watch) and leave it running: thecentral chronograph hand will playthe part of a normal seconds hand ofthe watch.

7ON THE FOLLOWING PAGE: thephoto shows the chronographmechanism of the Daytona, in thezeroed position. We will first look atthe switching system, for which thetraditional column wheel (3) waschosen, which controls the start, stopand zeroing of the chronographfunctions and is moved by a leverhook (5), actuated by the start/stopbutton of the chronograph (at2o’clock on the case middle).An unusual feature of the Rolexchronograph is the position of theentire chronograph mechanism ononly the caseback side of the watch.Therefore the central chronographwheel (6), chronograph minuteswheel (7) and chrono hours wheel(8) are positioned on the casebackside of the movement.The chronograph central wheel (6),on whose axis the chronograph handis keyed, is connected directly to thevertical clutch wheel (9), connectedto the continuous seconds wheel of

type of balance, whereas in recentyears very many companies havechanged to inertia-adjustment of thebalance, without index. We can seethe first difference between the twomovements in the balance-cock.While Rolex uses the characteristicbridge of the balance with two rests(see 4 in Figure 3), Patek Philippeuses a classic balance-cock (5, in theillustration), anchored to the plate atone end only.

5The drawing shows the system forstarting and stopping the RolexDaytona chronograph, with avertical clutch. The entire systemappears as a single wheel, preset inthe factory, which cannot thereforebe disassembled by service centresbut only lubricated. The verticalclutch is currently a favourite withwatchmaking companies and hasalso been adopted by Chopard, IWC,Jaeger-LeCoultre, Omega, Paneraiand Piaget in their latestchronographs. It is effectively thatwhich offers greatest precision onstarting the central seconds hand,which does not jump forwards orbackwards, and that which absorbsless energy from the movement (avirtually negligible quantity for thepurposes of maintaining theoscillation extent of the balance-spring), fully benefiting regularworking. Motion to the vertical clutchchronograph mechanism istransmitted by the fourth wheelwhose pinion (1) meshes with thetransmission wheel (2) on whose axisthe vertical clutch system develops.The transmission wheel (2) has adisc which, once the chronographhas started, is integral with the clutchdisc (3), through the action of aspring (4) which pushes the latteragainst the former. The friction thatdevelops between the two disks issufficient for the two to moveintegrally and for the chronographwheel (2) to then drive the clutch disc(3). The spring (4) that joins theclutch disc (3) and transmissionwheel (2) has fins turned upwardsthat hook the wheel (5) which finallytransmits motion to the central wheelof the chronograph (on whose axisthe chronograph hand is keyed) viaan intermediate wheel of the

changes for the new version, whichhowever only the experts mayrecognise. More particularly, in all thesports models of the latest generationRolex has introduced systems forprotecting the original features of thewatch such as the rehaut signed withthe company logo on its entireperimeter (the rehaut is the vertical orslanting surface surrounding the dial,under the glass).

2On observing the photos of the twoRolex and Patek Philippechronographs side by side, the formaldifferences appear enormous. Someof these relate to differences betweenthe two models in the movement.First of all the Ref. 5960P model byPatek Philippe, with a case only inplatinum, is not a “simple”automatic chronograph but doeshave a significant complication: theannual calendar with power reserve.The indications of the calendar areshown in the three windows in theupper part of the dial: day, date andmonth. The date changesautomatically every 24 hours withoutthe need for adjustment in 30-daymonths, but only at the end ofFebruary in non-leap years (thecalendar always indicates February29th, irrespective of the year, andshould therefore be put forward toMarch 1st by hand in the three yearsprior to a leap year). Under the date window is the smallpower reserve display, now a specialfeature of many complicated modelsby Patek Philippe.An essential feature of the PatekPhilippe chronograph is that theindications relating to actualchronograph timing are all on thesame dial, positioned at 6 o’clock.Here we can find the minute-counter

(on two concentric scales, one up to30, in red, and one from 30 to 60, inblue), with a red hand. The hour-counter (up to 12) is arrangedconcentrically to this, with indicationof the half hour between each one(small diamond shapes separate theblack numerals), indicated by a bluehand. Finally a circular windowinside the single chronographcounter displays the day/nightindication (after 6 pm the window iscoloured red). The continuousseconds are not included while thechronograph seconds hand istraditionally hinged to the centre ofthe dial.

3This is how the Rolex 4130 calibremovement appears when theDaytona back is opened. TheMicrostella adjustable-inertiabalance (1) is unmistakable: twopairs of screws (2), inside thebalance wheel, can be movedradially inwards or outwards,altering the moment of inertia of thebalance wheel and hence its workingfrequency. The frequency should beregulated according to the behaviourof the movement (gaining or losing)so as to obtain the maximumprecision, which depends on anumber of factors (state of

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conservation of the lubrication oils,temperature, average power reserve ofthe watch, etc.).

4The Patek Philippe automaticchronograph with annual calendarhas a sapphire glass back that enablesthe movement with central rotor (3)to be seen, hinged on a ball bearing(6) in zirconium of the latestgeneration (all top-level automaticmovements are now adopting

bearings with balls in ceramic, whichdo not require lubrication and showless wear in time). The balance (1) is also inertia-adjusting in this case and of theGyromax type, already adopted fordecades by Patek Philippe, with thedistinctive cylindrical weights forregulation (2) on the spokes. In thisrespect we have to underline howonce very few names, apart fromRolex and Patek Philippe, for exampleIWC and Audemars Piguet, used this

teeth) to fall on the transmissionwheel (5) below. The two wheels (4and 5) will adhere, thanks to thethrust of a “spider” spring, and thecentral hand of the chronograph (6),integral with the central wheel (4),will start to rotate on the dial. Whenthe chronograph stops, the two levers(1 and 2), again due to the rotationof the column wheel (3), movetogether, just like a pair of pincers,and are inserted between the twowheels just seen (4 and 5),separating them. The central wheel ofthe chronograph (4), above, stopstogether with its hand, while thetransmission wheel (5) is free tocontinue to rotate.Since this system does not absorb ahigh quantity of energy from themovement for its operation, thechronograph can be maintained inoperation, without sacrificing theprecision of the time indication orpart of the power reserve. For thisreason Patek Philippe has not fittedits chronograph with a continuousseconds hand. Those who alwayswant indication of the seconds onview only have to start thechronograph (possibly as the secondspass over the zero in a reference

chronograph (20).Until now we have observed theworking of the clutch enabled, i.e.with the chronograph started. We willnow analyse the mechanism whendisabled, when the chronographfunctions stop. During this phase a“pincer” comes into operation (forcontrolling the clutch), whose action iscontrolled by the column wheeldirectly. When the chronograph stops,the heads of the pincer (6 and 7) areinserted between the transmissionwheel (2) and the clutch disc (3),raising the latter and withouttouching the former, which continuesto turn freely thanks to the fourthwheel, while the chronograph handstops on the dial.

6Patek Philippe also uses the verticalclutch system on the new chronographmechanism developed for the Ref.5960P. It consists of two levers (1 and2), actuated by the column wheel (3),which form a kind of pair of pincers.When the chronograph is started, thelevers (1 and 2) move away from eachother (due to the rotation of thecolumn wheel), allowing the centralwheel (4) of the chronograph (without

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TECHNICAL EXAMPLES An analysis of technical and functional aspects of special interest, in a discussion of themost significant watches.

BY DODY GIUSSANI

THE CHRONOGRAPHACCORDING TO PATEKPHILIPPE AND ROLEX

These two watches – the Daytonawith original Rolex movement

and the first automatic Patek Philippechronograph with manufactured mo-vement (more specifically, Ref. 5960P,with annual calendar) were eagerlyawaited on the market. That is the rea-son why we are going to compare thetwo movements, as far as the chrono-graph part is concerned, which on pa-per have important features in com-mon: column wheel, vertical clutchand self-winding mechanism with acentral rotor.

1The Daytona in white gold withmovement by Rolex (the previousseries used the calibre 4030 from theZenith El Primero) was presented in2000. It is a chronograph with threecounters of a classic type, withchronograph hand, minute-counter(up to 30 minutes) at 3 o’clock, hour-counter (up to 12 hours) at 9 o’clockand continuous seconds (those notstopped or reset by chronographbuttons) at 6 o’clock. Greatly soughtafter by very many enthusiasts, theDaytona has also undergone style

the movement. The heart piece resetcam for zeroing the chronographseconds is also fitted on the clutchwheel (9). The three heart piece camsof the chronograph (A, B, C) serve toreposition the chronograph hands atzero, actuated by the reset lever (10),which in the case of the Rolex 4130calibre has three heads and actssimultaneously on the three cams. Aspecial feature of this reset lever (10)is its purely linear motion (notrotating), through the action of alever (11) actuated by the resetbutton (4). This configurationreduces regulations to a minimum:one single screw (12) regulates theposition of the third head (14) of thereset lever, so that the stroke of thelatter is sufficient for resetting thethree hands simultaneously. Theheads of the reset lever (14, 15 and16) cause rotation of the heart piececams (A, B, C), integral with thechronograph hands, until theyposition against the shoulders of thelatter (as illustrated); this position ofthe cams corresponds to thealignment on the zero of the threechrono hands. Thanks to the special configurationof the reset lever and the choice of thevertical clutch, the Rolex 4130calibre involves no regulation bycams. This means two advantages:on the one hand the chronograph isvery unlikely to lose its setting andwill maintain regular working for alonger period of time; on the otherhand the work of the watch repairerhas been simplified and theresponsibility for the proper workingof the chronograph is assumed in fullby the manufacture, which carriesout the first and definitive regulationof the mechanism during assembly.

8 The blown-up drawing showspart of the Patek Philippechronograph mechanism used on thenew CH 28-520 IRM QA 24H calibre.An interesting feature of the latter isthe position of the column wheelwhich, in relation to the calibres weknow well, is reversed, showing fromthe caseback side not the top of thecolumns (which in Patek Philippechronographs are traditionally

topped by a circular cover in steel)but instead the ratchet wheel (10).The column wheel controls both thepincer (1 and 2) and the reset leevr(3) of the chronograph minutes andseconds hands. The heart piece resetcam (4) of the chronograph secondshand is keyed on the axis of thelatter, central to the movement, whilethe heartpiece reset cam of thechrono minutes hand (5) is keyed onthe axis of the respective hand,hinged on the dial at 6 o’clock.Unlike the Rolex calibre, in this casethere are two separate reset levers:one for the chronograph minutesand seconds (2) and one for thechrono hours, whose wheel ispositioned on the dial side of thechronograph, according to the mostclassic mode of the chronographcalibres, albeit coaxially to thechrono minutes.

9The drawing reproduces the dialside of the Patek Philippechronograph mechanism, where thechronograph hours wheel (13) ispositioned, with its heart piece resetcam (12) and related reset lever (11).On all three chronograph wheels(seconds, minutes and hours) thewheel and heart cam, integral with

the relative hand, are connected bymeans of a clutch system, formed bya spring (14), which allows the heartcam (12) to rotate independently ofthe wheel (13) below. In the PatekPhilippe chronograph this operationcan in fact be performed with thechronograph both stopped andstarted, thanks to the flybackfunction: pressing the reset button atfour o’clock, while the chronographhands are in motion, makes allthree wheels (central seconds andchrono hours and minutes at sixo’clock) return to zero. Releasingthe button at four o’clock, thehands immediately start movingagain. Thus the operation ofstopping the chronographfunctions is skipped, whichexplains the name of the flybackfunction. This latter feature is animportant difference between theRolex and Patek Philippechronograph mechanisms.

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The price of the Rolex Daytona,chronograph with case and bra-celet in white gold, is SFr.30,800. The price of the PatekPhilippe Ref. 5960P, flyback andannual calendar chronograph,with platinum case and alligatorstrap, is SFr. 68,000*

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