Hall's Safe & Lock Co, Cincinnati, Ohio - 1 mvt. w/ Chronometric Time Attachment


Repairs to the movement 

When this time lock came to me it was not in working condition. There were several problems with the lock

The first issue was that the main wheel, the spring barrel wheel, was frozen. When one put a winding key on the square it would not move. At first it appeared that the ratchet may have been made immovable for some reason. It was impossible to try to dislodge it away from the teeth of the ratchet wheel. This lock was never equipped with maintaining power, so the secondary ratchet used in that system did not exist. The problem here was that given the fact the ratchet could not be dislodged, and the ratchet wheel was frozen solid to the main wheel, there was no conventional way to let down the main spring, which was also wound nearly all the way around.   


The first photo shows a close up of the escapement enclosure, circled area. The red arrow shows a temporary wire wrapped around the wheel work to hold the mechanism in check. Next I had to carefully loosen the two screws that held the escapement enclosure to the top plate resulting in the gap between the enclosure and the movement top plate. This allowed the fifth wheel, red arrow second photo, in the movement train to be disengaged from the escapement wheel within the enclosure. After removing the restraining wire, the movement could then be allowed to slowly spin down until the spring was fully released. This is not the recommended way of letting down a movement as damage to the delicate sixth escapement wheel is very real, but it was the only way given the incapacitated main ratchet assembly. Had this movement been made in a more conventional figuration with the the escapement on the same plate as the rest of the wheels and mor importantly not been within an inaccessible enclosure, this process would have been made far easier.


These first photo shows the top plate removed from the wheel works. Next the remaining wheels and other assemblies mounted to the bottom structure. The design of this movement varies from a conventional time lock. In the first photo one can see the entire escapement containing the balance wheel, escapement and escape wheel covered by the enclosure. Normally these components are secured with narrow bridges allowing one to readily see these components. Instead only two small observation holes are provided to let one see these components. In reality it is nearly impossible to properly observe anything. The other unconventional design is the fact that the escapement is not mounted on the same plate as the rest of the wheel train complicating reassembly. The implication of these two features made the repairs needed much more difficult.


The ratchet is seen under a 30x glass as a simple triangular piece spring loaded from beneath the ratchet wheel. It differs from a conventional design in that it lacks a separate ratchet click and spring. If it had this arrangement it would have been possible to push the ratchet click out of the way of the teeth. But here the small triangular piece is firmly wedged between the teeth. The conventional design would have required the ratchet wheel teeth to be above the surface of the brass decorated rim for the ratchet teeth to engage on the ratchet click mounted to the rim's surface. However, there is more than enough clearance for this so it is a mystery why this inferior design was chosen. I have not seen this method used on any other time lock, probably for good reason. The second photo shows the massive main spring, the barrel cavity is 2" in diameter. The full 48 hour duration of the lock requires one turn with setup of the spring being another turn. So it is curious why the need for the huge spring where the majority of its coil is never used.


After the ratchet wheel and main barrel wheel were disassembled it became apparent what the problem was. The ratchet itself was not the the cause of the frozen main wheel, but the green sludge that was certainly at one time the grease used to lubricate between the silver ratchet wheel and the face of the main wheel. It had over the past hundred years dried out to become a solid glue between these two parts. Failed lubrication is the primary reason why clock and watch movement have problems. The lubrication either dries out increasing friction or attracts dirt turning it into a grinding paste destroying the steel pivots of the wheel train. Abraham-Louis Breguet one of the most famous and respected watchmakers was reputed to have said "Give me the perfect oil and I will give you the perfect watch". It was as true in the later 1700's as it is today. The second photo shows the 108 parts that comprise the time lock.


One of the escapement jewel pallets was loose and had to be re-secured to the escapement. This was a rather simple and straightforward repair since it was secured fully flush into the jewel box of the escapement. 


The other jewel pallet was positioned in a most curious and precarious way. One can see it being slid halfway out of its box with the gap illustrated by the black indicator in the first photo. The reason for this arrangement becomes obvious in the second photo. Here the balance wheel, escapement and escape wheel of the lever escapement are shown. The pivot points for each are illustrated by the red dots between the two upper and lower white lines. A conventional lever escapement is a simple straight line as demonstrated in the line represented by (1) in the photo. This is the simplest, most common and efficient design and is used in just about any other time lock (and watch using this type of escapement) I have seen. However, in this example the geometry has been altered to introduce an angle as illustrated in (2), and following the actual pivot points of the three escapement components. This was done because all of the wheels in the train, excepting the central barrel wheel, run along the arc of the upper circumference of the open dial cutout. Since this was a prototype, the Hall company simply took a conventional escapement part and pushed the jewel outward to make up for the change in the angle of engagement with the escape wheel. Normally both jewels would have been adjusted to perfectly engage the escape wheel and the geometry and adjustment of these components is devilishly tricky and a specialty within watch making itself. At the time and even today, the final adjustments made with the escapement itself is an individual and skilled labor profession. There is a bit of space within the each pallet jewel box for adjustment. Here the red jewel is backed completely into the box, as might be expected with the change in geometry with its counterpart correspondingly being pulled out of its box. It is a tribute to the jewel setters (and a bit of luck) that this worked with the altered set of jewel positions used in an escapement not designed for this geometry. Another indication that this was a test piece is the fact that the escapement tail where it engages the impulse jewel of the balance wheel is a soldered-on piece. Apparently the 'off the shelf' escapement, in addition to being designed for a straight in-line  arrangement, was also a bit too long for this application. So the escapement arm was snipped and the impulse fork soldered on. Again, under magnification it all looks crude and ad hoc, but one must give credit to the people who created these one off experimental designs that ultimately had to be tested within the confines of a safe that required a 100% functionality to prevent a lockout.


The next problem was particularly vexing. The balance wheel roller jewel was also a bit out of alignment. This part is the smallest piece an any watch movement. It is also subjected to the highest degree of stress as this is part is engaging several times a second. Here the jewel is about 1mm long and about a 50th of a millimeter in diameter. It also has the profile of a cylinder cut longitudinally in half. The first photo shows the roller jewel, red arrow, in relation to the balance wheel and sewing needle. Next a closer view through the 30x glass.


The roller jewel is shown secured to the balance wheel. This was a tricky process. The hole in the balance wheel was very large in relation to the jewel so precise positioning was required verses the escapement impulse fork in two dimensions. For this application I chose to use conventional epoxy since it has a long set up time. I studied carefully the geometry needed for this part and to be honest, had nothing more than an eyeball guesstimate to position the jewel. Once the epoxy was partially set I inserted the jewel and set it to the correct position. Of course the part sticking out above the glue had to remain absolutely clean or the escapement would stick. The only redo would be to re-dissolve the glue and start over. Fortunately the first trial was a success. 

The time lock was now back to operational condition.