An inside report of De Bethune SA, La Chaux l'Auberson
by Magnus Bosse, November 2006
Bethune's bespoke movements and the unique "spider" balance
already mentioned (and visible in the large picture above), there
are several original aspects in this movement. Beneath the obvious
shape of the movement plate (small images, left), there is for a
start the scorpion-like anti-shock device, named by De Bethune as
"triple para-chute" (obviously referring to
A.L. Breguet's Parachute shock absorbing system), three-fold shock
protection (small images, middle left and middle right). Such a device
consists of - starting from the balance wheel - a widely used Incabloc
shock absorber (1st shock protection), mounted on a flexible titanium
bridge (2nd shock protection), which is itself supported on a the
main clockwork plate via two rubies, and a spring shaped like scorpion's
clams (3rd shock protection). De Bethune claims that any sudden movement
the watch is subjected to is damped three times before it reaches
the watch's most sensitive organ, the balance wheel.
So what were they thinking when developing such a system? Confronted with such concerns, De Bethune assured me that "... our triple para-chutes consists of a standard shock absorber in the center for the balance-wheel, this one is adjusted in the same way that all the shock absorbers in quality movements, and of two shock absorbers for the balance-wheel bridge which are calculated and regulated like springs in the precise watch industry. More precisely, if the titanium bridge of the triple para-chute undergoes a shock of 5000G (equal to a fall from 1 meter on wood), it becomes deformed to approximately 0.003 mm only! If it subjected to a force of approximately of 20 Newton, which corresponds to approximately 2kg, the use of a titanium bridge by De Bethune reduces the force hitting the balance to less 10 Newton." Judging from these rather impressive data (I have however no comparison to standard shock protection devices used in high-grade watch movements), it seems to me that indeed the triple para-chute is quite well conceived for every day usage, as it dampens any shocks significantly, while still maintaining the precise positioning of the balance needed for a contemporary high grade watch. To say the least, it occurs to me that such concerns have duly been taken into consideration while designing the movement. However, it seems that only the balance pivot on the dial side features the triple para-chute system. Thus, the question arises how the above mentioned figures are derived, as only one of the balance pivots is protected with the elaborate solution.
Spiders Webs and Legs... The De Bethune Isochronic Oscillation System
currently employed by De Bethune is termed Isochronic Oscillation
System (IOS). The name already hints the ends to which these
solutions are created: Optimal isochronism throughout an extended
period of autonomy (power reserve) of the watch movement. What initially
looks very futuristic is in fact a significant modification of the
well-known balance designs in terms of innovative balance and hairspring
two are the most advanced and interesting ones, and will be described
more detailled below:
designs, here shown are IOS 3 (top drawing) and IOS 4 (bottom drawing),
demonstrate the underlying concept. The
difference lies more in the metal than in the shape: IOS 3 combines
the De Bethune balance spring assembly with a
titanium base, with an adjustment device bridging two legs each.
The temperature correction is entirely implemented in the balance
system. The use of titanium for the base already results in a significant
reduction of weight compared to Glycidur by about 20%.
interest many of you, is that the IOS systems are interchangeable,
and thus a given movement can optionally be upgraded to the newest
balance version, given the technical and qualitative improvements
grant such a modification.
3.3 The De Bethune Moon - a sphere, not a disc, of course!
De Bethune knows well about mankind's fascination with astronomy, particularly with our constant planetary companion, the moon. The moon's cycle of approximately 29.5 days, during which he rises, glows in his entire beauty and then slowly disappears, determines decisive circumstances in our daily life, such as tides and most importantly, the secular calender. No wonder the Moonphase complication ever attracted many watch aficionados.
As many of you already know, De Bethune surprised the public with its mesmerising spherical Moonphase display at the Basel Fair 2003. De Bethune presented its unique design of a moon ball consisting of blued steel and platinum, each one half sphere, rotating on an axis parallel to the plane of the dial. The effect is quite dramatic, just as lookking at the real moon:
Bethune has devised a solution that, beneath being highly accurate
(for up to 122 years!), also gives the
moon a 3-dimensional shape: The moon is realised not as a common disk,
but instead as a sphere which rests upon the dial. The large picture
shows a Perpetual Calender plate (dial side) with the prominent moon
sphere at 11 o'clock. The moon is driven by the movement via a planetary
gear system (small images, left), which is conceiled by the finely
finished top plate of the Perpetual Calender module (small images,
of creating the moonphase ball is a fascinating example of traditional
watchmaking techniques at De Bethune. The half-spheres made from steel
and platinum are melted together, polished (small images below, left)
and are then subjected to a very demanding and precise blueing process
by heat. The process is, depending on the thickness of the materials,
very short and requires great skill, fast reaction and tremendous experience.
Heat-blueing always results in differences in the blue colour. Therefore,
many manufactures do batch-processing in order to achieve more consistent tones.
Even then, individual selection of, for example, hands are necesssary
to avoid tonal inconsistencies. Note that the moon ball cannot be
blued together with hands (as the difference in material dimensions
would be too big).
The steel part of the sphere changes its colour gradually from the typical steel colour (image sequence above, starting with the initial steel colour (a) over brown (b) and red to blue (c). Finally, the sphere is ready and can be mounted in a De Bethune watch (image below).
Now, after we tackled the characteristics of De Bethune's art of watchmaking and their impressive basic philosophy of timepieces, we are well prepared for a journey through De Bethune's collection of landmark watches. Please follow me through the next chapter!
1 - The Introduction