Motion work

The motion work is mounted on the front plate, and consists of four gears.  One is attached to the center wheel arbor, two on an offset arbor, and the hour wheel mounted coaxially with the center wheel arbor.  As described before, the motion work includes four gears giving a ratio of 1/12:

• Center pinion: 6 teeth (rotates once per hour)
• Offset wheel: 18 teeth
• Offset pinion: 8 teeth
• Hour wheel: 16 (rotates twice per day)

Here are the four gears:

The offset wheel and pinion are glued together.  To keep their centers aligned, I passed a steel rod through their common centers before clamping.

The center pinion hole was cut slightly smaller than the center arbor.  This allowed me to slowly enlarge it with a round needle file until it was a snug friction fit over the arbor.

The offset wheel has an arbor cut out of 1/8" steel rod with rounded ends.  To set the arbor location, I applied a small amount of chalk to the end, and manually depthed the wheel.

Since the offset wheel is solid (no cutouts), if I don't like the depthing, it's easy to move without making an obvious blemish.

Next, I marked out the hands on pieces of 1/4" birch plywood.  I opted for simple hands rather than something more elaborate.

Then, I cut the hands out with the scroll saw and finished shaping them with a file.  Notice that I predrilled the center holes slightly smaller than the arbors, but then made a cut on the rear of the hand to allow it to grip the arbor.

Here is the hour hand mounted on its hour wheel.  The minute hand is mounted on the end of the center shaft and holds the motion work in place.