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The Encyclopedia of Horology

Component record · Train

Alarm Hammer

Partially verified

The hammer sounding an alarm on a bell or gong.

What it does

Strikes rapidly when the alarm train is released.

How it works

A pinned or vibrating arrangement drives the hammer rapidly against a bell, gong or case back.

Evolution

Wristwatch alarms adapted the principle at much smaller scale.

Known variations

  • Bell alarm
  • Case-back alarm in wristwatches

Identification for collectors

  • A buzzing rather than ringing alarm usually means a hammer fouling its stop.

Common failure modes

  • Bent hammer arm
  • Weak hammer spring

Diagram

count wheel or rackdetenthammer and gongwarning piece
Schematic: striking and sounding work. 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., Practical Watch Repairing
  2. de Carle, D., Watch and Clock Encyclopedia
  3. Daniels, G., Watchmaking

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