The history of gears and the first evidence of their invention have been dated as far back as ancient Greece, ancient Rome, and ancient China. The ability to change the direction of a force, i.e., to transmit or move from one axis of rotation to another, is an important feature of many modern machines. These same basic functions are still widely used today and are based on centuries-old techniques in gears. The Antikythera Mechanism, an astronomical calculator unearthed in 1901 off the shore of the Greek island of Antikythera, is one of the oldest pieces of evidence in the history of gears, along with the South-Pointing Chariot from c. 235 AD (if not c. 2650 BC). The complex gear system inside the Antikythera Mechanism, which was likely constructed around c. 200 BC, was used to determine the whereabouts of the planets and the timing of eclipses.
What Are Gears?
Gears are mechanical devices made up of disks with teeth (“cogwheels”) that mesh with each other. A cogwheel is mounted on a central axis of rotation with many other cogwheels on the outside, and these cogwheels move together to form the gear. Torque, or rotational force, can be transmitted through the use of gears. The teeth of the wheel provide what is known as “transmission,” the method by which the angular velocity of one gear is transmitted to a neighboring gear. The ratio between the teeth of the two gear wheels determines the force and speed at which the “mechanical advantage” is gained by the second gear wheel turning; the smaller second gear wheel turns faster but exerts less torque or rotational force.
The Invention of Gears
Who and when were the first gears invented? The first gear was most likely invented by the ancient Greek mechanics of Alexandria in at least the 4th century BC. Aristotle (384–322 BC) and other ancient Greeks described gear-like machines. However, the gears are probably much older than that. The oldest known piece of gear is the Antikythera Mechanism from the end of the 3rd century BC.
Practical gear applications that harnessed the flow of water and wind gradually spread throughout the ancient world around this time in 200 BC. Gears were used in a variety of mills; flour mills were perhaps the most widespread, but sawmills also utilized gears to rotate their cutting blades, and hammer mills used the gears to produce metal bearings or to raise and lower the heavy hammers for minting coins.
Hero of Alexandria, a Greek mathematician, was the first to publish articles dedicated to gears in the year 50 AD. However, there is a chance that the gears were probably invented much earlier in China. The Chinese South-Pointing Chariot (or carriage) is one of the oldest known devices that utilized gears. It was a specialized navigation instrument that dates back to the 3rd century AD. However, some sources place its origin in the 27th century BC. That is why it is impossible to accurately date the invention of gears.
Around the 13th century, the latest advances in gears led to the development of the first mechanical clock in Europe. Both animal- and human-powered treadwheels in the early 19th century began to gain popularity over time. During the Industrial Revolution in the 18th to 20th centuries, more sophisticated gear systems were developed to control steam-powered machines, and the first steam car was invented in 1769 by Nicholas Cugnot. Today, gears continue to play the exact same role in modern devices as they did in ancient times.
The History of Gears
240 BC – Waterwheel
Waterwheels and toothed gearing were believed to have been invented by the ancient Greeks. In contrast to horizontal waterwheels, only vertical waterwheels make use of gears. In ancient Greece, the first watermills with horizontal wheels were invented in 280 BC, and they were first used in the Greek colony of Byzantium. Then, the watermills with vertical wheels and gears were first used in Alexandria during the Ptolemaic era, roughly 240 BC. The Greek waterwheels with water-powered gears spread throughout the Greco-Roman world after that.
In the 1st century BC, Chinese people developed a newer water wheel technology that was equipped with a gear mechanism capable of different motions. Remains and components of it have been discovered in burial mounds and ruins, suggesting that it was first employed extensively as a power source to mechanically move a spring hammer or millstone. A geared waterwheel was also put to use in astronomy as an armillary sphere by Zhang Heng (more on that below).
200 BC – The Antikythera Mechanism
The Antikythera Mechanism, an astronomical calculator unearthed in 1901 off the shore of the Greek island of Antikythera, is one of the oldest pieces of evidence for the invention of gears. The geared device was found in the remains of a merchant ship that sank in the 1st century BC. It is technically the oldest known analog computer.
The complex gear system inside the Antikythera Mechanism, which was likely constructed around c. 200 BC, was used to determine the whereabouts of the planets and the timing of eclipses. The biggest gear has a diameter of around 13 centimeters (5.1 in) and used to have 223 teeth. With 37 bronze gears (potentially 72) working together in an epicyclic way, astronomers could calculate the positions of the Moon and Sun, predict eclipses, and determine the Moon’s irregular orbit.
In ancient Greece, gear technology reached its pinnacle with the creation of similar devices. This intricate astronomical calculator showcases the mastery of gear technology in ancient Greece.
125 AD – Zhang Heng’s armillary sphere
An armillary sphere is a useful tool as a scientific representation of the night sky. A Chinese sage named Zhang Heng (78–139 AD) built an armillary sphere powered by water and gears. Heng’s model, which showed the movements of the Sun, Moon, and stars, went on to influence not only Chinese gear technology but also later watchmakers.
In 125 AD, the famed astronomer and inventor Zhang Heng of the Eastern Han dynasty (23–220 AD) used his in-depth understanding of gears to create an armillary sphere that included the horizon and meridian rings. He also built the first water-driven armillary sphere and used an inflow clepsydra clock to power the device.
Prior to this, astronomers in the Western Han (late 3rd to early 1st centuries AD) dynasty had made various strides in the design, with Geng Shouchang introducing the first permanent equatorial ring and Fu An and Jia Kui adding the ecliptic ring for the device.
235 AD – The South-Pointing Chariot
The South-Pointing Chariot, also known as the “Guide Car” in Chinese, is an instrument that uses gears to identify directions. The chariot had a gear arrangement that allowed the front of the body to always face south as the wheels turned and the car moved. In various sources, the Yellow Emperor (Huangdi) in c. 2650 BC or the Duke of Zhou in c. 1000 BC are credited with the invention of the South-Pointing Chariot. Since the first wheeled vehicle was invented in 3500 BC, this seems possible. The South-Pointing Chariot is the oldest known vehicle that uses gears.
However, according to Chinese historical records, various South-Pointing Chariot vehicles were also developed by Cao Wei State engineer Ma Jun (c. 235 AD) during the Three Kingdoms era. On it was a small wooden figure whose finger constantly pointed south. The figurine could always be pointed south thanks to differential gears controlled by the chariot’s wheels.
The oldest reliable proof of the South-Pointing Chariot can only be traced back to Ma Jun’s conception. This geared chariot was first recorded in “Xijing Miscellaneous Notes” from the 4th century AD. According to that, it was invented by Ma Jun in the third year of “Qinglong,” or 235 AD, and it was based on the principle of gears rather than magnetic poles or a compass. A few other sources also credit the device to Zhang Heng.
In 1924, the British researcher Moule wrote a paper on the study of the South-Pointing Chariot, according to the archives of “The History of Song.” He presented a precise restoration plan for the geared vehicle. Using Moore’s design as a starting point, Wang Zhenduo published “Investigations and Reproduction in Model Form of the South Pointing Chariot and the Hodometer” in 1937, detailing his modifications to the chariot and its successful manufacture as a model. His 1971 achievement was the effective recreation of Ma Jun’s “Yellow Emperor Guide Car (South-Pointing Chariot).”
700 AD – Windmill
Windmills can be physically dated back to the Persian Empire around the years 700–900 AD. The first functional windmill with horizontal sails powered by the rotation of a vertical shaft was developed in Persia. Since the blades were arranged on a vertical axis, there was no need for any of the intermediary gears present in horizontal-axis windmills to transfer the energy. Around the 11th century, Europeans began using windmills to drain land that was below sea level. This was particularly true in countries like the Netherlands.
In the past, windmills were built primarily for mills. More than 1700-year-old windmills have been shown in Chinese art, as seen in the paintings of the Han tombs in Liaoyang from the late Eastern Han Dynasty (25-220 AD). However, this is not fully confirmed. A scientist working in Roman Egypt in the first century, Heron (10–70 AD), wrote about gear wheels connected to a machine and powered by the wind. But the wind organ he described might have been just a toy.
850 AD – Book of Ingenious Devices
The Banu Musa brothers released their voluminous book, “Book of Ingenious Devices,” in the year 850. The book contains pictures of many mechanical devices with gears, some of which are self-powered. Under the patronage of the Abbasid Caliph Al-Ma’mun, the Banu Musa were engaged in productive activity in the “House of Wisdom” in Baghdad, Iraq. More than 100 different gadgets, some of which utilize gears, and their uses are detailed in this book. An illustration (above) from the book depicts a light that automatically trims itself.
Banu Musa amassed a library of Greek writings from monasteries and the intellectuals of the Roman Empire. Some of the authors included in this collection are the Greek engineer and mathematician Hero of Alexandria, the Byzantine philosopher Philo, and the Chinese, Indian, and Persian engineers who originally designed these devices. Their works served as inspiration for several of the geared tools mentioned in this book.
According to their book, the Banu Musa brothers built the first wind-powered fountain. The work provides a rare and in-depth look at a little-known facet of Greek technology: The full description of many mechanical fountains. The fountains use a worm and pinion gear to propel water in the form of a jet, splash, or “lily of the valley flower.” Occasionally, the water could sprinkle, and other times it could cup downward.
Inspired by the Book of Ingenious Devices, the Arab sage al-Jazari described the construction of 100 important machines in a later piece of writing in 1206, which he named “The Book of Knowledge of Ingenious Mechanical Devices.” The book included the crankshaft, and most of these machines were powered by various types of gears.
1283 – Mechanical clocks in Europe
In the 13th century, tower clocks were the first mechanical clocks built. Without dials or hands, these clocks instead displayed the time by ringing bells at predetermined intervals. One of these clocks was controlled by dropping a weight attached to a chain. In 1283 AD, this first weight-driven mechanical clock appeared in Salisbury Cathedral in England.
During the 13th century, monks in Northern Italy constructed bell towers with gears that were used as timekeepers for prayer reminders. In 1360, Zhan Xiyuan from China invented the “five-wheel hourglass,” another mechanical clock incorporating gears and time dials.
1478 – Leonardo da Vinci’s self-propelled car
Around 1478, Leonardo created sketches for what is widely considered to be the first-ever autonomous car. Ability to get going without needing to be dragged or pushed, Da Vinci’s design of the three-wheeled cart is only one of several innovations he made using gears for propulsion and transportation.
The car had gears, steering, and a brake, and its “programmed” steering was accomplished by placing wooden blocks between the gears at certain positions. The design featured a system of gears and springs. On the other hand, the vehicle could only turn right.
In many of his discoveries, such as lens sharpening and metal-rounding devices, the Italian scholar Leonardo da Vinci (1452-1519) made use of the intricate arrangement of gear teeth, demonstrating his deep theoretical understanding of the function of gears.
18th century – Industrial Revolution
The Industrial Revolution of the 18th century would not have been possible without the invention of gears. The ability of gears to transform linear motion into rotary motion was crucial to the success of the Industrial Revolution. During the Industrial Revolution, steam power spurred advancements in gear technology. The linear motion of steam pistons was harnessed to rotate locomotive wheels through a set of gears.
The gears cleared the door for mass manufacturing and the automation of formerly labor-intensive operations and made it possible to build machines with more efficiency and accuracy, which increased output and decreased expenses:
- Textile machinery – Revolutionizing the textile industry, gears were employed to drive the spinning jenny, water frame, and power loom.
- Steam engines – The transmission of power from steam engines, one of the most significant achievements of the Industrial Revolution, was made possible by gears.
- Machine tools – The transmission of power and regulation of cutting speed in machine tools such as lathes, drill presses, and milling machines were both facilitated by gears.
- Transportation – Gears were employed to transform the mechanical energy produced by steam engines in locomotives, ships, and other forms of transportation.
- Printing presses – Gears connected the steam engine to the printing mechanism of the rotary printing press, which enabled the mass manufacturing of printed items.
1781 – Murdoch’s sun and planet gear
Scottish engineer William Murdoch’s invention of sun and planet gears enabled steam power to be used to produce a continuous circular motion around the center of the gear. This motion was used to turn the wheels or shafts of other machines. The purpose of the invention was to create a new kind of crank motion. Since Murdoch was an employee in James Watt’s company, the patent for the invention belonged to James Watt, which he registered in 1781.
The gears in the shape of the sun (the inner gear) and planet (the outer gear) transformed the linear motion of the piston in an internal combustion engine or a steam engine into the rotational motion needed to power various mechanisms. The sun gear was fixed to the end of the rod connecting to the engine, and as the piston moved up and down, the planet gear rotated the sun gear. The sun and planet gears improved steam engine efficiency.
19th century – Invention of the bicycle
In 1680, German inventor Stephan Farffler created the first tricycle (and also the first self-propelled wheelchair), which was powered by gears and hand cranks instead of pedals. Two Frenchmen, Blanchard and Maguire, also designed a pedal-powered tricycle in 1789. Throughout the 19th century, vehicles changed from tricycles to pedal-powered two-wheeled bicycles and other machines in which gears moved a chain.
The invention of the first bicycle in the late 19th century included a chain drive and a gear-shifting system, so riders could choose between two and three speeds depending on the terrain. Some models had a steam-engine-inspired planetary gear system that the rider could adjust using a lever. With just one gear that couldn’t be changed, the “fixed-gear” bicycles that came before this design were clearly inferior. When gears were added to bicycles, they became a more useful and fun way to get around.
1835 – Gear-cutting machine
Gear cutting is a machining process for creating gears. The British engineer Joseph Whitworth invented the first gear cutting machine in 1835, which was the first industrial-scale process for high-precision gear production, including gear hobbing. The teeth that mesh with other gears would be carved into the gear blank by a rotating cutting tool. Gears with varying tooth counts, pitch circles, and profiles could all be cut using this machine. Since the lead screws allowed for exact alignment, uniformly sized gears could be manufactured with the invention of the gear-cutting machine in the 19th century. When Whitworth passed away in 1887, he left most of his wealth to the citizens of Manchester.
1950s – Plastic gears
Plastic gears have been around since the early 20th century, although they didn’t start seeing widespread usage in manufacturing until the middle of the century. Alexander Parkes invented plastic in 1862. Gears made of new plastic materials first appeared around the 1950s. They were weaker than properly machined metal gears but much easier and cheaper to produce.
There is no one person or company that can claim to have invented plastic gears since their creation and widespread adoption were a collaborative effort. Plastic gears are ideal for use in lightweight equipment and devices. They are resistant to corrosion, produce less noise than metal gears, and show high wear resistance. However, they offer limited load capacity, a limited temperature range, and limited availability compared to metal gears.
1990s – Nanotechnology
Geared machines built at the nanoscale are generally based on the same principle as large-geared devices, but the gear wheels made with nanotechnology are typically less than 100 nanometers in size.
Nanoscale gears, fabricated from carbon nanotubes or graphene, function in the same way that their macroscale counterparts do by transferring torque through meshing teeth. Since their compactness allows for tighter manufacturing tolerances, they provide excellent precision and accuracy. There is less jarring in the transfer of motion as a result.
Nanoscale gears, with their increased surface area to volume ratio, have improved frictional and wear qualities, making them more long-lasting and resilient. They are also very power-efficient, making them perfect for microelectromechanical systems (MEMS) and nanoelectromechanical systems (NEMS).
