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Medieval Clock

Oldest working mechanical clock

Probably the oldest working clock in existence, made of hand-wrought iron in or before 1386. The clock may be the work of three horologists from the Low Countries, Johannes and Williemus Vriemand and Johannes Jietuijt of Delft, who came to England at the invitation of Edward III. Bishop Erghum (1375-1388) consecrated at Bruges and may have known of these men. It is possible that corruption of Jietuijt was responsible for the name of LIghtfoot being connected with stories surrounding a later clock at Wells Cathedral which may have been made by same builders.


Salisbury's clock was originally housed in a detached bell tower north of the Cathedral. The tower contained 10 bells in 1531 and eight in 1635. In 1645 the tower was occupied by Parliamentary forces under Colonel Ludlow and attacked by Royalists who set fire to it, forcing surrender. When that tower was pulled down in 1792 the clock moved to the Cathedral tower and worked there until 1884, when a new clock was installed, a gift of officers and men of Wiltshire Regiment. 


The clock received no attention until it was re-discovered in 1929 when it was moved down to the North Transept in 1931 but it was not in working order. In 1956 the clock was completely repaired and restored to its original condition by Messrs John Smith and Co of Derby in consultation with antiquarian horologists  T R Robinson and R P Howgrave-Graham, including restoration of verge and foliot after it had been replaced in the late 17th century by pendulum and new weights made in Cathedral workshops.


Following its restoration, the clock was set up in its present position and connected at triforium level to bell and formerly in South Transept where it was used to warn the Bishop (in his nearby Palace - now called Cathedral School) of approaching times of services.


As is usual of the period, the clock has no face, being designed only to strike hours. In two sections, the right-hand one being known as Going Train and the left-hand one as Striking Train, each driven by falling weights which have to be wound up once a day, though the clock will run for slightly over 24 hours. 'Great' or hour wheel is attached to the drum of Going Train regulated by 'verge and foliot' escapement (like horizontal pendulum) so that it makes one revolution per hour and so set up that a protruding pin on it makes contact with a catch ('striking detent') exactly on the hour.  On the hour, therefore, the pin lifts striking detent, which is connected to 'locking detent' a little further to the left. Locking detent consequently lifts out of a gap hoopwheel (a thin metal ring attached to a toothed wheel), unlocking Striking Train.


Great wheel of Striking Train (the one on the right of the left-hand drum) has eight pins to activate the bell hammer lifting lever at the rear, which is connected by wire to the bell (usually disconnected nowadays because of the loud noise bell makes). When striking detent lifts, it raises not only locking detent but also 'count detent'. This lifts out of slot in countwheel (the one on the extreme left) and allows it to ride on the periphery until it reaches the next slot, corresponding to the correct number of strikes, when it drops down and consequently allows locking detent also to drop down and relock Striking Train. To overcome the problem of accelerating speed of striking when count detent is riding along the periphery for protracted time (e.g.. when striking 11 or 12) there is flyvane (a form of air brake) which revolves rapidly to stabilize the speed of Striking Train and which is equipped with freewheel to prevent damage when Train mechanism is brought suddenly to a halt.