Anchor escapement anchor in his invention of the longcase or grandfather clock around 1680. When Clement's clock appeared Hooke claimed the invention of the escapement, saying that he had shown a clock with the same escapement to the Royal Society soon after the great fire of 1666. The earliest known anchor clock is Wadham College Clock, a tower clock built at Wadham College, Oxford, in 1670, probably by clockmaker Joseph Knibb. The anchor became the standard escapement used in almost all pendulum clocks. A variation without recoil called the deadbeat escapement was invented by Richard Towneley around 1675 and introduced by British
Escapement is made from a special steel alloy with 36% nickel called Invar whose length changes very little with temperature, swings as free of external influence as possible sealed in a vacuum chamber and does no work. It is in mechanical contact with its escapement for only a fraction of a second every 30 seconds. A secondary "slave" pendulum turns a ratchet, which triggers an electromagnet slightly less than every thirty seconds. This electromagnet releases a gravity lever onto the escapement above the master pendulum. A fraction of a second later (but exactly every 30 seconds), the motion of the master