The Reason
An evolution of one of the most successful chronograph modules ever made by Dubois Dépraz for the watchmaking industry, combining an additional skeletonized big date and moon phases mechanism.
The module 4504 combines a chronograph with big date and moon phases. The chronograph has a 30 minute counter set at 9 o’clock, central chronograph hand and constant small seconds at 3 o’clock.
Diameter 30.00mm Thickness 4.40mm Number of components 112
The lever to the left of the moon phases wheel corrects it manually when it’s set up. The small spring to the right indexes the wheel holding it in place until the finger piece driving it each 24 hours pushes it by one tooth.
The wheel has 59 teeth, turning approximately one full rotation in two months.
The skeletonised moon-phase disc removed.
The big date mechanism is driven from the base movement via the cam shown above the date (21) below.
Below the two date rings removed.
The numbers are cut from a circular plate, the surface then re-finished before being plated. Lastly the driving pinions are push and riveted in place.
The pinions and cams on the hidden side of the date associate to the driving cam system turning them from ‘01’ to ‘31’ then back to ‘01’.
The big date module removed from the chronograph.
The driving cams for the two date discs are constructed on multiple levels, once correctly assembled the date can not become desynchronised.
The driving finger for the moon phase disc sits on a wheel which pushes the finger cam in one direction. If the setting is turned anti-clockwise the spring pushing the finger cam slides under it preventing any damage.
The Chronograph Module
In alternative versions of the chronograph module the addition of an hour recorder can be added, here removed to allow for the moon phases wheel and mechanism.
The large wheel below with the heart shaped cam is the 30 minute counter. The heart shaped cam returns to zero the minute counter through the pressure of the hammer to its right.
The various operating levers and cams below operate the chronograph and the vertical clutch system. The small ‘V’ shaped friction spring takes up any slack that is generated between the wheels in the train that drive the small seconds hand.
The solid wheel to the right of the centre post (at the top of he image) is part of the vertical clutch mechanism.
The main operating lever (with the gold coloured split ring) is to the right and the beak below it pushes on the ‘W’ shaped cam to activate the chronograph mechanism.
A selection of the chronograph levers.
The return to zero hammer piece.
Below is the base movement upon which the modules are fixed. The original date ring is replaced for a large steel wheel which then drives the big date system. In the centre, the seconds pinion is modified and a pinion added which drives the chronograph module including the new constant small seconds. The pinion below it drives the hour and minutes motion work, which is added on a higher level of the chronograph module.
The rose gold coloured (CuBe) pinion meshing with the chronograph module.
Summary
The chronograph in general has always been an under recognised complication which is mostly integrated into a purpose made chronograph movement. Dubois Dépraz have designed a Chronograph that can be successfully added to a multitude of different base calibres in different configurations with additional complications, such as the big date and moon phases shown here.
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