Hello there,

I replaced the bezel on my 105.003 Eddy this saturday, and while the guy was at it he asked if it was running properly, I said I think so but I do not track accuracy, so he put it on a timegrapher and then, disaster news: it looks like the movement has 330° of amplitude (if I recall correctly) and very poor precision (like -20/30 sec per day). The watch was serviced in 2016 by a family member, I have been impressed by a 60 hours power reserve and never wear it more than 2 days on a row so I wouldn't notice if they run really poorly...
My question is: could the machine be wrong (stupid question but you never know) and more importantly, have you ever heard of a 321 with such a bad amplitude ?
Fortunately I've met a cool dealer who can introduce me to his watchmaker who can service the movement in 2/3 weeks for an extremely competitive price.
I'll probably go for the service and some peace of mind, but what would you, knowledgeable people, suggest I do ?

Thanks a lot in advance !

PS: I've been collecting for some years but I only know the basics about how a movement functions, which is why I'm asking these questions which can seem stupid to some

 

There's a lot to unpack in there, so bear with me...

First some questions:

1 - what state of wind was the watch in for the readings?

2 - what positions did they check?

3 - what was the lift angle on the timing machine?

330 degrees is quite high amplitude and on this movement would be close to, if not already, causing rebanking. The lift angle has to be set correctly in order to get a proper amplitude reading, so if your watchmaker left the lift angle set to the default of 52 degrees, it is no where near the right setting (which is 40 degrees). Having the lift angle set to 52 when it should be 40 will mean that the amplitude is overstated by a lot, roughly 6 degrees of amplitude for every 1 degree the lift angle is off, so 12 X 6 = 72 degrees. So assuming this is what he did, the amplitude would be 258, which is low rather than high, assuming the watch is fully wound and was being measured in a horizontal position.

The data you have given can't be interpreted - data without details is of little value.

To other things in your post - the timing is certainly not great if it was running that slow. No idea how well it was serviced previously by your family member, but looking for an "extremely competitive price" is usually not the way to find the best watchmaker. It's up to you who you use for service, but I would make sure they are familiar with the movement, and ideally have a parts account with Omega.

Cheers, Al

 

Hi Al,

Assuming for the moment that the lift angle was set correctly when checking the OP's watch, could any reasonable correlation be made between amplitude, and whether the watch runs fast or slow? In other words, in his case, and others that are similar, is high amplitude associated with slow running, or is there no relationship between these factors at all? Thanks, Bob.

 

Thanks a lot for your thorough answer.

First of all, let me say that I haven't really paid a lot of attention to what the guy was doing because I thought the watch was running perfectly as it is supposed to have been serviced 2 months ago (before it became mine), I didn't notice any issues with precision/power reserve. He placed it on the machine horizontally, dial side up. I have no idea what the lift angle was. I am hoping that he did not set the machine correctly, but I doubt it since he has another 105.003 in the shop.
When he told me this, I went to a dealer I know who phoned his watchmaker who is known locally for being good and asked to service my watch for what he would pay himself. Obviously, I'm not going to put a 10k watch in the hands of an unexperienced guy just to save a couple of hundred €.
To show how little I understand of mechanical movements, I have no idea what the term "rebanking" implies or means !

Thanks again for taking the time to answer; I believe the next step is for me to bring it to a watchmaker and do a serious movement check in order to be sure that it needs a service.

 

Yes, in a couple of ways. The first is normal variations from amplitude variations due to the lack of isochronism. Although makers do as much as they can, the period of oscillation is not always constant when the amplitude of oscillation changes. This is why timing tolerances are often given for full wind, then 24 hours after full wind, when the amplitude has dropped. For the 321, Omega allows the positional variation (Delta) to increase by 10 seconds from full wind to 24 hours after full wind. In a modern COSC rated watch, the difference is only 3 seconds in the allowed positional variation between full wind and 24 hours after full wind. Clearly running 20 or 30 seconds slow is not something that would be considered normal variation for isochronism, in particular if the watch has 330 degrees of amplitude.

The other way is what I mentioned above - rebanking. This is when excess balance amplitude causes the roller jewel on the balance to turn so far that it strikes the outside of the pallet fork horn, causing a rebounding effect. The balance travels back the other direction faster than the balance spring would normally take it, and then it hits the other side of the fork horn, and it bounces back and forth like this while the torque remains too high. This drastically shortens the period of oscillation, so I commonly see 600 or even 900 seconds per day fast in this situation, depending on the movement. Since this only results in a fast rate, then it's clearly not happening here - the fact it isn't with such high balance amplitude tells me the lift angle is likely set wrong.

Cheers, Al

 

Rebanking I've described in my reply to M'Bob above, but to illustrate further here is a video I made a few years ago to show what it sounds like:

If you listen you can hear that as I add more torque by turning the crown after the movement is fully wound, the sound changes. It first gets louder, and then you can hear when the rebanking starts as there are extra clicks and the rate picks up dramatically. As noted this is also referred to as "knocking" and even "galloping" because it sounds a bit like a galloping horse.

In my experience amplitudes over 320 on a Cal. 321 will often start to rebank, so if yours was a 330 I would expect it to be rebakning and running quite fast, rather than slow. This is why I believe the amplitude was actually lower, and the machine was set incorrectly. I do agree that you should get it to a watchmaker who can do a proper assessment on it.

Cheers, Al

 

Al,

Really interesting. Many thanks for the info and clarification.

Best,

Bob

 

Thanks a lot for both of your replies, I'm going to study the video you posted !
Well it is much more clear, I'm going to test for the accuracy but it is entirely possible he didn't regulate the machine correctly. If I get a much better result than what he got I'm going to assume his test was complete bulls**t (to give all of the info I have, the guy asked me to let him restore the movement just after he tested it, for a "mere" 7-800€, so maybe he wasn't being that honest...
I'll keep you posted !