Sea Clock

In 1735 John Harrison produced an innovative, interesting and complicated clock in his search for an accurate timekeeper that could be used at sea. He had been working on it for seven years.
The most eye catching  feature of his clock was a pair of dumbbell balances gently rocking to and fro in synchrony. By being interlinked the aim was to negate the effects of a rolling ship.

My version has two interlinked compound pendulums which have a two second period but are gravity controlled rather than spring controlled as in the original. It also employs a grasshopper escapement which is frictionless and is ideally suited to wooden clocks.
The clock is weight driven and the weight is  rewound by a small electric motor every two minutes or so.  This is modelled after a Wagner remontoire. The electric motor itself is the driving weight.
The motor is derived from a modified radio controlled servo acting as a straight motor rather than a servo. The action of the rewinder can be seen in the video below.

Because it is modelled on a sea clock I thought it appropriate to send it to sea. Perhaps not literally but by mounting it on a tilting table which is operated by a small stepper motor. Both the stepper motor and the rewind motor are controlled by a small microprocessor. The microprocessor is powered by a 5 volt mains adaptor.

Below is a short video showing the clock in action


  1. What I like most of this clock is the weight system with the motor. Very ingenious!

    1. Hi Carlos, thanks for your comments. I have now added a just completed conical pendulum clock to this blog, Inspired partly by your clock this weight driven version has another interesting rewinding mechanism.
      Thanks for the link to your Pythgoras clock. I assume that it is powered by some sort of electromagnetic mechanism?
      Best Wishes