Quick Train—A watch movement balance vibrates 18,000 times per hour. Unequal mainspring pull is less felt in the quick train. Used generally in Switzerland and America, and a feature of practically all modern watches.
Rack—A straight bar, or segment of a circle, with teeth along one edge. It has a reciprocating motion.
"Radiolite"—Trade name adopted by Robt. H. Ingersoll & Brothers. for their watches having black faced dials with luminous hands and numerals. Composed of a substance in which genuine radium is used in minute proportions.
Radius of Gyration—The distance from the center of gyration to the axis of rotation.
Ramsey, Davis—One of the earliest British watchmakers of renown. He was appointed "keeper of clocks and watches" to James I, and appears to have retained his appointments after the death of the latter. He was the first master of the Clockmakers' Company tho he seems to have taken little active part in the management thereof. Scott introduces him into his story—"The Fortunes of Nigel" as a Keeper of a shop a few yards east of Temple Bar. Without doubt he was the leading clockmaker of his day. He died in 1655.
Ratchet—The pawl, or dog, which engages in the teeth of a ratchet wheel and prevents it from turning backward. It is held lightly against the periphery of the ratchet wheel by a small spring known as the ratchet spring.
Ratchet Wheel—A wheel with triangular teeth fixed on to an arbor to prevent the latter from turning backward. The fronts of the teeth are radial, the backs straight lines running from the tip of one tooth to the base of the next. In going-barrel, keyless watches the ratchet has epicycloidal teeth. By "the ratchet" in a watch, chronometer or clock with mainspring is meant the ratchet fastened to the barrel arbor to prevent the mainspring from slipping back when it is being wound.
Recoil—In recoil escapements the pallets not only stop the escape wheel but actually turn it backward a slight distance. This backward motion is called the recoil.