Strike warning wheel problems in old French Clock

I repaired a round French movement made ca. 1790 by Roque, Paris. It is a round time and strike movement about 3-1/2 inches in diameter. It is more delicate and looks more hand made than the typical round mass produced French movement from the mid-1800’s. After repair, the warning wheel kept getting out of synchronization with the locking wheel. Once or twice per day, the warning pinion would skip a tooth on the locking wheel, making the warning pin be in a different position when the strike train is as rest. After a while, the warning pin would end up adjacent to the warning lever, and the strike would fail to start. I re-synchronized the warning wheel, only to have the same thing happen again. The warning wheel was NOT loose on the hub, and the hub was tight on the arbor.

The arbors are very thin and delicate, and the fan fly tension seemed more than necessary. We thought that perhaps when the locking wheel is suddenly locked, the momentum of the fan fly caused enough flexing in the the locking or warning wheel arbor for a tooth to be skipped. My apprentice, John, suggested rebushing the pinion end of the warning wheel, as it was slightly loose.

First, I did the easy thing and reduced the tension of the fan fly tension spring, and the problem did not occur again until the 6th day (it had been occurring about every day). I looked closer and realized that the depthing between the locking wheel and warning pinion was very shallow, so I disassembled the movement and installed a bushing, at the same time moving the hole closer to the locking wheel.

French movement, rear view

French movement, front view

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