); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] Hi Brooke,
Back before the development of Elinvar, Metelinvar, and Nivarox hairsprings, and Glucydur balance wheels, watches used to need temperature compensated balance wheels. The temperature compensation principally compensated for the temperature variations in the springiness of the hairspring. It also compensated for the tendency of the balance wheel to grow and shrink in diameter with temperature. The rim of a compensated balance wheel was made of a bimetalic construction, and was cut so that each half of the rim was attached only to one arm of the hub. As temperature varied, the bimetallic rim would expand and contract, thus changing the rate of the watch. The hope was that the change in the wheel diameter would exactly match the change in the hairspring (with temperature), and the watch would keep good time. It is terribly difficult to get these two changes to match in way where they cancel each other out. With the advent of Elinvar, Metelinvar, Nivarox, and other alloys of Invar used in hairsprings such compensation is no longer needed, or desirable. Pretty much any quality watch made since the 1960's will have some variant of an Elinvar hairspring, and a Glucydur balance wheel. The screw weights on the rim of the balance wheel serve a double purpose. First, they make sure that the wheel balanced so that there is no heavy side of the wheel, and second, they are used to adjust the mass of the rim of the wheel to exactly match the spring constant of the hair spring so that the wheel will resonate at exactly the correct rate. I would say that given the age of the watch, the balance construction seems appropriate. -Chuck Harris Brooke Clarke wrote: > ); SAEximRunCond expanded to false > Errors-To: [EMAIL PROTECTED] > > Hi: > > I got this watch on eBay from Russia. After making the photo for it's web > page > I could see that the balance wheel appears to be all brass and is not cut > like > would be done with a bi-metal balance wheel. > > So now am thinking it's a fake. If you know watches have a look: > http://www.prc68.com/I/Watch-Real-Fake.shtml > > It's harder to see a very similar watch on eBay now at: > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250138676169 > With the watch running you can't tell if there's the cuts in the balance > wheel. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
