How does a mechanical clock work?

Let’s get back to basics. How does a mechanical clock function?

Pequegnat double spring time-only movement

A mechanical clock is a machine. It is a machine that is used to measure, verify, keep, and indicate time. It measures intervals of time shorter than the natural units of the day, the lunar month, and the year.

How many machines do you know of run almost as well as the day they were built 100+ years ago and still operate as they were designed to do? Not many! It is a testament to the inquiring minds of its inventors. Mechanical clocks are truly a wonder!

Clock mainsprings, one for the time side and one for the strike side

Let’s start with a sad but true story. A friend of my son was visiting our home a couple of years ago. He showed an interest in my clock collection and I was happy to answer any questions he had.

He asked me how a clock worked and I picked up an American time and strike spring-driven movement, explained how the spring provides power and how the wheels transmit energy, how the energy is released and he took the movement in his hands, examined it closely, and with a quizzical expression on his face said, “where do the batteries go?”.

Photo by Brett Jordan on Pexels.com

Let’s keep it simple. Five elements are required. They are Power, Gears, Escapement, Regulator, and Indicator. Let’s discuss each one.

Power

Double spring time-only movement with top plate removed revealing the gears

The power is in your hands. The energy from you is transferred to the mechanical clock when winding it. As you insert the key into a winding point, energy is converted from your hand to the spring or weight.

The spring when fully wound or the weight pulled to its highest point provides the motive power or releases energy through the gears and allows the clock to run for a fixed period of time. Without a source of power, a mechanical clock will not run and a mechanical clock will stop when power is spent.

Gears

Gears are also called wheels. The wheels have teeth. Each gear or wheel meshes or interacts with the next gear by way of pinions.

Energy is transferred to each wheel through what is called the train and in the process, the subsequent wheels turn faster. The time side gear train, for example, through a series of wheels leads to a wheel or gear called the escape wheel which turns much faster than the main wheel with the spring or weight. But the power that is released through the train must be controlled.

Escapement

The escapement is the last wheel in the time train. It is designed to release the power from the mainspring or weight in a controlled manner.

Bushing installed on escape wheel arbour
Escape wheel and verge

This is the tick and tock you hear when you are close to a mechanical clock. It is the sound of the verge catching and releasing the teeth of the escape wheel. The tick and tocks transmit an impulse to the pendulum to keep it swinging.

Similarly, the mainspring releases the energy through the gears or wheels on the strike side of a clock by means of a series of levers and pins.

Regulator

Bracket clock
Bracket clock showing pendulum leader and bob

A regulator controls the speed of the clock. An example of a regulator is a pendulum. Generally speaking, a pendulum with a longer rod will oscillate more slowly than one with a shorter rod.

Regulating or adjusting the length of a pendulum will speed or slow down a clock. On the same clock, lengthening the pendulum slows the clock, and shortening the pendulum makes the clock go faster.

Clocks without a pendulum have lever escapements, floating balances, and balance wheels that rely on a coiled spring and are regulated by means of an adjustment dial or lever on the escapement arbour.

Vienna Regulator clock face
Clock face showing hour and minute hand

Indicator

The indicator is the hands on the dial face. Regardless of the size of the dial, the style of the hands, how numbers are displayed, they all do one thing, tell the time.

The indicator is also the sound a clock makes at certain points in the hour whether it is quarterly, the half-hour or the hour on a bell or chime rod(s).

Summary

The five elements that come together result in synergy, that is, the parts that interact with each other to produce a result that is greater than the sum of their individual parts. Energy harnessed in a controlled manner is designed to make that machine do one thing, tell the time.

So, where do the batteries go?


2 thoughts on “How does a mechanical clock work?

  1. Hi Ron, Thanks for that. You mentioned elsewhere that the “escapement mechanism” on American clocks are different (and louder) than on non-American. Is it relatively simple (probably not!) to explain how and why? Also, the Regulator in the center top on some clocks: does turning this adjust the length of the pendulum or does it control speed in some more subtle way? Thanks again! And oh, I forgot, where do the batteries go again?

    Like

    1. Thanks, David. The loud ticking is the result of a long drop. Some clocks can be made quieter by moving the pallets closer to the escape wheel teeth. American clocks also have larger cases (generally) that act as a soundboard. German, French, and British clocks on the other hand have smaller and better-designed escapements and are generally in more compact cases. American clocks lack the engineering refinement of a German clock but will run well while quite worn. The regulating arbor on the front of the clock case controls the speed by using a small gear to change the length of the suspension spring and in effect make the pendulum longer or shorter. Can’t see where the batteries go but when I do I will let you know.

      Liked by 1 person

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