10 INTERVIEW
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soon got bored with long commercial flights to Japan so, being a keen pilot, he decided to fly himself. A growing interest in navigation blossomed further when he joined the Royal Yachting Association and became a yachtmaster ocean instructor, which entailed learning to navigate by means of a sextant, stars and time. This, in turn, led to an interest in John Harrison (1693-1776), an English clockmaker who invented the marine chronometer for establishing longitude while at sea. In the 18th century, the problem of determining longitude had seemed so intractable that the English Parliament offered a prize of £20 000 (equivalent to about £2.8 million or E3.2 million today) for a solution. Two of Harrison’s early
inventions were the virtually frictionless grasshopper escapement and the gridiron pendulum that consists of lengths of brass and iron arranged in such a way that the length of the pendulum from pivot to bob is always constant, regardless of the temperature. The grasshopper escapement, in common with other features such as lignum vitae (a self-lubricating wood) rollers mounted on non-corroding brass spindles, helped to virtually eliminate friction.
The Corpus Clock
When he retired in 1999 Dr Taylor decided to do something he had always wanted to: design and build a clock. He chose to create something that was both a homage to John Harrison and completely different to anything that had been made before. The result was the Corpus Clock, a gift to his old college at Cambridge University to adorn the new Taylor library for which he is the principal sponsor. “I decided to turn the clock inside out and put the escapement on the outside, hence the large, grasshopper- based monster at the top. With the escapement made into a visible feature, I wanted a new alternative to a set of hands for telling the time. Throughout my life I have been a hoarder of ideas; not writing them down but storing them in my memory. Years ago I played with circular verniers and, when I was thinking about the clock, I had the idea of using concentric rings of vernier
Fig. 3. A view inside the Corpus Clock, showing the concentric rings of LEDs and the pendulum that extends down from the ‘chronophage’ grasshopper escapement.
slits to expose lights that would indicate the time, with an inner ring showing hours, a middle ring showing minutes and an outer ring for seconds. I started out with 60 slits for the minutes and a disc behind with 59 slits to give the vernier effect. The trouble was that when the clock advanced from one minute to the next the lights appeared to dart round anticlockwise. After a while I realised that I could break with convention and use 61 slots on the rear disc to make the lights run clockwise” (Fig. 3).
However, building a clock
this size posed a problem, as Dr Taylor explains: “The clock – and therefore the escape wheel – is about 1.5 metres in diameter. We found that essentially it had too much inertia. But to overcome the inertia, the remontoire spring had to be so strong that the impulse on the pendulum increased its amplitude. “If you watch the finished
clock you will see that it sometimes seems to pause, run backwards or run faster, and the pendulum might only swing for half a cycle. It is the first clock ever to tell relative time. But whatever tricks the clock plays, it will always be accurate to within one one-hundredth of a second every five minutes, as it receives the MSF time signal from the NPL (National Physical Laboratory) transmitter at Anthorn.” The Corpus Clock is a mesmerising blend of art and engineering, incorporating six patented inventions. It is also laden with symbology, such as the centre drop and concentric ripples that allude to the Big Bang at the beginning of time and the pulsating waves that are still radiating outwards today. At the top of the clock, the sculpted chronophage has eyelids that close randomly, a mouth that slowly opens and snaps shut every minute (devouring time), and a sting in the tail that clicks up every fifteen minutes. Every hour, on the hour, the chronophage snaps its mouth and shudders, shooting its sting the number of times of the hour itself. Dr Taylor says that the Corpus Clock will last for at
least 200 years, which would certainly be a fitting tribute to the man who gave us something as elegant yet simple as the bimetallic strip, as well as something of such importance to world trade as the marine chronometer. n
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