The Double Impulse Chronometer Wristwatch
Although Charles Frodsham & Co. have been making precision clocks, pocket watches and marine chronometers for the last 180 years, we have only briefly touched upon the manufacture of a wristwatch. That was in 1947 when a joint undertaking, part funded by the British government, was proposed to set up a manufactory to produce wristwatches on the pattern of the Smith movement of the time. For a number of reasons this venture never came to fruition and the project was abandoned.
Over half a century later, Frodshams once again conducted a feasibility study, on the possibility of developing and producing a completely new caliper of wristwatch in-house. In pursuit of this aim, and drawing on our knowledge of the spring detent escapement, experiments were conducted to produce a movement with a fast train, low-inertia components made of modern materials, and an oil-less escapement, the latter contributing to long term stability of rate.
The advancement of these original goals then took a radical new direction in 2004. It was while discussing the merits of the detent escapement, in a brain-storming session at our workshops, that Derek Pratt suggested Frodshams try George Daniels’ Double Impulse Chronometer escapement, which Derek had ingeniously incorporated into one of his tourbillon watches, and George had used in seven of his celebrated pocket watches.
There was no doubt that the escapement offered everything that one could wish for in a wristwatch. However, the immediate practical problem that needed to be overcome was that the eight watches that used this escapement were of large pocket watch size, with movements in excess of 50mm diameter. The Frodsham movement needed to be around one third less in diameter, which, in practical terms, results in less than half the available area.
The lure of a truly oil free escapement proved far too enticing, so R&D commenced on how to adapt the escapement and the two power trains into a wristwatch caliper, whilst holding the tolerances necessary for such a precision mechanism.
Progression on the wristwatch occupied much development time, but in due course three first-generation prototype movements and four pre-production prototypes were made, in order to fully test the long term stability of the escapement.
Frodshams comprehensive infrastructure has enabled us to design and make all the parts in our workshops, except for the mainsprings, balance spring, and jewels. This efficient small batch production method of parts, including the case, dial and hands allows us to quality-control each component at every stage of production. Frodshams are now probably more autonomous than we have ever been in our history. Indeed, even the screws, of which there are over forty in each watch, are all made entirely in-house.
The hand-wound movement has several practical and mechanical advantages, some of which feature a number of unique elements:
- The symmetrical escapement does not need lubrication.
- The escape wheels give direct impulse to the balance in both directions, without the need for an intermediate component, as in the lever and many other escapements.
- The combination of two independent trains results in a more even and balanced delivery of power to the escapement.
- The low-inertia titanium detent is poised, and controls only the locking and unlocking of the escape wheels, and the safety action.
- The large Frodsham free-sprung balance, beating six times per second, has an over-coiled balance spring and Frodsham’s own shock system for better positional consistency of the balance staff. The aerodynamically designed balance is set with four eccentric timing weights.
- The movement plates are made of a ternary copper alloy for dimensional stability and good bearing properties.
- The train wheels are made of hard-rolled 18ct gold rather than conventional brass. This has many useful advantages, including better corrosion resistance and improved lubricity.
- The power source, giving ample reserve, employs an up-and-down-mechanism with differential planetary gearing (gear cluster, 7mm diameter).
The 41mm diameter case is just 10mm high across the two sapphire crystals and will be available in a choice of London hallmarked Gold, Palladium, and Platinum to special order, as well as in stainless steel. The dial and hands draw inspiration from historical Frodsham timekeepers and will be available in a small number of materials and finishes.
Currently, pre-production prototypes of the Double Impulse Chronometer wristwatch are undergoing extensive testing. News of the proposed market release will be announced in late 2016, but should you wish to pre-register your interest in receiving further information, please contact us.