So as mentioned on a previous thread I recently received my first mechanical; A Speedbird 3 automatic with ETA 2824-2 Top grade movement.
I've been monitoring its accuracy for the past couple of weeks and I thought I might share the data as well as ask a few questions for the experts out there.
To measure the accuracy I measured the deviation of the time on my mechanical from the time on my Digital Casio PRW3000 which receives a radio controlled time update at ~2am every night.
I did this at ~6pm every day so that I had the deviation over the last 24 hours and I did this for 16 days.
On receiving the watch I manually wound it twice and then I wore the watch almost continually for the duration presumably winding it automatically as I did so.
Here's the graph of deviation versus time:
As you can see the mechanical watch was always running fast compared to the atomic clock updated watch.
The first 24 hours it was +7secs and eventually it seems to have settled into ~ +1secs per 24 hour period.
I've read a number of other threads about 'settling' and I'm not sure that I've seen a consensus, so I've decided to start this thread hoping someone might clarify things for a mechanical newbie.
Here are my questions:
1) Is the above behaviour normal/typical?
2) What is the reason for the initial inaccuracy and the asymptotic behaviour as it 'settles'? Is it something to do with the increasing tension in the main spring as it is wound? I also read something about a new movement 'settling'?
3) Assuming the watch settles to a regular deviation (say +1 sec) then how confident can you be that it will remain reasonably constant? Should you check its accuracy at some interval to detect any trends?
If I know the watch has settled into ~ +1 sec/day behaviour then I think I'd be happy.
When changing the date I can set the time at ~ -30secs and then leave it for 2 months until I need to change the date again knowing the watch is unlikely to be more than about 30 secs inaccurate at any given time.
This level of accuracy would seem perfectly acceptable to me.
Thanks in advance for any help.
Finally, part of me would have liked to have taken the back off the watch and included a picture of the movement in this thread... but most of me knows that would be a bad idea!
So instead a quick hello from the Speedbird behind the data, sporting it's casual RAF strap for everyday wear