Lovers of mechanical watches are very familiar with the interplay between the balance wheel, pallet fork, and escape wheel. Sometimes visible through display case backs, this interaction – as well as its distinctive ticking sound – is responsible for the fascination many of us have with mechanical watches more than any other function or part. The escapement is simply the heart of all mechanical wristwatches.
Escapements have been beating in more or less the same fashion for over a quarter of a millennium now. When I say that, I’m referring to the anchor escapement, originally invented for grandfather clocks by George Graham in the 18th century, and later adapted to portable timepieces by his protégé Thomas Mudge. After several different structural iterations, Mudge’s work culminated in the Swiss anchor escapement, which retained the basic functionality of earlier models but included numerous improvements.
While various escapements were developed in subsequent years, many of which appeared to be superior to the Swiss anchor escapement in one way or another, most of the “advantages” only existed on paper. Aside from being used in select stationary clocks, none of the designs ever made it into mass production. This ultimately came down to their complexity and lack of adjustability, durability, reliability, or ability to withstand the demands of everyday life on the wrist.
The renaissance of mechanical watches caused a desire for innovative and unique designs, driving a resurgence in escapement development.
This is the first in a series of articles that will cover these new developments. We’ll be looking at concepts that are now well established and mass-produced across the industry, as well as promising innovations that are still in the early stages of development. Above all, I want to highlight what’s driven these inventions and what sort of advantages and disadvantages each offers.
George Daniels’ Legacy: The Co-Axial Escapement
We’ll start with the famous co-axial escapement. The basic idea behind this design can actually be traced back to Breguet, but it was later honed and perfected by a good friend of the famed watchmaker George Daniels.
It’s no exaggeration to say that Daniels is one of the most talented and important watchmakers of the modern era. That statement is only underscored by the fact that he questioned and ultimately redeveloped a concept that had been in use for some 250 years. He closely analyzed the weaknesses of the anchor escapement, but also sought to retain its strengths: its robustness, free construction, and precise transmission of the impulse with every half oscillation. The greatest shortcoming, in his opinion, was the need for lubrication on the faces of the escape wheel. The oil used for lubrication was sensitive to temperature fluctuations and had a limited lifespan.
This video demonstrates how a co-axial escapement works
The use of lubrication was necessitated by the fact that the escape wheel was subject to friction whenever it transmitted impulses via the pallet fork. If you’re looking to minimize friction (and thus the need for lubrication), it makes sense to look to an established, largely friction-free escapement: the chronometer escapement. Here, the escape wheel delivers the impulse directly to the balance wheel with each full oscillation (as opposed to every half oscillation with the anchor escapement). The impulse is transmitted tangentially, similar to how we would push a merry-go-round. This style of transmission doesn’t require a radial force component nor does it involve any relative movement, resulting in no friction.
But why did it take 250 years for someone to think of this, despite watchmakers being well aware of the weakness in the anchor escapement’s design? It wasn’t due to an absence of concepts or ideas, but rather a lack of market orientation and mindset for mass production.
Predecessors and Relatives of the Co-Axial Escapement
One prominent example of an escapement with tangential transmission is the “Echappement Naturel” by none other than Abraham-Louis Breguet himself. Breguet’s design can be recognized by its dual escape wheels interacting with the gear train, though a mainspring drives both wheels. In this design, the pallet fork merely serves to stop the gear train. The impulse is transmitted directly via the escape wheels in alternate fashion depending on the direction of the balance oscillation. On paper, this is an ingenious solution that promises virtually friction-free power transmission.
In practice, however, friction on the axis of the additional escape wheel and especially the play in the serially coupled wheels meant that the performance was much worse than that of anchor escapements from that era. Upon realizing this, Breguet resorted to the established anchor escapement construction to ensure his watches ran more precisely.
Nevertheless, his escapement design played a crucial role in the eventual development of the co-axial escapement. Watchmaker George Daniels devoted himself to improving upon the original concept. He sought to drive each escape wheel individually to minimize the backlash and avoid the issue of extreme tolerance requirements, both of which were responsible for the disappointing performance of Breguet’s design. Daniels achieved his goal with the addition of a second mainspring and gear train.
George Daniels and Derek Pratt
This is where a third party enters the story: Daniels’ no less talented contemporary and friend Derek Pratt. He worked alongside Daniels in his exploration of Breguet’s original design, as well as his eventual new variant. The relative underrepresentation of Pratt compared to Daniels in watch media probably comes down to the fact that he didn’t introduce a big name brand like Omega to what would go on to become a mass-produced component like the co-axial escapement.
Pratt was also known to be a humble character, which means he likely didn’t boast about making particularly intricate components like the highly complex escape wheel for Daniels’ watches. He also supported his friend in negotiations with Omega, the brand that eventually made the escapement concept a commercial success. Daniels, in turn, failed to publicly honor Pratt’s contribution during his lifetime – a minor smudge on an otherwise great character. Watchmaking was undoubtedly a major passion for both men, but unlike Daniels, who spent years seeking commercial success with the co-axial escapement, Pratt’s ambitions were of a different nature.
In addition to directly contributing to the production and commercial breakthrough of Daniels’ invention, Pratt made several other contributions to the area of escapement development.
Many of Pratt’s pocket watches – the majority of which were created for the Urban Jürgensen & Sønner brand – easily earn the title of masterpiece. But one watch in particular really stands out: the timepiece Pratt made for a competition in celebration of Breguet’s 250th birthday.
In this pocket watch, Pratt not only combined the Echappement Naturel with Breguet’s most famous invention, the tourbillon, but he also provided both escape wheels with a remontoire, a mechanism that ensures constant power transmission. He didn’t opt for Daniels’ design with two separate gear trains, since the concept couldn’t be combined with a tourbillon.
Pratt supposedly later served as the motivating force behind the realization of George Daniels’ version of the Echappement Naturel in a superlative timepiece: the Double Impulse Chronometer by Charles Frodsham. This watch drew on the genius of all three watchmakers: the original concept from Breguet, Daniels’ improved escapement design, and Pratt, who introduced the Frodsham brand to Daniels’ work and helped guide the project.
The Essence of the Co-Axial Escapement
So, why talk about all of these preceding variants? Well, the co-axial escapement is often presented as a perfected version of the anchor escapement, which – despite the visual similarity – is only partially true. The truth of the matter is that it is equally related to the chronometer escapement, at least conceptually. Breguet attempted to combine the principles behind the chronometer escapement with the reliability of the anchor escapement. It is no coincidence that in his classic text Watchmaking, Daniels starts out by mentioning the anchor escapement and chronometer escapement, before describing the Echappement Naturel as a combination of the best of both designs. He goes on to discuss his dual-drive variant, which he refers to as the independent double-wheel escapement, before landing on the development of the co-axial escapement. Co-axial simply refers to the fact that two wheels share the same axle.
Derek Pratt put it quite concisely in 2009, when he said that Daniels dedicated himself to developing the co-axial escapement to eliminate the complication of the second gear train. The co-axial escapement can, therefore, be thought of as a variant of the previous independent double-wheel escapement or even an improvement on the Echappement Naturel, at least when you consider the number of total components and the space required in the watch. It was probably this reduction in structural complexity that paved the way for the co-axial escapement to be mass-produced, while all prior variants of the double-wheel escapement are relegated to niche existences in high-end brands and select timepieces.
So, that more or less covers how we arrived at the co-axial escapement, but what does the future hold? Well, it’s looking bright! Thanks to Omega putting the escapement into series production, it is finding its way into more and more models that are significantly more affordable than the masterpieces linked to George Daniels. If you are a Daniels diehard, however, don’t despair. His protégé Roger Smith isn’t just curating the master’s legacy, but continues to push the co-axial design even further.