[time-nuts] Watches

[Didier Juges]

Chuck,

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,

Didier

> -----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
> > 
> > 
> > 
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at 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 at febo.com To unsubscribe, 
> go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.