Sir William Congreve invented a new type of rolling ball clock, early in the 19th century. He was granted a patent for the design in 1808.
Congreve's clock rolls a ball in a zigzag path across an inclined table. When the ball reaches the lower edge of the table, the table tilts, thus raising the low edge. The ball rolls back across the table, and the cycle continues. At each reversal, the hands on the dial are advanced.
The oscillator in a Congreve clock is the combination of the rolling ball and the tilting table. Congreve believed that this oscillator was equivalent to a pendulum. Unfortunately, a pendulum is not simply an oscillator but also a resonator. That is, it is an oscillator with a natural, or resonant frequency. The tilting table of a Congreve clock is a simple oscillator, not a resonator.
In practice, his design was a total failure, as the frictional resistance of the ball as it rolls down the inclined table varies greatly with the cleanliness of both the ball and the grooves. Consequently, they are notoriously poor time keepers that are often difficult to keep running. However, the design is beautiful and one of the more fascinating to watch in operation.
This model is loosely based upon Congreve's original design. Its main feature is the small steel ball that moves along a path on the tilting table.
The table changes its inclination every ten seconds under the influence of the ball itself which, at the end of its passage, strikes a lever that tilts the table, so reversing the ball's direction.Like its prototype, the clock is not very accurate. The best that can be achieved is something of the order of 10 to 15 minutes per day.
Despite this flaw, it is fascinating to watch the little ball moving restlessly across its continually tilting path.
The model was designed by John Wilding and published in Constructor Quarterly No. 73.
