Remontoire

It was used in a few precision clocks and watches to place the source of power closer to the escapement, thereby increasing the accuracy by evening out variations in drive force caused by unevenness of the friction in the geartrain.

Remontoires are used because the timekeeping mechanism in clocks and watches, the pendulum or balance wheel, is never isochronous; its rate is affected by changes in the drive force applied to it.

Harrison's working drawing of the device is preserved in the Library of the Worshipful Company of Clockmakers in London, England.

Etymologically the term is correct, the mainspring is "rewound" by some other force than a key, but these watches usually do not contain a remontoire as the word is used today.

Many Rover (P4 to P6), Ford (Mk1 Escort, Mk2 Cortina, and Mk1 Capri GT/RS), and Triumph (Dolomite, 2000/2500, and Stag), as well as some Jaguar (S3 E-type), Daimler (DS420), and Aston Martin (V8) cars were fitted with Kienzle clocks that were wound by such electric remontoires.

Internal mechanisms of an electric remontoire clock from a 1960s Rover P4 – the red solenoid is visible at the back and the switch points, through which the solenoid winds the spring, are to the right and in their closed position