The Amazing Universal laws of the Antique Clock Pendulum

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Nothing could be more important to a clock than the discovery of the pendulum swing oscillator.

It is set as a universal constant along with many of our universal laws of physics. Clockmakers used this law to their advantage by incorporating its law into the features of their clocks.

Many antique clocks from the 17th century onwards started using the pendulum feature. The word comes from the Latin root word "pendulus" meaning "hanging". When you hang a pendulum on a clock and set it swinging through the clock crutch, you set in motion a regulated feature  which means a pendulum of ANY length will swing back and forth at a regular interval, no matter how high it is swung. This is because the higher it is swung, the faster it moves through the longer distance, therefore t (the period of a pendulum) is the same.

Under normal circumstances the pendulum would rock back and forth and after a short time due to friction and gravity come to rest right on the lowest point due to gravity. This is where the escapement comes into its own. When each pallet raises over each of the escapement cog teeth, the escapement cog driven by spring or weight wants to move faster but the pendulum will not let it, so the escapement wheel has to wait for the swing motion of the weighted pendulum to reach its arched limit where the pallets ride over the top of each tooth. The escapement wheel will then motion forward giving momentum and actually nudging the pallets which in turn are connected to the pendulum crutch and this motion is enough to keep the pendulum swinging to each of the limits on the arched swing. So basically this momentum force of the escapement becomes greater than the friction force on the pendulum. The illustration above gives a layout of the features of the oscillator pendulum motion.

Of course, when you lengthen the pendulum the escapement slows down and when you shorten it the escapement speeds up. This enables the clockmaker to gain accuracy for timekeeping. Many French clockmakers would stamp pendulum length numbers on their plates which gives the exact length for that escapement setup on the clock. With some finer adjustments by means of a brocot pin, you could gain some great accuracies. 

There were many types of pendulums on antique clocks. Some had a simple rod, a hanging hook and a weighted Bob on the end. Others had more elaborate designs, for example, the gridiron pendulum has 2 types of grid rods in the middle often brass and steel and this would stop the main rod from expanding with heat temperature changes thus affecting the length of the pendulum and thus the accuracy. The early pendulums on Antique French Empire mantel clocks hung from silk threads and later they started to use suspension springs. 

So next time you see a pendulum swinging back and forth on an antique clock or even a modern mechanical clock, think about the universal law of the oscillator pendulum swing and be amazed at its discovery

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