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. |

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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 . |

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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 (3). |
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 wristwatches. 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. |
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