J Chilver



Perennial non-model favourite among model engineers is the Congreve rolling ball clock, although not as many seem to be being made today with the high cost of brass. This clock was shown by J Chilvers at a National Model Engineering and Modelling Exhibition at Doncaster.

The clock uses a ball rolling along a zig-zag track rather than a pendulum or balance wheel to regulate the time. Invented by Sir William Congreve in 1808, the ball runs down a zig-zag track, where it trips the escapement which in turn reverses the tilt of the tray and at the same time causes the hands of the clock to move forward. The angle of the plate reverses and the clock hands move forward between.

Congreve clocks are delightful to watch but unreliable timekeepers — the time taken for the ball to travel along the track varies greatly depending on the cleanliness of the track and ball, and because the plate is aligned horizontally, it is easy for dust to accumulate.

Congreve’s ‘Extreme Detached Escapement’ was patented in 1808. The first working version was presented to the Prince of Wales. That version was weight-driven. The second design was spring-driven and is in the Buckingham Palace collection.



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