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

[David C. Partridge]

My (non-chronometer) Breitling A17045 which came back from a service in May is running at about 1 seconds slow per day over a month (it is about a month since I last checked against the GPS, and it is about 25s slow).

However I think this is far better than should be expected

Dave
-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Hal Murray
Sent: 11 July 2011 06:13
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Am I the only Time Nut who doesn't wear a watch?


>> 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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