[time-nuts] Am I the only Time Nut who doesn't wear a watch?

[Will Matney]

Hal,

*********** REPLY SEPARATOR  ***********

On 7/10/2011 at 10:12 PM Hal Murray wrote:

>>> 4 seconds per day?  I'd expected better from a very expensive watch.
>>> Are belts nasty when it comes to keeping good time?
>
>> No, it shouldn't have nothing to do with the belts, as they're the same
as
>> timing belts, or toothed belts, and would work the same as gear teeth.
The
>> accuracy will come from the balance wheel arrangement, and with all the
>> jewels (bearings), one would think it would sure move free. However,
keeping
>> in mind they said they were ball bearings, I would say each uses at
least
>> four "jewel" balls to a bearing, and that is where the majority of them
is
>> used up. I would think that it all goes back to the balance wheel and
the
>> escapement, or type of, as to any accuracy issues, unless of course the
>> belts do slip somehow, but they shouldn't. I didn't get a good look at
the
>> balance wheel to see what type of temperature compesation it used, if
any. 
>
>I wasn't worried about the belts jumping a cog.  It was more a secondary 
>(tertiary?) quirk of the loading not being constant over temperature, or 
>something like that, and the loading having minor impacts on the overall 
>timekeeping.  (I was assuming the belts were at the hour level rather than

>the second level.)

Well, they said they had wire cores in the belts, and I would say that this
is over not just strengthening the belt, but controlling expansion and
contraction. Contraction could load a cogged wheel more, however, they
mounted them on ball bearings, or I think most were, and that should keep
them from binding less than one would one a single ruby.

>
>The other obvious question is: what is "good" accuracy for a modern watch,

>and what is "very" good for an expensive watch.  1 second per day is 11
PPM.

According to one website, a certified mechanical chronometers best is about
+/- 1 second per day, and typical is +/- 3.

http://www.chronocentric.com/watches/accuracy.shtml

>
>I'm not calibrated on mechanical balance wheels.  I'm pretty sure the 
>mechanical watch my grandparents gave me many many years ago (high school 
>graduation) was better than 4 seconds per day.  (I wasn't a certified 
>time-nut back then, but I think I would have noticed something like that.)
 I 
>wonder if I can still find it.
>
>The crystals on my PCs are ballpark of 1 PPM per C.  I'd expect a watch 
>crystal to be tuned to human temperature environments and be better than 
>that.   I guess I'll have to get setup to collect some data.
>
>4 seconds per day would be great if it were guaranteed over a wide 
>temperature range, but that web page didn't mention anything about 
>temperature.


The only thing mentioned, I think, was maybe the balance wheel's material
(Glucydur). I looked again, and noticed it didn't have any eccentric
screw-weights about the wheel, for fine tuning it, or it didn't look to
have more that one or two at the most, as it's hard to see the thing. It's
pretty thin to, which probably is why it has no screws. It did look to be
split though, like it should be, for a change in it's diamtater when the
temp. rises.

The thing is, for the price, and man can buy a certified chronagraph, with
a tourbillion escapement, for less than this costs. To me, the belt design,
which was used so they could place the extra hands around the face where
they wanted them, is a novelty, and not really built to be an exact time
keeper, like a tourbillion would be.

>
>
>-- 
>These are my opinions, not necessarily my employer's.  I hate spam.
>
>
>
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Best,

Will