Rotary pendulum clock
The pendulum clock is named after a torsion pendulum that rotates in a horizontal plane similar to a balance wheel. Typical representatives of this type of clock are the so-called “annual clocks”, which achieve a running time of several months to over a year with one winding.
Torsion pendulum clocks appeared in larger numbers in the early 20th century and were most common in the United States, England, and Germany. Their inventor is Johann Anton Harder (1811-1888), who, together with the clockmaker Lorenz Jehlin, received a patent for a torsion pendulum on September 16, 1877 for a torsion pendulum. After failed attempts by the clock companies A. Willmann & Co. and Gustav Eduard Becker, both based in Freiburg in Silesia, August Schatz was commissioned at the end of 1881 to produce annual clocks, which later developed into the annual clock factory in Triberg in the Black Forest. After the patent rights expired, several leading German watch manufacturers included this type of watch in their product range.
The movements are round or square pillar movements with Graham or pin escapement. Some early models also had a verge escapement. They were driven by a mainspring in the barrel. At first, the pendulum mass consisted of a solid brass disc, later bimetallic rifles with sliding weights and mercury compensating pendulums were used for compensation. More recent examples have four steel balls as pendulum weights.
The pendulum weight is suspended from a fine steel wire which is twisted about its axis and acts as a torsion spring. The oscillations of the torsion pendulum are isochronous. For a complete cycle of an oscillation, approx. between 15 and 30 seconds, a comparatively long time. Due to the slow rotation speed, only little energy is lost through the air resistance of the torsion pendulum, so long running times can be achieved even with a small energy storage. Disadvantages of the design are its sensitivity to vibrations and the generally only moderate accuracy. In conjunction with the long running time, this can add up to larger rate deviations.
In modern replicas, models are common that externally resemble pendulum clocks, but in which the pendulum rotates independently of the usually battery-powered movement and thus has no influence on the accuracy of the clock.
mechanical pendulum clock
electric time clock
Rotary pendulum clock without winding or battery
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