Complications  /  Automatic winding

Automatic winding

Also known as — Self-winding, perpetual, rotor winding

A pivoted weight that winds the mainspring from the wearer’s own movement, through a reduction train to the barrel.

How it works

A hand-wound watch must be wound daily, and each winding turns the crown, which turns the stem: the largest opening in the case and the main route by which dust, perspiration and water reach the movement. There was also the spring itself. A watch wound each morning runs at its highest torque in the hours afterwards and its lowest before the next winding, so its rate wanders across the day, and a watch forgotten for a day stops.

HARWOOD, 1923about half a turn, striking a bufferspring at each end; no crown at allROLEX, 1931a full circle, unobstructed:quieter, gentler, better at small movements
Harwood’s weight bounced between sprung buffers and wound in one direction only. Removing the buffers let the weight keep its momentum all the way round, which is the arrangement almost every automatic watch has used since.

John Harwood patented the first workable self-winding wristwatch in 1923 and reached production through Fortis in 1926. His weight was a pivoted segment swinging through a restricted arc between two buffer springs, winding in one direction only, and his watch had no crown at all: the hands were set by turning the bezel. Rolex’s Oyster Perpetual of 1931 removed the buffers and let the weight turn through a full circle, which wastes no energy striking anything and harvests small movements of the wrist far better.

Early rotors still wound in one direction, the other simply free-wheeling. Bidirectional winding uses reverser wheels, each a wheel and pinion coupled by hooked pawls that lock one way and slip the other. Two of them sit in the train so that whichever way the rotor turns, one locks and drives while the other slips, and the drive delivered to the barrel is always in the winding direction.

The costs are height and wear. A rotor and its reduction train add roughly two millimetres, which is why automatic chronographs and automatic calendars arrived so much later than their hand-wound equivalents, and the rotor bearing is the hardest-worked bearing in the watch. Because the wearer cannot be stopped from winding indefinitely, the mainspring is not anchored to the barrel wall but held by a sliding bridle that slips when the spring is full.

Recorded here

Milestones with this mechanism

1923The first automatic wristwatchJohn Harwood patented the first self-winding wristwatch in 1923; Fortis put it into production.Fortis1931The first free winding rotorRolex let the winding weight turn a full circle freely, the self-winding system nearly every automatic watch still uses.Rolex1945The first automatic chronometer with dateRolex’s Datejust of 1945 was the first self-winding, waterproof, chronometer-certified wristwatch with a date in a window.Rolex1953The first modern diver’s watchBlancpain’s Fifty Fathoms put together the features that define a diver’s watch, above all a rotating bezel that cannot be knocked out of place.Blancpain1956The first day-date wristwatchThe Rolex Day-Date of 1956 was the first wristwatch to show the day spelled out in full and the date, each in its own window.Rolex1969The first high-beat chronographZenith’s El Primero, calibre 3019 PHC, was the first chronograph to run at 36,000 vibrations an hour, fine enough to time a tenth of a second.Zenith1969The first automatic chronograph soldSeiko’s calibre 6139 was the first self-winding chronograph to go on sale, in Japan in May 1969.Seiko1969The first modular automatic chronographHeuer, Breitling, Hamilton-Büren and Dubois Dépraz built Calibre 11 by adding a chronograph module to a thin self-winding movement.Heuer1777The first self-winding watchAbraham-Louis Perrelet of Le Locle is credited with a pocket watch that wound itself as its owner walked.Perrelet