Thanks for the feedback Francois. The BHI specify that the range should be a maximum of 310 degrees and a typical amplitude of 270 degrees at full wind. So, with 280 in horizontal, I'm getting about 250 when vertical which is the natural position for a stopwatch. For me, this is a little low. At 24H, they would like a minimum of 200 degrees but they're obviously trying to cover all watches with this from new to vintage.
Witschi specify the following as general rules so, same ball park as the BHI -nothing changes except the rate per day in these lines:
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In reality, it depends on the type of the watch and the state of the mainspring (assuming everything else is good). Firstly, you see some people oiling the mainspring after they've fitted it with little blobs of oil. This won't help you to get higher amplitudes as I never got 300 degrees until I stopped that bad habit. You sometimes see people putting these little blobs of oil on both old and new mainsprings. Modern new mainsprings should go in in as they are as they are pre-lubricated. If you're re-using the spring, wipe it down with a little oil (there are special tweezers for this if you feel the need to spend money) before winding it into the winder. Al has some posts somewhere showing this and it's what the BHI teach.
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So, if this stopwatch was for me, I'd probably take this as is, because it is only a stopwatch for timing 30 minute intervals and it will pick up a little after it's been running for a week. But, I might submit this as one of my Unit D14 watches so, will replace the spring.
I've just done an ETA 2892 (similar to an Omega 1120) which is a great calibre and this one shows little wear. I just popped it on the timegrapher and at full wind it shows 305-315 in horizontal and 275-285 through all the verticals.As I remember, it only drops 10% maximum at 24H so, I'd rate this as very good and everything older is down from there (Al may disagree
).
Against that, I have quite a few Omega 550 series (561, 565 etc) and I can work hard at those and sometimes still not get better than 250-260 degrees in horizontal. I have one or two at 300 but that's not the rule. If you replace a lot of the wheels, you can get them up to 300 but, that's an expensive way to service a watch. I'd struggle to pass all the BHI requirements easily with these but I can do it.
I also have an Omega 601 here which is basically a manual 550 and even with very worn wheels, it's hitting 260 degrees horizontal and worst position after 24H is still 200 degrees. It's coming apart again as these are clearly too low but at the time, I didn't have a wheel to replace this one where the pivot is very worn so, it was a test. I don't have any issue with rebuilding movements a couple of times as it's all good practice at the bench and it shows me the effects of each problem - this pivot is obviously unacceptable but the movement made a good go of it.
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I only have a couple of the 86x but these are both better than the 550 series and I think they are more robust. On the bumper front, the 330 series, I'd say these were more like the 550 series but it's even harder to get parts so, I have to accept lower than I'd like.
I have no real experience with the Omega stopwatches or pocket watches so, it's hard to say very much but, this one will hit 300 degrees (if I have to drag it there ticking and screaming....
). There's not much wear and I've replaced one wheel so, it should do it.
Where to set the acceptable level when servicing is another matter which is why I'm not being too specific but, I'd say for the calibres I think are capable above, you'd want to meet the Witschi specs towards the top end and for those which have a parts availability issue, the specs at the lower end or even a bit below in terms of vertical. Of course, after 24H, you'd be aiming for the same but less 10% or 15% as they say so still better than 200 as an absolute minimum in any position.
This is a hugely interesting topic and there a lot of things you can do to increase (or reduce when required) the amplitude. We'll see if Al or anyone else chimes in but I doubt Al has a specific level for every watch either from my discussions with him. He of course, can comment on many other calibres as well but these are the ones I've worked with most.
Cheers, Chris
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