The dilemma or … Automatic watches with verge escapement, but without fusee! by Joseph Flores Comparative study of two automatic movements, of identical design, but signed and finished differently The verge escapement At the time of the first attempts in the 1770s to produce “watches which are wound by the movement of the persons who carry them”, according to the expression of the time, watches now known as “automatics”, the active brains of certain watchmakers were faced by a dilemma, whose explanation can make modern technicians smile. The question can be summarized as follows: Is it possible that a watch does not run while it is being wound? The answer these days is obvious, is it not, and yet at the time it was the case for the large majority of watches. Because practically all watches were equipped with the verge escapement, which is an escapement with recoil, and which could only function well with a part that has now disappeared: the fusee. And it is this fusee, which was essential, that caused the problem, … Except by modifying it or finding a device to replace it … Two questions are raised, and my answers given here: 1. Why does the verge escapement require a constant energy? 2. What is the problem arising from the fusee? Here are the explanations: The principle of operation of this escapement, the oldest of all, is known as “with recoil”. It should be understood that the phase of recoil we are considering occurs after impulse, and this kind of escapement has only 2 phases of operation: Impulse - Recoil. Whereas the escapements which followed, those known as at-rest and others known as free, comprise three phases: Rest - Release - Impulse. Thus the recoil of the verge escapement should not be confused with the recoil of lever escapements, due to draw, and which occurs before the impulse. The drawing and photograph in Figure 1 show this escapement. The verge is made up of 2 pallets, which successively operate the teeth of the escape wheel. These pallets are made up of a flat face, the plane of impulse. When a tooth of the escape wheel touches this face, it pushes back the verge, providing the energy to ensure the oscillation of the balance or the pendulum. It should be noted that the escape wheel always has an odd number of teeth, so that when a tooth acts on one pallet, the other pallet is between two teeth. [159] The photograph presents one of these positions in which tooth 1 transmits the impulse to the pallet (in the direction of the arrow) and the other pallet passes between teeth 2 and 3. But why does this escapement require a constant energy? Everyone knows that in modern escapements, the angle traversed during the phase of impulse is always identical. In this escapement, and this is the problem, it is not the case. 1 Figure 1: The verge escapement Indeed, it is seen that the angle of recoil produced by the impulse face of the pallet, is added to the angle of impulse. As this angle of recoil varies according to the intensity of the energy, the angle of impulse varies as much, and obviously isochronism suffers as a result. It is this detail of operation which is the reason that the very great majority of the old watches have a fusee, the element which creates the constant energy that this escapement requires, making equal, as far as possible, the angles of recoil and therefore the angles of impulse. But in addition, the fusee has a disadvantage which made the design of automatic watches complex. This is that it needs to run during winding, because it is precisely this that is the disadvantage of the fusee: the watch does not run when it is wound. Here the explanation. The fusee Figure 2 shows the traditional arrangement for providing the energy for the oscillations of the balance. It is made up of a barrel containing the mainspring, like now, but which was connected by a chain to the part which has disappeared from modern watches: the fusee. More precisely the body of fusee, a cone with a helical groove in which the chain is rolled up. [160] One can view the fusee as a pulley with a variable radius, and in addition remember that the spring in the barrel provides a variable energy according to its degree of winding. If it is fully wound it produces the greatest energy. As its unwinds, the energy produced decreases. Figure 2 The assembly in Figure 2 shows this arrangement. When the spring in the barrel is wound, it pulls on the chain making the fusee turn. The first wheel, on the base of the fusee, gears with the traditional train of the watch to make it function. Thus, with a fusee, when spring is wound to the maximum, the chain is at the top of the fusee, and pulls on the smallest radius. As the watch runs, the spring unwinds and loses strength, but the chain then draws on an increasingly large radius. And according to the principle of the lever, one gains on the outlet side of the fusee what spring loses in strength. But then, where does the problem lie? Why doesn't the watch run while it is wound? 2 The problem for the researchers of automatic watch construction, is inside the fusee, namely: not running simultaneously with winding. In Figure 3, the fusee has been opened up, with the body of fusee seen from underneath at the left, and the first wheel at the right. Under the body, one sees ratchet teeth 1 and on the wheel a click 2, acting under a light spring 3. When the fusee is assembled, the click acts on the teeth in the body of fusee, with 2 consequences: 1. While the watch is running, the body of fusee, drawn by the chain, makes the first wheel turn via the click catching in the teeth. 2. On the other hand, at the time of winding, which is done by turning the arbor of the fusee by the square (see Figure 2), one makes the body of fusee turn in the opposite direction, to roll up the chain, so that the click slides over the ratchet teeth. And because of this the first wheel is no longer activated. Thus the watch does not run during this period of time. Figure 3: Separated fusee; body of fusee left, first wheel right This point being understood, it should not be thought that it had a great importance in watchmaking at the time. Indeed, in the second half of the 18th century, the accuracy of watches was not very high, and it is only in the more elaborate mechanisms which required a higher precision, such as chronometers for the Navy, that a device, invented by Harrison around 1754, called maintaining power, was generally used to neutralize the detrimental effect of the fusee. Nevertheless this maintaining power is not suitable for a device which winds continuously, as is the aim of automatic systems. Solutions As stated at the beginning of this article, the fertile brains of the watchmakers of the time obviously found solutions. But these had no long term future because at-rest and free escapements were mastered by the decade of 1780s, and the problem no longer arose. It is thus, in my opinion, in the decade of 1770s that the methods, which will be discussed, were used. There are three known attempts: 1. The best known is that of December 1778, due to Hubert Sarton when he deposited a watch with the Academy of Science in Paris; the repercussions of which on modern watchmaking are incalculable. It is described in my article “Automatic Rotor Watches, Comparison of The Report of the Academy with Known Movements”. 2. Another solution cannot be attributed, because it exists in only 2 movements signed differently (Figure 4): Breguet à Paris and Papillion à Paris. Without documents it is impossible to be sure who is the inventor. These watches are presented below. 3. Then a patent granted to Recordon, n° 1249 dated March 18th 1780, but we do not know of a watch using this method. Option 2 concerns the adaptation of an automatic device to a watch with a verge escapement but without a fusee; which seems improbable and yet two exist. Three questions arise: 1. What date are these 2 movements? Can they be made before December 1778, the date of the deposit by Sarton of his modified fusee watch? For the moment, there is no confirmation, because to my knowledge there is no documentation on these watches. 2. Although they have differences in finishing, these two pieces are built on exactly the same caliber. Who is the originator of this caliber? One of the two signatories or a third person? Again, only a document will tell us. 3 3. This design uses a verge escapement, which obliged the originator to find a solution so that winding is done jointly with running, therefore needing a very complicated device having an obviously a high cost. Can one imagine that it was done when automatics with escapements with less need for a constant energy source were being made? Yet again, only a document can give an answer. Figure 4: Breguet à Paris (left) and Papillion à Paris N° 2069 (right) Supposing that the Breguet watch was made by the great Breguet, and that it can be dated between 1778 and 1780, why would he have chosen the verge escapement, which involved him with such a complicated and expensive construction? A plausible answer is that Breguet made this piece before he had sufficient experience with the “new” escapements, which certainly were essential shortly after.