Escapement

Specification

Technical parameters

Overview

The escapement does two jobs at once. It locks the gear train so the mainspring's energy is released in discrete portions rather than all at once, and it gives the balance a small push on each oscillation so the balance keeps swinging instead of dying out. Every tick you hear is a locking and unlocking event.

In a Swiss lever escapement an escape wheel tooth rests against a jewel pallet on the fork. As the balance swings past centre, its impulse jewel rotates the fork, which unlocks one pallet, lets the wheel advance, and pushes the balance on its way. Then the other pallet locks the next tooth. The cycle repeats twice per oscillation.

The geometry that matters is lift angle — how far the balance travels while it is being impulsed — and lock, the small margin by which a tooth rests safely on a pallet. Too little lock and the escapement can skip under shock; too much and amplitude suffers because more energy goes into unlocking.

What matters about it

• Locks the train and impulses the balance in one mechanism
• Lift angle must be known to read amplitude correctly
• Pallet jewels are the only lubricated bearing faces
• Lock and drop are set by geometry, not by adjustment
• Coaxial variants separate locking from impulse

Practical notes

• Always let the power down before removing a pallet fork.
• Oil the pallet faces sparingly and only on the locking faces — oil on the impulse faces causes sticking.
• A watch that gains dramatically and intermittently is likely knocking: check amplitude first.
• Enter the correct lift angle in your timegrapher, or every amplitude reading will be wrong.

Compatible with