SJX Watches
Insight: The Chronograph Reset Mechanism
Continuing with our series focused on the mechanical chronograph – we already explained the vertical and horizontal chronograph clutches, along with the advantages and shortcomings of each – we now turn to another vital component but rarely discussed: the chronograph reset mechanism. While the clutch enables energy transmission between the base movement and chronograph, it plays no role in returning the chronograph indicators to a zeroed position. This is accomplished by an altogether separate mechanism that is synchronised with the clutch action but functions independently. The reset mechanism indexes all the chronograph indicators (hours, minutes, and seconds) back to the zero position, and keeping them securely in place until the chronograph is started once again. Any reset mechanism generally comprises of two main components: a heart cam and reset hammer. The two interact based on clever geometry and illustrates mathematics is often the underlying basis of watchmaking, or more specifically, movement construction. The chronograph works of a Breitling B01 movement, with the reset heart cams (12, 13, and 17) in purple. Image – Breitling patent The heart cam Named after its distinctive outline, the heart cam is a seemingly simple component that is in fact the product of some ingenious engineering. While the cam has a turning axis and is a rotational system – in other words, it revolves on a fixed axis – a clear analogy can be made with linear systems. In order to...
