Escapement
The mechanism that divides time into equal steps
Watch the balance wheel oscillate as the pallet fork meters each beat of the escape wheel.
What it is
The escapement is the interface between the going train (which stores and delivers energy) and the regulating organ (the balance wheel and hairspring). It performs two jobs simultaneously: it releases the mainspring's energy in tiny, equal steps; creating the ticking sound; and it delivers a small impulse of energy to the balance wheel on each release to keep it swinging. Without the escapement, the mainspring would unwind in seconds.
History
The verge escapement, dating to medieval Europe (14th century), was the first practical escapement; crude, friction-heavy, and position-sensitive, but it made portable timekeeping possible. The cylinder escapement (George Graham, 1720) reduced friction significantly. The lever escapement, developed by Thomas Mudge around 1755, is the design that modern mechanical watches still use: it is robust, self-starting, and tolerates the shock and position changes of a watch on a moving wrist. George Daniels invented the co-axial escapement in 1974; a radically different impulse geometry that reduces sliding friction and extends service intervals. Omega licensed it in 1999; it remains the only fundamentally new escapement architecture to reach mass production in 250 years.
How it works
In a Swiss lever escapement, a fork-shaped lever sits between the escape wheel and the balance wheel. As the balance wheel swings, it unlocks the lever's banking; the escape wheel tooth slips forward one step and delivers an impulse to the lever, which passes that impulse to the balance wheel. The cycle repeats 5–10 times per second depending on the movement's beat rate. A 28,800 vph (beats per hour) movement ticks 8 times per second; a 36,000 vph hi-beat movement ticks 10 times per second. Higher frequency means finer time resolution and better shock resistance, at the cost of more energy consumption and faster wear on the pallets.
