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The Encyclopedia of Horology

Complication · Precision

Double Escapement with Differential

Partially verified

A movement using two separate balances and escapements linked by a differential gear.

Definition

A movement using two separate balances and escapements linked by a differential gear.

Historical origin

Averages the rates of two oscillators to improve overall accuracy.

How it works

A differential gear (similar to a car's) sits between the mainspring and the two escapements.

It distributes power to both and averages their output back to the hands.

Pocket watch context

Pioneered by Antide Janvier and later Ferdinand Berthoud.

Wristwatch context

Perfected in the modern era by Philippe Dufour (Duality) and Greubel Forsey.

Identification

  • Two balance wheels beating simultaneously
  • A differential gear visible in the centre

Servicing notes

Extremely difficult to regulate; both escapements must be closely matched.

General guidance only. Complicated mechanisms should be assessed and serviced by a qualified watchmaker or clockmaker specialist, not adjusted at home.

Diagram

balance wheel with timing screwsflat or overcoil hairspringregulator index
Schematic: balance, hairspring and regulator. An outline schematic drawn to show the arrangement of the parts discussed here. It is not a dimensioned working drawing and does not depict a particular maker's calibre.

Sources & references

  1. de Carle, D., Watch and Clock Encyclopedia
  2. Britten, F. J., Old Clocks and Watches and Their Makers
  3. Horological Journal (British Horological Institute), technical articles

Where sources disagree, the disagreement is stated rather than resolved silently.