pro & con: horizontal vs. vertical coupling - WatchTime

PRO & CON: HORIZONTAL VS. VERTICAL COUPLINGA prominent example ofhorizontal coupling:Zenith’s El Primero movement.Its latest versionticks inside the DefyXtreme Open (right).HORIZONTALTHIERRY NATAFPRESIDENT OF ZENITH:“Zenith’s decision to use horizontal couplingin the construction of our El Primeromovement was primarily motivated by itsgreater reliability. Horizontal coupling occursthrough the motions of mechanicalcomponents, such as levers, whose motionscan be precisely adjusted to remain constantover time. In addition to adjusting thetension in the spring, which is usually accomplishedby winding, vertical couplinggenerally also dependson frictionalelements which aresubject to the influencesof contact betweenmaterials, the attributesof the surfaces and lubricants,as well as to thermal and galvanictreatments. A watchmaker cannotdiscern these influences with his naked eye.It’s well known that tensed springs tend tolose their tension slightly as the years go by,especially if they’re used frequently. Furthermore,oils become more viscous withage. And surfaces that are continually incontact with one another suffer wear dueto friction. Consequently, it’s not only verydifficult to blindly adjust a vertical couplingor to regulate it when it’s manufactured; it’salso difficult to guarantee that it will continueto function properly over the long term.The horizontal system reduces costs, requiresa smaller volume of space and needsless complex components. For these reasons,Zenith uses a larger number of individualparts, although doing so generateshigher costs. The shapes andmotions of the individual partsare thoroughly studied prior totheir manufacture. The motionof the coupling yoke notonly triggers a rotation of thecolumn wheel (which is anepicyclic differential one), butis also precisely calculated toachieve optimal meshing incombination with the rotationalspeed of the pinion. Theclockwork of the chronograph’spinion has more than 150 microscopicallytiny leaves. Each of these individualparts undergoes a large number of precise,ultramodern manufacturing and quality-controltests. The axis of the couplingyoke and the teeth on the column wheel areadjusted using blued, eccentric components.This type of adjustment allows awatchmaker to intervene directly and visuallyin the functioning of the chronograph.Furthermore, this clockwork benefits fromthe latest advances in materials technology,like the use of ‘zenithium,’ first-rate modernoils and state-of-the-art surface treatments.”Horizontal coupling in its typical form: thechronograph mechanism is currently motionless.When started, the intermediatewheel (center), which is always connectedto the fourth wheel (left), is also made tomesh with the chronograph wheel (right).86 WatchTime April 2007