Generally all Japanese clocks divided the day into 12 “hour” divisions with optional intermediary “half-hour” markers. Some subdivided the “hours” even further.
Earlier models had dials with turning centres onto which the hour hand was fixed, the main dial being immobile. Later models had turning dials with fixed hands, although there was a large overlap of periods.
The Warikoma or Namagata dial was introduced in the late-1700’s and varied the position of the hour markers. Day and night at all seasons could be correctly indicated. The introduction of the dial made the double foliot unnecessary and provided a simpler solution to the problem. The figure on the left shows the numerals set for a period during which the hours of night and day are equal. This would not be at the equinoxes since the twilight hours counted as daylight. Few steel movements are connected with the movable hour dials.
As would be expected there is no “warning” in the striking train, the old “flail” type of release being used in the early clocks and the “nag’s head” type as found in early clock-watches in the later.
There are two other peculiarities, the fly, usually four bladed, has no slip but is pushed onto the squared arbor; and there is no heart-shaped cam for lifting the release out of engagement; instead there is a hoop wheel similar to those found in English lantern clocks and the inclined part of the locking arm is extended to give the required lift. The lifting pins for the hammer are on the great wheel whose arbor carries the pinion of report for driving the locking-plate. As in the European clocks of the period the hammer is moved through an intermediate crank in the same plane as the bottom of the bell. About the only time the direct hammer action is found is in some but not all of the iron clocks.
The alarum train is of two wheels – spring driven in the later clocks. The verge for the alarum hammer passes through a keyhole slot in the top plate and the upper end is bent backwards at right-angles, with the hammer in the shape of an arc. There is another type where the hammer is “dumbbell” shaped like those on the recently discovered Catalan clocks.