The Omega DeVille Co-Axial

Part 4



Upon first examination, the escapement of the
Omega Co-Axial offered one great surprise. The impulse (small) escape
wheel appeared to be heavily greased (right). Because the primary
objective of the co-axial design is to eliminate lubrication at impulse
surfaces (and the consequent deterioration of performance over time), this
discovery seemed unacceptable. At 35X magnification, it also seemed
possible that the “lubrication” was nothing more than
irregularities in the surface of the poorly made wheel. Part of Omega’s
purpose in this design was to test the co-axial escapement with parts that
required no hand finishing.

Examination at higher magnification (64X), as well as an
attempt to remove the “grease,” revealed that the impulse wheel was, in
fact, not lubricated on the impulse surfaces. As illustrated
right , the impulse surfaces of the teeth appear free of any
lubrication (1). The drive surfaces, which mate with the
half-oglive teeth of the fifth wheel, were, however, very lightly
lubricated (2 ). I do not know why Omega felt lubrication necessary
here given the oglive form of the wheels and the brass on steel
construction. I doubt that Daniels anticipated it. The lubrication,
however, seems non-critical and should not interfere with the long-term
functioning of the escapement.

On the subject of lubrication, it is interesting that the
pallet lever jewels, particularly the lower, were very heavily
oiled (right). In a conventional lever movement of this size, these
pivots are usually not oiled, or oiled with only a trace of lubricant.
Because the inertial response of the lever (which is very light for the
same reason) is important to escapement function and the loads are low,
oil is thought to provide more drag than benefit. I do not know whether
deterioration of this lubricant will ultimately affect the longevity of
operation, nor whether Daniels anticipated it .

In small calibers like the Omega, the co-axial escapement is aimed much
more at stability over time than “accuracy” per se. As delivered from the
factory, the Omega Co-Axial appeared to provide consistent rate, and was
adjusted about 15 seconds a day fast. Positional performance was
essentially perfect.

Timer tapes for dial-up and crown-down positions are
shown left after a rate adjustment (1) with the balance
weights. Note, particularly, the extraordinary consistent amplitude
between positions (2). We would normally expect a 20 to 40 degree
difference. This consistency virtually eliminates anisochronistic effects
in positions. Note also the (estimated) lift angle of 35 degrees

I suspect that the short, equal-radius locking
action, equal impulse to the balance in both directions, and, most
importantly, the small lift angle of the co-axial escapement contribute to
the remarkable positional performance of the Omega Co-Axial. In a
conventional lever escapement, a steeper locking angle is normally used on
the exit pallet than on the entry pallet. This difference may interact
with gravitational influences in positions (e.g. with the exit pallet
down). In the conventional lever escapement, differences in impulse to the
balance running in different directions may, likewise, interact with
gravitational effects in vertical positions.

In the co-axial escapement, the larger arc of free vibration should
contribute to better positional performance. The balance-spring unit is a
bit closer to being a true, free-sprung oscillator. (Point of attachment
issues, which apply to both escapements, are not in consideration here.
Although Daniels’ designs have all employed a Phillip’s overcoil to
address this issue, the Omega movement would not allow for the height
required and a flat spring is used.) Based on an amplitude of 275 degrees
and lift angles (or escaping angles, in Daniels’ terms) of 35 and
50 degrees, the co-axial balance operates free of escapement interference
for about 87% of its arc, the lever escapement for only 81%. This means
that the lever escapement works against escapement interference that is
143% of that in the co-axial escapement. In a vertical position, with the
balance beginning from center upwards, the inhibiting impulse that
occurs after center can exacerbate the positional problem, depending on
the poise errors in the balance. The co-axial escapement significantly
reduces such effects.

It is interesting that Daniels expects the co-axial to run at a
maximum amplitude of about 270 degrees, and expects a drop of about
40 degrees in vertical positions (which is about the drop one also sees in
conventional lever escapements). The lower maximum amplitude of 270
degrees is possible, according to Daniels, because there is no
deterioration of lubrication to account for. The advantage in a lower
maximum amplitude is that vertical positions would then (presumably) fall
to about 230 degrees. This is low enough to mask poising errors in the
balance, which introduce erratic rate changes dependent on amplitude.
Because the Omega Co-Axial appears to be running at about 300 degrees,
this does not seem a possible explanation for the excellent positional
performance of the watch.

Whatever the explanations, my sample of the Omega Co-axial showed
performance normally seen only in the very finest, hand-adjusted

Interestingly, because each vibration of the co-axial balance involves
contact between the balance impulse jewel and fork, and a locking action
on the large escape wheel, a conventional timer is able to correctly
interpret the co-axial escapement. Only the delivery of impulse to the
balance is different in the co-axial, and an electronic timer does not
normally interpret impulse sounds because of their irregularity.

Above: The geometry of an extra-flat co-axial escapement.
Balance to lever angles. Both from Watchmaking,
Revised Edition
, by George Daniels.

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Were we to discount the escapement, the Omega
Co-Axial DeVille would be a very modest, but worthwhile accomplishment.
The dial and case finishing is first class, and the movement is an
Omega-improved version of a reliable and worthy caliber.

King Louis XVI of France is purported to have asked
Louis Abraham Breguet for the perfect watch. “Provide me the perfect
, Sire,” responded the watchmaker, “and I will provide you the
perfect watch.” In the late 18th century there was no mention of a watch
with no oil, at least where it matters most.

The complexity of the Daniel’s escapement is
disconcerting. It is
significantly more complex than the excellent, stable, and
relatively consistent lever escapement it is intended to improve upon. The
lever pivots of the co-axial, apparently, require substantial lubrication,
and the non-impulse surfaces of the small escape wheel some. One suspects
that in the contemporary automatic watch, the mainspring barrel (with its
critical lubrication for the slip bridle) and balance pivots (which use
conventional Incabloc cap jewel assemblies) may well become the Achilles’
heels of the ten-year service interval hoped for with the co-axial.

On the other hand, the co-axial provides many
theoretical advantages that appear to translate into authentic consistency
of running. With no hand finishing and no hand regulation, the Omega I
tested appears to run as well as watches with the finest, hand-adjusted
lever escapements. Lubrication-free impulse surfaces; short, equal-radius
locking; a larger arc of free vibration; and an equal impulse in both
directions of vibration are important advantages.

Regardless of what we learn with time, and with more
expensive production iterations of the design, this Omega is a remarkable
achievement. It is a bold step for the technically-conservative Swiss, and
it is an all-to-rare contribution to horology. This is a watch that I
would like to have around for a long time and occasionally sneak a peek at
on the timer. To coin a phrase, time will tell. In the meanwhile, thank
you, Omega!








© 2012 Bourne In Time Inc.