Ulysse Nardin

Marcus Hanke
[PuristSPro Moderator]
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It's not a bug, it's a feature ....

irony aside, it is really true: The big advantage and most unique feature of UN's big date - and perpetual mechanism -, that it can be set both forward AND backward, also is responsible for an increased chance of misalignment in the indications. All conventional calendar indications are working with springs and detents, that are fixing a date wheel's position. However, this system permits only one direction of movement. Ludwig Oechslin developed an entirely new system of gears that permit two directions, and are used in all his date and astronomical indications, including his annual calendar that is now being released by Zenith.

The problem is that such a system MUST permit free movement to the wheels in both directions. Any part offering resistance on the geatrain in order to lock an indication in a desired position, must not be so strong that it canot be overcome by the power of an owner turning the crown. Unfortunately, sometimes, a shock or bump the watch might be subjected to, exerts a similar force to the geatrain, and voilà, you have a misalignment.

Very often, any apparent misalignment between the two figures of the big date tends to dissolve itself after a few switches of that disk. However, sometimes, it remains, and makes a readjustment necessary. From a technical point of view, the mechanism is not harmed in any way by the misalignment, and it is up to the owner's decision wether he feels bothered enough to send the watch for readjustment.

However, please permit me to be frank, if a perfect alignment of all indications is really decisive for you, then I fear that an Oechslin system calendar, permitting setting forward and backward, is not the right watch for you, and a more conventionally designed perpetual might be a better choice.

Btw, I have seen a very small misalignment on my own perpetual from time to time, as I found on the big date of my wife's GMT. However, being aware of its physical reason, I ignored it, and am very happy with my watch. The example you showed above, might be on the border, though. Have you tried setting your perpetual forward and backward again, and is the misalignment still there after the next automatic change of this number disk?

Regards,
Marcus
This message has been edited by Marcus Hanke on 2011-04-01 01:50:45