Pendulum Clock

Invented by : Christiaan Huygens

Invented in year : 1656

A Pendulum Clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. Pendulum clocks must be stationary to operate as any motion can affect the motion of the pendulum, causing inaccuracies. They are generally kept mostly for their decorative and antique value.  In most wall clocks that use a pendulum, the pendulum swings once per second. In small cuckoo clocks the pendulum might swing twice a second. In large grandfather clocks, the pendulum swings once every two seconds.
All mechanical pendulum clocks have five basic parts.

These are:

• A power source - Either a weight on a cord that turns a pulley, or a mainspring
• A gear train - A wheel train that steps up the speed of the power so that the pendulum can use it
• An escapement - It gives the pendulum precisely timed impulses to keep it swinging, and which releases the gear train wheels to move forward a fixed amount at each swing
• The pendulum - A weight on a rod
• An indicator or dial - It records how often the escapement has rotated and therefore how much time has passed, usually a traditional clock face with rotating hands.

A pendulum is a relatively long, thin rod made of wood or metal that terminates in a disk. The pendulum swings with a period that varies with the square root of its effective length. The rate of pendulum clocks is adjusted by moving the pendulum bob up or down on its rod, often by means of an adjusting nut under the bob. In some pendulum clocks, fine adjustment is done with an auxiliary adjustment, which may be a small weight that is moved up or down the pendulum rod. When a pendulum is displaced from its resting equilibrium position, it is subject to a restoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force combined with the pendulum's mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period.

History of the Invention

Galileo Galilei is sometimes credited with inventing the pendulum. He studied its motion as early as 1582 but Galileo's design for a clock was not built before his death.
So it was Christian Huygens, a Dutch scientist who is known for making the first pendulum clock in 1656. It was regulated by a mechanism with a natural period of oscillation.  Huygens' pendulum clock had an error of less than 1 minute a day, the first time such accuracy had been achieved. His later refinements reduced his clock's errors to less than 10 seconds a day.

Development in the invention of the Pendulum Clock

Around 1675, Huygens developed the balance wheel and spring assembly, still found in some of today's wrist watches. This improvement allowed 17th century watches to keep time to 10 minutes a day.

In 1671, at London, William Clement built clocks with the new 'Anchor' or 'Recoil' escapement, a substantial improvement over the verge because it interferes less with the motion of the pendulum.

In 1721, George Graham improved the pendulum clock's accuracy to 1 second a day by compensating for changes in the pendulum's length due to temperature variations.

John Harrison, a carpenter and self-taught clock-maker, refined Graham's temperature compensation techniques and added new methods of reducing friction. By 1761, he had built a marine chronometer with a spring and balance wheel escapement that won the British government's 1714 prize (of over $2,000,000 in today's currency) offered for a means of determining longitude to within one-half degree after a voyage to the West Indies. It kept time on board a rolling ship to about one-fifth of a second a day, nearly as well as a pendulum clock could do on land, and 10 times better than required.

Over the next century refinements led in 1889 to Siegmund Riefler's clock with a nearly free pendulum, which attained an accuracy of a hundredth of a second a day and became the standard in many astronomical observatories.

During 1898, R. J. Rudd introduced a true free-pendulum principle which stimulated development of several free-pendulum clocks. One of the most famous, the W. H. Shortt clock, was demonstrated in 1921. The Shortt clock almost immediately replaced Riefler's clock as a supreme timekeeper in many observatories. This clock consists of two pendulums, one a slave and the other a master. The slave pendulum gives the master pendulum the gentle pushes needed to maintain its motion, and also drives the clock's hands. This allows the master pendulum to remain free from mechanical tasks that would disturb its regularity.

Role of Pendulum Clock in the improvement of Human Life

• Pendulum clocks remained the world standard for accurate timekeeping for 270 years.

• It led to the development of Quartz clock technology which was far accurate than it's predecessor.

• They were status symbols that expressed the wealth and culture of their owners.