Comparative performance of watches with elinvar and with steel hairsprings

The performance of watches having the usual cut, bimetallic balance wheels and steel hairsprings is compared with that of watches having uncut, monometallic balance wheels and elinvar hairsprings. The latter combination of vibrating assembly is a new application intended to improve the general performance of watches. Twenty watches of each type, 10 each of 2 makes, were given performance tests at temperatures encountered in ordinary use. The temperature-rate errors of the watches having the new vibrating assembly were less than those for watches having the ordinary assembly, and instead of the usual parabolic curve, a curve approaching a straight line was obtained. Marked improvement in performance at temperatures within the usual temperature range 5 to 35 C is indicated by the use of the new assembly. The new assembly almost entirely overcomes the effects of magnetism so that, after the watch is removed from a magnetic field, the rate is not subject to fluctuations experienced with the ordinary assembly. There is no evidence of any marked difference in performance of the two types of watches in different positions or for isochronism. CONTENTS Page