When a watch is in the vertical position, gravity either accelerates or slows the balance and escapement mechanism that regulates the speed of rotation of the wheels. A tourbillon is comprised of a mobile carriage or cage containing the regulating mechanism (balance wheel with hairspring) and the lever escapement, with the balance in the center, and this mechanism rotates the wheels. The escape pinion turns about the fixed fourth wheel. By mounting the escapement in a rotating frame, all errors are reproduced and thereby cancel the effect of gravity when the escapement is rotated 180°. The frame makes one revolution per minute, thus annulling errors of rate in the vertical position. The rotation of the whole device around the axis of the frame suppresses the effects of friction or other effects caused by unbalanced components and gravity as all parts of the escapement are equally exposed to these influences. The movement’s mesmerizing rotations is the reason Breguet named his device a tourbillon - meaning "whirlwind" in French.
Invented in 1795 by Abraham-Louis Breguet to counter the effects of gravity and other forces that affect the accuracy of clocks and watches, a tourbillon is a high complication and remains one of the most difficult and complex movements to master. The tourbillon was originally designed to eliminate errors of rate in pocket watches, which were kept in vertical positions for long periods of time leading to deviations in timekeeping due to friction conditions caused by gravity either accelerating or decelerating the vibrations of the balance. Breguet's solution was to balance out all differences of position and he therefore developed a small "clock within a clock by mounting the rate determinative components - balance, balance spring and escapement - in a delicate lightweight carriage which rotated on its own axis once every sixty seconds. In this manner, fractions of a second lost during the first 30 seconds were regained during the next 30 seconds so that the negative effects of gravity cancelled themselves out allowing many watches to attain chronometer-like accuracy. To this day, the complex construction and exacting precision required to create a tourbillion remains a specialty of the most gifted watchmakers.
Two hundred years after the invention of the tourbillon, even today's high technology manufacturing methods and precise machinery combined with innovative materials cannot overcome the negative effects of gravity, upholding the tourbillon's status as a relevant and fascinating complication.
In an ordinary tourbillon, the carriages are pivot mounted on one side and bridged on the other, or bridged on both sides. A flying tourbillon, however, is much more complex. Invented by Alfred Helwig in the 1920s, the flying tourbillon's carriage is pivot mounted on one side with no supporting bridge, leaving a floating mainspring barrel. That means a flying tourbillon is actually a complication built onto the tourbillon complication. Ordinary tourbillons were effective for pocket watches, as these are held in the vertical position and therefore have only one dimensional displacement from lying flat. Flying tourbillons are designed to be effective at any angle.
Historically, tourbillons have commanded top prices and were out of reach of all but the extremely wealthy. Very few watch houses have the time and experience to produce tourbillon watches, driving up prices even higher. Watch houses usually produce a few dozen pieces of tourbillon watches each year as only the most skilled watchmakers are capable of making the handcrafted movement. Considered one of the most complex watch complications, tourbillons are prized for their engineering and design principles. Building a tourbillon is viewed as a testament to a watchmaker’s skill and the sheer intricacy and achievement of such miniature handmade mechanisms makes the movement one of the most valued complications.
The higher price is attributable to the complexity of the tourbillon mechanism, which is created within extremely tight mechanical tolerances with specialized tooling. Crafting a tourbillon requires more parts and time than in other movements. Dedicated tools and machinery are required to manufacture a tourbillon and special lightweight and durable metals are required. It is critical that energy expenditure be at a minimum as the same energy from the mainspring to power the gears is also needed to move the tourbillon. Any instability or disturbance in this energy flow will decrease the accuracy of the watch. Even to adjust the tourbillon movement requires specialists who have to disassemble and reassemble the tourbillon to regulate the balance.