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Credor Sonnerie: A Detailed
Analysis
by Ron DeCorte
March, 2007
Click the
images to view larger versions
As promised, this is
the technical follow-up to my
September ’06 review of the Credor Sonnerie.
Over the past 6 months I’ve had ample opportunity to think about
this watch and study its technical details. Now I would like to share my
observations and a second opinion in retrospect.
When I first saw the
Credor Sonnerie I was a bit surprised by the design, especially the dial
(or lack of a dial). For the first time in my experience a watch was
showing the intricate detail of the striking mechanism without resorting
to exaggerated skeletenization of the plates and bridges, or a sapphire
dial. Finally I can clearly see what is happening.
A great deal of
thought and study went into the design and construction of this sonnerie.
It astounds me that such a watch was spawned from such a young team at the
Micro Arts Studio and in such a short time.
Moving to some of
the finer details: in my first review I wasn’t able to photograph the
movement except through the front crystal. This time around I had
total access to the movement, and later we will make a complete disassembly
of the Sonnerie.
Now for a more
detailed look at the complexity of the Sonnerie movement; For those with
high speed internet access please click below to see a complete
disassembly of the Sonnerie. Please note that this is quite a large .mov
file and could take several minutes to download, but well worth the wait!
Click
here to view the Sonnerie slide show
For those who don’t
have high speed internet, or if you want to see a bit more detail than
is provided in the slide show, you may view and click to enlarge the
photographs used below.
I hope you’ve enjoyed
the preceding photographs and short disassembly movie. Let's move on and
explore the technical fundamentals of the Credor Sonnerie in greater
detail.
First I should start
with a basic overview of what a sonnerie is, and what
differentiates it from other striking watches. Unlike a repeater watch
that strikes the time (hour, quarter, minute, and other variations) only
upon demand, the sonnerie is capable of striking totally upon its own,
similar to a clock. Hence sonnerie watches are often called “clock
watches”. There are many different types of sonnerie watches, but they all
share one similarity in that they are capable of striking at least the
hours without user interaction, automatically or in-passing you might say.
Some sonnerie watches called “grand sonnerie” are capable of striking not
only the hours but also the quarter hour on-passing. Generally a grand
sonnerie has three modes; silence (no striking), grand (striking the hours
and quarter hours), and petite (striking only the hours).
The Credor Sonnerie
falls into a category that reflects its Japanese heritage. It is capable of
striking the hours or being silent as is the case with sonnerie watches in
general. But it also has a special function called “Original” that enables
it to strike three times every three hours. In other words the watch will
strike dong-dong-dong at 12:00, 3:00, 6:00, and 9:00 while the other hours
are silent. This Original mode is a most intriguing aspect of the Credor
Sonnerie and had me baffled for a short period of time trying to figure
how they accomplished the task.
At this point I’d
like to move ahead with a detailed technical review of the Credor Sonnerie
pointing out its unique mechanical achievements and giving you at least a
basic idea of how complicated it is to produce a sonnerie watch. I’ll try
to keep the message simple, but that’s not always easy in this case…
All sonnerie watches
have a second barrel with mainspring “A” to power the on-passing
(automatic) strike. The power from this barrel is passed in two different
directions. The wheels “B” deliver power to the silent governor “C”. It is
the silent governor that is quite special in this watch as it silently
regulates the speed of the striking. In the other direction power is
transferred via wheels “D” to the release/return mechanism “E”. Rack
assembly “F” drops finger “G” onto snail “H” to signal the number of hours
to be struck, and Hammer “J” strikes the bell in indication of the hours.
Another
characteristic feature of a sonnerie watch is the release/return
mechanism, sometimes called a ratchet. As it is that the sonnerie is
capable of striking automatically there needs to be an automatic method of
releasing power from the striking mainspring barrel to accomplish the
striking sequence. It’s the release/return mechanism that is responsible
for this automatic action and in my opinion is the heart of a sonnerie
watch, not to mention the most complicated component. Finger “A” is in
charge of the release function. On the left it is in a static position as
it is most of every hour, and on the right it is in the act of pushing the
release ratchet 25 degrees, as it does near the end of each hour, until
pin “B” raises click “C” high enough to release ratchet “D” allowing the
hour rack to fall (not shown yet).
In this example the
release mechanism has not released yet. Rack assembly “A” is being held
back, finger “B” has not contacted hour snail “C”, and a long tooth “D” of
the strike ratchet (unlike the other 12 teeth “E”) is holding the strike
hammer “F” away from the bell. This later holding back of the hammer
prevents the hammer from striking the bell if the watch is being used
during vigorous activity.
At this point,
exactly on the hour, the release mechanism has released hour rack “A”
allowing finger “B” to contact hour snail “C” at the 6th lobe,
or 6:00 o’clock. Also notice that the strike ratchet has rotated CW
allowing 6 teeth “D” to pass past the hammer trip “E”. The “release” has
taken place and the watch is ready to strike, now the “return” operation
will commence…
Let the music begin.
Now it’s time for the release/return mechanism to reverse roles and begin
the “return” process. The hour rack has fallen onto the hour snail and the
number of hours to be struck is determined, as well the hammer has been
released and is now in much closer proximity to the bell (but not quite
touching). At this stage the 6th tooth “A” of the strike
ratchet is about to engage the hammer trip “B” lifting the hammer until…
…their engagement is
completed and the hammer falls, striking the bell to record each hour of
the sequence until the hour rack and hammer have been returned to their
resting positions. (Notice that the hammer has been retracted, cocked, in
order to make the strike).
Of course the
sonnerie can be summoned at any time by simply pushing gently on the
button located along the outside of the case at the 8:00 position. But
that’s almost too simple, isn’t it?
One of the most
intriguing things about the Credor Sonnerie is its ability to be shifted
from full sonnerie mode to original mode easily (do you remember what
“Original” mode is?). With most sonnerie watches, such as a grand sonnerie,
silencing the hour and/or quarter hour strike is accomplished by a series
of blocking levers. But the Credor is very different in that it goes from
striking every hour in the sonnerie mode to only three strikes every third
hour in the Original mode. It took me two or three minutes to realize that
two different snails were needed for this to be possible. It took another
minute or two to comprehend that the two different snails needed to be
located in exactly the same space within the watch. So it is that the
Credor Sonnerie has two different snails, one for sonnerie mode and
another for original mode that are located concentrically on the same
shaft and shifted up or down as required.
Above we see the two
snails, the sonnerie mode snail “A” with 12 steps (one for each hour), and
the original mode snail “B” with 4 steps (one for each 3 hour increment) mounted on
the same assembly “D”. A split fork “C” moves the snail assembly up or
down on shaft “E”, as seen left and right, to facilitate the required
strike mode. Is this intelligent or what?
OK, I’d love to
continue this conversation and possibly write a book. But I’m sure by this
time you are falling asleep or your boss is looking over your shoulder.
Hopefully I’ve shed some light on the attributes of the Credor Sonnerie
and the extreme complexity of sonnerie watches in general.
Go
to:
TZ home page
TZ Seiko Forum
TZ
Public Forum
TZ
Watchmaking Forum
Official Credor
Spring Drive site
Ron DeCorte's
Notebook
Editor's Notes: An incomplete
version of this article was posted for a short time on February 26. TZ
regrets this error.
This article is presented as a
single web page so that readers more easily scroll between the technical
drawings and the images of the movement.
© Ron
DeCorte 2007, All rights reserved
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