Complications  /  Tourbillon

Tourbillon

Also known as — Tourbillon regulator

The balance and escapement mounted in a turning cage, so that gravity’s effect on the rate averages out.

How it works

A pocket watch spends its day upright in a waistcoat pocket. In that position gravity pulls the balance and its spring slightly off centre, and the watch gains or loses a little differently in every position it is carried. Breguet’s answer, patented in 1801, was not to fight gravity but to average it out.

HOURS AND MINUTESRead as on any watch.THE CAGE, SEEN THROUGH AN OPENINGIt turns once a minute, so itsthree-armed bridge sweeps roundlike a small seconds hand.USUALLY AT SIX O’CLOCKThe position varies, and some makersshow the tourbillon only throughthe caseback.
On the dial, a tourbillon usually shows itself through an opening, most often at six o’clock, where the escapement can be seen turning. Some makers show it only on the back.
THE CAGECarries the balance, the lever and theescape wheel. The train turns itonce a minute.ESCAPE WHEEL AND PINIONIts pinion rolls round the fixed wheel,so the escapement keeps workingwhile the cage turns.FIXED WHEELScrewed to the plate. It never moves.BALANCEOn the cage’s axis. Its position againstgravity keeps changing, so the errorsof each position cancel over a turn.
The balance, lever and escape wheel ride in a cage that the watch’s train turns once a minute. The escape pinion rolls round a wheel fixed to the plate, so the escapement keeps working as the cage turns.

The price is complexity and energy. The cage is among the hardest assemblies in watchmaking to make, adjust and balance, and turning it takes power that would otherwise go to the escapement. On the wrist, which changes position constantly, its benefit to timekeeping is disputed.

Breguet sold his first tourbillon in 1805 and made about thirty-five. The device stayed a rarity for a century and a half, then returned from the 1980s as a showpiece of fine watchmaking, which is mainly what it is today.

Recorded here

Milestones with this mechanism

1801The first tourbillonAbraham-Louis Breguet patented the tourbillon in 1801: the escapement turns inside a rotating cage, so gravity’s pull on it averages out.Breguet