Spelter Mystery Clock with Plumb Bob Pendulum
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- Bob Pendulum - A bob pendulum consists of a brass or steel rod with a disc shaped metal weight at the end. The most common use of a bob pendulum is in a grandfather clock where it oscillates to keep the time. The length of the rod and the weight of the bob are the key parameters for determining the period of oscillation, and the timekeeping of the clock can be accelerated or slowed by altering the height of the bob.
- Spelter - Spelter was the name given to an alloy of zinc and brass or copper used in the 19th century for statuary and lighting. It is a brittle bluish-white metal. It was used as a cheap replacement for bronze, but being brittle easily breaks and can't be repaired. When finished it can often be mistaken for bronze, but if discreet a scratch on the base displays shows a greyish colour, the metal is spelter, if a golden colour the metal is most likely bronze.
- Pendulum - The pendulum was discovered around 1602 by Galileo Galilei, and was adopted for time keeping by the Dutch mathematician and natural philosopher, Christiaan Huygens, who excelled in astronomy, physics, and horology.
The pendulum comprises a metal rod usually of brass or steel with a metal disk, known as a bob, at the end. The movement of the pendulum is driven by weights or a spring, and as a pendulum swings in a regular arc, it was found accuracy could be controlled to within a few seconds a week.
Timekeeping can be adjusted by changing the height of the bob on the rod, making the pendulum either swing slower or faster.
The disadvantage of the pendulum was that changes in temperature also changed the length of the pendulum, interfering with the accuracy of the clock, and so in the 18th century two types of mercurial pendulums were invented which countered the movement in the steel rod.
The pendulum was the world's most accurate timekeeping technology until the invention of the quartz clock, regulated by a quartz crystal, in 1927.
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