Bluffer’s guide to mechanical watches

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A 60 second guide to the science and art of watch making.

 The defining difference between a mechanical watch and all other watches is the power source. In a mechanical watch, the power comes from a coiled spring, which is manually tightened.

Controlling how this power is released to turn hour, minute, second and several types of date indicators to exact time is the essence of horology, and it is infinitely more complex than simply using a battery or quartz to make a watch keep perfect time.

The workings of a mechanical watch, known as a movement or calibre, have changed little since the days of pocket watches in the 18th century.

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The mainspring is the power source, which is wound to store the energy needed to drive the watch. It sits within a barrel that would spin wildly with the instantly discharging power from the mainspring if it were not controlled by the balance wheel, which catches cogs on the outside of the barrel, forcing it to rotate in a precisely engineered period of time. An escapement mechanism provides the power and timing for the balance wheel.

The power of a spring, which would instantly discharge to the barrel, is thus regulated to control time.

From here, a series of gears, springs and yokes known as the gear train converts the precisely timed rotation of the barrel to any unit of time: seconds, minutes, hours, days, months and even, in the case of the most complex timepieces, phases of the moon, movement of the stars and sunrise/sunset times in different cities around the world.

The ways in which these units of time and date are displayed are known as complications, and their accuracy is dictated solely by the precise engineering of the gear train.

To understand the magic of this engineering, it is useful to think of how a road bicycle works with 15 gears – three at the pedal axel and five at the back wheel axel. The combination of the two sets of gears means that a single revolution of the pedals will rotate the back wheel at 15 different speeds.

The mechanical watch is the same. A single rotation of the barrel can cause a minute hand to rotate in 60 seconds or a date dial to rotate every 24 hours.

The level of engineering and craftsmanship required to achieve this is mind-boggling, and is part of the reason for the colossal prices of mechanical watches, despite the fact that they are intrinsically less accurate than equivalent automatic watches and need to be frequently rewound to work at all.

The fundamental mechanics may be broadly the same across mechanical watches, but there is still scope for extraordinary invention and artistry in the industry. Mechanisms are constantly fine-tuned in search of the holy grail of horology: a mechanical watch that keeps perfect time.

Presenting a simple watch that is easy to read often gives way to faces where the hour and minute hands rotate on different dials; the mechanics are visible through skeleton watch faces; and dates are presented in confusing combinations of day, month, year and even phases of the moon and tides.

These ‘complications’ may seem simple enough at a glance, but are driven by the astonishing mechanisms that can contain over 500 moving parts.

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