Bartrum's free pendulum clock

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Bartrum's free pendulum clock
Manufacturer	(unknown)
Production years	20th century
Production location	(unknown)

A clock first described by C. O. Bartrum of Hampstead in 1917, embodying the principle of the free pendulum and slave clock first employed by Rudd in 1899. It was probably the first clock of this type to work reliably.

[edit] How it works

The free pendulum, on the left, swings freely between impulses, and receives an impulse of a fraction of a second’s duration every minute: after the impulse it transmits a synchronising signal to the slave clock, on the right. At the end of the ensuing minute the slave clock releases the next impulse to the free pendulum. The impulse imparted to the free pendulum is a gravity one of constant amount, and the lever which applies the impulse is released by an electro-magnet operated by the slave clock. As the impulse arm falls away after giving the impulse, it makes an electric contact which transmits a synchronising signal to the slave clock and also actuates an electro-magnet which restores the gravity arm to its rest position. The slave clock then measures out the ensuing period of just under 60 seconds before it releases the free pendulum’s impulse arm for the next impulse. As described in an adjacent label, the nature of the synchronising action is such that any error arising in the slave is rocked with decreasing amplitude until it has disappeared and the two pendulums are exactly synchronised again. The synchroniser has the great theoretical merit of correcting both the rate and phase of the slave. The slave clock itself, on the right, is a weight-driven timepiece with dead-beat escapement.

[edit] Memories

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[edit] In the Science Museum's Records

Inv. No: 1939-310