[time-nuts] Watches

[Daun Yeagley]

Hi Chuck

Have you ever attempted, or know someone who has rewound or repaired the coils?
There was a guy on the Yahoo Accutron list that was experimenting with it, but I
don't know the final outcome. Seems that wire is thinner than most normally
available wire.
Seems that the "usual" way to deal with the silver oxide vs. mercury battery
problem is to use a schottkey diode in series with the battery (there's even
someone marketing a battery assembly with the diode imbedded, called an
Accucell).  I've been thinking all along that the best way to do it is to
re-bias the transistor.  I've wanted to experiment with that, but I need to come
up with another Accutron, as I don't want to ruin the Spaceview that I got from
my wife on our first Christmas way back in '67!   Know any reasonable sources?
I've been looking on Ebay, but they always seem to get bid way up, even for one
that doesn't run.
Glad to get another time-nuts take on this!

Daun 

-----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 7:51 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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