by Ian Skellern
(c) October 2005
The F.P. Journe calibre 1505
Why a steel case?
While there are a great many details that go into making F.P. Journe’s Sonnerie Souveraine a very special watch, one of the most obvious, especially for a watch of this value, must be that it is only available in a steel case; in fact is the only model in F.P.Journe’s entire collection with a steel case.
When asked,’ Why steel?’, Journe himself responds immediately with, ‘Simply because steel, which unlike platinum or gold is crystalline in structure, conducts and transmits sound better.’
Wondering why nobody else making repeaters and sonneries is utilizing steel cases if the metal is so acoustically superior, I asked a number of master watchmakers experienced in chiming watches their opinions. The general consensus was that steel is widely recognized as a better metal for transmitting sound, and that it is an ideal material for the casing a chiming watch; however, nobody had the confidence that clients would pay the hundreds of thousands of dollars a sonnerie costs if it is not cased in a precious and noble metal – nobody but François-Paul Journe that is.
Calibre 1505: Manually wound. 40 jewels. 400+ pieces in movement
Movement Dimensions: 35mm x 7.8mm
Balance: 4 adjustable weights. 21,600 v/h. Free-sprung.
Power Reserve: 120 hours/5 days without chime. 48 hours with grand strike. 24 hours of autonomy after strike runs down.
Case: Steel. 42mm x 12.25mm
Design RequirementsBefore we look at just what goes into making the Sonnerie Souveraine such a special timepiece, let us remind ourselves of some the attributes François-Paul Journe, looks for in a watch for it to bear his name.
In no particular order:
1. The design of the dial should be elegant, i.e. balanced, unclutted and in harmony with the case.
2. The movement/case should be as thin as possible. Not only does this make for a more wearable watch, it is also evidence of technical excellence in design and conception: it is relatively easy to simply pile complications on top of each other. The preference is for simple solutions using as few parts as possible (less to go wrong)
3. The watch should be reliable, wearable and usable, which means as idiot-proof as possible.
In a watch as complicated and with as many parts as a grand et petite sonnerie with minute repeater, you would be forgiven for thinking that Journe deliberately set himself an impossible challenge if he was to keep true to those guiding principles.
Forgetting the seemingly unsurpassable tasks of making such a complicated movement thin and idiot-proof, let us have a look at the relatively simple issue of dial design. The grand sonnerie traditionally has two barrels: one driving the going-train (timekeeping) and one powering the strike-train (chimes). This ensures that the watch continues to function if/when the chimes have used up all of their available energy.
Being able to see the hammers operate through the dial was a key design feature as well incorporating sub-seconds. Two barrels would have
meant that the dial displayed: hour/minute sub-dial, seconds sub-dial,
Two barrels trains also means more parts; these would both increase the size of the movement and its complexity, while reducing reliability. Using only one mainspring would appear to be an obvious solution; however, there are a number of excellent reasons why the majority of clock watches have two separate barrels (main springs). These include: ensuring that the striking mechanism does not use all the available power and stop the movement plus ensuring that the striking mechanism does not reduce the amplitude of the balance unduly so resulting in poor timekeeping performance.
Even if these two problems could be solved, how to show the power reserve available of both the going-train and strike-train if they both run off the same mainspring?
As the saying goes, “ . . . the impossible takes a little longer.”; five years longer in Journe’s case with the Sonnerie Souveraine.
Journe spent years overcoming the numerous problems with innovative solutions; designs were drawn up and modified; prototype mechanisms were tested; a modern and comprehensive manufacturing facility was built, staffed and trained; all of which leading to this one watch: the Sonnerie Souveraine.
Elegant, thin and reliable: three simple words, the pursuit of which resulted in F.P.Journe’s grand sonnerie being awarded ten patents. These are:
1. The single barrel. (shown left)
Without a single barrel Journe would have not been able to achieve any of his principle aims. Two barrels would not have allowed: elegance (cluttered dial), thinness (many more parts), or greater reliability (increased complexity/more things to go wrong). The center of the mainspring is attached to an arbour (around which it unwinds), while the outside is attached to the drum of the barrel. A toothed edge on the barrel (pink in diagram) drives the going-train, while the arbour drives the strike-train through a toothed wheel (yellow in diagram).
A mainspring unwinding through both its barrel and arbour - with both driving separate power trains - requires a very sophisticated power-reserve indicator mechanism. Three coaxial differentials were needed: the top differential links the arbour and barrel; the lower differential moves according to if the mainspring is being wound or is unwinding, while a third differential links the other two showing the mean power-reserve of both. The same power-reserve indicator automatically shows the power reserve available according to the strike mode selected.
When the watch is set to silent-strike (time only), the power-reserve indicator shows the reserve of that function (up to 120 hours/5 days). Despite running off the same barrel/mainspring, when the power-reserve of the strike mechanism runs down, 24 hours will remain for the going train (normal time keeping). Set the watch to either grand or petite strike and the power-reserve indicator shows the reserve available for the strike mechanism (up to 24 hours).
3. Blocking the strike automatically.
When the power-reserve for the going-train falls below 24 hours the striking mechanism is automatically blocked. This ensures that the watch will continue to run and tell the time accurately without the user having to keep a close eye on the power-reserve indicator or worry about over using either the sonnerie or minute repeater complications. Winding the watch up so that the power reserve is greater than 24 hours automatically releases the strike mechanism allowing it to function normally.
4. Blocking the strike and winding stem.
One of the most common causes of damage to a striking watch mechanism is caused when the crown is pulled out and/or turned while the
strike mechanism is engaged. Using a locking-cam and pivoting arm connected to the hours-rack, Journe has come up with a mechanism
which prevents both the winding-stem from being pulled out when the Above dial-side, below back-side.
5. Strike release.
Journe has designed and constructed (invenit et Fecit) an innovative mechanism for activating the strike. This uses a four toothed star wheel (quarters) to activate the chimes in passing and which also triggers a rocking arm/clutch allowing the racks to fall on their respective cams. This mechanism also controls the minute-repeating strike which is released by pressing the a button (at 2 o’clock).
6. and 7. The strike selection and strike sequence.
New and improved techniques and designs Journe made to the mechanisms controlling the strike selection, which is controlled by a column wheel, and the strike sequence were awarded patents
Taking advantage of the off-centered hours and minutes, Journe was able to mount the striking racks in the centre of the movement. This allowed extra large racks which in turn provide greater precision and control.
9. Winding and setting system.
Journe has come up with a compact and efficient winding and setting system which does away with a long stem and sliding pinion. In this new system the crown wheel is permanently meshed with the transmission wheel.
10. The chiming gong.
Traditionally, chiming gongs are circular in cross-section and circumvent the movement. Placing the gong around the movement- between the outside circumference of the movement and the inside circumference of the case - has the advantage of maximising their diameter/size, thereby increasing the amount of metal able to resonate. All other things being equal, a bigger bell or loud-speaker will be louder than a smaller one.
Unfortunately, all other things are not equal: positioning the gong between the movement and the case may maximize the size of the gong, however, it also reduces the size of the movement; a larger bell is little use without a correspondingly larger and/or more powerful hammer: with the limited space and power available in a wristwatch you cannot have both. Another method of increasing the sound of a bell/gong is to make it in a more efficient shape.
After much research, development and practical trials of various gong shapes and sizes, Journe found that this unusual flat gong, produces a louder, clearer sound than traditional circular wire gongs. At only 0.3mm thick, the flat blade gong has enabled Journe to place the gong on top of the movement rather than surrounding it. This allows for a larger movement completely filling the case: allowing for a more robust, easier to service calibre, with a larger power reserve, than would otherwise be possible.
Every chiming watch has a different natural frequency of resonance; this includes watches of exactly same model made by the same watchmaker. Reasons for this include: materials such as parts, cases and crystals being made from different batches so having a miniscule variation in compounds; even if from the same batch there will be different tolerances in manufacture. If parts are being produced to tolerances as tight as 1 micron (0.001 mm) you will still have pieces at minus one, some at plus one, and some in between. As most parts are made to larger tolerances than that, and considering the fact that there are over 440 parts in the Sonnerie Souveraine (including the case), you can see that no two watches can be exactly the same.
Add to that the fact that the watchmaker is unlikely to tighten every microscopic screw to exactly the same torque and that even the crystals may need different pressures to attach them to the case - all of these factors change the natural resonance of the completed watch. Even using identical gongs (impossible), in apparently identical watches, will result in differences in the sound produced.
To both maximize both the quality of sound in the Sonnerie Souveraine and the consistency of sound between individual watches - similar but not the same – Journe matches the resonance of the gong to the resonance of the cased movement. He does this by starting with a gong longer than necessary, assembling the movement then casing it - in its actual final case; not a working prototype. Journe then listens to the sound produced, dismantles the watch and cuts a little off the gong. The watch is then re-assembled and the procedure is repeated over and over until he feels confident that the gong is the correct length so that it will resonate at the same frequency of its movement and case.
A time consuming procedure to be sure, however, one where the results speak – or should I say peal- for themselves.
The first Sonnerie Souveraine nearing completion. The pusher at 2 o'clock activates the minute-
repeater, while the pusher at 4 o'clock selects the strike function: Grand, Petite or Silent.
One further point I feel is worth mentioning: I am not a fan of large watches and my first reaction on learning that the
Sonnerie Souveraine was going to be 42mm was dissappointment. When I first saw the grand sonnerie on François-Paul
Journe's wrist however, I did not immediately recognize it as it did not look at all like a 42mm watch. I believe that is due
to the lack of thickness in the watch; at just over 12mm it is a remarkably flat watch for its size and sits very nicely (and unobtrusively)
François-Paul Journe working on his Sonnerie Souveraine.(3MB courtesy of MaxH)
Ian Skellern - October 2005
Copyright October 2005 - Ian Skellern & ThePuristS.com - all rights
Copyright October 2005 - Ian Skellern & ThePuristS.com - all rights
*I would like to thank the staff at F.P.Journe for their unfailing hospitality and welcome not matter how many times
I turned up at their door and especially to François-Paul Journe for his time and patience in explaining his Sonnerie Souveraine to
to someone barely able to understand a simple handwind watch, as well his trust in allowing me to photograph him while working
on an incredibly precious and sensitive work of horological art.