Brief description

The escapement is the “heart” of a mechanical clock or watch. It is a mechanism that blocks the gear train and allows it to advance a fixed amount at each swing of the oscillator (pendulum or balance wheel). It serves two crucial functions: counting the oscillations and providing energy to keep the oscillator moving.

Use / Function

Regulation: Controls the speed at which the clock’s gears turn, ensuring accurate timekeeping.
Energy Transfer: Delivers a tiny push (impulse) to the pendulum or balance wheel to overcome friction and air resistance.
Sound: Creates the characteristic “tick-tock” sound of mechanical timepieces.

Operating principle

The escapement converts the continuous rotational force of the gear train into the back-and-forth motion of the oscillator.

Lock: A tooth of the escape wheel is caught by a pallet on the anchor or lever, stopping the gear train.
Impulse: As the oscillator swings, it moves the pallet, unlocking the wheel. The wheel turns slightly, and a tooth pushes against the pallet, transferring energy to the oscillator.
Drop: The tooth escapes the pallet, and the wheel turns freely for a brief moment until another tooth locks against the other pallet.
Repeat: The process repeats with each swing.

How to create it

Creating an escapement requires high precision. The geometry of the teeth and pallets is critical.

Escape Wheel: Cut a wheel with specially shaped teeth (e.g., pointed for anchor, club-shaped for lever).
Pallets: Fabricate the locking components (pallets). In high-quality watches, these are made of synthetic Ruby to reduce friction. In clocks, hardened Steel is common.
Geometry: Ensure the distance between the escape wheel center and the pallet axis is exact so that the locking and impulse actions occur correctly.

Materials needed

Escape Wheel: Brass (work-hardened) or Steel.
Pallets: Hardened Steel or Ruby (Jewels).
Arbors: Polished Steel for low-friction pivoting.

Variants and improvements

Verge Escapement: The earliest type, used with a foliot. High friction, low accuracy.
Anchor Escapement: Used in Pendulum Clocks. Allows for a smaller pendulum swing and better accuracy.
Deadbeat Escapement: An improvement on the anchor that eliminates recoil, providing higher precision.
Lever Escapement: The standard for Mechanical Watches. It is detached, meaning it only touches the balance wheel briefly, improving accuracy.
Co-axial Escapement: A modern invention reducing friction further.

Limits and risks

Friction: Sliding friction between teeth and pallets requires lubrication (oil), which degrades over time.
Wear: The constant impact of teeth against pallets wears them down, changing the geometry and timing.
Adjustment: Extremely sensitive to position and alignment. A small error can stop the clock.