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

Hal Murray hmurray at megapathdsl.net
Mon Jul 11 05:12:42 UTC 2011


>> 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.)

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.

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.


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






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