Hywel Lambert’s

HARRISON’S CONTRIVANCE

John Harrison of Longitude fame was a carpenter by trade and built his early clocks in wood. Three of them survive, notably the clock at Nostell Priory, which has been in continuous use there since 1717. Two others survive at the Clockmakers’ Company and the Science Museum.

However, his famous sea clocks were mainly metal structures. While working on the clock we now know as H3 Harrison decided to replace his existing wooden workshop regulator with one that contained the elements of H3 minus the complications needed for a clock that would have to work at sea.The resulting regulator was highly accurate, although it was never finally adjusted. Harrison reckoned that adjusted it would have been accurate to one second in 100 days.

It was about 180 years before that accuracy was achieved - first by William Shortt in the 1920s with a free pendulum clock. Experiments in modern times have shown that Harrison’s clock could have achieved that goal in the 1740/50s. However, he was too busy working towards the longitude prize, switching his efforts from clock to a watch to reach the goal.

The clock has been known as the RAS Regulator for many years now, after it became owned by the Royal Astronomical Society. It is kept at Greenwich.

Recently Stuart Harrison (no relation) researched the regulator and produced a great book, which gives lots of information for anyone, at least anyone with a wealth of clockmaking experience, wanting to build a replica. It is also a new insight into the life of Harrison. In a review on MEWS, Roger Bunce described the book as “the finest horological book I've had the pleasure to review since 'Woodward on Time'.”

At the 2012 Bristol exhibition, Hywel Lambert told MEWS that he had started to build one of these clocks. A year later remarkable progress had been made.

This is a complex clock. Many of the parts are difficult to make. Cutting those deep teeth on large wheels, for example, without bending them. Bearing rollers are made from lignum vitae, and the grasshopper escapement arms carved from snake wood. Bearings are replaced by friction wheels, and there are one or two things whose function is not at all clear!

However, it might just be that making the clock is the easy part. Getting it to work will be the real test. No doubt all those making one of these clocks are in touch, comparing notes. Another builder’s work can be seen here.

Above: parts of the remontoire and the arms for the grasshopper escapement, made from snake wood.

Below: weight and weight pulley.

Gridiron pendulum.