Sinclair Harding Navigation Clock :

This sea clock was inspired by John Harrison, who won the board of Longitude prize established by the British government in the 18th century for a clock, which could accurately tell the time at sea, hence establish a ship’s longitude at any moment. A pendulum is useless on a boat, and as a result, Harrison invented the unique twin balance arms and grasshopper escapement.

This Meccano replica of John Harrison’s clock embodies two of the most important features of his first sea clock. The linked balance arms, which give the clock a visually fascinating, restful and attractive quality and the unique frictionless “grasshopper” escapement with the subtle lock and release action of the clock pallets.
The clock is not an exact replica of the Harrison no.1 clock, but it does follow quite closely the design of Sinclair Harding, a leading firm of clockmakers, who made a version of the design.

The clock is powered by a gravity weight which gives motive power to the clock’s going train. This weight will automatically rewind when at a low point with no effect upon the motion. The Escape wheel has thirty divisions with each pallet locking and unlocking each division at second intervals, thus giving the escape wheel one revolution each minute. Timing is set by the adjustment of the weights upon each balance arm to give a second beat, fine adjustments then are made with the counterbalanced weights on the link arms at the rear of the clock to bring the clock running to perfect time.

The clock rewinds every thirty seconds and the rewind motor is powered from a series of alkaline cells which keep the clock running for several months. A slipping drive clutch is also employed for adjusting the hands while the clock is in motion.