Hampton Court Clock

 This is a table top model of the Astronomical Clock overlooking the courtyard at Hampton Court Palace near London

The clock was installed in 1540 on the gatehouse to the inner court. It was designed by Nicholas Crazter and made by Nicholas Oursian. It was built at a time when it was believed the sun revolved around the earth so that the earth appears at the centre of the dial

The clock is 15 feet (4.6 m) in diameter with three separate copper dials revolving at different speeds and displays the following information .

   Time of Day, Month and  Date. The daylight hours are read at the lower half of the 24 hour dial.

  Twelve signs of the zodiacPosition of the Sun in the ecliptic relative to the background stars (zodiac).

  Number of days since the beginning of the year.

 The current moon phase and days since the last new moon.

 The time of high water at London Bridge

The latter information was of great importance to those visiting this Thames-side palace from London, as the preferred method of transport at the time was by barge. Two consequences flowed: journey time, which departing around high water would speed instead of hinder; and all but the most skilled or reckless watermen above the bridge would avoid nearing London Bridge at times of great surface-water ebb under the (then famously built-up, barrage-like) bridge to avoid being swept into the starlings (cutwaters) or arches above.

The time keeping mechanism which I have not reproduced has been replaced several times in its life and the dial which is original was lost for about 200 years before being re installed in 1879.

The mechanism of the dial consists of two epicyclic gear trains which are mounted on and revolve with the large wheel.

The large wheel rotates once in 24 hours and is driven by the clock mechanism. Here I have chosen to drive the 24 hour wheel with a variable speed stepper motor. At its slowest speed it keeps real time.

One gear train drives the lunar dial and the other the ecliptic dial. Each train meshes with one of two fixed, non rotating gears on the main shaft effectively driving the trains. 

The schematic below may or may not make it clear !

Below is a short video of the dial in operation.