshave, and the word spoke itself first referred to the split sections of that log rather than the finished part.
The Sintashta culture produced the earliest known wooden spoked wheels, at Krivoye Lake around 2000 BCE. Lighter and swifter, the spoked wheel let horse cultures of the Caucasus field horse-drawn war chariots for the better part of three centuries. Those riders pushed deep into the Greek peninsula and merged with existing Mediterranean peoples, a current that fed, after the fall of Minoan dominance, into the consolidations of pre-classical Sparta and Athens. Celtic chariots wrapped an iron rim around the wheel during the 1st millennium BCE, the same era that saw an iron rim fitted around the wooden wheels of chariots more widely. In China, wheel tracks dating to around 2200 BCE turned up at Pingliangtai, a Longshan Culture site, with similar ruts at Yanshi, an Erlitou city, around 1700 BCE. The earliest Chinese spoked wheels show up as two wheel hubs from Qinghai, placed between 2000 and 1500 BCE, and the technology reached China from the west. Britain offers its own late chapter. At the Must Farm site in East Anglia, excavated in 2016, a wooden wheel about 1 metre across and dated from 1100 to 800 BCE is the earliest and most complete of its kind found there. Its hub survives, and a horse's spine nearby hints the wheel belonged to a horse-drawn cart in a settlement raised on stilts over wetland.
Across the Americas before European contact, the wheel never carried a load. Small wheeled artifacts identified as children's toys turn up at Mexican archaeological sites, some near 1500 BCE, yet Mesoamericans never built a wheelbarrow, a potter's wheel, or any other practical wheeled object. The likely obstacle was animal, not intellectual. No large draft beast was available to pull a carriage. The American bison, the closest relative of cattle in the pre-Columbian Americas, resists domestication and was never tamed by Native Americans. Several horse species lived until about 12,000 years ago before dying out. The one large domesticated animal of the Western hemisphere, the llama, served as a pack animal but was not suited to drawing wheeled vehicles, and its use barely spread beyond the Andes. The Maya may have come closest to a working wheel through the spindle whorl, and some scholars think those pull toys began as spindle whorls and spindle sticks standing in for wheels and axes. Elsewhere the wheel was adopted but narrowly. Aboriginal Australians rolled circular discs along the ground for target practice. Nubians after about 400 BCE used wheels to spin pottery and as water wheels, possibly ox-driven, and drove horse-drawn chariots imported from Egypt. From the 18th century in West Africa, wheeled vehicles served mostly ceremonial roles in places like Dahomey, while transport by wheel stayed rare across Sub-Saharan Africa, except in Ethiopia and Somalia, well into the 19th century.
The rim is the outer edge of a wheel that holds the tire, the large hoop on a bicycle attached to the outer ends of the spokes. At the centre sits the hub, which typically houses a bearing and is where the spokes meet. A hubless wheel, also called a rim-rider or centerless wheel, inverts that idea: its hub grows almost as large as the wheel itself while a hollow axle follows the rim at very close tolerances. Wire wheels reconnect rim to hub through wire spokes that, though stiffer than ordinary rope, behave as tensioned flexible wires keeping the rim true under load. Aeronautical engineer George Cayley invented the wire wheel, and James Starley first used it in bicycles, a craft still called wheelbuilding. The tire, or tyre in some Commonwealth nations, is a ring-shaped covering fitted around the rim to cushion shock and hold the wheel against the ground. Its name may trace back to tie, the outer steel ring that bound a wooden cart wheel's segments together. Modern tires combine synthetic rubber, natural rubber, fabric, and wire, built from a tread for traction and a body for support. Before rubber, the earliest tires were simply metal bands guarding wooden wheels against wear. Today most are pneumatic, doughnut-shaped bodies of cords and wires encased in rubber and filled with compressed air.
The reason a wheeled vehicle spares so much effort is that the frictional work no longer happens at the surface the vehicle crosses, but inside the bearings. In the oldest and simplest case, that bearing is just a round hole through which the axle passes, a plain bearing. Even then the work drops sharply, because the sliding distance shrinks for a given distance of travel and the coefficient of friction at the interface is usually lower. Consider the four-wheeled object again. With a wheel diameter of 1000 millimetres and an axle diameter of 50 millimetres, the object covers 10 metres while its sliding surfaces rub against each other by only 0.5 metres. Some energy still escapes at the wheel-to-road interface as rolling resistance, a loss driven mostly by deformation and shaped by the ground, the wheel material, tire inflation, engine torque, and more. A large enough radius also helps a wheel ride over irregularities in the ground. On its own the wheel is not a machine. Only when joined to an axle through a bearing does it become the wheel and axle, and a driven wheel is one example. Wheels predate driven wheels by about 6000 years, both descended from round logs used as rollers, a practice so old it has never been dated.
Extreme off-road terrain pushed engineers past the plain round wheel entirely. Snow chains wrap the tire for grip in deep snow, while the Dreadnaught wheel uses permanently hinged panels connected to each other rather than to the wheels. The Pedrail wheel carries panels on a system of rails and need not form a circle at all, blurring into continuous track. A similar paneled device appeared on heavy World War I artillery, including the Cannone da 149/35 A and the Big Bertha, installed over a contemporary wheel. In 1998 a Canadian truck shop owner invented and patented the wheel rotation indicator, a colored plastic strip on the rim that lets a driver spot a locked wheel in the side-view mirrors. Beyond mechanics, the wheel turned into a metaphor for cycles and repetition, surfacing in the chakra, in reincarnation, and in Yin and Yang. Difficult terrain and that symbolism together meant wheeled vehicles were forbidden in old Tibet. The Kalachakra, or wheel of time, runs through some forms of Buddhism alongside the dharmachakra. A winged wheel marks progress on the coat of arms of Panama and the logo of the Ohio State Highway Patrol, and the wheel stands as the prominent figure on the flag of India, representing law, or dharma. It reappears on the flag of the Romani people, a nod to their nomadic past and Indian origins. The sixth-century monk Dorotheus of Gaza drew a spiked wheel to show how compassion binds people: those who draw nearer to God draw nearer to one another. In medieval Europe the Wheel of Fortune dramatised how a person risen to the top might descend again with a single turn.
Common questions
What is a wheel and how does it work?
A wheel is a rotating component, usually circular, that turns on an axle bearing. Joined to an axle through a bearing, it forms the wheel and axle, one of the six simple machines, reducing friction by moving the frictional work from the travelled surface into the bearings.
When was the wheel invented?
The solid wooden wheel, a disk with a hole for the axle, dates to the late Neolithic. The Copper Age window of 4500 to 3300 BCE saw the potter's wheel, the earliest solid wooden wheels, and the earliest wheeled vehicles, while miniature clay wheels north of the Black Sea before 4000 BCE give the oldest indirect evidence.
Where is the oldest surviving wheel and axle found?
The Ljubljana Marshes Wheel from Stare Gmajne near Ljubljana in Slovenia is dated within two standard deviations to 3340 to 3030 BCE, with its axle dated to 3360 to 3045 BCE. A wooden wheel about 1 metre across found at Must Farm in East Anglia in 2016, dated from 1100 to 800 BCE, is the earliest and most complete of its type in Britain.
When was the spoked wheel invented?
The earliest known wooden spoked wheels come from the Sintashta culture at Krivoye Lake, dating to around 2000 BCE. The spoked wheel allowed lighter, swifter vehicles and enabled horse-drawn war chariots.
Why did the Americas not use the wheel before European contact?
Mesoamericans built small wheeled toys, some near 1500 BCE, but never a wheelbarrow, potter's wheel, or other practical wheeled object. The likely obstacle was the absence of a large domesticated draft animal, since the bison resisted domestication and the llama was a pack animal unsuited to pulling wheeled vehicles.
How much energy does a wheel save compared with dragging?
Dragging a 100 kilogram object 10 metres over a surface with a coefficient of friction of 0.5 requires 4905 joules. Giving the object four wheels, with a 1000 millimetre wheel diameter and 50 millimetre axle, drops the work to 123 joules, about one fortieth of the dragging effort.
What does the wheel symbolize in different cultures?
The wheel is a metaphor for cycles and repetition, appearing in the chakra, reincarnation, and Yin and Yang, and in the Kalachakra or wheel of time in some forms of Buddhism. It is the prominent figure on the flag of India, where it represents law or dharma, and it reappears on the flag of the Romani people.
All sources
46 references cited across the entry
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- 13Wheel I Never: Europes Oldest Stone Age Cart Tracks Found29 April 2022
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- 28Real smart folks, but no wheelHerman Smith — Dig It
- 29"Aboriginal people never even invented the wheel."koorihistory.com — 2019-12-01
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