Clocks
The great wheel and the motion work
A clock is a gear train with a job: take a falling weight or a coiled spring and turn it into a minute hand, then an hour hand.
The wheelwork, or train, of a clock is the series of moving wheels (gears) that transmit motion from a weight or spring, via the escapement, to the minute and hour hands. Britannica Scholars: clock The wheels and pinions of a clock need to be made accurately, and the tooth form designed so that the power is transferred as steadily as possible. Britannica Scholars: clock
In a clock driven by a weight or a spring, the power is first transmitted by the main, or great, wheel. Britannica Scholars: clock A pinion is a gear with a small number of teeth designed to mesh with a larger wheel. Britannica Scholars: clock An arbor is a turning rod to which gears are attached. Britannica Scholars: clock
The gear ratios are such that one arbor, usually the second or third, rotates once an hour and can be used to carry the minute hand. Britannica Scholars: clock A simple 12-to-1 gearing, known as the motion work, gives the necessary step-down ratio to drive the hour hand. Britannica Scholars: clock
A clock built for Wells Cathedral in England is preserved in the Science Museum in London. Britannica Scholars: clock
Clockwork already tells the clock’s story
Clock trains, escapements, pendulums and John Harrison’s sea clocks are covered in depth on clockwork.mechanics.im. This site explains the ratio idea — the great wheel, the motion work, and the 12-to-1 step-down to the hour hand — and then points you there.
For escapements, pendulums and John Harrison’s sea clocks, visit clockwork.mechanics.im.