The coaxial escapement is a type of modern watch

escapement An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to t ...

mechanism invented by English watchmaker George Daniels in 1976 and patented in 1980. It is one of the few watch escapements to be invented in modern times and is used in most of the

mechanical watch A mechanical watch is a watch that uses a Movement (clockwork), clockwork mechanism to measure the passage of time, as opposed to quartz watches which function using the vibration modes of a piezoelectric quartz tuning fork, or radio clock, radio ...

models currently produced by

Omega SA Omega SA is a Swiss luxury watchmaker based in Biel/Bienne, Switzerland. Founded by Louis Brandt in La Chaux-de-Fonds in 1848, the company formerly operated as ''Louis Brandt et Fils'' until incorporating the name ''Omega'' in 1903, becoming ' ...

History

During the

quartz crisis The quartz crisis (Swiss) or quartz revolution (America, Japan and other countries) was the upheaval in the watchmaking industry caused by the advent of quartz watches in the 1970s and early 1980s, that largely replaced mechanical watches aroun ...

, English watchmaker George Daniels accepted a commission from American industrialist and watch collector Seth G. Atwood to create a timepiece that would fundamentally improve the performance of mechanical watches. As a result, Daniels invented the coaxial escapement in 1974 and patented it in 1980. The ''Atwood watch'' for Seth G. Atwood was completed in 1976.

Influences

Charles Fasoldt

Charles Fasoldt, a German-American watch- and clockmaker, was instrumental in the development of the escapement mechanism. His patented escapement of 1865 introduced a novel duplex design with co-axially mounted twin escape wheels and a three-pallet lever. This design was aimed at reducing friction and enhancing the accuracy of timekeeping, which would later influence modern escapement designs. George Daniels' co-axial escapement, a significant advancement in the field of

horology Chronometry or horology () is the science studying the measurement of time and timekeeping. Chronometry enables the establishment of standard measurements of time, which have applications in a broad range of social and scientific areas. ''Hor ...

, drew from Fasoldt's concepts, refining them further for contemporary watchmaking.

Abraham-Louis Breguet

Abraham-Louis Breguet's 'natural escapement' also significantly influenced Daniels. Breguet's design involved two

detent A detent is a mechanical or magnetic means to resist or arrest the movement of a mechanical device. Such a device can be anything ranging from a simple metal pin to a machine. The term is also used for the method involved. Magnetic detents are ...

-like escape wheels arranged in a mirrored layout. Daniels evolved this by removing the meshing gears between the twin escape wheels, thus creating two independent gear trains, enhancing the escapement's practicality for contemporary watchmaking.

Technical overview

The coaxial escapement is a modification of the

lever escapement The lever escapement, invented by the English clockmaker Thomas Mudge in 1754 (albeit first used in 1769), is a type of escapement that is used in almost all mechanical watches, as well as small mechanical non-pendulum clocks, alarm clocks, a ...

with some features of the

detent escapement An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to t ...

. One of the few advances in escapement design which have been adopted since the invention of the lever escapement by Thomas Mudge in the 18th century, the coaxial escapement functions with a system of three

pallet A pallet (also called a skid) is a flat transport structure, which supports goods in a stable fashion while being lifted by a forklift, a pallet jack, a Loader (equipment), front loader, a Jack (mechanical), jacking device, or an erect cra ...

s that separate the locking function from the impulse, avoiding the

sliding friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of friction include dry, fluid, lubricated, skin, and internal -- an incomplete list. The study of t ...

of the lever escapement. This makes

lubrication Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology. Lubrication mechanisms such as fluid-lubr ...

of the pallets theoretically unnecessary Archived article page
2

3
an
4
and thereby minimizes one of the shortcomings of the traditional lever escapement. In practice, a small amount of lubrication is used on the locking and impulse surfaces of the pallet stones, reportedly to minimize impact corrosion.

Critical virtue

The critical virtue of the Daniels escapement is the virtual elimination of the sliding friction component; i.e., the sliding of the

pallet stone A pallet (also called a skid) is a flat transport structure, which supports goods in a stable fashion while being lifted by a forklift, a pallet jack, a front loader, a jacking device, or an erect crane. Many pallets can handle a load of ...

s over the teeth of the

escapement gear An escapement is a mechanical linkage in mechanical watches and clocks that gives impulses to the timekeeping element and periodically releases the gear train to move forward, advancing the clock's hands. The impulse action transfers energy to ...

. What little sliding friction remains is due to the impossibility of maintaining an exact tangential geometry throughout the duration of an impulse.

Radial friction vs. sliding friction

By utilizing radial friction instead of sliding friction at the impulse surfaces the coaxial escapement significantly reduces friction, theoretically resulting in longer service intervals (though many factors influence this including lubricant aging) and greater accuracy over time.

Commercialization

The escapement was commercialized in 1999 by

when it introduced the first mass-produced watch incorporating the technology. It is the only escapement other than the Swiss

that is produced on an industrial scale. When it first came to the market as the Caliber 2500, it had an oscillation rate of 28,800 beats per hour (8 beats per second), considered a "hi-beat" movement. But the rate was reduced to 25,200 beats per hour (7 beats per second) in the Caliber 2500C. "While Daniels has recognized the advantages of higher beat movements, he has also noted that they aggravate the problem of sliding friction in the escapement (at the escape teeth and pallets). Higher beat movements produce increased speed and pressure at these critical surfaces."Zbinden, H., Zbinden, H., Of Larger Balances, High Beat and Important Oils, TZ Classics No. 1591, Timezone, Dec. 26, 2000, quoting Odets, W.

References

External links

Description and animation of Omega's co-axial escapement

A technical perspective The co-axial escapement
by Xavier Markl
Questions in Time column about the history leading to the co-axial escapement
{{Webarchive, url=https://web.archive.org/web/20100421085157/http://www.europastar.com/europastar/watch_tech/nicolet8.jsp , date=2010-04-21 by Professor J. C. Nicolet
Clear images, and an animation, of the co-axial escapement
by Siméon Lapinbleu

Mark Headrick's Horology Page Escapements