The Vocational School I.P.S.I.A. Galileo Galilei
in Castelfranco Veneto (Treviso, Italy) has built Galileo's pendulum clock, a clock that was designed but never built by the Italian scientist. The invention of the pendulum clock is attributed to Huygens who built and patented it in 1656 after Galileo's death. Viviani, one of Galileo's followers, challenged Huygens' paternity of the idea, but Huygens made a scornful comment on Galileo's project: It can't work!
. The challenge issued in the 17th century has been accepted by some teachers who have decided to reconstruct the pendulum clock with their students, starting from Viviani's description of the device and from a nineteenth-century copy of the drawing of the clock preserved at the Museum of Science History in Florence. The model that has been built not only works properly but it also looks nice. We have succeeded. We have won the challenge!
The project Galileo's clock
involved teachers of various subjects and students from many classes. Moreover, many local companies contributed to the project by supplying advanced mechanical technology that was not available in the school.
The pendulum clock was illustrated by Galileo in a letter to the Dutch Laurens Reael in june 1637. The control of the clock rate depended on the isochronism of the oscillation of pendulum of equal length that Galileo had demonstrated in his researches of Mechanics.
In 1583, observing a lamp swinging in the dome of Pisa, the scientist found that its period did not change (he measured it with the heartbeat of his wrist) and noticed that the pendulum's period of swinging appeared to be independent from the swing arc
(isochronism of pendulum). He also tried to find out the relations between the length and the weight of pendulum and its period.
Many years later, in 1641 when he was under house arrest at his villa in Arcetri, Galileo realised that the pendulum had potential for timekeeping and suggested of using a swinging weight to control the speed of a clock; he sketched a plan that did not carry out because he died before his work could be completed.
His pendulum was made up of:
The escapement wheel is supplied with teeth, which lock against the containment lever. The top pallet is necessary to disengage or unlock the escapement wheel, while the bottom to impart the impulse. At the end of every swinging the top pallet meets the containment lever and lifts it, thus unlocking the escapement wheel. This one, turning, hits the inferior pallet and pushes it out towards the bottom, giving the necessary impulse to maintain the pendulum motion. The clock was partially constructed by Galileo's son, Vincenzo, who died before completing it. The first pendulum clock was realized and patented in 1657, from the Dutch scientist Christian Huygens.