Pendulum clocks

The pendulum clock was invented and patented in 1657 by the Dutch scientist Christiaan Huygens, inspired by the superior timekeeping properties of the pendulum, discovered beginning in 1602 by the Italian scientist Galileo Galilei. These watches were much more accurate than earlier foliot watches, improving the timekeeping accuracy of the best precision watches from 15 minutes per day to perhaps 10 seconds per day. Within a few decades, most tower clocks throughout Europe were rebuilt to convert the previous foliot mechanism to a pendulum one. Almost no examples of the original balance and foliot mechanisms of these early watches have survived to this day.

The accuracy of the pendulum clock increased with the invention of the lever escapement in 1657 by Robert Hooke, which quickly replaced the primitive foliot in pendulum clocks. The first tower clock with the new mechanism was the Wadham College Clock, built at Wadham College, Oxford, United Kingdom, in 1670, probably by the clockmaker Joseph Knibb. The lever escapement reduced the swing width of the pendulum from 80 to 100° in the foliot clock to 3-6°, which greatly reduced the energy consumed by the pendulum and allowed longer pendulums to be used. While domestic clocks typically use a 1-second pendulum, 1 meter long, tower clocks typically use a 1.5-second pendulum, 2.25 m long, or a two-second pendulum, 4 m long.[1]​ [2]​.

Tower clocks had an error not found in other clocks: varying torque in the gear wheels caused by the weight of the clock's huge external hands as they rotated, which was made worse by seasonal snow, ice, and wind loads on them. [3]​ The variations in force applied to the pendulum by the escape wheel caused the period of the pendulum to vary. During the century specialized escape mechanisms were invented to mitigate this problem. In the most common type, called gravity escapements, instead of applying the force of the gear mechanism to push the pendulum directly, the escape wheel lifted a weighted lever, which was then released and its weight pushed the pendulum during its downward swing. This isolated the pendulum from variations in the driving force. One of the most widely used types was the three-legged gravity escapement invented in 1854 by Edmund Beckett (Lord Grimsthorpe).

Electric watches

Electric tower clocks and hybrid mechanical/electrical clocks were introduced at the turn of the century.

Some mechanical tower clocks are wound by an electric motor, which are still considered mechanical clocks.

Flywheel and foliot clocks

The first fully mechanical watches that emerged in Europe at the end of the century kept time with a foliot and a regulating balance. In the second half of the century, more than 500 tower clocks were installed in public buildings throughout Europe. The new mechanical clocks were easier to maintain than water clocks, as the energy to run the clock was obtained by turning a crank to lift a weight on a rope, and they also did not freeze during the winter, so they became the standard mechanism used in tower clocks that were being installed in bell towers of churches, cathedrals, monasteries and town halls throughout Europe.

The balance and foliot timekeeping mechanism in these early mechanical watches was very inaccurate, as the primitive foliot balance did not have a balance spring to provide a restoring force, so the balance was not a harmonic oscillator with an inherent resonant frequency or "rhythm"; Its speed varied with variations in the strength of the gear mechanism. The error in the first mechanical clocks could be several hours a day, and therefore the clock had to be reset frequently by the passage of the sun or stars.

Pendulum clocks

The pendulum clock was invented and patented in 1657 by the Dutch scientist Christiaan Huygens, inspired by the superior timekeeping properties of the pendulum, discovered beginning in 1602 by the Italian scientist Galileo Galilei. These watches were much more accurate than earlier foliot watches, improving the timekeeping accuracy of the best precision watches from 15 minutes per day to perhaps 10 seconds per day. Within a few decades, most tower clocks throughout Europe were rebuilt to convert the previous foliot mechanism to a pendulum one. Almost no examples of the original balance and foliot mechanisms of these early watches have survived to this day.

The accuracy of the pendulum clock increased with the invention of the lever escapement in 1657 by Robert Hooke, which quickly replaced the primitive foliot in pendulum clocks. The first tower clock with the new mechanism was the Wadham College Clock, built at Wadham College, Oxford, United Kingdom, in 1670, probably by the clockmaker Joseph Knibb. The lever escapement reduced the swing width of the pendulum from 80 to 100° in the foliot clock to 3-6°, which greatly reduced the energy consumed by the pendulum and allowed longer pendulums to be used. While domestic clocks typically use a 1-second pendulum, 1 meter long, tower clocks typically use a 1.5-second pendulum, 2.25 m long, or a two-second pendulum, 4 m long.[1]​ [2]​.

Tower clocks had an error not found in other clocks: varying torque in the gear wheels caused by the weight of the clock's huge external hands as they rotated, which was made worse by seasonal snow, ice, and wind loads on them. [3]​ The variations in force applied to the pendulum by the escape wheel caused the period of the pendulum to vary. During the century specialized escape mechanisms were invented to mitigate this problem. In the most common type, called gravity escapements, instead of applying the force of the gear mechanism to push the pendulum directly, the escape wheel lifted a weighted lever, which was then released and its weight pushed the pendulum during its downward swing. This isolated the pendulum from variations in the driving force. One of the most widely used types was the three-legged gravity escapement invented in 1854 by Edmund Beckett (Lord Grimsthorpe).

Electric watches

Electric tower clocks and hybrid mechanical/electrical clocks were introduced at the turn of the century.

Some mechanical tower clocks are wound by an electric motor, which are still considered mechanical clocks.