View all articles

Feature: How Does A Tourbillon Watch Work?

Maybe you’ve seen that little round thing on the front of some seriously expensive watches, spinning around and around, and you’ve wondered what it is and what it does? Well, that could very well have been a tourbillon, and today we’re going to take a closer look at the one in the $110,000 Lang & Heyne Anton to find out what it’s all about.

What Is A Tourbillon For?

To understand why the tourbillon exists, first we need to cover a little background on the mechanical watch. Rather than being powered by a battery, a mechanical watch draws from a coiled spring, housed in a barrel.

In any kind of clockwork mechanism, that power in the spring needs two things to work: one, gearing that converts the speed and torque to an appropriate level, and two, some kind of resistance to stop it unwinding all at once. Think about a wind-up toy car: fully wound and off the floor, the wheels spin like crazy. The resistance caused by propelling its own mass along the floor is what regulates it.

A mechanical watch has both these things. There’s the gear train, a series of wheels that converts the speed of the mainspring into the hours and minutes on the dial, and then there’s the escapement, made up of three parts, the escape wheel, pallet fork and balance wheel.

The escapement is like the interaction between the wheels and the ground in the toy car, controlling the speed of the movement. Except, instead of the entire thing being the mass it has to move, there’s a much smaller mass instead, the balance wheel. The balance wheel spins around like the wheels of the car, but with no real weight to control it, a smaller spring, the balance spring, is added to add resistance.

This adds a further problem, that when the spring compresses it reaches a point of maximum compression and wants to spring back. And so, rather than spinning in one direction like the wheels of the toy car, it bounces backwards and forwards, like the round version of a pendulum in a grandfather clock. The pallet fork and escape wheel are specially designed to cope with that changing direction.

So, why the tourbillon? Because the balance wheel doesn’t spin continually in the same direction, instead bouncing back and forth, it means its position relative to gravity has an effect on its performance. Imagine the pendulum in the grandfather clock, but the grandfather clock isn’t kept at the same upright angle. It wouldn’t be able to swing properly, and that’s the problem the balance wheel has, on a much smaller scale. The tourbillon is here to fix that.

Who Invented The Tourbillon?

The story of the tourbillon’s invention surrounds one Abraham-Louis Breguet, a Swiss watchmaker of the 18th century who’s considered one of the best to have ever lived. To his name is credited the invention of the self-winding movement, the balance spring overcoil, the gong spring, balance jewel shock protection and, of course, the tourbillon.

It was in fact on the turn of that century, in 1795, that Breguet conjured the idea. By 1801, the single axis tourbillon was patented, and would become the precision tool of the best watchmakers for many centuries to come.

During the chronometer trials of the early 20th century, where watchmakers were put to the ultimate accuracy test, the tourbillon became a must-have piece of tech to stand any chance of performing. Each one was hand-crafted and tuned individually, like the engine of a Formula 1 car. No two were identical, built to perform in gruelling competitions lasting 16 weeks, during which hundreds of entries were tested to the extreme. The trials were actually revived in 2009 to celebrate the 150th anniversary, and once again, a tourbillon took the prize, a Jaeger-LeCoultre.

The type of tourbillon you see here in the Lange & Heyne Anton is known as a flying tourbillon, invented by fellow German watchmaker Alfred Helwig. Rather than have the central shaft of the tourbillon mounted at both ends, Helwig devised a system stable enough to secure it from just one end, such that it can be enjoyed unobstructed. If you pay $110,000 for a handcrafted work of art, you want to be able to see it!

How Does A Tourbillon Work?

So, how does the tourbillon work exactly? Well, just like the wheel of the toy car we described earlier. Whilst the escapement anchors the position of its components relative to one another, there’s nothing stopping the entire thing being encapsulated and continually rotated in one direction, just like a wheel.

To be a bit more specific, it’s not just the impact of gravity on the balance wheel, but the impact of gravity on the balance wheel’s imperfections. No matter how hard a watchmaker tries, the poise, or balance, of a balance can never be perfect, and those inconsistencies in the balance wheel are amplified by being stuck in the same position.

That’s why Technical Director Jens Schneider has gone to extreme lengths to make sure the tourbillon in the Lang & Heyne Anton is balanced as close to perfect as possible. The outer cage that holds the balance is thicker on one side than the other, and has an opening in the top layer on the thinner side, to compensate for the weight of the escape wheel and pallet fork.

And those two components are adjusted as well to make the tourbillon lighter and more compact, by building it in vertical stages so the escape wheel can overlap the cage. The pallet fork has also been redesigned to sit alongside the escape wheel instead of between it and the balance wheel, so the centre of gravity is closer to the middle and needs less counterweight to balance.

Where the tourbillon gets incredibly clever is when it comes to the next logical question: well, hang on, if the balance wheel can’t spin all the way around because it’s locked in place by the rest of the escapement, how is it possible to rotate everything?

The answer, although difficult to see and visualise, is surprisingly simple. The gear train, instead of rotating the escape wheel as it would in a standard movement, rotates the tourbillion cage and everything in it. Below the tourbillon cage is a static gear, which meshes with the escape wheel, so as the escape wheel orbits within the cage, it spins as well, just as it would ordinarily, allowing the escapement to function as normal. This rotation usually happens once a minute, which means the cage can also double up as a convenient second hand.

You might think this complication isn’t as useful as it seems, because, unlike the pocket watch it was invented for, which hangs in a fixed position, a wristwatch moves around a lot. Well, given today’s sedentary lifestyle, often sat stationary at a desk for hours on end, it’s never been more relevant. You’ll just have to work more hours at that desk to be able to afford one.

With thanks to Lange & Heyne for letting us use their beautiful Anton to demonstrate the inner workings of the tourbillon.