Detent (Chronometer) Escapement
Also known as: Chronometer escapement, Spring detent escapement
Record status
Individual type · partial
Period
1748 onwards (final form about 1800)
The detent, or chronometer, escapement was used in marine chronometers, and in some precision watches of the eighteenth and nineteenth centuries. It is a detached escapement: the balance wheel swings undisturbed for most of its cycle and receives an impulse only once per cycle, on every other swing.
Because the driving escape-wheel tooth moves almost parallel to the pallet, the escapement has little friction and does not need oiling. For these reasons, among others, it was considered the most accurate escapement for balance-wheel timepieces until the early twentieth century, when lever-escapement chronometers began to outperform it in competition. Its drawbacks limited its use in watches. It was fragile and needed skilled maintenance; it was not self-starting, so a balance stopped by a jolt would not start again; and it was harder to make in quantity. The self-starting lever escapement therefore became the dominant watch escapement.
Evidence at a glance
- Linked sources
- 1
- Photograph views
- 1
- Catalogue references
- 0
Counts describe this entry’s documentation, not authenticity, rarity or completeness. Photographs may show one specimen; check each caption and licence.
Historical context
Pierre Le Roy made an early, pivoted form of detent escapement in 1748, though it was theoretically deficient. John Arnold devised the first effective design around 1775, also with a pivoted detent, and later a spring detent. Thomas Earnshaw modified the escapement in 1780, and it was patented in 1783 by Wright, for whom he worked, although the version shown in the patent was unworkable. Earnshaw's spring-detent version eventually prevailed; its final form appeared around 1800 and was used until mechanical chronometers became obsolete in the 1970s. Arnold was the first to combine the detent with an overcoil balance spring, patented in 1782, and his watches made from 1783 kept time to within one or two seconds a day.
Technical characteristics
- Type
- Detached escapement
- Impulse
- Once per cycle (every other swing of the balance)
- Lubrication
- Not needed; little friction at the impulse
- Self starting
- No
Identification
- Source note
- Background drawn from Wikipedia (“Escapement”), a tertiary source; details have not yet been checked against a standard horological reference.
- Identification
- Found chiefly in marine chronometers and some precision watches; a detached escapement that impulses the balance only on every other swing and is not self-starting
Catalogue references
No catalogue numbers recorded. Numbers are only published once transcribed from a verified edition of a standard catalogue — they are never inferred.
Research required
- Signed, dated marine chronometers from institutional collections still to be linked as examples.