Crank (mechanism): the story on HearLore

Crank (mechanism)

The first true crank-and-connecting rod mechanism to appear in the historical record dates back to the Western Han dynasty, between 202 BC and 9 AD, yet for centuries scholars believed the earliest evidence was a Han era glazed-earthenware tomb model of an agricultural winnowing fan dated no later than 200 AD. This ancient Chinese invention fundamentally changed how humanity converted human effort into mechanical work, utilizing a combination of a hand-crank and a push-and-pull connecting rod by a hinge to operate rotary querns and grain decortication items. The technology did not remain static; it evolved rapidly to power flour-sifting machines, treadle spinning wheels, water-powered furnace bellows, and silk-reeling machines, establishing a mechanical foundation that would eventually drive the industrial age. While the Chinese were perfecting these systems, the ancient Egyptians possessed manual drills resembling a crank during the Old Kingdom between 2686 and 2181 BCE, but these early tools did not operate as true cranks, lacking the essential connecting rod that defines the mechanism's ability to convert motion types.

Roman Engineering And Greek Precision

A Roman iron crank excavated in Augusta Raurica, Switzerland, dates to the 2nd century AD and features a long piece fitted with a long bronze handle at one end, though the other handle was lost to time. This artifact, alongside a true iron crank found in Aschheim near Munich with a pair of shattered mill-stones of diameter, pushes the date of the crank and connecting rod invention back by a full millennium compared to previous assumptions. The ancient Greek Hierapolis sawmill in Roman Asia from the 3rd century AD stands as a monumental testament to this technology, where a waterwheel fed by a mill race powered two frame saws through a gear train and connecting rods to cut rectangular blocks. The accompanying inscription on the pediment of the Hierapolis mill is in Greek, confirming the sophisticated understanding of mechanical necessity required to operate such a system. Further evidence appears in two stone sawmills at Gerasa in Roman Syria and Ephesus in Greek Ionia, both dating to the 6th century AD, which worked without a gear train, demonstrating that the crank and connecting rod mechanism was versatile enough to function in diverse mechanical configurations across the Roman Empire.

The Medieval Awakening

The earliest representation of a rotary grindstone operated by a crank handle appears in the Carolingian manuscript Utrecht Psalter, a pen drawing from around 830 that goes back to a late antique original. By the mid-9th century, the Banū Mūsā brothers described hydraulic devices in their Book of Ingenious Devices that utilized cranks, although these devices made only partial rotations and could not transmit much power without significant modification. The Italian physician Guido da Vigevano, living between 1280 and 1349, planned a new crusade and created illustrations for paddle boats and war carriages propelled by manually turned compound cranks and gear wheels. The Benedictine monk Theophilus Presbyter, active between 1070 and 1125, described crank handles used in the turning of casting cores, while a musical tract ascribed to the abbot Odo of Cluny, who died in 942, described a fretted stringed instrument sounded by a resined wheel turned with a crank. These medieval innovations laid the groundwork for the compound crank, which began to appear in carpenter's braces between 1420 and 1430 in various northern European artworks, marking a shift from simple rotary motion to complex reciprocating systems.

Common questions

When did the first true crank-and-connecting rod mechanism appear in history?

The first true crank-and-connecting rod mechanism appeared in the Western Han dynasty between 202 BC and 9 AD. This historical record predates previous assumptions that the earliest evidence was a Han era glazed-earthenware tomb model of an agricultural winnowing fan dated no later than 200 AD.

What is the earliest known example of a crank used in ancient Egypt?

The ancient Egyptians possessed manual drills resembling a crank during the Old Kingdom between 2686 and 2181 BCE. These early tools did not operate as true cranks because they lacked the essential connecting rod that defines the mechanism's ability to convert motion types.

Which Roman artifact provides evidence of a crank dating to the 2nd century AD?

A Roman iron crank excavated in Augusta Raurica, Switzerland, dates to the 2nd century AD and features a long piece fitted with a long bronze handle at one end. This artifact pushes the date of the crank and connecting rod invention back by a full millennium compared to previous assumptions.

How did the crank function in the ancient Greek Hierapolis sawmill?

The ancient Greek Hierapolis sawmill in Roman Asia from the 3rd century AD used a waterwheel fed by a mill race to power two frame saws through a gear train and connecting rods to cut rectangular blocks. The accompanying inscription on the pediment of the Hierapolis mill is in Greek, confirming the sophisticated understanding of mechanical necessity required to operate such a system.

When did the crank become common in Europe and who documented its adoption?

The crank became common in Europe by the early 15th century, often seen in the works of the German military engineer Konrad Kyeser. The Anonymous of the Hussite Wars, an unknown German engineer, documented the rapid adoption of the compound crank and noted that double compound cranks began to be equipped with connecting-rods.

What was the last car model to incorporate a crank for engine ignition?

The last car model which incorporated a crank was the Citroën 2CV, produced from 1948 to 1990. This marked the end of an era where human strength was the primary method of engine ignition before electric starters came into general use.