Hi Tom, Yep, there was a weak point there, but not for the reasons you might imagine. The big 300 tooth wheel was a ratchet wheel that was driven by a pair of sapphire pawls that were attached the tuning fork by a thin springy wire. The 300 tooth wheel directly drove the second hand of the watch. That is why the watch had that velvet smooth second hand. If the watchmaker forced the second hand to rotate, it would bend the springy pieces of wire (not wire actually), and that was that.
It was difficult adjusting the phase of the two ratchet pawls relative to the teeth on the wheel. One pawl had to be half way between a root and a crest when the motive pawl ligned up with a crest. A 20-30x microscope was necessary.... that and a very steady hand. Electrically the biggest failure item was the tuning fork coils themselves. The coils were wound with wire that was around #48 AWG. It would break, or corrode at the solder joint, and the watch would stop. Rewinding the coils is a doable task if you can get the wire, and you know how to deal with it. Now days, the 1.35V mercury cells that the Accutron used are no longer available, and the 1.5V silver oxide cells overdrive the tuning fork, causing lots of noise, and motion problems. Changing a resistor, and adjusting the phase of the pawls will usually allow the use of politically correct cells. -Chuck Harris Thomas A. Frank wrote: >> Real tuning form Accutrons are collectibles now, and it is not >> unheard of for >> an unscrupulous watchmaker to steal the movement out of one, and >> replace it with >> a cheap quartz movement, all in the name of doing the watch's owner >> a favor. > > Not just unscrupulous watchmakers, that's what happens if you send > your watch back to Bulova for repair! > > If you know enough to include a note saying do not replace, they > return it untouched, as they no longer service the tuning fork > movements (I imagine they would put in a battery and new o-rings for > the case, but anyone can do that, so why risk a possible error?). > > There are now folks who specialize in repairing these nifty pieces of > technological ephemera. > > I understand the weak point in the design is the 300 tooth escape > wheel which rides the tuning fork. Fragile teeth. > > Tom Frank > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.