Factors affecting chronometer accuracy.
Discussion
I have a Rolex 14060M which is a 2012 model that I have been wearing for about 4 months. It was brand new when I started wearing it (new old stock).
Before I started wearing it I had it running in the box and wound it every 2 days, it gained 2 seconds per day.
When I started wearing it, it gained about 2 seconds per day.
A few weeks ago I noted that it was 16 seconds slow. I did nothing. Two weeks later it was keeping perfect time give or take a second per day. So it had made up time.
This week it's losing about 1.5 seconds per day.
So it seems to be running within COSC tolerances, but with some variation. Can anyone give me an explanation as to why though please?
Before I started wearing it I had it running in the box and wound it every 2 days, it gained 2 seconds per day.
When I started wearing it, it gained about 2 seconds per day.
A few weeks ago I noted that it was 16 seconds slow. I did nothing. Two weeks later it was keeping perfect time give or take a second per day. So it had made up time.
This week it's losing about 1.5 seconds per day.
So it seems to be running within COSC tolerances, but with some variation. Can anyone give me an explanation as to why though please?
Do your wearing habits vary? Mechanical watches will run faster / slower dependant on the position that they're in due to gravitational forces on the parts within the movement, for example if you leave the watch face up it may run at a different pace to when it's moving about on your wrist. If it has been regulated to run to within COSC standards (where watches are tested in different positions and at different temperatures) that doesn't mean that the run rate will be the same regardless of the position, just that it'll run within COSC.
Try keeping the watch wound for a couple of days or so off the wrist dial up and see if the daily rate varies, if it does then there may be an issue.
Try keeping the watch wound for a couple of days or so off the wrist dial up and see if the daily rate varies, if it does then there may be an issue.
That's (probably) well within COSC specs. It's impossible to know for certain without running through the full 10 day test, because some of the standards won't show up in the average rate over time.
Briefly, a mechanical watch's rate will be affected by:
Temperature: COSC allows up to 0.6 seconds per day variation for every degree C of temp change
Position: COSC allows between -6 and +8 seconds per day variation depending whether the watch is horizontal or vertical. It also allows any one position (such as "pendant up") to be +/- 10 seconds per day compared to its average. That alone can give an error of up to +16 / -14 seconds in a singe day if the watch happens to be left in its "worst" position.
"Random" errors: COSC allows a +/- 2 second per day variation in the daily rate for no specified reason. So, with all other things being equal, it can run +1 second one day, +3 seconds the next and +5 on the third, then back to +3 again, while still being within COSC spec with an average of +3 seconds.
In your case, losing 16 seconds over maybe 10 weeks (guessed from your "worn for 14 weeks [...] I noticed a few weeks ago[...]" gives a long-term average in use of about -0.2 seconds per day and the behaviour since (gained those 16 seconds in 4 weeks) gives a long-term average of +0.6 seconds per day. That change of 0.8 seconds per day in the average is well within the 2 sec / day allowed for random errors, so looking for reasons is likely to be a fruitless task!
Briefly, a mechanical watch's rate will be affected by:
Temperature: COSC allows up to 0.6 seconds per day variation for every degree C of temp change
Position: COSC allows between -6 and +8 seconds per day variation depending whether the watch is horizontal or vertical. It also allows any one position (such as "pendant up") to be +/- 10 seconds per day compared to its average. That alone can give an error of up to +16 / -14 seconds in a singe day if the watch happens to be left in its "worst" position.
"Random" errors: COSC allows a +/- 2 second per day variation in the daily rate for no specified reason. So, with all other things being equal, it can run +1 second one day, +3 seconds the next and +5 on the third, then back to +3 again, while still being within COSC spec with an average of +3 seconds.
In your case, losing 16 seconds over maybe 10 weeks (guessed from your "worn for 14 weeks [...] I noticed a few weeks ago[...]" gives a long-term average in use of about -0.2 seconds per day and the behaviour since (gained those 16 seconds in 4 weeks) gives a long-term average of +0.6 seconds per day. That change of 0.8 seconds per day in the average is well within the 2 sec / day allowed for random errors, so looking for reasons is likely to be a fruitless task!
Variomatic said:
That's (probably) well within COSC specs. It's impossible to know for certain without running through the full 10 day test, because some of the standards won't show up in the average rate over time.
Briefly, a mechanical watch's rate will be affected by:
Temperature: COSC allows up to 0.6 seconds per day variation for every degree C of temp change
Position: COSC allows between -6 and +8 seconds per day variation depending whether the watch is horizontal or vertical. It also allows any one position (such as "pendant up") to be +/- 10 seconds per day compared to its average. That alone can give an error of up to +16 / -14 seconds in a singe day if the watch happens to be left in its "worst" position.
"Random" errors: COSC allows a +/- 2 second per day variation in the daily rate for no specified reason. So, with all other things being equal, it can run +1 second one day, +3 seconds the next and +5 on the third, then back to +3 again, while still being within COSC spec with an average of +3 seconds.
In your case, losing 16 seconds over maybe 10 weeks (guessed from your "worn for 14 weeks [...] I noticed a few weeks ago[...]" gives a long-term average in use of about -0.2 seconds per day and the behaviour since (gained those 16 seconds in 4 weeks) gives a long-term average of +0.6 seconds per day. That change of 0.8 seconds per day in the average is well within the 2 sec / day allowed for random errors, so looking for reasons is likely to be a fruitless task!
Interesting stuff, thank you.Briefly, a mechanical watch's rate will be affected by:
Temperature: COSC allows up to 0.6 seconds per day variation for every degree C of temp change
Position: COSC allows between -6 and +8 seconds per day variation depending whether the watch is horizontal or vertical. It also allows any one position (such as "pendant up") to be +/- 10 seconds per day compared to its average. That alone can give an error of up to +16 / -14 seconds in a singe day if the watch happens to be left in its "worst" position.
"Random" errors: COSC allows a +/- 2 second per day variation in the daily rate for no specified reason. So, with all other things being equal, it can run +1 second one day, +3 seconds the next and +5 on the third, then back to +3 again, while still being within COSC spec with an average of +3 seconds.
In your case, losing 16 seconds over maybe 10 weeks (guessed from your "worn for 14 weeks [...] I noticed a few weeks ago[...]" gives a long-term average in use of about -0.2 seconds per day and the behaviour since (gained those 16 seconds in 4 weeks) gives a long-term average of +0.6 seconds per day. That change of 0.8 seconds per day in the average is well within the 2 sec / day allowed for random errors, so looking for reasons is likely to be a fruitless task!
So does this mean that the -4 +6 is an average, assuming that the watch is in various positions during a day?
I have been laying it on its back at night in the belief that this will make it gain slightly. But I cannot say I am noticing much difference.
Yes, the -4 / +6 is the average daily rate taken over the entire test (10 days). They keep it in various positions and temperatures for the 10 days then, at the end, divide the total error by 10. So a total loss of 40 seconds or gain of 60 seconds will be (just) acceptable.
For the positional errors, they compare the difference in daily rate averaged over the time spent with the watch vertical (one day with the crown down and one day with it at "9 o'clock") with the average while it's horizontal )one day dial up, one day dial down). the difference between those two averages mustn't be more than -6 or greater than +8 seconds per day.
They also compare the "worst" single-day position (it doesn't matter which position that is) with the overall average rate. There mustn't be more than 10 seconds per day difference in either direction (+ or -). So, say the average daily rate is +2 s/d and in "dial up" it's running -8 s/day that would be ok provided the -8 dial up is compensated enough by dial down to pass the second test above.
For the positional errors, they compare the difference in daily rate averaged over the time spent with the watch vertical (one day with the crown down and one day with it at "9 o'clock") with the average while it's horizontal )one day dial up, one day dial down). the difference between those two averages mustn't be more than -6 or greater than +8 seconds per day.
They also compare the "worst" single-day position (it doesn't matter which position that is) with the overall average rate. There mustn't be more than 10 seconds per day difference in either direction (+ or -). So, say the average daily rate is +2 s/d and in "dial up" it's running -8 s/day that would be ok provided the -8 dial up is compensated enough by dial down to pass the second test above.
Variomatic said:
Yes, the -4 / +6 is the average daily rate taken over the entire test (10 days). They keep it in various positions and temperatures for the 10 days then, at the end, divide the total error by 10. So a total loss of 40 seconds or gain of 60 seconds will be (just) acceptable.
For the positional errors, they compare the difference in daily rate averaged over the time spent with the watch vertical (one day with the crown down and one day with it at "9 o'clock") with the average while it's horizontal )one day dial up, one day dial down). the difference between those two averages mustn't be more than -6 or greater than +8 seconds per day.
They also compare the "worst" single-day position (it doesn't matter which position that is) with the overall average rate. There mustn't be more than 10 seconds per day difference in either direction (+ or -). So, say the average daily rate is +2 s/d and in "dial up" it's running -8 s/day that would be ok provided the -8 dial up is compensated enough by dial down to pass the second test above.
Thanks for a comprehensive answer.For the positional errors, they compare the difference in daily rate averaged over the time spent with the watch vertical (one day with the crown down and one day with it at "9 o'clock") with the average while it's horizontal )one day dial up, one day dial down). the difference between those two averages mustn't be more than -6 or greater than +8 seconds per day.
They also compare the "worst" single-day position (it doesn't matter which position that is) with the overall average rate. There mustn't be more than 10 seconds per day difference in either direction (+ or -). So, say the average daily rate is +2 s/d and in "dial up" it's running -8 s/day that would be ok provided the -8 dial up is compensated enough by dial down to pass the second test above.
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