Foliot

The foliot is an early oscillator used to regulate time in medieval mechanical clocks. It consists of a horizontal bar mounted on a central pivot, with weights attached to its ends. The bar swings back and forth, and its oscillation serves as the regulating element that controls the release of the gear train.

In practice, the foliot operates as part of the verge escapement system that was common in the era. As the powered gear drives the verge and its pallets, the foliot’s oscillation determines when the pallets engage and disengage, allowing a measured amount of gear teeth to pass with each swing. The rate of the clock could be adjusted by changing the bar’s length, the position or amount of the weights, or by altering the friction at the pivots.

nors The foliot is distinct from later pendulum and balance-wheel regulators. Its period is highly sensitive to changes in driving force, friction, air resistance, and temperature, making it less accurate and less stable than later solutions. Nevertheless, the foliot represents an important transitional technology, providing a practical means of time regulation before the invention and widespread adoption of the pendulum clock.

Usage and decline: Folior oscillators were common from roughly the 13th through the 16th centuries in European clocks and remained in occasional use into the early modern period. By the late 17th century, pendulum clocks had largely supplanted foliot regulators, offering greater accuracy and reliability.