The Omega DeVille Co-Axial Escapement
Limited Edition
Copyright (c)
Edward Hahn
Thanks to Walt Odets, Gerard Luppino, Walt Arnstein, and
Ei8htohms for technical background.
Introduction
Among the more anticipated releases at the
The Daniel's escapement has been under development for over
20 years by Dr. Daniels, who has been trying to solve some of the fundamental
issues regarding the reliability and accuracy of mechanical watches. That
Omega, the most recognized brand of the SMH group after Swatch, worked to bring
this to market first yields some clue as to the potential importance of this
development. One could argue that only SMH had pockets deep enough to
move forward with the tooling for the Co-Axial escapement; however, the fact
that this tooling has been developed means that we can look forward to
regular use of this escapement as SMH recovers the development costs.
An interview
with Jean-Claude Biver of SMH indicates that the Co-Axial escapement will
be showing up in several other brands in the near future.
This was one watch which I kind of fell into. I told
myself some time ago that while I would never actively seek one of these
timepieces, if I saw one unspoken for in a shop, I would buy it. That day
came in November of 1999 in downtown
I chose the white dial because (1) it was a more classic
look, and (2) I have too many dark faced watches. Nevertheless, the blue
dial version is stunning in person as well.
Packaging, Appearance, and Physical Characteristics
The DeVille comes in a pretty standard looking box - a
white paper covered outer box and a black leather inner box with beige felt
interior. The watch is not fastened around a pillow, but instead is
secured flat via a felt-covered clip in a padded area. On the inside top
of the packing is a pocket with a special hand-signed certificate and booklet
on the Co-Axial escapement, along with the more normal warranty and operating
manual information. The actual COSC certificate is not included.
:-(
The watch actually does not look like any of the other
models in the current DeVille line. Rather, it recalls the look of the
famous Omega Constellations of the 1950's. The pie-pan dial, the large
applied markers, and the shaped lugs all were characteristics shared by the
Constellation of yesteryear.
The overall image and heft of the watch is that it is a
substantial piece. With a basic case diameter of 38mm (not including the
crown, crown protectors, and lugs), the watch itself is sized fairly normal by
today's standards, but lugs and crown protectors add a lot of bulk to the
appearance of the watch. Furthermore, this watch is somewhat thicker than
usual for a simple calendar with a movement height of 4.05mm: the watch itself
measures 9mm (in comparison, it is about 12% thicker than the regular Omega
DeVille automatic using a similar movement). These dimensions yield a
total watch weight of about 80g including clasp and strap.
The initial impressions upon seeing it in person was that
this was a truly stunning piece, with a high polish everywhere. All of
the elements of the dial, case, crown, and strap are complementary and in
balance. As the first gold dress watch of my collection, I'm happy to say
that it would fill in that role handily even without the Co-Axial escapement.
Movement and Accuracy
Inside the beautifully engraved (but solid, alas) back of
the watch is an Omega Caliber 2500. This appears to be a development of
the Omega 1120 with the addition of the Co-Axial escapement and Free Sprung
balance. The Omega 1120 itself is a modification of the ETA 2892A2 -
modified with a unique autowinding bridge to yield a smaller ball-bearing rotor
hub. Unfortunately, I do not have a scan of the movement itself, but as
part of the literature which comes with the watch is a booklet is a description
of the Co-Axial escapement. (Note the following couple of pages describe
the theory behind the Co-Axial escapement, and can be skipped.)
The Daniels Co-Axial escapement is touted as the first
practical advancement in escapement design since the design of the lever (or
anchor) escapement by Thomas Mudge in the 1700s, and was designed to overcome
some of the weakness inherent in the lever escapement. Specifically, the
traditional lever escapement uses each pallet jewel to both lock the escapement
AND transmit force from the wheel train to the balance (to keep the balance
going). Part of its design is that the "impulse surface" of the
jewel must slide along the escapement tooth to transmit the force, as
illustrated in the picture to the left. The issue here is that the the
sliding surfaces must be lubricated sufficiently to allow this to take place
smoothly. As oil ages and becomes more viscous, the ability of the force
to be transmitted efficiently is reduced, which leads to lower balance
amplitudes and poorer performance. (This photo is referenced from Walt's
Horologium Article, "The Anchor Escapement".
I highly recommend this article to understand the principle of operation of the
lever escapement. For a quick reference, here's a link
to Walt's page of a sequence of 6 pictures which shows the lever escapement
in action.)
The Co-Axial Escapement, as developed by George Daniels
instead splits the locking and force transfer functions of the escapement among
four jewels. In the photo above (from the Omega literature), Wheel (A) is
a modified Fourth Wheel of the wheel train, and provides the torque to the
escapement. (C) & (D) is the "Co-Axial Wheel", which
functions as the escape wheel. The two wheels (C) and (D) are rigidly
mounted together, on the same axis (B) - hence the name "Co-Axial".
Taking the place of the anchor is the lever assembly (E),
with locking jewels (F) and (H), and impulse (force transmission) jewel
G. Note that (G) is on a different plane compared with (F) and (H), so as
to engage the upper set of teeth on the Co-Axial wheel.
The balance (I) is only slightly modified in this
arrangement. It retains the balance pin (K), but adds an additional jewel
(J) to directly receive the force from the lower set of teeth on the Co-Axial
wheel. Note that there is still a guard pin and safety roller built into
this movement - these functions identically as in the traditional lever
escapement.
Since there is much less sliding going on during the force
transfer, there is a reduced dependence on the quality of lubrication on the
force transmitting surfaces of the escapement. This (in theory) leads to
extended service intervals without adverse effect on the amplitude of the
balance.
Another nice feature of the Co-Axial escapement is the
reduction of the lift angle - or the angle through which the lever must turn
during unlocking and force transference. This is reduced from about
50 degrees for a traditional escapement to about 30 degrees. The benefit
of this is that the system will behave more linearly, as the impulses will be
received when the balance is closer to the "neutral" or zero phase
position. The more linear the system operates, the better the
isochronism, or consistency of rate regardless of state of wind. (Walt
Arnstein and ei8htohms had a long discussion (with equations!) on the benefits of
a zero-phase impulse on isochronism in a series of Timezone forum posts, which,
alas, were not archived.)
Clockwise
Escapement Action
The photo above (from the Omega literature) shows the
initial conditions of the escapement when the balance is rotating in a
clockwise direction, with the lever locked at (F) against the lower teeth of
the Co-Axial wheel. In Step 1 (marked with a red arrow labeled "1"),
the balance pin (a.k.a. roller jewel) is entering the fork of the Co-Axial
lever. As it continues to rotate clockwise, the lever assembly will be
moved counterclockwise, which will release the entry pallet (F) from the lower
teeth of the Co-Axial wheel (Step 2). This frees the Co-Axial wheel to
unwind (always counterclockwise), and results in the following action (picture
from the Omega literature):
Once the lever has been unlocked, the extra jewel on the
balance itself (J) is now in position to take an impulse from the lower teeth
of the Co-Axial wheel directly (marked in red). This will provide energy
to the balance to keep the amplitude high, and simultaneously will also rotate
the lever through to the locked position via the action of the balance pin.
Counterclockwise
Escapement Action
This photo (from Omega literature) shows the initial,
locked condition of the escapement as the balance wheel rotates
counterclockwise. The balance pin enters the lever's fork, thus rotating
the lever assembly clockwise (Step 1 in red). As the lever assembly
rotates clockwise, the exit pallet jewel (H) is pulled out of contact from the
lower teeth of the Co-Axial wheel (Step 2). This frees the Co-Axial wheel
to unwind again, yielding the following action (from Omega literature):
Impulse jewel (G) is now in a position to receive an
impulse from the upper Co-Axial wheel (marked 2 to be consistent with the
caption). This force is transmitted through the lever to the balance pin
in the fork of the lever (marked 1 to be consistent with the caption), which
will keep the balance moving. The lever will also be pulled through so
that the escapement is locked once again after the balance pin leaves the lever
fork.
Note the counter clockwise escapement action differs from
the clockwise escapement action: here the impulse is transmitted
indirectly via the lever. In the clockwise case, the balance receives the
impulse directly from the Co-Axial wheel. However, due to the design of
the lever assembly, the force transmitted in either case is similar.
Finally, for more information regarding the Daniels
escapement, with photos from some of George Daniel's handmade prototypes, I'll
point you toward Gerry
Luppino's TZ Classic on the subject.
The Free
Spring Balance
The other significant design feature of the Caliber 2500,
separate from the Co-Axial escapement, is the introduction of Omega's Free
Sprung Balance system. This is a regulator-less system similar to the
Patek Gyromax and Rolex Microstella system. The absence of a regulator
leads to better position performance, as there are no regulator pins to affect
the action of the hairspring as it coils and uncoils. (Note there is a
fourth spoke to the wheel, it just didn't come out in the scan.)
To control the rate of the watch, two microscrews are embedded
into the rim of the balance. These are adjusted as a pair using a special
tool calibrated to give precise advancement or retardation of rate.
Other than these two features, the remainder of the
movement appears to be a standard Omega 1120, with possibly some modifications
to the wheel train gear ratios to accomodate the new escapement.
Accuracy to
Date
Since acquisition in November, the daily rate of the watch
has been truly outstanding. The overall rate appears to be slightly slow
when kept partially wound on a winder (less than 1 second per day), but runs
slightly fast when worn on my wrist (your mileage may vary, of
course). The net result is that I have not had to reset this watch
for well over a month, and it has stayed within 10 seconds of radio-controlled
clock time (even during a ten day stretch on the winder).
Since the Free Sprung balance and the Co-Axial escapement
should both work to improve the overall performance, I cannot attribute the
accuracy to one or the other. Regardless, the combination of the two
appears to work well.
Case and Clasp
The finishing of the case is truly outstanding, comparable
to the two JLC's in my collection for smoothness and mirror sheen of the
polished surfaces. Omega did not spare any expense on getting the case
right. (Note - the color balance is a bit off on the following close-ups.
The color in the above photo is correct.)
The crown is embossed with the Omega logo, and does not
screw down. It is protected by two horns, and is of sufficient size and
shape to allow comfortable manual winding and setting. The winding and setting
itself has a standard ETA feel to it, nothing special.
The watch comes with a first-quality padded crocodile
strap, in a rich medium brown which complements the yellow gold
perfectly. The deployant clasp is also 18k yellow gold and it differs
from the usual clasp in having two pins to grasp holes in the strap. Note
that the free end of the strap is folded under the buckle, rather than the
usual through-the-buckle design. The clasp itself is very firm, with a
good tactile feel to closing, and doesn't show any tendency to open on its own.
Well thought out, and well executed.
The Dial
The dial on this watch, which lies under a flat sapphire
crystal, is really something special. The surface of the white dialed
version is finely textured, which yields a slight opalescence to the
appearance. It is also pie-panned and quite thick, as the following
close-up illustrates:
Note the pie-panning, visible as a bevel in the date window
(A), and as a bend in the shadow of the second hand (B). Note also the
fine polish given to the hour markers and the inside of the case band.
This highly reflective inside is actually put to good use as shown below:
This close-up of the dial edge reveals two interesting
design features. First, the printed minute markers are actually only half
as long as they appear! The appearance of the full length is given by the
combination of the marker itself and its entire reflection in the inner case
band surface (A). Second, there is a vertical step to the dial right at
the edge before the minute markers (B). This gives an appearance of a
finely printed circular track where none actually exists. (You can also
see the non-tritium luminous diamond-shaped areas in the polyhedral hour
markers in this photo).
Summary
This is the first watch that I've collected for a
particular purpose beyond the visible - that is, the Co-Axial movement hidden
behind the solid back.
Some may argue that the Co-Axial escapement is wasted on an
ETA 2892 based movement. I'll disagree somewhat, only because the
escapement is the single most important piece of any watch. Rather than
develop an entirely new automatic winding system and wheel train, Omega took
the conservative step in releasing it within a time tested and reliable
architecture. While purists may disagree, Omega chose to ensure that the
world premier of the Co-Axial escapement would NOT be hindered by unrelated
development problems elsewhere in the movement. This, to some extent,
reduces the risk involved with introducing a radical (by horological standards)
new technology.
In any case, I'm very pleased with the watch. It has
great styling of the dial and case, and is priced reasonably for a substantial
gold watch even at full retail. The fact that it has the initial serial
production run of a new escapement, and is also a limited edition is icing on
the cake.
About the photographs in this article: I used a Nikon Coolpix 950, with a tripod on a
desktop. For many of the images, a light tent made of a white diffusion
filter was placed over the watch, using a dark grey textured cardboard
background. No flash was used; instead, a combination of direct and
indirect halogen and regular incandescent lighting was used. Note that
many of the photos have been resampled to half size using Adobe Photoshop 4.5.