Richard Towneley - The Tompion Clocks at Greenwich and The Deadbeat Escapement

The Tompion Clocks At Greenwich and The Deadbeat Escapement

Once at Greenwich, Flamsteed asked Towneley to help him prove that the Earth rotated at a constant speed. Towneley designed a novel clock escapement for this purpose and two astronomical clocks were commissioned to his design from the clockmaker Thomas Tompion and installed at the Greenwich Observatory. The clocks were paid for by Sir Jonas Moore, Surveyor General of the King's Ordnance and a friend of Towneley. Towneley had recognised that the second hand of pendulum clocks, using an anchor escapement, jerked backward due to recoil, causing inaccuracy. Towneley's design eliminated the recoil and was the first of a kind that came to be known as a deadbeat escapement. The clocks were installed on 7 July 1676. The deadbeat escapement, widely introduced by clockmaker George Graham around 1715, was significantly more accurate than the anchor and in the 19th century became the standard escapement used in quality pendulum clocks.

Flamsteed wrote often to Towneley about the clocks, which were made to run for a year between windings. It proved difficult to keep both clocks running for a whole year and, in January 1678, Tompion replaced the original escapement with one of his own design. The clocks eventually went for four years without stopping and Flamsteed was able to prove to his own satisfaction that the Earth rotated at a constant speed.