F.P. Journe Complications: The Tourbillon Souverain

Welcome to the second installment in our technical series on F.P. Journe’s complications. Our first installment was a detailed analysis of the principles behind the Chronomètre à Résonance – in particular, how it works, why it works, and the problems it addresses. In this second installment, we’ll look at the history and purpose of the tourbillon and the remontoir, and why combining the two in a single wristwatch was a major milestone in horology.

The number of variations on the tourbillon are enormous – there are flying tourbillons, carrousel tourbillons, conventional tourbillons driven at various speeds (although the majority of tourbillons still have one minute carriages) as well as a number of different high speed, inclined axis, and multi-axis tourbillons – and then, of course, there are all the exercises in miniaturized and ultra-thin tourbillons. One of the most unusual variations on the tourbillon, however, is the pairing of a tourbillon with the constant force device known as a remontoir. There are despite the variety of tourbillon wristwatches, pocket watches, and clocks, still relatively few mechanical timepieces that combine the remontoir and the tourbillon, and they were not both included in a wristwatch until 1999, when F.P. Journe launched the Tourbillon Souverain.

The basic motivation behind the tourbillon, which was patented by Breguet in 1801, was to do something about the fact that a watch tends to run at slightly different rates in different physical positions. In Breguet’s time, the only watches were pocket watches and so the problem was how to ensure that the different rates in the vertical positions could be as closely matched to the rates in the flat positions as possible (a watch is timed in six different positions, typically: crown up, crown down, crown right and left, and dial up and dial down. Ideally the rates in all positions would be exactly the same.

Precision is defined in watchmaking less as accuracy (the ability for a watch to match a reference time from an external time standard) and more as precision (the ability to keep a close rate). For ships at sea, for instance, it didn’t matter if a chronometer was off by +5 seconds per day; if it was off by +5 seconds every day, then it was a simple matter to calculate the correct time at Greenwich and derive the longitude.

The tourbillon has been controversial almost since its inception. It is a theoretically viable solution to the problem of positional variation in rate, but it presents new problems. It is a complex, delicate mechanism which introduces a considerable additional inertial load. Normally the last load on the going train of a watch is the lever, which gets energy from the balance to impulse the escapement. In a tourbillon, the going train has to move the entire mass of the balance, escape wheel, escapement, and the cage itself every time the balance unlocks. At the same time, despite the additional load, the going train still has to be able to deliver enough power to keep the balance oscillating at an amplitude consistent with precision. In order for the tourbillon to deliver on its promise, it has to be made with a very high degree of precision and moreover, the cage has to be as light as possible and yet, very rigid.

F.P. Journe’s Tourbillon Souverain is, with respect to the tourbillon, a very traditional construction. It is also a textbook example of a tourbillon done to an extremely high standard of quality. The cage is very fine, in order keep inertia to a minimum, and the balance is as large as possible given the size of the cage, in order to maximize effective inertia and therefore, rate stability. The balance spring is a Breguet overcoil type, which reduces variations in rate due to positional error by ensuring symmetrically concentric expansion and contraction of the balance spring, and the balance is freesprung, with timing weights for fine rate adjustment. One interesting aesthetic detail is the fact that the upper pivot of the tourbillon cage is under a cock rather than a balance bridge – a sort of half-flying tourbillon, you might say.

While there is nothing revolutionary about the tourbillon itself in the Tourbillon Souverain, it is an excellent example of a tourbillon executed to the highest standard of quality and craftsmanship, which is what you’d expect from a watchmaker who began construction of his first watch – a pocket tourbillon – at the age of 20, in 1978.

Movement, F.P. Journe’s first watch, with tourbillon and chronometer detent escapement

Where the Tourbillon Souverain really distinguishes itself from other tourbillon wristwatches is of course in the presence of the remontoire. The remontoir like the tourbillon itself, is usually referred to as a complication although more precisely (and again, like the tourbillon) it is a regulating device, which is intended to provide a more or less constant supply of torque to the balance. You might reasonably ask why you would need such a thing in the first place and for an answer, you have to go back in time in the history of watchmaking – several centuries, as a matter of fact. From the beginning, watches were powered by mainsprings (the first extant timepiece with a mainspring is a clock in the shape of a cathedral, built for Phillip the Good, Duke of Burgundy, in 1430) but unlike modern mainsprings, these were made of plain steel, rather than the modern high performance alloys found in today’s mainspring barrels and as a rule, such springs would deliver significantly greater power when fully wound, than when they began to unwind significantly and as mainspring torque dropped, so would balance amplitude, and rate stability would begin to suffer.

To solve this problem the remontoir was invented. The first version was the so-called gravity remontoir, which was created by the Swiss mathematician and horologist Jost Bürgi, which was a mechanism for rewinding the weight driving a pendulum clock. For portable timekeepers powered by mainsprings, a different approach was needed – this was the so-called spring remontoir. The spring remontoir was invented by John Harrison, during the development of his experimental H2 sea clock, in 1739; Harrison would go on to use the invention in H4, the sea clock – that is to say, marine chronometer – which was the first successful seagoing precision timekeeper.

In contrast to the gravity remontoir, which periodically resets a driving weight – the primary power source – a spring remontoir is a secondary power source, consisting of a driving spring, which is periodically wound up by the going train; the escapement is therefore getting energy from the remontoir rather than the mainspring.

The remontoir is an ingenious mechanism; it is not the only constant force mechanism available to watchmakers. The other best known solution is of course, the fusée, which works very well (they are commonly found in mechanical marine chronometers) but in a watch they have the disadvantage of taking up a lot of room in the movement, as well as adding a lot of thickness. The fusée chain is a potential point of failure as well; the fusée chain is what connects the fusée cone to the mainspring barrel, so it’s under a lot of tension (just like a bicycle chain) and can be prone to breakage.

F.P. Journe remontoir, with blade spring visible

The remontoir and the tourbillon would seem therefore to be a perfect marriage as they each address different but complementary problems – the remontoir, that of constant and unvarying energy to the escapement and balance over the entire power reserve, and the tourbillon, that of variations in rate across positions. They have however very seldom been put together in the same watch. F.P. Journe obviously understood what putting these two complications together in a wristwatch meant. His implementation of the remontoir is as technically interesting, and cuts as close to the problem the remontoir is meant to solve, as his tourbillon. A remontoir, bear in mind, is meant to provide unvarying torque; it consists of a secondary spring rewound periodically by the mainspring via the going train. How even the torque actually is, depends on how often the remontoir is rewound. The remontoir in the Tourbillon Souverain is reset once per second (which also advances the deadbeat seconds hand) and the remontoir spring is actually a blade spring, visible through a cut out in the mainplate.

Putting the remontoir and tourbillon together in the same watch was an unprecedented technical feat, still rare today. In 1999 it was revolutionary. The two complications represent two solutions to two of the most fundamental problems in watchmaking and in the Tourbillon Souverain, we have them in groundbreaking, first-of-its-kind wristwatch.

Read Part I of F.P. Journe Complications: The Chronomètre à Résonance.