By the end of the 15th century, the Grandfather clocks had not been invented yet, but things were about to change. The basic design of the clock had remained the same for over 400 years. It still used the verge-and-foliot control mechanism first invented around 1285. The antique clocks of this period were not accurate and sometimes would exhibit hours of deviation.
The astronomers and naval navigators needed grandfather clocks to be accurate to a few seconds during a 24-hour period. Galileo Galilei (c. 1564-1642), an Italian physicist, mathematician, and astronomer, conceived of a new type of escapement using a pendulum in 1641, but he never produced a working prototype. At this stage in his life Galileo was blind and months away from his death.
The Dutch mathematician and astronomer, Christiaan Huygens (c. 1629–1695), was designing an oscillator using the pendulum from an idea proposed by Galileo. By 1656, Christiaan Huygens had completed the Galileo’s designs, refined them, and implemented the first working model of a pendulum clock. Although the first working model used the older style of the verge escapement, the new clock was accurate to within one minute a day. Christiaan’s original grandfather clock hung on walls and were affectionately entitled by the English clockmakers as “wags-on-the-wall” due to their short pendulums.
Dr. Robert Hooke (c. 1635-1703) was an English natural philosopher and mathematician. In 1656, he was working on a new type of escapement called the anchor escapement that would vastly improve the new clock Christiaan Huygens had designed. The chief disadvantage of the verge escapement was that it needed a wide pendulum swing. 300px-huygens
The Hooke anchor escapement required a much smaller swing and replaced the verge style. A smaller swing made it possible to use a much longer and heavier pendulum. This reduced wear in the escapement and provided a more stable swing that closely resembled simple harmonic motion. This change greatly increased the accuracy of the pendulum clock.
In 1657, Christiaan Huygens was granted a patent for the pendulum clock. Salomon Coster (c. 1620-1659), a Dutch clockmaker of Hague, contracted with Christiaan Huygens to build the pendulum grandfather clocks. Coster’s earliest pendulum clocks were signed “Samuel Coster Haghe met privilege” indicating that he was authorized by the inventor to make such grandfather clocks.
John Fromanteel, the son of a London clockmaker, went to work for Coster. He was one of many foreign Clockmakers to make pendulum clocks following the prototype by Huygens and Coster. A contract signed on September 3, 1657, between Salomon Coster and John Fromanteel allowed Fromanteel to make the new pendulum clocks.
Because of the long pendulum, required by the anchor escapement, they named the clock the Long-Case. This new generation of grandfather clocks would lose only a few seconds per week. Dr. Robert Hooke discovered the law of elasticity around 1660. Hooke, using this law, applied a spring to the balance wheel of a watch with a verge escapement, creating the balance spring. This balance spring, made of tempered spring steel, was of a straight design. He later designed a spiral spring.
Parallel to Hooke’s spring development, Christiaan Huygens and Abbé Hautefeuille worked on a spiral formed balance spring, which we now know as the hairspring. Since the advent of the balance spring, virtually every quality clock made with a pendulum has a balance spring. The importance of the balance spring increased when used with the modified anchor escapement to eliminate unnecessary recoil action, further reducing the rate of error to one second a week.
We have seen these beautiful antique grandfather clocks most of our lives, but the antique clocks build before 1680 did not have a minute hand. Somewhere between 1680-1690 the accuracy of clocks had increase to an extent that the minute hand was added, and eventually a glass front was introduced to better display the internal workings of the pendulum, chains, and weights.