How They Work
The rack and snail striking mechanism used in repeaters is described in detail in the striking clock article. Repeater clocks often had a cord with a button on the end protruding from the side of the clock. Pulling the cord actuated the repeater mechanism. This was called a pull repeater. Repeating carriage clocks have a button on the top to activate them.
Early watch repeater mechanisms were actuated by pushing and depressing the pendant (the top) of the watch. Later ones are activated by pushing a slide along the side of the case. This winds a separate spring to power the repeater. Releasing the slide releases the spring, and its force as it unwinds moves the repeater mechanism through its chiming sequence.
A problem with very early repeaters was that the slide could be released before it was fully cocked, causing the repeater to only chime part of its sequence. Around 1720 French watchmaker Abraham Breguet invented a reliable 'all-or-nothing' mechanism that prevented this, making watch repeaters considerably more reliable and popular. The first repeaters had a single bell mounted in the back of the case,on which 2 hammers would strike. This bell was made of "Bell metal", a mixture of copper and tin. The later gongs are made of long hardened steel wires that are coiled inside the watch case. Tiny hammers actuated by the repeater mechanism strike them to make the chiming sounds. Some of the complex repeaters, such as the minute repeater, need to produce three different sounds, to distinguish hours, quarter hours, and minutes in the striking sequence. Since it is difficult to fit three bulky wire gongs into a watch movement, virtually all repeaters use two gongs, made from the two ends of a single length of wire supported in the middle, and if a third sound is needed it is made by striking the two gongs rapidly in sequence, first the high tone and then the low: "ding-dong".
The repeaters have a mechanism that allows the pace of the repeater strikes to be changed. The owner of a repeater watch can ask a watchmaker to change the pace, making it faster or slower. According to the book "Etablissage et Repassage des Montres à Répétition" by John Huguenin (page 39 of the original edition), "a minute repeater with an average speed takes about twenty seconds to strike 12 hours, three quaters and forteen minutes".
Read more about this topic: Repeater (horology)
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