Countwheel striking clock movement
From Object Wiki
| Striking clock movement | |
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| Manufacturer | (unknown) |
| Production years | 1880 |
| Production location | England |
An English clock movement, made about 1880, with a locking-plate or count-wheel striking mechanism similar in principle to the striking arrangements of the earliest known clocks of the fourteenth century.
[edit] How it works
Two mechanisms have been devised by clockmakers to enable striking clocks to correctly count out the hours. The earlier, which appeared in the first striking clocks in the 14th century, is called countwheel striking. This uses a wheel that contains notches on its side, spaced by unequal, increasing arc segments. This countwheel governs the rotation of the striking train. When the striking train is released by the timekeeping train, a lever is lifted from a notch on the countwheel; the uneven notches allow the striking train to move only far enough to sound the correct number of times, after which the lever falls back into the next notch and stops the striking train from turning further.
The countwheel has the disadvantage of being entirely independent of the timekeeping train; if the striking train winds down, or for some other reason the clock fails to strike, the countwheel will become out of synch with the time shown by the hands, and must be resynchronized by manually releasing the striking train until it moves around to the correct position.
In this example the locking plate consists of a circular flange with a number of gaps, the distance between the successive gaps being proportional to 2, 3, 4, 5, etc. up to 12. The striking train of wheels is locked when the bent end of a lever falls between one of the gaps. In detail the series of operations involved in striking are somewhat complicated, but it is the distance between successive gaps which determines the number of blows struck. As the locking plate moves with the striking train, its position is independent of that of the hands, and when the latter are moved it is necessary to wait for the striking at each hour.
[edit] Memories
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[edit] In the Science Museum's Records
Inv. No: 1883-53