Reply With QuoteDropping it
I recently received a lovely watch and it had been serviced by an excellent watchmaker a few months ago. However, it very consistently lost an average of 16s/day.
These things happen and, for the avoidance of doubt in these troubled times, my post is in no way a passive-aggressive go at the watchmaker, who has has kindly re-regulated it for me, or at the seller, for that matter.
There are well-known factors which can affect the accuracy of an otherwise well-maintained, moisture-free movement: temperature (especially big changes in it), shock/vibration, magnetism, and position/gravity.
I'm not primarily interested in why my particular watch might have gone out of regulation but rather, and out of intellectual curiosity, are there any other, lesser-known factors which impact accuracy?
Many thanks,
LP
Dropping it
It's just a matter of time...
You mention temperature, I've noticed my automatics running 10+ secs faster per day when on the past 2 summer holidays (daily temps 30+c). Different watches.
I posted a thread about it last summer but no-on seemed to have shared that experience. If it happens again this summer with a 3rd watch, then I'm right and everyone else is wrong...........
I assume you behave differently when on holiday than when at home? This may well play into it, such as increased or decreased states of wind (if automatics) compared to when home due to being more or less active.Originally Posted by stefmcd
Logical points.
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You may be confusing causes. When on holiday it's hotter...but your pattern of activity is probably very different as well. Which will bring into play the factors you mention....
Part of the fun of a mechanical watch is the way it reacts to the world around it.
+1.......they don`t like the shock imparted by contact with hard surfaces.
However, for reasons I can`t fully explain, some watches take a while to settle down after servicing. If it's a modern ETA in good condition it'll usually settle within 48hrs and behave consistently, but old watches can take longer. The only explanation I can offer is that the oil film/lubrication in some areas needs to stabilise and that's why it's important not to over-oil in critical areas. I also think the mainspring needs to settle into the barrel, particularly if there's some wear on the barrel itself; this is only achieved by the watch going through cycles of winding and unwinding. This is my own theory, I've never seen it proved or disproved, but it makes sense to me. Minor changes effect the torque being imparted to the movement, in an ideal world a new barrel would be fitted and the bushing in the barrel bridge and mainplate replaced, but often this isn't feasible.
I`ve known watches take around 10 days to completely settle after service. Owing to the very limited scale I work on I usually regulate watches by wearing them for a few hours. Usually a watch will give fairly consistent 'on the wrist' performance but that may differ from the rate when left dial-up overnight. Obviously it's easy to measure the dial-up rate and to look for consistency over a few days. When the dial-up rate is consistent it's a good indication the watch has settled and can be fine-tuned. The relationship between dial-up and 'on the wrist' is usually consistent and once it's been established the watch shouldn`t need more wrist time to check, the regulation can be made based on the dial up rate. It should be possible to regulate a watch based on the different positional rates and the performance on a cyclotester, particularly if the watch is good quality and in very good condition, but older/lesser watches are less easy to regulate and that's where my somewhat laborious and empirical procedure scores.
Ideally, I like to run a watch for around 10 days before sending it back, but if it's bang-on consistent after 3-4 days I`d run it for less.
One problem that can occur, and can sometimes slip through un-noticed, is caused by the amplitude becoming too high when an automatic is fully wound. This is known as 'knocking the banking' or over-banking, the impulse jewel hits the pallet fork as the balance rotates too far and this causes it to bounce back. In this condition the rate will be fast and the watch will gain time. It's caused by the mainspring not slipping correctly in the barrel or the mainspring being too strong. Using different lubricant on the barrel wall will sometimes fix it, but there are other ways and means too. Usually, old watches suffer from low amplitude but that's not always the case. Replacement mainsprings can sometimes be stronger than the original and this problem can occur. There are ways to test for it and it's something to look out for if the amplitude's a bit too good, but it's an easy one to miss. sometimes the amplitude improves on a watch after a few days running and it can move into the area where 'knocking the banking' is possible, I had one recently that did this and it needed the barrel lubricating with a different grease to mitigate the effect.
Finally, on the rare occasion that someone's questioned the timekeeping on one I`ve fixed, I always ask what it's being checked against. Computers and phones can be unreliable unless a specific site is being used. The inbuilt clocks/timers can tell misleading lies, I use a quartz watch on the bench or a 'current time' website...or my Casio F91 digital! Before anyone complains about a watch I suggest they establish what it's really doing, repairers hate to be told that a watch has a problem only to find that the watch is running perfectly and the owner's not checked correctly....trust me it's infuriating.
Paul
Paul - that's really interesting, thank you, especially about the mainspring barrel. A couple of years ago I took delivery of a lovely Omega and it was initially all over the place before settling down after a a few days and several full winds. It's run true ever since. (I seem to recall over-banking being a particular issue with the Mark Xii until it was fixed?)
I have a jlc reverso hand wound which is generally extremely accurate. However I noticed it sometimes runs a little slow (-1 or 2s per day) and sometimes similarly fast.
I somehow worked out (not entirely sure how) that it runs a little slower when fully wound and a little faster when left to run quite low on power reserve.
If I wind it approx 24 hourly, it usually runs very slightly slow over a few days, but I can then self regulate by winding 36 hourly a few times and vice versa (12 hourly) to slow it down a bit!
IIRC when fully wound the balance amplitude is larger, so the period is longer and the watch runs slower. Vice versa when run down.
Dave
Dave - Do you know if that’s a factor variable by design of those parts alone or is it an absolute that needs to be accounted for in the overall design?
If only it was that simple, where it is pinned and how this is in relation to the stud will change this. Most watches made are adjusted to make them gain at low amplitude. Even the position of the balance in the movement (usually referred by position from the crown) makes a difference, a difference that changes with how the watch is worn.
In theory balance wheels and springs are resonant oscillators so they also vibrate at the same frequency irrelevant of power supplied. Reality is very different.
Modern oils are great but they too are effected by temperature causing a very minor change in rate.
Other things to change rate are variations in the wheel train, mainspring age and design, if the watch has regulator pins or not, if it is a waterproof case or not, type of shock system used (or not), poise of balance wheel, flatness of hairspring and evenness of coils, automatic watch or not and how it is worn, etc etc.
If you really want to go deep then read Watch Adjustment by Hans Jendritzki.
Yes, I posted the very much simplified version of what happens. I don’t think that I could write a full explanation, but the basics can still be useful hopefully
Dave
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