BORREL - WAGNER successor company to JEAN WAGNER, PARIS, FRANCE c. 1860 -1869. 'Rocking frame' style remontoire. Invented by Verite, Beauvais, France. Gravity driven, train type. 20 second cycle. Remontoire dimensions: 12"w x 12"h x 12"d.
This system relies on the fact that a wheel will continue to mesh satisfactorily with it's mating pinion within a very small arc before failure. It works best with larger wheels as the arc can be greater giving the wheel a longer time during which it is in a favorable position vers. it's pinion. The necessity of a small arc requires a short re-load period. This one is operating on a fairly large diameter wheel with large teeth allowing for a long period (for this type of remontoire). Typically the time is from 4 to 10 seconds - this one having 20. It's advantages are it's simplicity (lower cost) than other remontoire. It's direct drive to the escape wheel theoretically makes for better accuracy. However, there are some serious drawbacks. The first being that the remontoire drive pinion is almost never in it's ideal meshing profile. The second is due to it's small travel and direct drive. It has less ability to isolate the escape wheel from larger disturbances that may effect the movement from external forces than do other differential types - one of the main reasons for a remontoire.
This particular remontoire also employs the same characteristics as the addition of another wheel in the train, i.e. a further stepping up of the ratios increasing duration of time between windings. Usually remontoire are 'neutral' acting as would an idler wheel for purposes of mechanical ratios.
Text of voice over narrative below:
What you see is a greatly speeded up sequence of events that in real time would take 20 seconds per release of the fly fan. The entire clip encompasses 60 seconds in real time.
Notice first the frame shaped like a sideways Y near the rear of the remontoire. On the left leg is mounted a weight. The center of the Y is fixed to an arbor which has on its other end fixed a cock. This forms a cage in which is mounted the remontoire wheel. On the cock side is the wheel. Opposite is its pinion on the lower, right leg of the Y frame. The upper, right leg has a detent. The cage has pivots on each end which rotate in bushings mounted in the rear clock frame and a cock mounted from below the upper frame support. This allows the entire cage with its wheel to rock up and down. The remontoire wheel meshes with the escape wheel and its pinion meshes with the second wheel in the main movement train. Upon the same arbor as the second main movement wheel is mounted a helical gear. This meshes with a worm attached to a vertical arbor that has mounted on it a three legged cam as well as the remontoire fly fan. The rear weight counter-balances the entire swinging frame with its mechanism along with enough mass left over to drive the escape wheel.
The cycle begins with the end of one of the three cam arms at rest upon the face of the detent located on the upper leg of the Y frame. This is the driving phase and lasts 20 seconds. Throughout this period the clock train powered by the main movement weight is locked. During this time the fall of the small, disk-shaped weight mounted on the left end of the Y frame is powering the entire escapement and pendulum. As it pulls the end of the Y frame downward, it causes the other end containing the remontoire cage and wheel to rotate upward in a counterclockwise direction. The pinion of the remontoire wheel meshes with the locked second wheel causing it to rotate in a clockwise direction. This drives the wheel attached to the same arbor to turn clockwise and the adjoining escape wheel to turn counterclockwise. Since the second movement train wheel is locked and the remontoire wheel is free to move through to the escape wheel, power is directed from the remontoires weight through the remontoire pinion; its associated wheel and to the escape wheel. The upper leg of the Y frame is also rotating counterclockwise; rising until the point that the detent mounted on its end moves out of the way of the cam arm allowing it to rotate clockwise; releasing the main movement train.
Now begins the recoil phase and lasts about 1 second. At this point the main movement train unlocks and the now unlocked second wheel in the movement, powered by the main weight of the clock, begins to turn counterclockwise, meshing with the remontoire pinion. This happens at a faster rate than the wheel it is attached to is turning the escape wheel. This difference causes the pinion to ride along in the direction of the second wheel. Pulled by the remontoire pinion the cam and frame assembly reverse direction and begin to rotate clockwise raising the remontoire weight upward while the cam armature makes one third revolution. During this time power is directed from main movement to raise the remontoire cage as well as advance the clockwork by 20 seconds. This is demonstrated by the slight clockwise movement of the large main movement wheel which turns once an hour To avoid jarring the remontoire, the speed at which the frame recoils is mediated by the large, adjustable fly seen at the top of the picture. The recoil phase continues until the detent has moved back into its starting position, blocking the cam arm and locking the main movement wheel train again. All the while power is uninterrupted to the remontoire wheel driving the escapement and keeping a constant power supply throughout the cycle.
This sequence of events should be seen as the small weight giving a constant source of power to the escapement at all times. The small weights kinetic energy is recharged periodically from the larger clock movements main weight before it exhausts its energy by reaching the end of its limited travel. The remontoire wheel meshing with the escapement is always being driven, the main movement wheel is always a driver, while the remontoire pinion always drives and is periodically driven.
This is the principal of a differential gear system. The differential is the general mechanical concept employed in all gravity driven train remontoire.*
The action you see, especially in the rotation of the escape wheel and the still pendulum are necessarily distorted. The time the remontoire is driving is far greater than its recoil phase. So to make the animation clearly show the details of the driving phase in relation to that of the recoil phase the first was speeded up while the second was correspondingly slowed down.
* The Robin type is excepted. While it is gravity driven, it uses a flexible line or chain to achieve what is done via differential gearing.