22.  The Tower Clock

22 Tower Clock web.jpg

         This reconstruction of a mechanical tower clock is based on the 14th century Salisbury Cathedral clock and the almost identical 1564 Winterthur clock mechanism in Switzerland.   It has a verge and foliot escapement to control the rate of advance of the clock gears at regular intervals, or ‘ticks’.   Such a mechanism could have achieved at best an accuracy of only 15 minutes per day.   The more accurate pendulum clocks did not emerge for another 80 years, along with the addition of another hand so that both hours and minutes could be displayed.

         The clock mechanism is in two logical parts.   The going train has the great wheel which continuously turns at one revolution per hour.   It is regulated by the escapement, which makes a full swing every 8 seconds, i.e. 4 seconds for each half swing.   Every hour, the going train releases the strike train, which can then rotate to cause the bell to be rung the appropriate number of times.  The rate at which the hammer strikes the bell is regulated by the ‘fly’ – large paddles which have to rotate 8 times per strike.

                The tower clock at Kenilworth Castle is very unusual, almost certainly unique, because the mechanism was installed in the chamber above the chamber which is level with the clock faces.   Why the more logical chamber was not used is unknown.   As a result, the clock hour hands have to be driven by a more complicated arrangement via shafts within the outer walls.   These shafts, detailed by the historian Sidney Toy in the 1930’s, and still evident today from above, also accommodate the falling weights which would have been wound up every day.   Note that the clock chamber has no openings, apart from doorways, so would have been dark without candle or torch light.