Amateur clock with two pendulums, 1925

In depth

Bradford-born ffolliot Gray worked for many years as an engineer, completing this clock design in his spare time from the loft of his house in Luton. Gray was granted a patent for a ‘twin pendulum’ clock in September 1926. He put the patent number on the dial of this clock, which he also numbered: the third he had made. ‘The Duo’ was exhibited at the International Exhibition of Inventions at the newly opened Central Hall, Westminster in October of the same year, where it was ‘warmly commended’ by the judges.

As its name suggests, the clock’s innovation is its twin pendulum system. The electro-mechanically powered drive pendulum on the left advances the motion work using a pecking pawl. It also has the job of lifting the gravity arm, leaving the pendulum on the right with nothing to do except keep time, which it thereby does to a good level of precision. ‘The Duo’ is thus a novel solution to the quest for a ‘free pendulum’; an early ambition of horology, and a live topic in the 1920s, William Hamilton Shortt and the Synchronome Company having manufactured their own observatory-grade ‘free pendulum’ clock in 1921 (TCW 1073).

Although Gray’s clock was presumably envisaged primarily as a domestic timekeeper, he was clearly also interested in its potential as a networked controlling clock: as well as exhibiting a separate clock with a ‘Repeater-Transmitter’ in 1926, he created a later transmitting version of ‘The Duo’ with a subsidiary dial (his fifth known clock), although this is unsigned and undated.

The Clockworks clock is one of the most developed of the five known ‘Duos’: it includes an amplitude restriction for the drive pendulum, and full crossing-out on all the wheels, visible through a partially skeletonised dial. Very much an independent amateur enterprise, the clock exemplifies the ingenuity brought to bear on perennial horology problems by engineers and inventors often working outside the formal discipline of clock and watchmaking.