The third generation
In 2010, the first impressive manifestation of the new MORITZ GROSSMANN GLASHÜTTE I/SA brand was given the name BENU. Now, with the BENU Tourbillon, the watchmakers at Grossmann have put the crown on the launch model line of the up-and-coming manufacture. With a flying three-minute tourbillon, its mechanical movement definitely qualifies as a work of art. The fascinating choreography at 6 o’clock makes the subtle face of the BENU Tourbillon come alive. Originally developed to neutralise gravity-induced rate deviations in pocket watches, a well-formed tourbillon design today ranks among the genuine challenges that confront calibre engineers. At the same time, the tourbillon is unquestionably one of the complications that watch enthusiasts covet most.
Pairing the Grossmann balance with a tourbillon made it necessary to question some classic principles of horological design. For the BENU Tourbillon, key movement functions were reconceived to accommodate the aspirations of Grossmann’s watchmakers with respect to precision, efficiency, and aesthetics. The Grossmann three-minute tourbillon is based on the insights of respected Glashütte watchmaker Alfred Helwig, who developed the flying tourbillon. The unusual size and the seductive gestalt of the tourbillon are beautifully showcased with a longer periodicity. A patent-pending stop-seconds mechanism with a fine-tipped brush made of human hair completes this stunning tourbillon implementation. The BENU Tourbillon comes in an exclusive limited global edition of 50 watches.
Case: Three-part, 750/000 white gold, diameter 44.5 mm, height 13.8 mm
Crown: 750/000 white gold
Dial: Solid silver, three-part, argenté with Arabic numerals, off-centre displays for hours and seconds
Hands: Hand-crafted, steel, annealed to a brown-violet hue
Glass: Sapphire crystal, antireflective coating on one side
Strap: Alligator, hand-stitched
Clasp: Butterfly clasp, 750/000 white gold
Limited to 50 watches worldwide
Calibre: 103.0, manually wound, adjusted in five positions
No. of parts: 245 (wheel train 186 / cage 59)
Jewels: 30 (wheel train 17 / cage 13), of which 4 in screwed gold chatons
Cage: Diameter 16.0 mm, 1 revolution every 3 minutes
Balance: Diameter 14.2 mm
Power reserve: 72 hours when fully wound
Frequency: 18,000 semi-oscillations per hour
Functions: Flying three-minute tourbillon with screw-secured driving wheel, minute, off-centre display for hours and seconds, patent-pending stop seconds, Grossmann winder with pusher
THE MANUFACTURE CALIBRE
The calibre 103.0 movement of the BENU Tourbillon represents a new concept with a lineup of surprising solutions. The pillar movement with the main plate and the 2/3 plate, a typical hallmark of Grossmann watches, embodies the traditions of Glashütte pocket chronometers. A balanced ensemble of components in untreated German silver with different types of finissage and two pillar spacers constitute the tiered calibre that features a separately removable winder module. The delicate engravings are all fashioned by hand.
A very rarely used, optimised bearing system was chosen for the barrel. The bilateral jewel bearing with a maximised distance between the ratchet wheel and the main plate provides perfect stabilisation for the mainspring barrel. The modified Glashütte stopwork holds the tension of the mainspring. Because it slides in a slotted hole, the stop click allows the ratchet wheel to recoil somewhat after winding, which slightly relaxes the mainspring.
THE WHEEL TRAIN
The train configuration of the Grossmann three-minute tourbillon exhibits several special facets. An additional wheel extends the periodicity of the cage to three minutes, thus reducing overall kinetic energy and the exposure of the escapement to stress. The pinion for the seconds is segregated from the power flow of the wheel train and driven with reduced torque. To prevent arbor and seconds-hand backlash, the pinion is constantly braked by a spring. Grossmann’s watchmakers designed this function in a sustainable and maintenance-free manner by choosing guaiacum, a very oily wood with the highest degree of hardness (“rock-hard”), for the brake ring of the fourth-wheel arbor. This solution was inspired by the extremely dependable marine and tower clocks that carpenter John Harrison crafted in the 18th century thanks to his insights into the properties of different wood species.
Grossmann’s latest-generation precision timepieces stand for HERITAGE IN TIME beyond our era. It was also a key objective to preserve the beauty of the wheel train of the BENU Tourbillon, with its precious decorations and polishes, by precluding oxidation and damage to coated surfaces. Long-term brilliance of the train wheels is assured by ARCAP, a coppernickel-zinc alloy. The balance, crafted from beryllium bronze, has a stately presence above the silvery shimmer of the going train.
Optimised for artisanal manufacturing techniques, the new design of the Grossmann balance improves the adjustability of inertia and achieves high kinetic energy combined with minimised air resistance and the smallest possible mass. With poising weights and equidistant bores in the balance-wheel rim, the mass can be varied and the balance trued. In the BENU Tourbillon, the size of the balance and of the cage was optimised with a creative spatial arrangement. The Nivarox 1 balance spring, with a terminal overcoil as calculated by Glashütte regleur Gustav Gerstenberger, is located beneath the balance so that the motion of the balance and tourbillon cage can be observed without obstruction.
THE MAGNUM OPUS IN THE MOVEMENT
The BENU Tourbillon reflects the talent of famous Glashütte watchmaker Alfred Helwig who developed the flying tourbillon in 1920. From 1911 onward, Helwig crafted watches in his own workshop and taught classes at the German School of Watchmaking in Glashütte after having been enrolled there himself as a student. His reference book entitled “Drehganguhren” also provided guidance in 2013 when the Grossmann three-minute tourbillon was developed.
In the BENU Tourbillon, the cage is suspended from a cantilevered, hand-engraved German-silver cock. Its design is totally new, resulting in minimal-art aesthetic appeal. The elaborately crafted upper part of the cage is a striking V-shaped balance bridge for which a design patent has been registered. Its hairspring is located beneath the characteristic Grossmann balance wheel. Thus, the aficionado’s glance is instantly directed to the heart of the BENU Tourbillon.
As understood by Grossmann’s watchmakers, the precision of a tourbillon calls for a stop-seconds mechanism. The lavish execution of the cage with only two triangular posts paves the way for this extra complication. For trouble-free immobilisation of the balance, any kind of interference between the stop device and the triangular frame posts must be prevented. An elastic brush with human hair solves this problem gently and reliably. This patent-pending stop solution allows precise handsetting and delivers proof of the superiority of the BENU Tourbillon.