B March 2009 orological H ournal I J In Breguet's Footsteps... Derek Pratt FBHI describes double wheel . When Abraham Louis Breguet made the Previous escapements such as the balance directly. This, too, was first ever , No. 282, in the early the verge, cylinder or duplex impulsed surely a good idea. The new detached years of the 19th century, he used an the balance directly via the escape- functioned somewhat in Arnold detent escapement. Later, wheel teeth. In the the manner of detent escapements but he modified a watch, which impulse was not delivered directly to the gave direct impulse in both directions of he then returned to its maker fitted with balance by the escape wheel, and it the balance. a tourbillon carriage and Peto cross- required oil between the escape-wheel Breguet used the échappement detent escapement. Although this watch teeth and pallets. On the other hand, the naturel in his finest early series of was converted a few years after No. 282 various versions of the detent but eventually abandoned it was made it had a lower number, 169. escapement impulsed the balance in favour of the lever escapement. Detent escapements impulse the directly via the escape wheel and did Although the design showed great balance only once per oscillation, which not require oil on the teeth. By promise, and fulfilled his requirements is not ideal for a portable timekeeper. At combining the best features of both of natural lift and non-dependence on this , Breguet was experimenting these escapements, Breguet sought to oil, there were inherent faults which he with escapements and eventually produce a superior double-impulse never completely overcame, despite developed a design which he called the escapement that did not depend on oil. various changes in the design. échappement naturel. Breguet has been quoted as There were two main problems. The The échappement naturel 1, was exclaiming, ‘Give me the perfect oil and first was that the twin escape wheels devised to combine the advantages of I will give you the perfect watch!’ As the were mounted on which linked both the lever and detent escapements. stability of 19th century oils was very them together. The escape wheels The then relatively new lever uncertain, Breguet was clearly on the therefore moved at the same time but escapement had the advantage that it right lines to dispense with oil rotated in opposite directions. This is an impulsed the balance at each vibration, altogether. He favoured what he called unfavourable arrangement because the or twice per oscillation, but it achieved natural lift, which is simply another term inertia of the system is high and it would this via an intermediary component, the for impulse but with little sliding action, be better for the wheels to move lever. This was an entirely new concept. where the escape-wheel teeth engage alternately anyway. The

After Daniels: ‘Escapements’

1. Breguet's échappement naturel. The left-hand escape wheel and pinion are driven by the train.The right-hand escape wheel is driven by the pair of toothed wheels from the left-hand wheel. Therefore both escape wheels move together but turn in opposite directions. A triangular locking jewel on the lever (shown in green) locks each wheel alternately. Unlocking is controlled by a ruby pin on the balance roller engaging a fork on the lever in a similar manner to that of a lever escapement. After The balance is impulsed by one or other of the wing-like impulse pallets (dark blue). As shown, the balance is turning in a 2. The Ulysse Nardin Dual-Direct escapement has much in clockwise direction and the tooth of the right-hand escape common with the échappement naturel. The inertia problems wheel locked on the triangular pallet is about to be unlocked. experienced by Breguet have been overcome by using new The next tooth will impulse the balance. On the return vibration technology. A later version is more efficient and is in regular of the balance, the left-hand escape wheel will deliver the production. impulse in the anti-clockwise direction.

106 March 2009 Horological Journal problem was caused by the necessity to discard the échappement naturel in Thomas Mudge’s lever escapement for clearance between the teeth. favour of the lever escapement with its was developed steadily during the 19th As only one wheel is driven by the dependency on oil. His various attempts and 20th centuries until the optimum power of the train, the other wheel is to retain oil on the pallets of his lever proportions were established. Work on merely a follower and the clearance escapements, with drilled or slotted other escapements gradually ceased allows it to ‘flutter’ slightly. This means escape-wheel teeth, confirm that he and the lever escapement became the that it is not precisely positioned at all was well aware of the importance of standard watch escapement. It is , a condition which leads to lubrication but he also knew that it capable of putting up an impressive variable impulse, especially with would be better not to depend on it at performance, especially in the short changes of position of the watch. This all. term. However, in the long term the gives rise to small but unpredictable The Ulysse Nardin Dual-Direct problem of oil dependency remains. errors of rate. Escapement 2, and its derivatives are a Better oils and greases have been Breguet made various versions of the revival of the échappement naturel developed to lubricate the pallets during escapement to try and reduce the principle. Silicon, a new material as far the sliding friction of impulse, but errors. Some had a smaller as mechanical is concerned, attempts to eliminate lubrication driven escape wheel, with as few as has been introduced to combat the dependency fundamentally have not three teeth, thus reducing the inertia of inertia problem. The escape wheels are generally been pursued until recently. that wheel. It was not necessary for plasma etched from this material, which both wheels to be the same, providing has a lower specific gravity than the George Daniels that the ratio of the drive and number of traditional metals used to make escape In the 1970’s, George Daniels took escape-wheel teeth remained correct. wheels. The use of silicon in this way, another look at Breguet’s échappement Other versions had vertical pins in the plus the diamond-like coating of the naturel. He had unparalleled experience bands of the linked gears to serve as surfaces, is a very interesting hi-tech of Breguet’s work having handled, the tips of escape wheels. This reduced development which we are likely to hear examined and restored most of the the inertia considerably. Another more about in the future. Although the surviving watches. The definitive book, problem, which Breguet apparently did problem of clearance between the gear ‘The Art of Breguet’ was written by not realise at the time, was that there teeth must remain, presumably that of George Daniels in 1974 and by this time was no draw on the locking pallet. The draw on the lever has been addressed. he was already deeply involved with his effect of this was that the lever carrying Time will tell if the Dual-Direct self-imposed task of reviving the the locking pallet was not positioned Escapement has solved Breguet’s flagging fortunes of the mechanical against the bankings with certainty problems with the échappement watch in the face of the quartz watch during the supplementary arc of the naturel. revolution. balance. The concept of draw was still in its infancy. Although the escapement showed much promise Breguet finally abandoned it, rather than gradually eliminate the remaining faults by yet more development work. He concentrated on the lever escapement and made a number of valuable contributions to its development. One may well imagine that he was reluctant

3. In the Daniels Independent Double- Wheel Escapement, the contra-rotating escape wheels are independently driven 4. The first of a series of lever-escapement tourbillons with a one-second by separate wheel trains. The escape made by Derek Pratt (HJ July 1991). The remontoire is a second escapement, co-axial wheels are alternately locked and with the normal lever escapement. Its purpose is to rewind the small spiral spring unlocked by the lever with 3 pallet jewels which provides the impulse to the balance. This spring is the sole connection between for locking. The balance is impulsed the escape pinion and the escape wheel. The action of the remontoire is controlled by a directly by the escape wheel teeth acting 3-lobed cam (Reuleaux Triangle) embraced by a fork. Later watches had ruby cams. on the roller impulse pallets. Photo: Toni Baggenstos.

Horological Journal March 2009 107 5. The Pratt Independent Double-Wheel Escapement for use in a tourbillon watch. Once again, the sole link between the escape pinions and the escape wheels is the spiral 7. The lower pivot of the tourbillon impulse spring. The escape pinions engage the two fixed 4th wheels. The outer wheel carriage is located in the central jewel. has internal teeth and the inner wheel conventional teeth. Note that the teeth are on The 3rd wheel driving the carriage is just slightly different planes. The escape wheel units turn in opposite directions. visible adjacent to the jewel. As the carriage rotates, the twin escape pinions (drawing left) rotate around their axes, driven by the fixed fourth wheels, but in opposite directions. The fourth wheels and escape pinions have the same tooth counts but the internally-toothed wheel has a larger module.

6. The tourbillon carriage with the bridge and balance removed. Note the black polish giving the impression of a blued carriage! The insets show an extension of the 8. The complete tourbillon carriage. remontoire-spring stud, fixed to the stop arm, resting on a fine radial pin in the band of each escape wheel. With no power applied to the watch, this arrangement is necessary it did not take long to realise that the to retain the pre-set tension in the remontoire springs. In operation, the stud extension problem was much more complex than operates in the space between the radial pin and the adjacent wheel spoke but does not this. Two escape wheels pivoted in the contact either of them. Each escape wheel alternately serves the dual purpose of carriage would both have to move impulsing the balance directly and serving as the control wheel of the remontoire together and all that the two fixed fourth spring rewinding. As one escape wheel is delivering impulse to the balance, the other wheels achieved was to give the remontoire is being rewound. Then the rôles are reversed. The remontoires provide a required contra rotation. My original near-constant impulse to the balance, in each direction, and isolate the tourbillon sketch on a scrap of paper has carriage from the inertia of starting and stopping the entire train of the watch at each survived, complete with my comment at locking and unlocking of the escapement. the time. I consigned the idea to the ‘needs further thought’ file in my mind I well remember seeing the first of to make a number of watches using this but ‘took it’ out every so often for review. George’s watches with his Independent escapement, culminating in the brilliant Many years passed but I simply could Double-Wheel Escapement 3. The two ‘Space Traveller’s Watch’. not just forget the idea because the escape wheels are each driven by I could immediately appreciate the escapement had really captured my independent trains. This eliminated considerable merit of this escapement imagination. most of the problems suffered by the but my first thought was that it was a Meanwhile, George Daniels went on échappement naturel in one masterful pity that it could not be readily used in a to develop the Co-Axial Escapement to stroke. Draw on the locking pallets gave tourbillon because of the independent dispense with the of the the final security that was required for a trains driving the escape wheels. I second train. He immediately put the first class escapement that did not started to think of ways around this new escapement into a tourbillon depend on oil. The escape wheels problem and soon thought that two fixed where it performed very move alternately, the inertia is low and fourth wheels, one with conventional well. Subsequently, he reduced the the lockings are secure. The teeth, the other with internal teeth, dimensions of the Co-Axial Escapement escapement is extremely lively in action would give the necessary contra to wristwatch size and the rest, as the and very elegant, too. George went on rotation of the escape wheels. However,

108 March 2009 Horological Journal 9. An underdial view of the twin-barrel watch. The mobiles of the Daniels-type power reserve indication are beneath the cock near the left-hand winding wheel. The associated cone is visible on the front-cover view of the . The bimetallic blade of the thermometer is just visible passing below the right-hand winding wheel. saying goes, is history. But in this case it was history in the making as the Co- Axial Escapement entered series production at Omega a decade ago.

Independent Double Wheel with Single Train Returning to the Double-Wheel Escapement, I found that the solution to the problem of both escape wheels moving at the same time arrived rather 10. The silver engine-turned dial is made from one piece of silver, with the exception of unexpectedly during a session of lateral the chapter ring which is a separate piece, held in place by three tiny screws. thinking. My brain suddenly gave out The linkage between the power-reserve cone and the indicator hand is a system of the message ‘It is not strictly true that small levers which convert a linear movement into a rotary one. the escape wheels are obliged to co-axial, with the wheel which is the twin escape wheels serves a dual move at the same time; it is the powered by the spring. In the case of function. At any instant, one escape escape pinions to which this the other remontoires that I have made wheel is the impulse wheel and the applies.’ That was exactly the 4, this is the wheel with three teeth, other is the locking, or control, wheel. information I needed and the rest fell fitted below the conventional escape The carriage itself, via the pinions, into place very quickly. Having made wheel with fifteen teeth. The control provides the necessary connection. several tourbillons with remontoires mechanism is a subsidiary escapement. After delivery of an impulse, by one or between the escape wheels and pinions I realised that the control wheel did not the other wheel, the roles reverse. I did it was at last obvious in which direction have to be concentric with the escape the opposite to George Daniels, who the solution lay. wheel, provided that there was a direct had made the two escape wheels co- In a remontoire mechanism, the connection. Such a connection is axial. I separated them, but for very wheel and pinion concerned are not provided by the carriage itself, so the different reasons. rigidly connected to each other, as is the original problem now offered the I drew a layout of the escapement at case with a conventional train mobile. solution! If a remontoire mechanism 20X to explore the idea in depth and Generally the wheel runs on the arbor of could be applied to each of the escape then made some cardboard escape the pinion and some kind of spring, wheel-pinion units, both pinions would wheels and a lever. I call this design-aid often a spiral one, connects the two be able to turn at the same time but one ‘CARD’, rather than ‘CAD’, which I do parts. Additional parts provide a control would use this rotation to rewind its not use. The cardboard components are mechanism which defines when the remontoire spring while the other then correctly positioned on the drawing spring is re-tensioned and by how previously wound spring delivered the board with pins and the action of the much. The control mechanism is usually stored energy to the balance via its parts can be readily investigated. I took another wheel which is concentric, or escape wheel 5-8. In this way, each of this a stage further and animated the

Horological Journal March 2008 109 wristwatch with a pivoted-detent escapement. This ran reasonably well but I felt that it would be very difficult indeed to make the watch absolutely reliable under all circumstances of normal wear, without adding excessive complications to an otherwise very pure escapement. Meanwhile, other good friends in England were thinking about detent escapements for wristwatches (see Val Carr: HJ September 2004 p318-21 ‘Developing a Wristwatch with a Chronometer Escapement’) and we discussed the pros and cons at length. In particular, the team at Charles Frodsham had several spring-detent prototype wristwatches running very well. However, the watches did sometimes fail, despite well-made countermeasures, and we eventually came to the conclusion that a single- impulse escapement was never going to perform with the absolute reliability 11. Charles Frodsham’s wristwatch version of the double-wheel escapement. To give an that we were seeking. idea of the scale, the balance diameter is almost 14 mm. In May 2004 we spent a long day Note the sophisticated attention to detail in the design of the timing weights on the free- together at the Charles Frodsham sprung balance, the Frodsham balance shock-proof settings and the bankings (shaped workshops in Sussex talking around the screw heads visible below the balance). Also note the great rigidity of the balance and unfortunate truth. At this point, the escapement bridges. The frequency is 21,600 vph (3 Hz). inevitable question arose; ‘What can we do now?’ I mentioned my thoughts on previously static parts with elastic bands that I needed to start work in earnest. I the Daniels Double-Wheel to provide power and the resulting just managed to complete the watch 9, Escapement, indeed I had the tourbillon model is even capable of a few ticks, 10, by the deadline for entries at the end with me, and a new chapter of albeit with some hand assistance. The of March 1997. I did not win the horological history began that evening idea looked feasible and it was time to competition but the watch now existed as the ideas started to flow again. get to work in metal. This was in 1996 and worked. I felt that at least Abraham Within nine months a prototype and the successors of Abraham Louis, Louis Breguet would probably be quite wristwatch was running 11, and Breguet SA, announced a competition intrigued by my solution to the problems showing great promise. Since then a for innovation in mechanical horology. that he had experienced with the great deal of careful development and The competition was to celebrate the échappement naturel in a tourbillon. pre-production work has been 250th anniversary of Breguet’s birth in completed and ‘Independently Driven; a 1747. I had less than a year to make the Postscript Work in Progress’, together with three watch as my entry in the competition, I continued to think about the Double- pre-production movements, was although the rules did not call for Wheel Escapement after completing the presented at the BHI 150th Anniversary anything to be made, just an innovative tourbillon, but for a wristwatch, without Seminars by Charles Frodsham & Co. concept. However, I was impatient to tourbillon. I made an initial design study in June 2008. actually make the watch now that the to investigate the layout possibilities of long process of solving the basic design the keyless work and other details but Derek Pratt FBHI problems had been completed. The didn't progress much further. Soon after, competition was exactly the stimulus I was asked to make a prototype

110 March 2009 Horological Journal