pro & con: horizontal vs. vertical coupling - WatchTime

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PRO & CON: HORIZONTAL VS. VERTICAL COUPLINGHORIZONTALANNEGRET FLEISCHERDESIGN ENGINEER AT A.LANGE & SÖHNE:“Vertical couplings are particularlysuitable for watches with center-mountedseconds hands. Here, the coupling sequenceoccurs directly at the fourthwheel. Our Datograph model has an offcenterdisplay for the seconds, and a horizontalcoupling is better suited for thisarrangement. The chronograph’s couplingwheel and the chronograph’s centerwheel are located side by side. Theymesh with each other as soon as thechronograph is switched on. From thestart of the Datograph’s developmentprocess, we knew we wanted to create aLange Datograph Caliber L951.1classical chronograph with the characteristicelements, and that includes horizontalcoupling. This system is more interestingfor Lange’s customers, who can observethe sequence of motions throughthe case’s transparent back. They enjoywatching the complex interplay of the severalcomponents. A vertical coupling, onthe other hand, puts the participatingwheels one atop the other, so anobserver sees much less excitingtechnology in action.”watch with a seconds hand thatcould be halted without stopping themain mechanism. This timepiece lacked areturn-to-zero mechanism, so before beginninganother stop-time measurement, the userhad to wait until the restarted seconds handcompleted its leisurely passage around the dialand back to the zero point. This shortcomingwas overcome in 1844 by Adolphe Nicole, whoinvented a small heart-shaped cam that madeit possible to instantaneously return a watch’sA. Lange & Söhne’s Datograph Flybackhand to its starting position. In 1880, AugusteBaud shifted the position of the chronographmechanism onto the back side of the movement,making it much easier for watchmakersto repair or service the device.A chronograph is essentially based on an ordinarywatch movement. The forward end ofthe arbor of its fourth wheel bears the smallseconds hand. Toward the rear, the arbor’s pivotis elongated beyond the plate so that a socalled“driving wheel” can be affixed to the arbor.Like the seconds hand, the driving wheelcompletes one rotation around its own axisevery 60 seconds. The connection and disconnectionbetween the movement and the chronograph’shand occur with the aid of a couplingmechanism. Because the chronograph’shand should rotate in a clockwise direction, thedriving wheel cannot be directly connected tothe chronograph’s center wheel; an intermediatewheel is necessary. These three wheels constitutethe traditional geared coupling. The intermediate(or “coupling”) wheel is affixed toa moveable coupling lever. When the startstopbutton (usually situated at the 2 o’clockposition) is pressed, either the column wheelrotates one position farther along or else theoperating cam is moved. The coupling leverpivots slightly toward the right, allowing the intermediatewheel to create a connection betweenthe driving wheel and the chrono-Continued on page 8884 WatchTime April 2007
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
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