Too much amplitude
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  1. #1
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    Too much amplitude

    Hi everyone!

    I'm running into an issue with an old Tissot Cal 27 movement (just 27; not a variant) that I recently overhauled. I'm getting way the heck too much amplitude. I've worked on Cal 27s before, including those in my two watches that I ordinarily wear. I'm used to seeing too little amplitude and having to work on that; never had this sort of problem before. After hearing significant knocking, I checked with the timegrapher software I had as well, and got over 350 degrees lying flat and 320-330 or so in pretty much any other position. The software has worked fine for me in the past (and in comparing with high speed video), so I don't have much reason to doubt it. I didn't take extensive measurements as I didn't want to keep running it like that. However, I anticipate it would have continued in that manner, since I seem to get over 270 on well-short of a full wind.

    I tried swapping in a couple other barrels I had on hand, including one whose mainspring I'd been planning to replace for being too weak. Even with that one, I'm getting like 320 or so. As far as other maladies go, I can't really find any. If I just partially wind it, it seemed to keep fine time. Hairspring motion looked OK (but maybe I missed something). It also seemed like I had the collet and regulator adjusted alright. Beat error showed up as 0.0ms flat, and was below 0.5ms in all positions. Positional variance in rate was better than what I've seen on average with this caliber. So, I'm not sure what to make of this one.

    My inclination at the moment is to just try putting in a weaker (than standard) mainspring, and see how that goes. However, I'm wondering if I should try something else (or look for some other issue). Anyhow, if anyone has any advice or suggestions, it would be much appreciated. Thank you all for your time :)

  2. #2
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    Re: Too much amplitude

    Mic the springs and post the results.
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    Re: Too much amplitude

    I had this problem with an Elgin 671 (15/0, 19j). Started knocking at 1/2 wound. I had to order the weakest mainspring I could find to get it down to a reasonable amplitude. My guess is that some previous repairer put in a really strong mainspring, rather than cleaning it, to bring the amplitude up.
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    Re: Too much amplitude

    Please do mic the springs as Pithy suggests. The 27 mainsprings vary from .115mm to .13mm over the variants, my Generale Ressorts book gives a .12 for the straight 27, could be yours was replaced with a .13 at some point. The weak spring you used is giving 320, which is a little high (my opinion) but not too high.

    I frequently see watches with way too much lock on the escapement; occasionally they come in with too little. A watch with too little lock can run very well up to having excessive amplitude, while being 'unsafe' so there's a risk of it malfunctioning. Many mass produced watches tend to have more than textbook lock from the factory, I've always figured it was so the watch could be brought to proper amplitude after a few decades of wear without slamming in a stronger spring. I can imagine a scenario where somewhere in your watch's history a thoughtful and thorough watchmaker adjusted the escapement to get the amplitude up with an original mainspring, then down the road the spring getting replaced with something slightly stronger after perhaps a mediocre service, and now you have your massive amplitude. It doesn't take much change in lock to boost or diminish quite a few degrees of amplitude, and a 5 micron thicker (or thinner) spring will also have a very large effect.

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    Re: Too much amplitude

    How is the rate...and what is the delta?
    Hs may be vibrated nicely to the balance...but may be too weak...hence the same performance with the other barrels (albeit somewhat mitigated by using the weaker ms).
    Choices:
    -weaker ms
    -replace balance complete or vibrate a stronger hs to the balance.
    -might try oiling the pallet arbor pivots...possibly with hp1000 or hp1300.
    (first two suggestions would likely be the direction pithy is leading...third suggestion is a kind of a hack in some regards...or perhaps an attempt to mitigate the issue without re-inventing the wheel)...
    I have seen several ROL 3135s lately where this issue was mitigated by introducing beat error...rather than using the weaker mainspring (ROL offers two strengths...). "Out of beat" is definitely a hack...
    Regards, BG

  6. #6
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    Re: Too much amplitude

    Hi everyone! Thank you for the help and advice. I sincerely appreciate it :)

    Specific responses below...

    Quote Originally Posted by pithy View Post
    Mic the springs and post the results.
    A bit embarrassing now - I can't seem to capture a recording at the moment. I'm able to get live feeds, but when I try to record to e.g. Audacity I get nothing. After trying everything in program configuration, I've been futzing with pulseaudio and alsamixer (linux) since yesterday in an attempt to sort it, but no success so far. Lucky me :(

    I'll keep working at it.

    Quote Originally Posted by GeneJockey View Post
    I had this problem with an Elgin 671 (15/0, 19j). Started knocking at 1/2 wound. I had to order the weakest mainspring I could find to get it down to a reasonable amplitude. My guess is that some previous repairer put in a really strong mainspring, rather than cleaning it, to bring the amplitude up.
    I had a similar suspicion, so I did try a couple other springs. Actually tried a third last night and got similar results still. It does seem like a weaker spring might be the way to go at the moment, but I'm guessing I'll need a closer diagnosis first...

    Quote Originally Posted by maillchort View Post
    Please do mic the springs as Pithy suggests. The 27 mainsprings vary from .115mm to .13mm over the variants, my Generale Ressorts book gives a .12 for the straight 27, could be yours was replaced with a .13 at some point. The weak spring you used is giving 320, which is a little high (my opinion) but not too high.

    I frequently see watches with way too much lock on the escapement; occasionally they come in with too little. A watch with too little lock can run very well up to having excessive amplitude, while being 'unsafe' so there's a risk of it malfunctioning. Many mass produced watches tend to have more than textbook lock from the factory, I've always figured it was so the watch could be brought to proper amplitude after a few decades of wear without slamming in a stronger spring. I can imagine a scenario where somewhere in your watch's history a thoughtful and thorough watchmaker adjusted the escapement to get the amplitude up with an original mainspring, then down the road the spring getting replaced with something slightly stronger after perhaps a mediocre service, and now you have your massive amplitude. It doesn't take much change in lock to boost or diminish quite a few degrees of amplitude, and a 5 micron thicker (or thinner) spring will also have a very large effect.
    Thank you for the explanation regarding lock. This was really helpful. Now that you mention it, I feel like I should have thought about lock being an issue, but it totally escaped me. It's nice to have a place to ask about these things :)

    Quote Originally Posted by BenchGuy View Post
    How is the rate...and what is the delta?
    Hs may be vibrated nicely to the balance...but may be too weak...hence the same performance with the other barrels (albeit somewhat mitigated by using the weaker ms).
    Choices:
    -weaker ms
    -replace balance complete or vibrate a stronger hs to the balance.
    -might try oiling the pallet arbor pivots...possibly with hp1000 or hp1300.
    (first two suggestions would likely be the direction pithy is leading...third suggestion is a kind of a hack in some regards...or perhaps an attempt to mitigate the issue without re-inventing the wheel)...
    I have seen several ROL 3135s lately where this issue was mitigated by introducing beat error...rather than using the weaker mainspring (ROL offers two strengths...). "Out of beat" is definitely a hack...
    Regards, BG
    I tested this with the weakest barrel (mainspring) I had on hand, which gave me about 320 degrees when flat. This gave somewhat odd, and different results than last time. I can swap things around (and do a partial wind) if it would be helpful.

    Rate when flat was fairly stable at 0s loss/gain when regulator is set dead center. I see some occasional oscillation +/- 1-2s, but that could be attributed to a lot of things outside the movement (e.g. error-compensation in the computer's timebase, averaging of noise on the input, maybe other stuff). Less happily, it drops to about 265-270 degrees pendant up/down/right, and 260 pendant left. Up/down/right, rate goes to about +25s, while left seems a touch higher. I also see about this rate when flat when amplitude is around 270. So, rate seemed more amplitude-correlated than positionally-correlated in this case.

    At the moment, I'm definitely inclined towards a non-hacky solution. I've tried twice now to get a new balance complete, both times unsuccessfully (first one was never sent, second arrived damaged). I don't have an account with a supplier, so I'm otherwise finding this to be a rather difficult part to get :(. It may just generally be difficult, though. I'm not sure.

  7. #7
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    Re: Too much amplitude

    machinist speak

    mic = micrometer

    Measure the width and thickness if the various springs.

    While you're at it measure the diameter of the arbor exclusive of the spur and the ID of the barrel as well as its interior height.
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  8. #8
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    Re: Too much amplitude

    I wish I had this problem. I often have too little amplitude. I do like the idea of oiling the pallet arbor or replacing the mainspring. Adjusting the escapement is a little above my pay grade. Very elementary as you seem very knowledgeable, but is the correct lift angle programmed? Is it knocking?

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    Re: Too much amplitude

    Quote Originally Posted by jcoffin1981 View Post
    I wish I had this problem. I often have too little amplitude. I do like the idea of oiling the pallet arbor or replacing the mainspring. Adjusting the escapement is a little above my pay grade. Very elementary as you seem very knowledgeable, but is the correct lift angle programmed? Is it knocking?
    Perfectly reasonable questions to ask. I just checked - I have the lift angle set at 51, which is what I understand to be the spec for this model. I think some of the later variants were 52. I do hear knocking at full wind with at least a couple of the mainsprings I tried. I'm perfectly happy with adjusting lock if that seems the way to go, but a weaker mainspring seems like an OK option as well.

    My micrometer appears to have gone missing. I can't seem to catch a break on this one. Consequently, all I have handy at the moment is old SPI polymer vernier calipers. Doubt I can really tell the difference between e.g. 0.12 and 0.13 on them, but I guess I could have a crack at it.

  10. #10
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    Re: Too much amplitude

    monax...hello...I'm a bit late on this one, but, Pithy's comment is where I'd start: measure your mainspring! You must know if it's correct...non-standard springs DO show up, and you could save yourself a lot of trouble, by making sure the one that's in front of you is good. Keep your micrometer handy...!

    How are you @ reference books...do you have a few?...many texts dealt specifically with escapements & regulating...a Google search should point you in their direction. Michael.

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