I had written before about the fact that not enough run on the chime warning wheel can cause the 4th quarter chime to not activate. As a result it can skip every other hour in chiming properly. Yesterday, I discovered a new and unlikely problem. It turned out that the lack of enough rotational action in the chime warning wheel (shown left) can randomly cause the warning pin to land exactly on top of the warning lever and lock. This causes not only the jamming of the chime train, but the stoppage of the time train.

The lesson learned is that there must be a minimum of 180 degree rotation of the warning wheel when it is activated. If it does not have that, although it may be unlikely, it is entirely possible to have chiming or stoppage problems.