Striking clock
[1] The development of mechanical clocks in 12th century Europe was motivated by the need to ring bells upon the canonical hours to call the community to prayer.
Before European clocks, China developed a water-driven astronomical clockwork technology, starting with the first century AD scientist Zhang Heng (78–139).
The Tang dynasty Chinese Buddhist monk and inventor Yi Xing (683–727) created a rotating celestial globe that was turned by a water clock mechanism driven by a waterwheel.
[2] It is recorded that Confucian students in the year 730 were required to write an essay on this device in order to pass the Imperial examinations.
It is the subject of a book, On the Construction of Clocks and their Use (1203), by Riḍwān ibn al-Sāʿātī, the son of a clockmaker.
[5] The Florentine writer Dante Alighieri made a reference to the gear works of striking clocks in 1319.
In 1497, Simone Campanato moulded the great bell, which was put on the top of the tower where it is alternately beaten by the Due Mori (Two Moors), two bronze statues handling a hammer.
The clock of the Beata Vergine (later San Gottardo) in Milan, built around 1330, was one of the earliest recorded that struck the hours.
Some rare clocks use a form of striking known as "Roman Striking" invented by Joseph Knibb, in which a large bell or lower tone is sounded to represent "five", and a small bell or high tone is sounded to represent "one".
[8] One small table clock of this type sold from the George Daniels collection at Sotheby's on 6 November 2012 for £1,273,250.
[11] Two mechanisms have been devised by clockmakers to enable striking clocks to correctly count out the hours.
There was a misconception during the 20th century that the rack and snail mechanism was invented by British clergyman Edward Barlow in 1675–6.
As the change of the hour approaches, this projection slowly lifts the release lever, allowing the rack to fall until its point rests on the snail (N).
As it turns, the pins (G) repeatedly lift the hammer (F) and allow it to drop, ringing the gong (E).
