Brief description

An ultra-high precision mechanical clock designed specifically to work at sea. Its main purpose is to allow navigators to determine geographical longitude by measuring the exact time at a reference meridian (such as Greenwich).

Use / Function

• Navigation: Determine longitude by comparing local time (solar) with chronometer time (home port time).
• Expeditions: Precise mapping of coastlines and islands.

Operating principle

Works like a refined mechanical watch but solves critical sea problems:

1. Balance Wheel: Replaces the pendulum (which doesn’t work on a moving ship).
2. Gimbal Suspension: Keeps the clock level regardless of the ship’s roll.
3. Thermal Compensation: Uses bimetallic strips in the balance wheel to adjust its shape and maintain a constant period under temperature changes.
4. Constant Force: A mechanism (fusee) equalizes the mainspring’s force as it unwinds.

How to create it

1. Mechanism: Similar to a pocket watch but larger and more robust.
2. Box: A wooden box with brass suspension (gimbals).
3. Adjustment: Requires months of calibration and testing at different temperatures.

Materials needed

• Essential: Brass (corrosion resistant), Steel (springs), Glass (cover), Wood (protective box).
• Tools: Maximum precision watchmaking tools.

Variants and improvements

• Atomic Clock: Modern successor, based on atom frequency (Cesium, Rubidium).
• Quartz Clock: Common electronic version today.

Limits and risks

• Cost: Historically extremely expensive and difficult to manufacture.
• Maintenance: Requires specialized cleaning and oiling.
• Cumulative Error: Even the best mechanical chronometer has a small drift that must be accounted for.

Related Inventions

• Timepieces
• Mechanical Clocks
• Mechanical Watch
• Sextant
• Escapement
• Balance Wheel