Timepieces

At Oxford Hooke applied himself to the improvement of the pendulum and in 1657 or 1658, he began to improve on pendulum mechanisms, studying the work of Riccioli, and going on to study both gravitation and the mechanics of timekeeping

Hooke recorded that he conceived of a way to determine longitude, and with the help of Boyle and others he attempted to patent it. In the process, Hooke demonstrated a pocket-watch of his own devising, fitted with a coil spring attached to the arbour of the balance. Hooke's ultimate failure to secure sufficiently lucrative terms for the exploitation of this idea resulted in its being shelved, and evidently caused him to become more jealous of his inventions.

There is substantial evidence to state with reasonable confidence, as Ward, Aubrey, Waller and others all do, that Hooke developed the balance spring independently of and some fifteen years before Huygens, who published his own work in Journal de Scavans in February 1675. Henry Sully, writing in Paris in 1717, described the anchor escapement as "an admirable invention of which Dr. Hooke, formerly professor of geometry in Gresham College at London, was the inventor." Derham also attributes it to Hooke.

Realising the weakness of the pendulum clock in keeping time on a ship which was pitching and tossing, he wondered about the " ... use of springs instead of gravity for making a body vibrate in any posture."

Rather than the balance wheel being controlled by a pendulum which in turn operated through gravity, he reasoned that controlling the balance wheel with a spring would have huge advantages for a portable timekeeper that one might carry around or one which would have to continue to keep the correct time on a ship. Beginning his experiments around 1658 he had made two significant steps by 1660, namely the use of a balance controlled by a spiral spring and an improved escapement called the anchor escapement. In 1660 he discovered an instance of Hooke's law while working on designs for the balance springs of clocks. However he only announced the general law of elasticity in his lecture 'Of Spring' given in 1678.

In fact 1660 was the year when a rather strange event happened regarding Hooke's spring controlled clocks. In that year he was backed by Wren, Moray and Brouncker in his design of a spring controlled clock and a patent was drawn up. It could have led to him making a fortune, but when he realised that the patent would allow anyone who improved on his design to receive the royalties, he refused to continue with the patent.

In 1658 applied circular pendulum to watches, discovery unknown until 1675.

The development of more exact clocks, unaffected by external influences, was an important step for solving the determination of longitude at sea. According to his own accounts, Hooke had already developed an improved pendulum clock by 1658, with which he was of the opinion that it would contribute to solving this problem. At the end of 1663 or the beginning of 1664 a meeting was arranged by Boyle with Moray and Brouncker, at which the conditions for a patent for Hooke's pendulum clock was to be worked out. Hooke did not however agree to the proposed conditions as all further improvements would likewise enjoy a claim for a patent.

1660 anchor escapement

In 1671 William Clement produced a clock with an anchor escapement leading to dispute.

verge escapement

Huygens

Huygens had a pendulum clock patented in 1657, which showed a clear improved accuracy compared with traditional clocks. When Huygens spend time in London in 1661, the Royal Navy showed interest in his invention and experimented with his pendulum clock for the next four years.

1662 - Robert Holmes testd the clock on a voyage to Guinea, and seemingly reported favorably on it. An improved version of Huygen's pendulum clock was awarded a patent in 1665 by Robert Moray. The income accruing from this was shred by Huygens with the Royal Society.

In 1673 he produced cycloidally shaped suspension curbs producing isochronous swinging of the pendulum

On 18th. February 1675, Oldenburg read to the Royal Society an extract from a letter from Christiaan Huygens, which was intended for publication in the Philosophical Transactions. Huygens announced that he had invented a new type of compact watch with a spring balance which a displayed an accuracy never before achieved. Hearing this, Hooke reacted strongly and protested that the copyright for this invention lay with him. He had alreasdy presented a few watches with a spring balance to the members of the society in the 1660s.

Henry Oldenburg, secretary of the Royal Society and long-term correspondent of Huygens, strongly supported the concept of Huygens receiving an English patent for his new clock. Immediately after Huygens' letter had become known Hooke had, together with Thomas Tompion (of Water Street, nr Fleet Street), begun to produce a working watch in line with his ideas, using a spring. In April 1675 Jonas Moore (16171679), who as Surveyor-General of the Ordnance carried responsibility for English military research and development, arranged an audience with the King for Hooke and Tompion, at which the prototype of the watch was presented.

Oldenburg urged Huygens as a result to send a functioning clock to England. The example sent by Huygens in June to Brounker showed itself to be unreliable, but even Hooke and Tompion were forced to make adjustements repeatedly to the watch which was shown to the king.

In order to prove his claims to priority, Hooke pointed to the records of the Royal Society, but could find no record of his demonstration of his spring-driven watch. He suspected manipulation and betrayal by Oldenburg.

Jonas Moore advised Hooke on patent for spring watch

The Council of the Royal Society, who perceived their repuation as being damaged by this patent dispute, backed Oldenburg and rebuked both and John Martyn, the Royal Society's publisher. When Hooke was elected as Secretary of the Royal Society in Autumn 1677 after Oldenburg's death, he could examine Oldenburg's correspondence. He found two letters from the year 1665, one from Huygens to Oldenburg as well as one from Moray to Huygens, showing that Huygens had received from both important information on Hooke's experiments with clocks

'Animadiversions' accuses Huygens of giving account of circular pendulum without giving his own prior invention of it

Hooke used a second watchmaker as well - Bennett of Clerkenwell

1678 - 'De Potentia Restitutiva' or 'Of Spring'

Hooke's Law

1675 Hooke's Law

notes : paired or double balance, double spring watch balance, 9 3/4 inch half-second pendulum, balance spring, pendulum through smaller angle hence more dynamically stable angle