· By Buffy
Cylinder and Duplex
The watch escapements between the verge and the lever: the deadbeat cylinder, the clever duplex, and why both were displaced by the detached lever.
Between the crude verge and the modern lever sit two clever compromises that powered the pocket-watch century: the cylinder and the duplex.
The cylinder escapement
Patented in refined form by Thomas Tompion and others around 1700 (the idea is credited to Graham, c. 1720s), the cylinder escapement replaces pallets with a hollow, notched cylinder on the balance staff. Escape wheel teeth pass inside the cylinder wall, giving impulse through the cylinder’s lip.
- Virtue: flat — perfect for the slim pocket watches the 18th century adored. Cheap enough for mass production.
- Vice: the balance staff is a wearing part (it is the escapement surface), so it wears out; and the balance is never detached — the tooth rests against the cylinder between beats, so rate depends on driving torque.
A well-made cylinder watch keeps a few minutes a week; a worn one owns your patience. Breguet and the observatory makers never loved it.
The duplex
The duplex separates the two jobs: a tall tooth locks the balance’s ruby roller directly (frictionless-ish lock), while a second set of teeth gives impulse through a single impulse pin on the balance.
- Virtue: near-detached locking, so it can be very accurate — duplex pocket watches won prizes.
- Vice: fragile under shocks (“trip” failures), tricky to start after stopping, and it cannot tolerate a slipping seconds hand.
Why the lever won
The Swiss lever offered almost the duplex’s detachment with the cylinder’s robustness — and, crucially, it tolerates the modern shock setting era: a knocked wrist doesn’t double-unlock it, thanks to the safety action. By the late 1800s the lever had won the wrist; the cylinder survived only in cheap mass production into the early 20th century.
The escapee’s-eye view of progress: each design pushed friction into a smaller window until the window became the co-axial and detent debates of today.