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The Encyclopedia of Horology

Component record · Plates & finishing

Bridges

Verified

Individually shaped metal supports, fixed at both ends (or more), each carrying the upper pivot(s) of one or more train components.

What it does

Support and locate wheel and escapement pivots in movement architectures built from separate bridges rather than a single full plate.

How it works

Rather than a single full plate covering the entire train (as in the English full-plate tradition), a bridge (or 'bar') movement supports each wheel, or a small group of wheels, on its own separately shaped and fitted bridge, screwed to the main plate.

This construction makes the train more accessible for assembly, adjustment and repair — a technician can remove a single bridge to service one wheel without disturbing the rest of the train — and became strongly associated with Swiss ébauche manufacture as production scaled up in the 19th and 20th centuries.

Bridge shapes and finishing (Geneva stripes, bevelled and polished edges) are also a visible marker of movement grade and manufacturer style, distinct calibres often being recognisable by their characteristic bridge layout.

Evolution

The bridge/bar construction progressively displaced the English full-plate and three-quarter-plate architectures in mass production through the 19th and 20th centuries as Swiss manufacture came to dominate the industry.

Known variations

  • Full-plate architecture (English tradition)
  • Three-quarter plate architecture
  • Separate bridge (bar) architecture (Swiss/French tradition)

Identification for collectors

  • Movement architecture — full plate, three-quarter plate, or separate bridges — is one of the fastest ways to place a movement's national tradition and rough period

Common failure modes

  • Bent or cracked bridges from mishandling
  • Stripped screw holes from repeated servicing

Photographs

US Navy 061116-N-2959L-096 Lt. Cmdr. Christopher Mercer and Lt. Cmdr. Karen Sray converse with the Conning Officer about the ship's movement while standing watch on the bridge
US Navy 061116-N-2959L-096 Lt. Cmdr. Christopher Mercer and Lt. Cmdr. Karen Sray converse with the Conning Officer about the ship's movement while standing watch on the bridge — U.S. Navy photo by Mass Communication Specialist 3rd Class Dominique M.Lasco, Public domain. Wikimedia Commons file page

Photographs are illustrative examples of the type, not necessarily the exact object described. Verify details against the source file page.

Sources & references

  1. Daniels, G., Watchmaking

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