For this year’s BaselWorld, the DeWitt brand has combined the tourbillon with a constant force device that is designed to transmit to the tourbillon regulating element impulses whose energy remains identical in order to exert optimum force control, whatever the degree of winding.
The two devices, placed apart, highlight the elegant ballet of these masterpieces of the art of regulation.





Constant Force: a passion for perfection
The principle of the constant force device resides in the insertion in a traditional movement of an additional mechanism which will favourably influence regularity: its purpose is to exchange a motive power which can be variable or irregular (effort of a gear-train or barrel spring) for another perfectly constant force, whatever the degree of winding of the barrel, or more simply of the watch movement. In other words, contrary to a classical movement which experiences a progressive decrease of the force transmitted to the regulator between the initial winding torque and the end of the power-reserve, the constant force device is designed to transmit impulses whose energy remains identical and regular whatever the degree of winding of the barrel spring.
The constant force device absorbs the force generated by the barrel once every second and redistributes it every 10 seconds to the tourbillon. This principle can be observed by watching the elegant inertia weight of the constant force system, in the shape of a cross terminating in four hammers, as it completes 6 revolutions per minute. To technically guarantee that the whole system around the constant force device functions effectively, three wheels had to be incorporated: one wheel to obtain a correct meshing ratio, and two intermediate wheels (see illustration).

The watch
The Tourbillon Force Constante Academia (43 mm) is fitted with a DW8003 hand-wound mechanical movement and is housed in the famous Academia case in platinum, with bezel and middle section sculpted with DeWitt’s instantly recognizable ‘Imperial Columns’ decoration. The charcoal grey dial with vivid red relief figuring reveals two original openings, one at 8 o’clock for the constant force device, and the other at 5 o’clock for the tourbillon frame, while the hour can be read in the central axis in the upper half. There are sapphire crystals front and back and the watch is water-resistant to 30 metres. This watch is available in a limited series of 25 pieces in platinum on a dark grey alligator leather strap with a platinum folding buckle.




Description of functions
A. The barrel is a thin cylindrical drum whose toothed disc drives the train of the watch (movement motor).

B. The teeth of the barrel meshes with the centre pinion, which is integral with a centre-plate.

C. The centre wheel meshes with the pinion of a first going train component known as the second wheel.

D. The second wheel engages with the pinion of a second going train component known as the third wheel.

E. The third wheel in turn meshes with an intermediate wheel (E1). The latter transmits the power from the barrel spring to the constant force device which, via a second intermediate wheel (E2), sends impulses to the tourbillon which are of identical and constant energy, whatever the degree of winding of the barrel.

F. The constant force device is made up of several superimposed moving parts forming a single compact column, which separates it clearly from the tourbillon. It consists of a regulator known as the inertia weight (F1), which in this case is shaped like a cross for aesthetic reasons. Its action enables the constant force balance-spring (F2) to perform its role as an energy accumulator. This energy is then redistributed every ten seconds (6 revolutions/minute) to the tourbillon via the constant force pinion (which is not shown in the illustration) and the second intermediate wheel (E2).

G. The bottom carriage of the tourbillon is toothed in order to mesh directly with the second intermediate wheel (E2) of the constant force device.

NB: To ensure that the entire constant force device operates correctly, three wheels which do not exist on a classical movement have been included, i.e. the third wheel (D) to guarantee a correct engagement ratio (i.e. the complete rotation of the tourbillon in one minute), and two intermediate wheels (E) to adjust the direction of the device.


Source: Europa Star April-May 2006 Magazine Issue