The fully in-house manufactured tourbillon calibre 103.0 comes as a line extension in the Benu collection to the markets in the next days. It´s the first wristwatch that also uses human hair…
Honestly I was surprised to see such a sophisticated timepiece from the Grossmann team yesterday. The Benu Tourbillon, in a white gold case, with the Reference 001.G-221-11-1 has an argenté dial and is limited to 50 watches world-wide. When I first heard it is a tourbillon I said to myself: Oh no, not another meanwhile boring tourbillon. When learning more about its technical features I then had to admit that the Grossmann engineers and watchmakers did not just do a conventional job by just repeating what we had seen hundreds of times before…
Please do always click once and then again on my pictures to enlarge them…
So these are the technical key features of the new Moritz Grossmann Benu Tourbillon in brief:
- The Grossmann three-minute tourbillon according to Alfred Helwig
- The flying tourbillon cage with a V-shaped balance cock for which a design patent is pending
- The patent-pending stop seconds with a fine-hair brush
- The asymmetric-arm lever escapement
- The new configuration of the Grossmann balance and hairspring with an overcoiled terminal curve
- The newly developed mainspring barrel jewel bearing
- The brake ring on the fourth-wheel arbor made of guaiacum
- The ARCAP alloy for the going train wheels
- The patent-pending dual minute display with an extension of the minute hand
Now let´s go into the details:
The Grossmann three-minute tourbillon according to Alfred Helwig …
Alfred Helwig (1886-1974), the famous watchmaker, strongly influenced the evolution of Glashütte as a stronghold of German watchmaking. Alfred Helwig was a teacher at the German School of Watchmaking from 1913 to 1954; in 1920, he applied for a patent for the flying tourbillon. In 1922, he earned his master craftsman’s credentials with a unilaterally suspended five-minute tourbillon. As the author of the book entitled “Drehganguhren”, Alfred Helwig was a source of inspiration for Grossmann’s calibre designers while they were developing their three-minute tourbillon.
You know of course that originally the tourbillon served the purpose of offsetting gravity-induced rate deviations in pocket watches that were worn vertically mostly all day long. Today, a well-formed tourbillon ranks among the genuine challenges for master watchmakers.
The flying tourbillon cage with a V-shaped balance cock for which a design patent is pending …
The tourbillon cage is freely suspended from a cantilevered, hand-engraved cock made of German silver. Its design is totally new, resulting in a distinctive manifestation of functional purity. The novel configuration of the tourbillon, which has an unusually large diameter of 16 mm, is beautifully showcased with a longer periodicity. Elaborately crafted, the upper part of the cage is a V-shaped balance bridge that requires only two posts, a significant hallmark for which a design patent has been registered.
The patent-pending stop seconds with a fine-hair brush …
For the watchmakers at Grossmann, the ability to accurately set the time is a crucial precision requirement for a tourbillon mechanism. To reliably immobilize the balance, the stop device must bypass the cage frame posts. An elastic human-hair brush (the hair used to produce the hair-brush belonged to CEO Christine Hutter) can easily glide past the triangular posts and gently brake the balance at the circumference of its rim.
The asymmetric-arm lever escapement …
Given the ambitious expectations imposed on a precise manually wound watch, the classic lever escapement was reworked for the Moritz Grossmann Benu Tourbillon. Because of the use of a pallet lever with unequal arm lengths on a shared locking circle, all entrance and exit adjustment points are on the same lever arm, and even slight deviations can be precisely rectified. The pallet lever is composed of two parts: a thin fork with a blade-type guard pin, fashioned in the manner of Glashütte pocket watches, and the lever body with the visible sapphire pallets. A pin at the extension of the fork, which significantly improves the lever’s mass distribution and equilibrium, limits the deflection of the lever.
The new configuration of the Grossmann balance and hairspring with an overcoiled terminal curve …
The spatial configuration of the balance and hairspring in the tourbillon cage was optimized for the Benu Tourbillon. The hairspring is attached upside down to the lower cage base beneath the Grossmann balance, resulting in an even more exquisite balance bridge design. Optimized for artisanal manufacturing techniques, the design of the Grossmann balance improves the adjustability of inertia and achieves high kinetic energy combined with minimized air resistance and the smallest possible mass. The number of screws in the balance wheel rim was minimized, and the bores in the rim are equidistant. This makes it possible to vary the moment of inertia by inserting screws with different head lengths in the bores. The Grossmann balance interacts with a Nivarox 1 balance spring. Its terminal curve is overcoiled according to calculations performed by Glashütte regleur Gustav Gerstenberger.
The newly developed mainspring barrel jewel bearing …
An extremely rare solution was chosen for the barrel bearings in the calibre 103.0. The bilateral jewel bearings are located on the ratchet wheel and main plate sides. A gold chaton on the ratchet wheel carries the upper jewel for the mainspring barrel and tastefully complements the traditional finissage of the ratchet wheel. As customary, the lower jewel is embedded in the main plate. The mainspring barrel arbor extends through the hollow core to the chaton in the ratchet wheel; the barrel is perfectly stabilized with a maximized distance between bearings. A modified Glashütte stopwork secures the tension of the mainspring. After winding, it allows the ratchet wheel to reverse somewhat and slightly relax the mainspring. The stop click is firmly secured with the addition of a steel cover.
The brake ring on the fourth-wheel arbor made of guaiacum …
The train configuration of the Grossmann three-minute tourbillon exhibits several unusual features. To reduce the kinetic energy of the tourbillon and the exposure of the lever escapement to stress, the periodicity of the cage was extended to three minutes with an additional wheel. 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 spp., an oily wood species, for the brake ring of the fourth-wheel arbor. It is classified as “rock-hard” and has good long-term tribological properties.
By the way: This solution was inspired by the extremely dependable marine and tower clocks that John Harrison (1693-1776) crafted with great success in the 18th century. As a master carpenter, Harrison accrued considerable experience with various types of woods, especially the very durable ones he selected for his marine chronometers.
The ARCAP alloy for the going train wheels …
It was also a key objective to preserve the beauty of the wheel train of the Moritz Grossmann Benu Tourbillon, with its precious decorations and polishes, by precluding oxidation and damage to coated surfaces. The train wheels are made of ARCAP, a copper-nickel-zinc alloy coveted for its long-lasting brilliance. Crafted from beryllium bronze, the balance has a stately presence above the silvery going train.
The patent-pending dual minute display with an extension of the minute hand …
That´s technically speaking nothing particular, but just a clever feature that helps to read the correct time also when the minute hand passes along the huge tourbillon cage at “6 o´clock”.
Technical data Moritz Grossmann Benu Tourbillon
Manufacture calibre 103.0, manually wound, adjusted in five positions
No. of parts:
245 (wheel train 186, cage 59)
No. of jewels:
30, 4 of which in screwed gold chatons (wheel train 17, cage 13)
Grossmann three-minute tourbillon with stop seconds; shock-absorbed Grossmann balance with 4 inertia and 2 poising screws, suspended Nivarox 1 balance spring with No. 80 terminal curve, Gerstenberger geometry
1 revolution in three minutes, anti-clockwise when viewed from dial side
14.2 mm, frequency 18,000 semi-oscillations per hour
72 hours when fully wound
Functions / features
Flying three-minute tourbillon with screw-secured driving wheel and V-shaped balance bridge (design patent pending)
Sweep minutes, off-center hours and seconds with stop seconds, replacement of the missing minute scale segment from 25 to 35 minutes with a separate scale swept by the extension of the minute hand on the opposite side (patent pending)
Stop seconds at the balance wheel rim with a pivoting fine-hair brush (patent pending)
Asymmetric-arm lever escapement with counterweight and lever banking pin
Grossmann balance with suspended balance spring, adjustable with poising screws in the rim
Newly developed mainspring barrel jewel bearing
Brake ring on the fourth-wheel arbor made of very hard, oily guaiacum
ARCAP train wheels
Grossmann winder with pusher to deactivate the hand setting mode and start the movement
Modified Glashütte stopwork with backlash
Pillar movement with 2/3 plate and frame pillars in untreated German silver
Hand-engraved 2/3 plate and tourbillon cock
Broad horizontal Glashütte ribbing
3-band snailing on the ratchet wheel
Raised gold chatons with pan-head screws
White sapphire bearing jewels
Separately removable clutch winder
Operating elements: Crown in 750/000 white gold to wind the watch and set the time, pusher in 750/000 white gold to start the movement
Diameter: 44.5 mm, height: 13.8 mm
Diameter: 38.4 mm, height: 7.1 mm
Three-part, in 750/000 white gold
Solid silver, three-part, argenté, with Arabic numerals
Handcrafted, steel, annealed to a brown-violet hue
Crystal/display back Sapphire crystal, antireflective coating on one side
Hand-stitched alligator strap with butterfly clasp in 750/000 white gold
50 watches world-wide
168.000 Euro including 19 % VAT in Germany