You don't have to spend long around the watchmaking industry to hear about the tourbillon complication. But despite it frequently popping up in the conversation, its meaning is very rarely explained.
So what is a tourbillon? A tourbillon (theoretically) eliminates gravitational poise error, which should improve the timekeeping performance of the watch. Gravity affects the hairspring and balance wheel, which comprise the delicate heart of the regulating organ within the watch. Due to material inconsistencies in the weight of the balance wheel and hairspring, as they work in tandem to keep good time, it is possible for a watch to perform differently depending on its position.
In tourbillon watches, the regulating organ sits within a cage. This cage rotates around one, two, or three axes (theoretically the more axes around which the regulator rotates the fewer amassed poise errors there will be). Normally, it takes the tourbillon cage one minute to complete a full revolution, but this varies from version to version. The idea is that by moving the regulating organ at least 360 degrees, errors are more likely to cancel each other out over a day.
Of course, this is entirely dependant on the wearer's habits or the storage situation of the watch.
The tourbillon was invented around 1795 by Abraham-Louis Breguet (whose eponymous brand is now owned by the Swatch Group). The patent for this visually arresting complication was granted on the 26th of June in 1801.
Originally, the tourbillon was designed for use in pocket watches (Breguet would die long before wristwatches were the norm). This is notable because of how a pocket watch is worn. Pocket watches spend the majority of their time, sitting vertically in a waistcoat pocket. For that reason, the variation of the daily rate in the "edge" or "hanging" positions (i.e. when the watch is on its side rather than laying flat on its back or face) was what Breguet was most concerned with eliminating.
A single-axis, 60-second tourbillon rotates in a clockwise direction, once every minute. When the watch is lying on its back or dial-side down, this kind of tourbillon will not affect the daily rate. But when the watch is lifted into a vertical position, the benefits of the tourbillon begin to be seen.
Nowadays, multi-axis tourbillons are far more relevant in the manner a wristwatch is worn due to the fact the arm passes through several planes of motion throughout the day, putting an immense gravitational strain on the regulating organ.
The first double-axis tourbillon was patented in 1977 but it would be many years before it made it appeared in a wristwatch, finally presented by Thomas Prescher at Baselworld 2004. Prescher backed-up this achievement by unveiling the world's first triple-axis tourbillon at the same fair. The miniaturization of the multi-axis tourbillon had been mastered and more mind-blowing developments were set to follow.
Another alternative style of the tourbillon complication that happens to be far more effective in wristwatches, is the inclined tourbillon pioneered by Greubel-Forsey. In addition to their inclined tourbillons, Robert Greubel and Stephen Forsey were behind the development of double and quadruple tourbillon mechanisms, which used off-set tourbillons to balance out the errors in each other, culminating in supposedly superior isochronism.
Although many will deride the tourbillon as nothing more than an exercise in watchmaking skill (which it very much is), it does perform a practical function. Exactly how measurable or ultimately useful that function is will forever be down to context. Each individual tourbillon performs differently on a different wrist. Multi-axis tourbillons or multiple tourbillons fitted to the same watch will behave one way on one wrist, and another way on another.
One thing that few would disagree with, though, is the wonder and beauty of tourbillon in full flight. That such a mechanism could be conceived by human minds and wrought by human hands seems almost the stuff of fantasy. But it is very real, and, unsurprisingly, very expensive.
If you desire to own a tourbillon watch (a good one made with the love, care, and attention of a watchmaking master) you must be willing to shell out at least five figures. Some newer brands are emerging with far cheaper options, but the quality of machining makes the whole exercise a moot point.
When it comes to something like a tourbillon, the best advice is either go hard or go home. There is no middle ground here. If you can afford it, then spend, spend, spend. At this kind of price point, there's no sense in holding back. If the tourbillon is the complication that makes you feel something every time you glance it whizzing around the dial, then don't shortchange yourself.
Back a watchmaking master. Own a piece of history. Support the industry with your wallet. If you want a tourbillon, there's no other way to go...