Hi KKC,

This sounds like a great addition to a clock to add some additional flair.

Adding an AM/PM indicator sounds easy. Just divide the hour hand by 2. One way would be to attach 2 gears to the hour hand gear. This would typically be 30 or 32 teeth. Use an 8 tooth intermediate gear to drive a 16 tooth gear that will rotate once every 24 hours.

I searched for moon dial gear ratios. The moon phase is 29 days 12 hours 44 minutes and 3 seconds. This is typically rounded off to 29.5, which will leave an error of one day every 32 months. This is definitely within the tolerances of the wooden clock accuracy.

A classic moon phase dial has 2 moons on it and needs to rotate half way around every 29.5 days, or once per 59 days. Since the hour hand rotates 2 times per day, the gear ratio needs to be 118:1 relative to the hour hand. Alternatively, it could use a 59:1 ratio relative to the AM/PM indicator that rotates once per day.

A 59:1 ratio can be done with 2 gear sets. Add an 8 tooth gear to the AM/PM indicator to drive a 59 tooth gear. This will rotate 8 times per 59 days. Add an 8 tooth gear driving a 64 tooth gear to divide again by 8X.

Steve