Dover Castle clock, c. 1600
Image number: 1884-81
This is one of the few surviving public clocks that still uses its original ‘foliot balance’ for its time control. Most foliot clocks were converted to pendulum control in the 1600s.
A foliot balance is a horizontal weighted bar which is pushed in one direction (a ‘tick’) and then the other (a ‘tock’) by a crown-shaped toothed wheel, pulled round by a falling weight.
The crown-shaped wheel is part of an ‘escapement’. The potential energy in the falling drive weight is allowed to escape a little at a time. All mechanical clocks have some form of escapement. This clock was removed from Dover Castle in 1872.
Source: English Heritage
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- Science Museum/Science & Society Picture Library
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