The Journe Annual Calendar

by Watchbore

November 2002

The styling of F.P. Journe’s watches might not appeal to everybody, but few will
deny its originality.

The face of the annual-calendar watch shows a fly-back date, the day and the
month. The calendar accounts for months of 29, 30 and 31 days. In the non-leap
years, when February has 28 days, you have to advance the date manually to March
1.

Journe seems to get away with messing up the face with screws. Note the screw on
the lip at 14 on the dates-scale. The dates-hand on the minutes-track of the
dial is also unfortunate. But who can deny that this deliberate rejection of
perfect harmony gives the watch a very functional character?

The crown controls everything — no pushpieces. You pull it out to its second
position, turn it one way to advance all the calendar indications, and the
opposite way to advance the days only. In its third position, the crown sets the
time.

Most of the cases are in platinum. The face is frosted gold and the dials are
silver.

The annual calendar is the third watch based on the F-P. Journe Octa automatic
calibre. He called it the Octa because he hoped he would get eight days
power-reserve out of it. As it happens, the fully wound movement will run for
about 150 hours off the wrist, but there is an unacceptable loss of amplitude
after 120 hours.

Despite a long mainspring (1000mm), the Octa construction leaves room for a
full-sized free-sprung balance (10.1mm) vibrating 21,600 times an hour on a flat
Anachron spring with a microflamed terminal curve. Two opposed pairs of weights
on the four-armed balance give up to 100 seconds of adjustment.

The rotor, winding in both directions of spin through a reverser gear, is said
to be particularly effective. It needs to turn the arbour 13 revolutions to wind
up the mainspring fully. You will note that the rotor is slightly off centre,
presumably to allow for indications on the back in a future model.

The Octa’s peculiarity is a type of construction unheard of in these days of
bolt-on modules. It allows a variety of complications to be inserted in the
movement on the same baseplate. Hence the Octa movement with the large date and
power-reserve indicator (shown here) has the same dimensions (30mm x 5.7mm) as
the Octa chronograph or the annual calendar movements.

The main advantage is economic — one baseplate fits all, and you don’t have to
make bigger cases for bigger complications. It also results in more compact,
less wasteful mechanisms.

The complications have to be configured into a 1mm-high space between the
base-plate and the bridges, using holes and recesses common to the other
complications. That means Journe cannot use a standard horological design, but
has to re-invent each mechanism. These complications have to be as efficient as
possible, performing their functions with no mechanical superfluity.

All three Octas demonstrate this mechanical elegance, but the annual calendar is
particularly satisfying for its ingenuity and simplicity.

This is how it works in two diagrams:

A great, green wheel (W) with internal teeth drives the annual-calendar
mechanism. In particular, it activates that long pink lever (L) every 24 hours
so that it reaches across to pull the dates-wheel (D) forward
(counter-clockwise) day by day. The dates-wheel with 31 teeth is held by the
jumper spring on the left.

On the dates-wheel is fixed a blue snail-cam. As the snail rotates
counter-clockwise, a yellow beak (B) rides up on its back, moving the rack (R).
The rack turns a pinion on which is mounted the dates-hand. The counter-rack,
also engaging the pinion, provides the tension. You can see the blade spring
along its right edge.

When the dates-wheel reaches the end of the month, the yellow beak falls off the
top of the snail and allows the sprung racks to bring the dates-hand smoothly
back to the first of the following month.

Perpetual and annual calendars rely on a cam to tell them how long each month is. The
months-cam, which makes an annual revolution, is essentially the program for the
year’s calendar.

The months-cam (M) is fixed under the 12-pointed months-wheel, which is rotated
clockwise by the dates-wheel (D) via a train. The recesses represent months of
fewer than 31 days.

The cam acts on the beak in the middle of the pink lever (L). As the beak rises
out of a recess at the end of April, June, September and November, it makes the
lever advance the dates-wheel twice. The dates-hand thus moves directly from the
30th to the 1st.

You will notice that February has a deeper recess than the other months. When
the lever climbs out of the February recess at the end of the 29th day, it
advances the dates-wheel and its snail three days. The beak (B) falls off the
snail, allowing the sprung racks to bring the dates-hand back to 1.

In leap years, the calendar moves automatically from February 29 to March 1.
When February has 28 days, the calendar has to be advanced manually.

The days, on a regular cycle of seven, are clicked forward every 24 hours by the
great circumference wheel (Pic 3) through a separate system of levers.

For such a system to work, profiles have to be closely calculated, machined and
adjusted to micron tolerances. The correlation between the tiny curve of the
snail cam and the wide arc of the dates-hand on the dial has to be exact, as do
the profiles of the lever and the months-cam. The toothed racks ensure that the
dates-hand points precisely to the intended date and flies back smoothly. The
system uses very little power to change the date, which remains isolated from
the movement between changes.

The entire mechanism fits into a 1mm-high space within the Octa calibre, using
the same baseplate as the movement.


Copyright © Alan Downing, November 2002
 
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