Grossmann‘s watchmakers fulfilled a long-standing wish when they created the innovative winding mechanism for the TEFNUT. The quest for a robust alternative to the conventional crown winder ended with an exceptionally original solution: The Grossmann strap winder makes it possible to wind the watch hands down, so to speak, with just a few turns of the strap attachment at 6 o‘clock.
To enable this remarkable feat, the calibre 102.2 was extensively reworked and the exterior form of the TEFNUT modified. A first glance is enough to see that the Grossmann strap winder has strikingly different strap attachment points and an unusual setting crown position. With its three distinctive versions – „Classic“, and „Fancy“, and „Gent“ – in rose-gold or white-gold cases, the TEFNUT Twist stands out prominently in terms of both appearance and mechanical ingenuity.
The TEFNUT Twist remains true to the slender design vocabulary of its family and attracts attention with charming elegance. Its bezel and the striking strap attachments please the eye with balanced proportions. With the seconds subdial at 7 o‘clock and the setting crown at 4 o‘clock, the visual focus is subtly shifted to the strap winder.
To assure that the strap comfortably hugs the wrist, both the winding stem and the strap bar on the opposite side are inclined inward by 22°. Depending on the version, the strap bar tips are fitted with gold screws or, like the crown, with glowing precious stone cabochons, identifying the TEFNUT Twist as a manifestation of pure watchmaking artistry.
THE GROSSMANN STRAP WINDER
As simple as it may seem, the concept of winding with „a twist of the wrist“ calls for an elaborate mechanism. The power needed to tension the mainspring is built up with the winding stem that enters the case at 6 o‘clock. Via a wheel train that is visible on the movement side of the watch, it transmits the power to the spring barrel. When winding with partial turns of about 90°, the strap can deliver much more torque than a crown because it is easy to grasp. The energy is transmitted via a bevel gear with a high-efficiency ratio. Moreover, a backstop ratchet allows bidirectional winding. Thus, all it takes to wind the TEFNUT Twist is a few turns in both directions.
THE SETTING CROWN
Since the strap winder gear ratio is not suitable for handsetting, the winding and setting functions were separated in the TEFNUT Twist. As usual, the hands are set with the crown, which is in the less exposed 4 o‘clock position. When the crown is pulled, the clutch lever engages the sliding pinion with the setting wheels and activates the stop seconds mechanism. A spring firmly attached to the main plate presses against the safety roller and thus prevents inadvertent contact with the polished outer surface of the balance-wheel rim or maladjustment of the delicate poising screws. Once the hands have been set, the setting crown is pushed home again to restart the movement.