Review: Frodsham Double Impulse Chronometer

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The Charles Frodsham Double Impulse Chronometer Wristwatch is an enigma of sorts. Not only is the watch utterly traditional in the way it is made, it is also very innovative in that it is the only working example of the direct impulse chronometer escapement designed by George Daniels which is in regular production. We had a close look at it during the Dubai Watch Week, and here is our impressions review.

Charles Frodsham & Co. are the longest continuously trading firm of chronometer manufacturers in the world, and are synonymous with precision timekeeping instruments of the highest quality; watches, clocks, regulators and wristwatches.

The Charles Frodsham Double Impulse Chronometer with ceramic dial. Shown here is the 18k red gold case version.

Charles Frodsham founded the firm in 1834. The Victorian era was one of consolidation among the great English watch and clock makers and by the end of the 19th century, there were just two great firms trading in London – Dent and Frodsham. Dent built the clock in the tower of Pugin’s new Houses of Parliament, while Frodsham built chronometers for the Royal Navy and regulators for astronomical observatories around the world.

The Royal Warrants issued to the Charles Frodsham Co.

The firm survived two world wars (including being bombed out of their premises in 1941) and continued production. Activity was mainly in mantel and carriage clocks, producing amongst other things the ‘Princess’ clock, presented in 1947 to HRH Princess Elizabeth on the occasion of her marriage. In the mid 1990s it was purchased by Philip Whyte, one of London’s leading dealers in marine chronometers and precision timekeeping. He brought in as a partner, watchmaker Richard Stenning, who had previously worked in the watch and clock department at Sotheby’s. By then, the Frodsham business specialised in buying and selling timepieces from their premises in St James and servicing & repairing them from their workshop in Heathfield, Sussex. The firm now employs 7 other watchmakers who work on the Frodsham wristwatch as well as special projects.

Charles Frodsham Double Impulse Chronometer

The Frodsham team of Whyte and Stenning introduced the Double Impulse Chronometer in 2018, after 16 years in development. The developmental history is rather interesting, and perhaps deserves an article on its own. But for now, suffice it to say that the origins are from an invention of George Daniels being inspired by Abraham Louis Breguet’s échappement naturel. Daniels had used the system in several pocket watches, including the landmark Space Traveller’s watch. But he never made a wristwatch with this invention. The journey also saw significant contributions from the late Derek Pratt, one of the most gifted English watchmakers, and perhaps also one of the least well known of our time. Derek too used the escapement in a modified form to accommodate a tourbillon in his pocket watches, but also never used the pure form in a wristwatch.

Derek Pratt.

The new wristwatch is time only, and the outward appearance is a sober, elegant and dressy wristwatch. Though the case is rather large, the dial covers most of the face side, and its slimness allows for it to slip discreetly under the sleeve.

The case, dial and hands

The case gives the first overall impression that it has a very streamlined and sleek appearance. This is due in no small part to the large sapphire crystal (no anti-reflective treatment, thus the reflections in our photographs), and the very thin, highly polished bezel. The lugs extend from the case center and sweep in a gentle, elegant swoop, almost suggesting a seductively curvaceous nature.

The watches are offered in cases measuring 42.2mm in diameter with a height across the sapphire crystals of 10.5mm. The case is a 3 piece design and is milled out of a solid metal block, requiring no soldering. The cases are made in-house.

The London hallmark on the precious metal versions shows the leopard’s head, which is the assay mark of the Goldsmiths’ Company in London. The 750 is the indication of the purity of the gold.

The cases are finished with a fine grained case middle with polished bezels for the front and back. Cases are offered in stainless steel, in 18k white and red gold and in a 22k yellow gold case. The 22k yellow gold case (not shown here) is rather interesting. Typically gold content of more than 75% makes the metal too soft for case duties. Frodsham tell us that they are able to achieve the ruggedness and hardness needed in a two step process. The case is first cold forged, and then hard rolled. This process is perhaps similar to cold forging used by Grand Seiko. This two step process makes the 22k gold as hard as regular 18k gold.

The dial is only available in only in white, with options of either Arabic or Roman numerals. Even though the watches are made in very small production numbers, no customization of the dials are possible. The only option being the optional addition of two medallion ciphers showing Royal Warrants on the dial.

At first glance, the dial looks like grand feu enamel, the material is actually ceramic. The whiteness of the dial is very pure, and almost translucent. The hour markers are appliques in blued steel, as are the hands.

The minute and hour hands are equal in length. However, it is easy to differentiate between them as their shapes tricks the mind to feel that the thicker hour hand which terminates in a spade is shorter than the long, pointed minute hand.

A railway track for the minutes is punctuated at 5 minute intervals with inward pointing triangles to allow for minute tracking, a design inspired by a Frodsham tourbillon watch from the early 1900s. The subsidiary seconds hand is countersunk, and is rather large, with a diameter just shy of the radius of the main dial. A needle like seconds hand is used as the seconds hand tracking another small railway track which is a miniature of the larger minute track.

The dial is made in-house at Frodsham, but the tracks which feature a muted blue finish is made by vapour deposition of chromium oxide by a contractor. It’s a highly technical process which is made by heating up the chromium oxide in a vacuum, which turns it into a gas that can be then deposited onto the dial to create an extremely thin but strong layer. Vapour deposition markings are fade-resistant in comparison to the standard transfer pad printing method. It also allows for the track to be very thin, contributing to the elegant looks of the dial.

Shown here in a stainless steel case, the Charles Frodsham Double Impulse Chronometer is also available in 18k red or white gold, and 22k yellow gold.

The crown is offset by 15 degrees, between 2 and 3 o’clock, an unusual position. Richard tells us that this is to accommodate proportions which they deem ideal. And though it is possible to design the crown in the standard 3 o’clock position, they have chosen not to do so, as it would require that many of the watch components to be smaller and in their mind less ideal.

The watches are tested to a water resistant depth of 30m, by using a crown that is sealed with two independent O-rings, and a soft metal gasket to seal the back.

The movement

The movement is developed from the plans drawn up by George Daniels. As mentioned, the development was a collaboration between the Frodsham team and Derek Pratt.

The movement is manufactured in-house to a very high degree of independence. While Greubel Forsey went on to make a statement on what they mean by hand-made, Frodsham make no open claims. Richard tells us that despite this lack of statement, almost everything is made in-house. The only exceptions being the balance springs which are made to order by a specialist German company to Frodsham’s design. These springs are delivered flat and Frodsham makes the curves by hand. Other than the spring, the only other elements not made in-house are the sapphire crystals, the mainsprings, the straps and jewels. Though in a nice touch, the jewels are all old Frodsham stock, originally made for small pocket watches.

The double impulse escapement

The movement features a dual train which is completely separate, each powered by its own barrel. The barrels are not linked, and only provide 36 hours of reserve, which is a bit low by today’s standards. But this is done to ensure that the trains are totally able to impulse the escapement independently. The visual side benefit of this dual train arrangement is the symmetrical layout it affords.

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. This independence is expressed by the inertia ratio between the train and balance. In the Frodsham Double Impulse Chronometer, this is an extremely high value of 13,000:1 (compared to the 4,300:1 of a Swiss lever escapement).

The action of the double impulse is best seen, and becomes self explanatory in the video attached:

Movement finishing

All of the wheels of the going train are made of hardened 18k rose gold, but the winding wheels are all high carbon steel.

The main plates are a special copper-nickel-tin alloy with high tensile strength, and excellent bearing properties in conjunction with hardened steel. And frosted in a traditional method, which is typically English, and less impressive than the visually attractive Geneva Stripes applied in Swiss style finishing. However, the edges of the plates are high polish, as are the small but evenly applied shiny anglage. All the screws and steel parts are black polished. No plating or electrolytic polishing is used in the movement. Escape wheels and detent made from aircraft certified high strength titanium alloy for low inertia.

The snail is a “hidden” power reserve indicator, the small teardrop shaped arrow pointing at roughly the amount of power left in the movement.

The steel winding wheels, shown above, are finished with a combination of graining and frosting – matte in the centre and black polished on the outer rim – that’s based on early Frodsham pocket watches from the 19th century that had exposed wheels with two forms of finishing.

The three armed bridge is another example to showcase the excellent finishing. The arms are each conical in shape, ending in cylindrical pillars held in place by screws. Each part of the arm is black polished and appear perfectly even and true, a testament to the high level of finishing applied. the cylindrical feet and the screws are also black polished.

The competitive landscape

The landscape for such a wristwatch with such a unique operating principle is barren. No other wristwatch is equipped with a double impulse chronometer escapement. Much less one with a storied history with origins from George Daniels, and linkages to Derek Pratt, and in combination with an English watchmaking company which has been in continuous commercial existence since 1834.

Perhaps we might make an oblique comparison in terms of the frosted movement style, also with lineage to Daniels, in the form of the Roger Smith Series II. But even Roger has not attempted to recreate his master’s double impulse escapement system in a wristwatch.

Concluding thoughts

The Charles Frodsham Double Impulse Escapement wristwatch is a fascinating watch. A veritable study in restraint, which that stiff upper lip, unfazed by anything which is the very core to the English character. The watch stands as a testament in technical achievement clothed in an unassumingly quiet package. It is elegant and as well presented as an Englishman in a bespoke Savile Row suit, the design is sober but elegant. And like that Savile Row suit, there is more than meets the eye. It is the product of careful planning, meticulous execution and a very high level of skill.

The movement is peerless in the technical virtuosity of the double impulse escapement a marvel. At the current asking price starts at £68.500, it is not an inexpensive proposition, but one which is perhaps rather unique in this mass produced world. Many collectors would agree, and current waiting time for one is in excess of two years, or more.

Charles Frodsham Double Impulse Chronometer Specifications

Technical Facts

Double Impulse Chronometer Escapement based on George Daniels’ design, completely symmetrical, with two independent barrels and wheel trains, impulsing the balance in both directions.

Truly oil-less escapement.


Diameter: 42.2 mm
Case across the lugs: 48 mm
Height of Case: 10.7 mm
Two sapphire crystals
(Dimensions are similar to an Omega Speedmaster Moonwatch, but it is 3.3mm slimmer)


Diameter of movement: 36.60 mm (16¼ lines)
Height of movement plate and bridge: 4.50mm
Height of movement including visible part of balance brake mechanism: 4.97 mm
Duration: approx. 38 hours
Meant for daily winding. The high tooth count of the centre pinion (12 leaves) would have to be sacrificed to obtain a longer duration, also the balance break stops any one train from running down, and therefore has to come into operation with running time to spare.

Number of Jewels: 43.
Proprietary shock protection system, which keeps the depthing of the balance position unchanged.
(Radial shock: flexible pivots, fixed jewel holes. Axial shock: mobile endstones.)

Frequency: 3Hz, 21600 vibrations/h. Indirect seconds at 6 o’clock.
Balance brake mechanism with Up & Down indication visible on movement side.

Up & Down mechanism with differential (sun and planet wheel gears).

Highly detached escapement, very efficient in its use of mainspring power:

Mass of Detent Body (Ti6Al4V): 0.0037 grams Mass of Dart (Ti6Al4V): 0.00032 grams
Mass of Detent complete (jewelled): 0.0049 grams
(Swiss lever for similar inertia balance: approx. 0.012 grams)
Inertia of Detent Complete: 0.0148 grams · mm²
(Swiss lever for similar inertia balance: approx. 0.057 grams · mm²)

Ratio inertia balance to detent: 13000 : 1 (Swiss lever about 4300 : 1. This figure is a measure of the inertia-dominion of the balance over the detent/lever.)

Impulse angle static (as per drawing; impulse angle starts with unlocking and ends with the locking of the escape wheel): approx. 30 degrees. Impulse angle dynamic (from the point escape wheel tooth has caught up with impulse stone, to locking of escape wheel): approx. 14 degrees.
Dynamic impulse: happening during approximately 2% of the time.
The above figures are taken from high speed footage of the running movement.


1 Comment

  1. Thank you for this review on this extraordinary watch in such depths; detailing only found in your publications on, so much appreciated. I still crave for further detailing, like a comparison between the Daniels-Pratt-Frodsham double impulse escapement and Daniels’ coaxial escapement and the classical single impulse detent escapement. I do expect that the coaxial does not bear the advantage of a higher inertia ratio between balance wheel and detent compared with the classical swiss anchor escapement (no idea how the detent escapement compares). But that the coaxial bears a similar advantage compared to the swiss lever escapement with respect to the static impulse angle. A real world measured lift angle for the Omega coaxial escapement shows a low 32 degrees compared to the approximately 50° for the Swiss lever design. A single impulse detent escapement may still beat the natural escapement with a lower dynamic impulse angle per period? All theory, I even would like to see real world data on amplitude and rate stability over time, their fluctuations over different periods.