didier at cox.net
Mon Dec 3 21:23:06 EST 2007
My dad has one of the original tuning fork Accutron. I know he stopped
wearing it a while back, but I am not sure why. I will ask him if he still
has it and if it works and in case he does, I would like to go back to you
for more information in order to make it work again, if that's OK.
Thanks in advance,
> -----Original Message-----
> From: time-nuts-bounces at febo.com
> [mailto:time-nuts-bounces at febo.com] On Behalf Of Chuck Harris
> Sent: Monday, December 03, 2007 6:51 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Watches
> 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
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