Olivier Laesser: the great escapement

By Hubert de Haro / HdH Publishing

July 2023

At the end of an unprecedented investigation, this doctor in horology has drawn a “family tree” of the escapement through the centuries, introducing some fantastical anecdotes along the way. Such a colossal achievement could rekindle interest in what is still a rather abstruse subject for the general public. We review the book and speak to its author.

Olivier Laesser: the great escapement

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By Hubert de Haro / HdH Publishing

July 2023

livier Laesser isn’t one to shirk a challenge. Holder of a PhD in theoretical and experimental horology, he spent almost a decade immersed in the vast and complex subject of escapements. The result is a fascinating book published by Les Éditions Simonin: “Les échappements en horlogerie mécanique - Histoire des multiples solutions apportées à un seul problème” (Escapements in mechanical watchmaking – A history of the multiple solutions applied to a single problem).

Over the course of the book’s 446 pages, Olivier Laesser presents almost two hundred escapements for clocks, marine chronometers, pocket watches and wristwatches. Prior to this, in 1913, Charles Gros had drawn up an inventory of 214 mechanisms in his “Échappements d’horloges et de montres”. There are thought to be many more. Rather than list these escapements alphabetically or chronologically, Olivier Laesser has classified them per type: frictional rest, lever, grasshopper, detent, virgule, double wheel, constant-force, et cetera.

In 1913 Charles Gros drew up an inventory of 214 different escapements. There are thought to be many more.


Chronomètre Optimum by François-Paul Journe (2011), fitted with a High-Performance Bi-Axial Escapement (patent n° EP11405210.3) that draws on Abraham-Louis Breguet‘s natural escapement.: ©Montres François-Paul Journe

As they work their way through this vast maze, readers can spot “family ties” between these ingenious solutions and the escapements found in wristwatches today. An example would be Abraham-Louis Breguet’s natural escapement, with its two direct-impulse escape wheels. Developed in the early nineteenth century, it has inspired numerous watchmakers, most recently George Daniels for a watch displaying solar time and sidereal time, François-Paul Journe for his Chronomètre Optimum (calibre 1510), Laurent Ferrier for his Classic Micro-Rotor, as well as Kari Voutilainen. Each has interpreted Breguet’s concept in his own way to develop a specific and unique escapement.


Laurent Ferrier’s Square Micro-Rotor Blue (2015) shown next to its Dual escapement, inspired by Abraham-Louis Breguet’s natural escapement.: ©Laurent Ferrier

Maciej Miśnik, the 2022 winner of the Young Talent Competition whose judging panel includes Philippe Dufour, Giulio Papi and François-Paul Journe, opted for the pivoted detent escapement, presented in 1772 by John Arnold. The same escapement also inspired some of Arnold’s most renowned contemporaries: Ferdinand Berthoud, Pierre Le Roy and Robert Robin.


Demonstration models of the detent escapement. John Arnold (1736-1799) and Thomas Earnshaw (1749-1829) disputed its invention and the matter was settled before the English courts. The detent escapement remains popular and was used by self-taught watchmaker Maciej Miśnik, winner of the 2022 Young Talent Competition. Pages 343 and 344.: ©Olivier Laesser

The balance and spring, which joins the escapement in regulating the flow of power through the geartrain, is unchanged since 1675. Every watch mechanism stops and restarts 6, 8 or even 10 times a second. In watchmaking parlance, these are vibrations (“tick”) or oscillations (“tick-tock”) and are measured in Hertz. A mechanical movement with a frequency of 4 Hz makes four oscillations (four “tick-tocks”) per second. This sudden and repeated stopping and starting of the power source creates no end of difficulties: imagine having to brake and accelerate four times a second when driving a car! Yet this is what we expect from our mechanical watch, 24 hours a day, seven days a week, for decades.

This sudden and repeated stopping and starting of the power source creates no end of difficulties: imagine having to brake and accelerate four times a second when driving a car!


Four direct-impulse detached escapements (clockwise from top left): 1. Robert Robin, 2. Antoine Tavan, 3. George Daniels’ Co-Axial escapement, patented in 1979 and now used in Omega watches, 4. Unknown, similar to Grand Seiko’s Dual Impulse Escapement. Page 438.: ©Olivier Laesser

The mechanism whose job it is to release power in regular portions is called the escapement. The majority of escapements comprise an escape wheel, which meshes with the last wheel in the geartrain, and an anchor-shaped part called a pallet fork. This configuration is found in practically every mechanical watch in the form of a Swiss lever escapement. Any watchmaker will tell you that a considerable amount of power is lost by the escapement… perhaps the reason for its name?

Reducing power loss extends power reserve or increases chronometric precision, hence the escapement is a critical part when developing a new movement. As mentioned, the Swiss lever escapement has a virtual monopoly on today’s movements, but this hasn’t always been the case, as Olivier Laesser demonstrates in his book.

Europa Star: Who is the target readership for your book and what feedback have you had?

Olivier Laesser: Antoine Simonin, my publisher, and I agreed on a target audience of historians, technicians, engineers and scientists in the watch industry, and that’s who I wrote the book for. I think I’ve done what I set out to do, judging by the very different backgrounds of the people who’ve shared their thoughts. The first comments were to congratulate me on what I’d achieved, after which I got more specific feedback. Some of the nicest was from a teacher at CIFOM [Centre Interrégional de Formation des Montagnes Neuchâteloises - École Technique Le Locle] who said he used my “primitive” schemas to explain transmission of energy by the escapement.


Olivier Laesser imagined a method based on equivalences between complex gearing (left) and so-called primitive circles (right) to produce clearly understandable illustrations of any escapement.: ©Olivier Laesser

On page 326 you write that “I had to find every mechanism ever made, no matter who invented it, when they invented it or the intended application.” What was the biggest obstacle when completing this Herculean task and how long did it take?

This wasn’t actually the most time-consuming part. The method I used, plus a bit of practice, meant I could construct each model in just a few hours, although prior to that I did have the time it takes to write a doctoral thesis [around 4 years] to develop my method. The real work was sourcing and reading piles of books and articles in order to find correspondences between my “theoretical” escapements and actual escapements. As my reading progressed, I started to make connections between the stories surrounding these mechanisms and it became clear that the circumstances were just as important, if not more important, than the inventions themselves. That’s when I found myself face-to-face with the mammoth task of telling the stories that produced the most fantastic escapements.

“The method I used, plus a bit of practice, meant I could construct each model in just a few hours.”


Two examples of tree diagrams devised by Olivier Laesser that group several escapements. Each escapement is shown in its “primitive” (Laesser’s own concept) form to facilitate understanding. Left: tree diagram of primitive recoil escapements. Right: tree diagram of frictional rest escapements. Pages 316 and 323.: ©Olivier Laesser

In a “moment of grace”, as you describe it, you realised that any escapement can be broken down and simplified as equivalent primitive circles. This methodological discovery set you on an unprecedented mission to group every known escapement in a single tree diagram. With each turn of the page readers are willing you to reach your goal and conceptualise your own escapement. Looking back, how do you view your methodology and are you still adding to your first diagrams?

The method works and I have to say I am quite proud of it. I decided to focus on escapements that function in a plane or on parallel axes, and those diagrams are complete. I could add escapements on perpendicular axes but I don’t see the point. My aim was to give readers an overall view, so I left out a few peculiar escapements, ones that have their own unique functioning: gravity escapements that aren’t constant-force, others that act on the balance spring rather than the balance wheel, ones that give two impulses from the same pallet, that kind of thing. If anything, I could work on those. Maybe I will, one of these days.

The envelope method is fascinating. Where did the idea come from?

It’s the same envelope method that’s used to draw gear teeth. Exactly the same principle. Only the profiles change. It is a very elegant method.


Readers (and who knows, maybe their children, too!) can try their hand at the envelope method and, step by step, draw the contour, or profile, of a gear tooth that will mesh with another gear tooth.: ©Olivier Laesser

There is a remarkable graphic coherence across all the illustrations that facilitates understanding while leaving the reader free to make their own comparisons. Did you produce every one of these hundreds of schemas yourself?

Every single one, taking care that each mechanism was fully functional on paper at least. My main objective was to facilitate comprehension. Let me give you an example: if you illustrate a clock escapement with 30 teeth in a drawing that’s 148 x 105 mm, you won’t see which tooth engages with which pallet, whether it’s the top or bottom face that makes contact, and whether it happens during the locking or impulse phase. You couldn’t even objectively say which direction the wheel is turning. If, on the other hand, you take the same type of escapement but with a dozen teeth, you immediately see how the wheel and the pallet fork interact. Hopefully, as you say yourself, this will encourage the reader to focus on what makes an escapement, what it is rather than what it looks like.

You’ve listed and described some 150 escapements: cylinder, frictional rest, crown-wheel, detent, virgule, etc. In your remarkably modest epilogue, you own the failure of your “primitive dual-impulse escapement” and, in doing so, confirm an impression that runs throughout the book: every escapement is the result of human ingenuity and a certain amount of luck. The harder you work, the “luckier” you are, obviously, but do you really believe watchmaking’s greatest inventions come down to a happy coincidence?

Absolutely! Out of the 150 escapements in the book and the several hundred others that exist, look at how many, or rather how few, have actually been used. At best a dozen escapements have been used over a prolonged period by multiple watchmakers. Overall, it seems that luck does play a part. Having said that, figures such as Robert Hooke, Thomas Mudge and Pierre Le Roy, Galileo and Christiaan Huygens brought about advances in horology less by chance and more through talent.

“Of the 150 escapements in the book and the several hundred others that exist, at best a dozen have been used over a prolonged period by multiple watchmakers.”


In 1802 watchmaker Ferdinand Berthoud published his “Histoire de la mesure du temps”, a richly illustrated compendium of horological knowledge at that time. In these pages, Berthoud shows how “various escapements” function. The curious reader can try and recognise the different types using Olivier Laesser’s book as a reference. For example, the crown-wheel escapement (fig. 1), George Graham‘s cylinder escapement (fig. 2) and the Le Roy-Robin direct-impulse detached escapement (fig. 13).

Some readers will enjoy the historical aspects of the often extraordinary tales behind certain discoveries: Huygens’ balance spring and the calculation of longitude to name but two. Others will find valuable information for developing new escapements. In your opinion, what’s the main benefit of reading your book?

I know some readers use it as an encyclopaedia, to research a particular escapement or person. I wrote the book along historical, technical and scientific lines and, with hindsight, I don’t think these can be separated. If you want my opinion, you have to read it from start to finish to fully benefit.

If you had to do it again, would you?

Not on your life!

TESTIMONIAL

“There was a gap to be filled and this book does just that.” ANTOINE SIMONIN, PUBLISHER

“It was my dream to publish a book that would trace the history and development of the escapement. While much had already been written on the subject, no author had as yet presented a global view.

As a teacher of watchmaking, the question of escapements comes up almost daily. When talking with students, from apprentices to experienced watchmakers and fellow teachers, it became clear that the majority had no idea how escapements had developed over time and were unfamiliar with the finer details of their functioning. Something was missing and, as a publisher, I wanted to fill that gap.

When I met Olivier Laesser, I knew he was the ideal person for the job. His thesis, “Analysis, synthesis and creation of horological escapements using gear theory”, written within the framework of the Micromechanical and Horological Design Laboratory EPFL-STI-IMT Instant-Lab, had been widely praised. This book is a remarkable accomplishment on his part while his innovative approach of grouping escapements by family provides a new basis for understanding.

The introductions to each of the 20 chapters narrate the history of escapements from the seventeenth century to the present day. A novel in themselves, they relate the adventures and misadventures, successes and failures, joys and frustrations of all those who have turned their attention to the escapement.

We have received numerous congratulations and compliments for this book which, despite existing only in French, has been sent to readers in England, Australia, Japan, China and the United States. Thank you Olivier Laesser for making this dream a reality!”

CLOSING THOUGHTS

Espionage and other adventures

The quest to build the perfect escapement is filled with intrigue and adventure… not least the longstanding rivalry between the eighteenth century’s two great maritime powers, France and England. Olivier Laesser describes in detail George Graham’s “frictional rest cylinder escapement” and John Harrison’s “frictional rest crown-wheel escapement”. Furious at progress made on the other side of the Channel, Louis XV of France ordered a delegation of watchmakers, among them Ferdinand Berthoud, to travel to England and glean as much information as they could. Industrial espionage, eighteenth-century style…

A new pedagogy

In writing this book, Olivier Laesser has given readers of every level the means to understand escapements. Thanks to the innovative pedagogical approach which he has developed, based on the so-called “primitive” method, interested amateurs, collectors, engineers, even teachers of watchmaking can understand these mechanisms at a glance. This is a major contribution.

The escapement: problem or solution?

Olivier Laesser is not about to revolutionise watchmaking with his “primitive dual-impulse escapement”. In his own words, “I’ve given up my experiments, becoming gradually convinced that escapements are not the solution to the problem of counting and maintaining oscillations. In fact I am beginning to think the reason there are so many escapements, and so many different types, is because they are the problem.” Regardless, the journey he takes us on through these 446 pages is a wonderful gift to anyone with an interest, be it passing or professional, in horological mechanisms. Naturally, we can only recommend this excellent book.

ANNEXES


Jost Bürgi (1552-1632): the Swiss clockmaker and mathematician equipped his second experimental clock with a remontoire and a revolutionary cross-beat escapement. Its accuracy of one minute a day was unheard-of at that time.: ©Olivier Laesser


William Clement (1620-1713): pendulum and anchor escapement for a clock. One of the earliest examples of the escape wheel and pallet fork construction found in the detached escapements that equip virtually every mechanical watch today. Pages 36-38.: ©Olivier Laesser


Christiaan Huygens (1619-1677): crown-wheel escapement for balance spring. On January 30th, 1675, for the first time ever, a spring was mounted on a balance wheel to replace the pendulum or the foliot in a mechanical clock. Isaac Thuret, Jean de Hautefeuille and Robert Hooke all claimed to have originated this technological advancement, whose invention is credited to Christiaan Huygens. Page 60.: ©Olivier Laesser


Thomas Tompion (1639–1713): frictional rest escapement for the “Great Clocks” at Greenwich Observatory. Page 41.: ©Olivier Laesser


Ferdinand Berthoud (1727-1807): cylinder and rack escapements for marine chronometers. Berthoud delivered his marine chronometers Nº6 and Nº 8 to Louis XV of France on November 3rd, 1768 and, in exchange, was granted the title of “Horloger Mécanicien du Roy et de la Marine”. He also received the sum of 9,600 livres tournois, a colossal amount for that period. Page 229.: ©Olivier Laesser


Thomas Mudge (1717-1794): detached lever escapement for the pocket watch presented to Queen Charlotte, wife of George III. Page 219.: ©Olivier Laesser


Abraham-Louis Breguet (1747-1823): natural escapement with two direct-impulse escape wheels. Page 441.: ©Olivier Laesser


Ludwig Oechslin: Dual Ulysse Escapement with two indirect-impulse escape wheels (bottom), with its recoil ancestor (top left) and a hypothetical frictional rest ancestor (top right). Page 433.: ©Olivier Laesser