Hands-On: Charles Frodsham Double Impulse Chronometer

Dr. Magnus Bosse

Positive Vibrations (Ten Years Later)

The Frodsham team around Richard Stenning and Philip Whyte had something spectacular to show at the 150th Anniversary Conference of the British Horological Institute (BHI) held some 10 years ago in July 2008: the first working prototype movement of a new, entirely British made chronometer wristwatch using an escapement which so far has never been realised within the confines of a wristwatch case.

Philip Whyte introducing the Frodsham Chronometer at the BHI 150th Anniversary Conference in 2008 (photo by Don Corson) @alphaluxe

Later that year, in October, I visited Frodsham at their London gallery, and personally experienced the new piece. At that time, the prototypes had already been running steadily for 3 years.

Frodsham’s Richard Stenning and the author discussing the Chronometer in 2008 (photo by M.Bosse) @alphaluxe

Charles FrodshamReviving a Premier Name in British Chronometry

Charles Frodsham & Co is a long-established British chronometer maker and were named Official Supplier to the Admiralty, and a certified innovator in chronometry. Moreover, Frodsham the company has an unbroken link to the founding family, with Charles’ great, great, great nephew, Simon Frodsham on the board of Directors.

Frodsham Advertisement from 1911 (from Frodsham)

Mainly active as a trading company of timekeepers of the highest quality and maker of bespoke wall and mantle piece clocks, Frodsham ventured into the development of a new British wristwatch in 2004, at a bleak horological time for the U.K., when only George Daniels (own watches and the OMEGA-adopted Co-Axial escapement pieces), Derek Pratt (mostly commissions from other brands) and Roger Smith had notable activity.

What the Frodsham team had in mind was the construction of an entirely British-made wristwatch that would have an ‘efficient & pure’ escapement. To understand this one might refer to the late George Daniels, who in his landmark book ‘Watchmaking’ (p. 233f ) recommended that advanced escapement constructions provide alternate impulses for each vibration (what the Swiss lever escapement already does), but directly to the balance axis (e.g. via a roller) and using essentially oil-free impulse surfaces in order to secure long-term performance. Daniels himself considered using a detent as the best practical approximation, which indeed delivers a direct impulse to the balance and lets it swing freely directly after the impulse (p. 224f).

*¹ George Daniels (2011; revised edition) Watchmaking. ISBN: 978-0856677045. Wilson Publishers

A George Daniels pocket watch from 1976 equipped with his Double-impulse Chronometer escapement. Image courtesy of British Museum

George Daniels’ Double-Impulse Chronometer Escapement and Derek Pratt’s Idea…

One has to keep in mind that Dr. Daniels mainly created pocket watches, thus his theories do not always translate directly to wristwatches. The use of a conventional detent, for example, is not advisable in a wristwatch due its single-sided impulse. It was at the suggestion of Derek Pratt, after he had successfully fitted the first of Daniels’ escapement inventions, the Double-Impulse Chronometer into his Tourbillon pocket watch in 1997, that Frodsham adopted the idea. This Daniels’ invention solves the above issue and appeared workable in a wristwatch scenario – efficient, with a safe & robust operation and no risk of galloping (giving impulse twice) or setting (stopping).

The Double Impulse escapement catches the attention through the two escape wheels acting on a single detent and on a single balance. It is functionally unique as well: In difference to the lever escapement, but like the conventional spring detent it serves only for the locking and unlocking of the escape wheels, whereby all impulses are tangentially fed to the balance (through the escape wheels). A run through a full sequence of the escapement illustrates this nicely:



First, note that the two escape wheels rotate in opposite directions and are released alternately. In image (1) the balance rotates clockwise, with the left escape wheel locked by the lower left (secondary) locking stone, whereas the right escape wheel gives an impulse to the balance.

As the balance continues its clockwise path, the detent is tilted to the left, and the locking of the left escape wheel is now achieved via the central primary locking stone (2).

The three sequences of the Double Impulse escapement. Image courtesy of Frodsham

When the impulse comes to its end (3), the right escape wheel will be stopped by its respective secondary locking stone, at which point both escape wheels are locked, causing the balance to move freely. When the balance returns from its highest angle of rotation and reverses its direction, the sequence begins once more, this time mirrored with the left escape wheel being unlocked and delivering the impulse.

A New British Chronometer Movement is Born!

For the first time ever in the history of watchmaking a version of George Daniels’ Double Impulse Chronometer escapement had been implemented in a wristwatch movement. In 2005, the Frodsham team successfully completed a proof-of-concept watch with the new escapement (using the trains and winding work from a couple of Unitas 6497 movements), and immediately started the construction of a fully in-house movement, of which three were made.

Double Chronometer Proof-Of-Concept of 2005 (photo from Frodsham)


The Frodsham Chronometer movement prototype in 2008 (photo by M.Bosse) @alphaluxe

(Side-note: this is strictly speaking not Frodsham’s first wristwatch: a small batch of steel watches were made in the late 1940s using Smiths movements).

The movement’s functionality also has aesthetic implications: note its symmetry, owing to its double gear train starting from the two barrels all the way through to the two escape wheels acting on the single balance – which, has roughly the same diameter as the barrels. This layout, to accommodate the up-and-down mechanism, naturally puts constraints in respect to the placement of the crown: handling considerations (ease of winding) had to be balanced with aesthetic aspects, while keeping the mechanical construction pure, thus the ultimate answer was to rotate the entire movement through 15 degrees.

Frodsham Chronometer – movement side (photo by M.Bosse) @alphaluxe

The specific design of the movement requires that each train is separate from the other and is powered by its own barrel as a source of energy. Thus, the two barrels are not linked (be it in parallel or in series) with the other correspondent to give a longer autonomy. The power reserve thus, although not as high as in a number of other modern manually-wound watches, is a sufficient 36 hours, thereby safely bringing the owner through an entire day. Still, Frodsham considers the movement as ‘efficient’ as they compare to classical chronometer movements. Thus, the construction goals were set to achieve a high and stable amplitude (the balance has a frequency of 21,600 vibrations per hour) as well as a high degree of detachment between train and balance – and this, in fact, has been achieved: the inertia ratio is an astounding 13,000:1 (compared to the 4,300:1 of a Swiss lever escapement), attesting to the dominance of the balance over the detent (the disturbance to the balance is less, giving a higher degree of detachment).

As a neat little addition Frodsham included a deceptively simple looking power reserve indicator on the movement in the form of a snail wheel providing a relative value of the available power left in the mainspring. However, despite its simplistic looking layout, it is actually quite complex, requiring altogether 12 wheels, a few of them forming epicyclic gears. The power reserve has a second function, as it stops the movement after 36h. The reason for this is again stability and safety, as this not only enshrines the torque limits fed to the escapement wheels, but also prevents the movement from damaging itself (that might happen if one of the escape wheels runs out of power before the other). Furthermore, the power reserve is constructed such that it releases the balance, via the balance brake, only after the watch has been fully wound again.

Power reserve indication on the back (photo by M.Bosse) @alphaluxe

There is a second stop lever that operates like a hack feature and acts on the balance and activates if the crown is pulled out for time setting and winding.

In terms of finishing details, the movement offers all that one can expect from a hand-finished, high grade British movement: matted surfaces, black polished steelwork (note the wonderful three-legged upper support bridge for the balance) and grey frosting. All train wheels, except the escape wheels, are made from hardened 18kt rose gold.

Close-up of the escapement section with balance, two escapements and the polished balance bridge (photo by M.Bosse) @alphaluxe

The watch is a manufactured in-house to the greatest extend possible – with the exception of the balance springs which are crafted by a specialist firm in Germany to Frodsham’s design. The springs are delivered flat to Frodsham where each is fitted with the terminal curve. The only other elements that are not made by them are the sapphire crystals, the mainsprings, the leather straps, and the jewels (which are all old Frodsham stock, so technically they are in-house as well, just created at a different time, century even!).

Frodsham uses vintage stock of their own jewels (photo by M.Bosse) @alphaluxe

10 years into the future: after all, Rome wasn’t built in one day either…

George Daniels himself thought it is impossible to shrink his escapement to wristwatch size, he also assumed that the double unlocking would consume considerable balance energy (see: G. Daniels, Watchmaking, p 239). However, Frodsham succeeded, and when they soft-launched the watch at the BHI anniversary in 2008, the prototypes had already run for three years. Back then, the official launch was scheduled for the subsequent year but… only now, another 10 years later, the completed wristwatch could be presented. The movement appears essentially unchanged. So, the question is: What happened in between?

10 years after: discussion on the now released Frodsham Chronometer with Richard Stennings (left) (photo by M.Bosse) @alphaluxe

Well, it was not only the watch or its construction, it was mainly other activities which commanded lots of resources. As well as repairing and restoring vintage pieces and other commissions, Frodsham had undertaken the production of two replicas of the famous marine timekeepers by John Harrison; H3 and H4, the latter as a continuation of work originally started by the late Derek Pratt. They also created a carriage clock for H.M. The Queen Elizabeth’s Diamond Jubilee.

All components of a Frodsham Chronometer movement. Image courtesy of Frodsham

Furthermore, the practical wearing tests suggested a number of fundamental changes to the prototype movements, including escapement geometry (the escapement had only ever been fitted to pocket watches of a much larger size), different materials for the escape wheels (settling on titanium), different balance bridges and the aesthetics and finishes. Frodsham were also designing and testing different cases and dial options.

A No-Nonsense Design with Many Lovely Touches

This, then, brings us finally to the presented Frodsham Chronometer Wristwatch and its design. With the technology behind its movement already explained, let’s focus on the design aspects.

Case variants of the Frodsham Chronometer. From left: stainless steel, 22kt yellow gold, 18kt red gold and an exceptional version in 22kt yellow gold and special dial (photo by M.Bosse) @alphaluxe

The cases (42.2mm diameter) can be ordered totally according to the clients’ preferences: be it stainless steel, 18kt gold (both rose & white) or even 22kt yellow gold. The latter comes in a higher density and is purer. For the remainder, I’ll focus on what I consider the purest version, the stainless steel one.

All cases are milled out of a solid metal block, which thus require no soldering, making even the 22kt gold a robust option. The cases are created in-house, and in the case (pun intended) of precious metal carry the respective London hallmarks.

The Frodsham Chronometer with a stainless steel case (photo by M.Bosse) @alphaluxe

The dial of the watch evokes a slightly disturbing feeling if one looks at it, and there are several reasons for it. First, there is the unusual arrangement of the hands – both the minute and hour hand have exactly the same length, and its respective information is thus read on one single railroad track around the dial. With this layout, Frodsham continues the language used in the clock for Queen Elizabeth II, which in turn draws its inspiration directly from a vintage Frodsham tourbillon pocket watch No. 08964, created in the early 1900s.

Unusual layout: hours and minutes hand are of the same length (photo by M.Bosse) @alphaluxe

The base material of the dial is quite an unusual one: it is made from zirconia, a material 8x harder than tool steel and highly chemical resistant as well. Frodsham receive the blank plates and applies the surface finishing in-house.

The zirconia baseplate as Frodsham receives it (photo by M.Bosse) @alphaluxe

This material is the second cause of some initial consternation, as its surface finish is indeterminate like deep snow, with the indices apparently floating over its surface. It is also extremely difficult to photograph, causing a lot of focus hunt. The dial is composed of two parts, to create the sunken seconds indication.

Dial Details (photo by M.Bosse) @alphaluxe


Dial Details of Frodsham Chronometer (photo by M.Bosse) @alphaluxe

The railroad track and signature are not printed but laid down using vapour deposition. Being a metal oxide, it is both extremely corrosion resistant and inert, and thus, does not age. The hands as well as the individually applied indices are crafted from hand-polished and blued steel. Again, very little ageing to be expected. The above details have aptly exemplified Frodsham’s quest for a ‘durable’ watch.

Speaking of marks: For those who are more experienced with vintage Frodsham watches the bridges carry an interesting detail: the engraving ‘AD. Fmsz’. This cryptogram stands for the year Anno Domini 1850 and signifies the date that Charles Frodsham introduced his new calibre lever watch, in readiness for the Great Exhibition of 1851. It is composed of the numerical sequence of the letters in ‘Frodsham’, with the addition of Z for zero, and was used from that date on by the firm to indicate its first quality watches.

The famous ‘AD. Fmsz’ engraving symbolising Frodsham’s ambitions; it was historically reserved for their finest quality (photo by M.Bosse) @alphaluxe

This engraving serves as a token for the ambition that drove and motivated Frodsham to develop this piece.

On the expected production schedule and the order situation, Richard Stenning told me: “We hope to make 12 watches a year. As we are not yet through the first year it is difficult to say whether this will be possible, but thus far we are on track and a number have been delivered ‘into the wild’. At present we have orders taking us through to delivery in 2022.”

Current prices start at £68,500 plus applicable local taxes.

The Frodsham Chronometer on the author’s wrist (photo by M.Bosse) @alphaluxe

I personally applaud Frodsham not only for creating one of the technically most interesting timepieces recently presented, but also for focusing decidedly on chronometric performance over time, i.e. in a robust, reliable way. This does not break any new ground in terms of styling, but it offers superb watchmaking content in a consistent package. The attention to detail is amazing, albeit entirely differently executed than we are used to from Swiss (or for the matter, German) watches.

It is encouraging to see such an ambitious and thorough project has finally reached the state of completion, with collectors worldwide appreciating the result!

The Second Opinion – Don Corson:

I am so glad to see this watch finally getting out of the shop. I was present at the watch’s presentation at the BHI congress in 2008, and of all the products I saw there, this was the one that most fascinated me the most. It is a logical extension of the theoretical escapement work of recent years based on the high precision pocket watches of the beginning of the last century (note that those old pocket watches are still more precise than almost all wrist watches).

I have not seen the present version of this watch and speak only of the watch presented 10 years ago now (from memory). The most outstanding feature I found was the complete symmetry of the movement. Having a complete train for each escape wheel takes much space but eliminates possible torque variation in the second escape wheel if it is driven by the first. As I remember it the balance wheel is big and of high inertia. This is as in a pocket watch and will certainly be a factor in the good timekeeping. That is also probably the reason for the average autonomy, such high inertia balance wheels need much energy to keep them moving but are also less inclined to be disturbed by external influences.

All in all, a great watch which I would love to have in my collection. I applaud Frodsham as to their obstinate determination to get this watch done, and done right.

P.S.: The authors would like to extend their gratitude to Richard Stenning of Charles Frodsham & Co., London for the opportunity to handle and discuss the watch, and also for the willingness to clarify minute details which came up during preparation of this article.

Please join the discussions on Luxe178 community forum.

Author’s Biography: Dr. Magnus Bosse

Dr. Magnus Bosse is co-founder and Managing Director of AlphaLuxe’s community portal Luxe178.com

Dr. Bosse is both a Molecular Biologist and Diplomat by training, and served many years in the United Nations system. Being more fond of substance than protocol, he left international relations eventually and now concentrates, professionally, on select topics in network biology of complex microbial communities in areas such as bio-mining and bio-remediation.

Having missed a train as a student and being forced to waste some time waiting for the next, he ventured out of the ordinary (train station building) and sampled a flea market right in front. He went back with a solid gold mechanical wristwatch purchased at the frivolous amount of 1€ (it lacked the crown, ok?), and the rest is history: Dr. Bosse is a noted writer on horological themes, with a clear focus on technologies and independent watchmakers. His work has been featured extensively on online watch collector’s fora such as PuristS.com, but also in print publications and newspapers globally. Most recently he published a book on the most complicated wristwatch in the world, a masterpiece known as the ‘Superbia Humanitatis’, created by Louis Élysée Piguet, Franck Muller and Paul Gerber.

All his in-depth knowledge about watchmaking and the namesake industry has not prevented him from exposing his masochistic soul, and thus he founded with a group of likeminded friends around noted theoretical physicist, business strategist and acclaimed photographer Ming Thein an independent watch brand MING, for which he serves as stakeholder and Director of Production (whatever ‘director’ means in a startup).

About Dr. Magnus Bosse

Contributing Editor on AlphaLuxe web magazine View all posts by Dr. Magnus Bosse →

      alphaadmin says: 03/09/2019 at 3:00 am

      As Editor, I read lots of articles and I have to agree with your assessment of the quality of this one! I will let the author know.
      Thank you.

    Anthony Rinella says: 03/08/2019 at 4:05 am

    That was one of the best watch articles on a newer release that I’ve ever read. I wasn’t familiar with the brand so revisiting your experience from 2008 up to the current date was a great read. I wish Mr. Stennings and his team the best of luck with the distribution of those beautiful timepieces!


      alphaadmin says: 03/09/2019 at 2:58 am

      Magnus is traveling right now but I will convey your kind response to him.
      Thanks for reading.


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