Montblanc 4810 ExoTourbillon Slim. Housed in its 42mm diameter case in 18K 5N red gold is Montblanc’s Manufacture Calibre MB 29.21 automatic movement featuring the quick stop-second function. Water-resistant to 5 bar (50m). Priced at SGD48,100 / EUR34,500. Photo: © TANG Portfolio. Elfa / Timmy. 2016 Salon International de la Haute Horlogerie.

In part I of our article on Montblanc’s 4810 ExoTourbillon Slim, we explained the quick stop-second feature which allows one to halt the movement, set time to the precise second and restart it manually via the crown.

In addition, the brand claims that its ExoTourbillon outperforms standard tourbillon constructions.

This is because the weight of the tourbillon cage is disconnected from the balance wheel and since it is also lightweight, some 30% of energy can be saved. The result is higher precision and improved isochronism.

The self-winding Calibre MB 29.20 found in Montblanc’s 4810 ExoTourbillon Slim is only 4.5mm thick which means it is one of the slimmest automatic tourbillons around. Its tourbillon bridge is in steel. Photo: © TANG Portfolio. Elfa / Timmy. 2016 Salon International de la Haute Horlogerie.

Precision is also aided by the 9.7mm diameter balance wheel with 18 screws, four of which can be adjusted and 14 that are fixed.

The Montblanc Manufacture Calibre MB 29.21 ExoTourbillon automatic movement is the result of three years of development. From what we were told, there was much work done on the teeth of the train wheels.

The Calibre MB 29.21 features a new micro rotor and has 50 hours of autonomous power reserve when fully wound. The design layout of the movement realises optimal equilibrium between the barrel, rotor and balance wheel. Photo: © TANG Portfolio. Elfa / Timmy. 2016 Salon International de la Haute Horlogerie.

The Calibre MB 29.21 has a new micro rotor and a 50-hour power reserve when fully wound. The design layout of the movement achieves optimal equilibrium between the barrel, rotor and balance wheel.

The micro rotor is made of tungsten carbide and it has the Côtes de Genève en Eventail decoration.

 

 

Development efforts centred on obtaining the perfect diameter, height and weight of the micro rotor. Montblanc’s micro rotor is 2.3 times smaller in diameter and 1.9 times taller, but similar in terms of volume and weight when compared to a standard one.

The new micro rotor used in the Calibre MB 29.21 is made of tungsten carbide. When compared with a standard micro rotor, Montblanc’s micro rotor is 2.3 times smaller in diameter and 1.9 times taller but it is similar in terms of volume. Photo: © TANG Portfolio. Elfa / Timmy. 2016 Salon International de la Haute Horlogerie.

There are three engineering achievements to be highlighted with regards to the ExoTourbillon Slim. Firstly, its high velocity micro rotor; secondly, the high balance wheel inertia and thirdly, the high performance barrel.

The brand’s internal target for the ExoTourbillon Slim was to have a case thickness of 10mm and 50 hours of power reserve. These have been met.

With the movement thickness of 4.5mm, the ExoTourbillon Slim ranks as one of the slimmest automatic tourbillons around.

Related articles on timewerke.com that may be of interest include:
i. Montblanc 4810 ExoTourbillon Slim: Stop and Go! (Part I)
ii. Montblanc TimeWalker Pythagore Ultra-Light Concept: Super-Dan, Super Light