Things that come apart

Popular Mechanics (South Africa) - - Contents -

Get­ting inside a wrist­watch

NOTES: Sure, Shi­nola’s move­ments use Swiss parts. If you want a good time­keeper, you get the parts from Switzer­land. But the folks do­ing the hard part – as­sem­bling the tiny pieces into a watch – are all-amer­i­can. Even Olivier de Boel, Shi­nola’s fac­tory man­ager, who ex­plained to us in ex­act­ing de­tail how the watch works, was in awe of the keen eye­sight and steady hands re­quired to build one of the com­pany’s time­pieces. And with the ex­cep­tion of dis­pens­ing lu­bri­cat­ing oil and check­ing for im­per­fec­tions, the crafts­men do the work with­out mag­ni­fi­ca­tion. Which is more than we can say for the picture at right.

THE QUARTZ

The move­ment – the parts of the watch that pro­duce its mea­sure­ments of time – is con­structed like a round metal sand­wich. The main plate (13) is the bot­tom piece of bread. The fill­ings are the power sys­tem, the pro­ces­sor and the gear train that turns the watch’s hands. Bridges (18) are like the in­ter­me­di­ate piece of bread in a dou­ble-decker: metal plates that prop­erly space the parts and pro­vide pro­tec­tion and rigid­ity. The top piece of bread is the dial sup­port (12), which cir­cum­scribes the date rings, the up­per­most por­tion of the move­ment.

The Run­well has a quartz move­ment, in which the tick­ing is reg­u­lated by a quartz crystal that is in­te­grated with a mi­crochip in the elec­tronic mod­ule (16). Quartz is piezo­elec­tric: elec­tric­ity causes it to vi­brate. When cur­rent from the bat­tery (2) is sent through the crystal, it vi­brates at 32 768 Hz. From this the mi­crochip de­rives an elec­tric sig­nal that pulses once ev­ery sec­ond.

THE CUR­RENT TIME

The elec­tric pulses are di­rected to­wards a coil (3) to gen­er­ate a mag­netic field. The coil is linked to a sta­tor (23) through which a ro­tor (14) pro­trudes. The mag­netic field causes it to ro­tate 180 de­grees ev­ery sec­ond. In ef­fect, this cre­ates an elec­tric mo­tor whose en­gine speed is mea­sured, not in revo­lu­tions per minute, but sec­onds.

The gear that links the mo­tor to the read­out on the dial (4) is called the can­non pin­ion (8); the gears that cor­re­spond to spe­cific units of time are called, un­sur­pris­ingly, the sec­ond wheel (5), minute wheel (22), and hour wheel (27). The watch’s hands (1) mount to the gears with a press-fit sys­tem: posts on the un­der­side of the hands seat in cylin­ders cen­tred on the gears. The sys­tem is lu­bri­cated with small amounts of oil in lit­tle red com­part­ments called jew­els (17) be­cause they used to be made of hard pre­cious stones that would re­sist wear. To­day, they’re smooth, syn­thetic ruby.

The time is set man­u­ally by pulling the crown (9) on the end of the set­ting stem (10) to the sec­ond of its two po­si­tions. In this po­si­tion, its set­ting lever (15) en­gages the minute wheel, so that as the crown is ro­tated, the minute and hour hands turn. (The can­non pin­ion acts as a clutch so the mo­tor doesn’t fight the wearer as they set the time.)

THE DATE

The date func­tion is linked to the time­keep­ing gear train, and is set by pulling the crown to its first po­si­tion. Whereas some watches use a sin­gle date ring num­bered from one to 31, the Run­well uses two rings, the units in­di­ca­tor (19) and the tens in­di­ca­tor (20). The tens in­di­ca­tor is po­si­tioned on top and has win­dows (21) that show the units digit, un­less it is the 20th, 30th, or 31st day of the month.

THE CHRONO­GRAPH

There are three more small elec­tric mo­tors reg­u­lated by the quartz’s vi­bra­tions, all for the chrono­graph: one for its tenths-of-a-sec­ond hand, lo­cated on the six o’clock sub­dial (25); an­other for minutes and hours, lo­cated on the nine o’clock sub­dial (26); and one for the large sec­ond hand. If the chrono­graph is not be­ing used, none of these mo­tors re­ceives elec­tric­ity. But if the wearer presses the top but­ton (6) on the case (24), its spring (7) ac­ti­vates a cir­cuit that de­liv­ers power to the mo­tors and the hands turn. When the bot­tom but­ton (11) is pressed to re­set the chrono­graph, the mi­crochip de­liv­ers enough pulses to re­turn all the hands to the 12 o’clock po­si­tion. – Kevin Dupzyk

A PHO­TO­GRAPH BY TODD MCLEL­LAN

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