The Risborough Clock
In Greater Detail
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The clock frame dimensions are 30ins x 20ins x 39ins high. It and
the shafts are made of wrought iron, as are the 1.25ins and 1.75ins
cogs. The other cogs are made of cast brass.
A weight is suspended from the rope which is wound up around the 8ins diameter wooden drum once a day. The weight causes a turning force on the drum on no.1 shaft, which has a 13ins/72 teeth cog at its end. This meshes with the 1.5ins/6 teeth cog on one end of no.2 shaft above. At the other end of which, a 9.5ins/60 teeth cog meshes with a 1.75ins/10 teeth cog on the end of no.3 shaft above it. Half way along this shaft is a 6.25ins/25 teeth cog, and above this, catching on its teeth, is the 5.25ins wide escape anchor that restrains the turning force in the mechanism. The anchor is on a shaft from which the pendulum is suspended via a piece of flexible steel. The wooden pendulum is 14ft long with a bob weight of approximately 40lbs fitted near its bottom end. The distance from the end governs the time of the swing, which is set at about 2 seconds. As the pendulum reaches the end of its swing, it lifts the escape anchor allowing shaft no.3 to turn by 1 tooth and so also the winding drum. The 72 teeth cog on the end of the winding drum also meshes with a 6.5ins/36 teeth cog on the end of shaft no.4. The other end of which has a 4.5ins/35 teeth crown gear that meshes with a similar one on the vertical shaft no.5. This has another crown gear of 5.75ins/48 teeth meshing with a similar one on the end of horizontal shaft no. 6. which runs back under and parallel to the winding drum, and out through the centre of the 5ft 2ins diameter clockface. Shaft no.6 turns the 2ft 4ins minute hand. An arm attached part way along the shaft, with a weight of approx 3lbs, counterbalances the hand. The 1ft 10ins hour hand is attached to the end of a tube through which the minute hand shaft runs. This shaft has a 2ins/20 teeth cog around it which meshes with a 4.5ins/60 teeth cog attached to a 1.5ins/15 teeth cog on a sub-shaft. This turns a 5ins/60 teeth one which is fixed around the end of the hour hand tube. A counterbalance is fitted similar to that on minute shaft.
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