Hairspring stud position/level: effect on timegrapher reading

[ifibrin]

After reassembling the Tissot 2700 hairspring into the balance cock, I faced perplexing timegrapher readings. The amplitude looked good visually, but the timegrapher could not get a reading, and showed “snow” in the short instances where it got a reading.

After repeated reassembly, cleaning and oiling, during which I wondered if I had damaged the escapement, or hairspring, I found out that the hairspring was rubbing onto the Center wheel. I got a clue when I heard some squeaking faintly. After pushing the hairspring stud lower, the timegrapher could get a reading!

initial timegrapher read out

 

initial hairspring stud position.

 

Final timegrapher reading

 

final hairspring stud position

Reason I am posting this is because I couldn’t find any mention of this in the forums, although it is implied in some other posts.

[jdm]

  On 3/31/2022 at 1:23 PM, ifibrin said:

final hairspring stud position

Reason I am posting this is because I couldn’t find any mention of this in the forums, although it is implied in some other posts.

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The height of the stud is important not just in troubleshooting but in regulation and adjustment also. Some teach to loosen the screw and let the stud find its own natural position. I suppose that more on the matter is in watchmaking books, of which I must admit I'm not a big reader myself.

[nickelsilver]

The hairspring must be flat. Imagining a watch where there aren't any twists or bends at the stud, the hairspring is good, if you look at the spring it will be flat; not just not tilted, but not cupped up or down. If the stud is too high the spring will be cupped up, in a concave shape; if too low, the hairspring will be cupped down, in a convex shape. The correction is to adjust the height of the stud*. Perhaps you didn't notice that it was cupped up, and have now corrected it- but check that it isn't cupped down now! Too far and the spring can touch the balance arms, but regardless for good timing it should be nice and level and flat.

 

*Some watches have no height adjustment at the stud. That's a whole other can of worms.

[LittleWatchShop]

  On 3/31/2022 at 3:31 PM, nickelsilver said:

be nice and level and flat.

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as a student of geometry...I would say "coplanar spiral."  In my other life, I read patents and provide technical analysis in a legal setting to same...so I get all wrapped around the axle on terms...it is an affliction.

[ifibrin]

  On 3/31/2022 at 3:31 PM, nickelsilver said:

The hairspring must be flat. Imagining a watch where there aren't any twists or bends at the stud, the hairspring is good, if you look at the spring it will be flat; not just not tilted, but not cupped up or down. If the stud is too high the spring will be cupped up, in a concave shape; if too low, the hairspring will be cupped down, in a convex shape. The correction is to adjust the height of the stud*. Perhaps you didn't notice that it was cupped up, and have now corrected it- but check that it isn't cupped down now! Too far and the spring can touch the balance arms, but regardless for good timing it should be nice and level and flat.

 

*Some watches have no height adjustment at the stud. That's a whole other can of worms.

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I haven’t gotten to the step of adjusting the hairspring to be flat yet. I’m still doing all adjustments of the hairspring on the balance wheel. I will get around to it one day. It’s quite difficult to judge if the hairspring is flat when the balance cock is on, because the balance wheel is so tiny on this ladies movement.

I have a suspicion there is a deformity in the hairspring though, because the balance wheel has a slight wobble to it in the dial down position, but not dial up. I’ve checked the hole jewels and shock springs, both look fine. 

[ifibrin]

  On 3/31/2022 at 2:52 PM, jdm said:

The height of the stud is important not just in troubleshooting but in regulation and adjustment also. Some teach to loosen the screw and let the stud find its own natural position. I suppose that more on the matter is in watchmaking books, of which I must admit I'm not a big reader myself.

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Do you have any literature on how the stud position affects regulation? I know that the position of the terminal curve between the pin and curb has an effect on the regulation, but I think you have to reshape the terminal curve for this?

Would like to know more, but not much mention of this on the forum or elsewhere. I’m getting -20s to +30s positional variation on the tissot 2700 now, which is not very good. The amplitude looks good though, with 290deg in the horizontal positions, and 240deg to 250deg in the various vertical positions. However, lacking a seconds hand, I’m not sure this movement was ever meant to be regulated…

[Woolshire]

  On 3/31/2022 at 3:50 PM, ifibrin said:

I have a suspicion there is a deformity in the hairspring though, because the balance wheel has a slight wobble to it in the dial down position, but not dial up. I’ve checked the hole jewels and shock springs, both look fine. 

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Check the balance pivots. Sounds like one may be slightly bent. Also make sure the balance cock screw is fully tightened. The hairspring is unlikely to cause the balance to wobble. 

[ifibrin]

  On 4/1/2022 at 4:46 AM, Woolshire said:

Check the balance pivots. Sounds like one may be slightly bent. Also make sure the balance cock screw is fully tightened. The hairspring is unlikely to cause the balance to wobble. 

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The balance cock is fully secured, and the pivots look straight at 10x magnification. I will investigate this further if I get a microscope. However I do recall the balance wheel not wobbling as much when the stud was higher. It is possible I bent the pivot slightly while adjusting the stud height with tweezers, might have nudged the balance wheel, but I don’t think it’s very likely. After all, people do grab the balance wheel by the rim with tweezers to check end shake and side shake, don’t think I would have bent the pivots by nudging it accidentally.

In any event, straightening pivots is risky.

[Klassiker]

  On 4/1/2022 at 3:39 AM, ifibrin said:

I know that the position of the terminal curve between the pin and curb has an effect on the regulation, but I think you have to reshape the terminal curve for this?

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You mean between the pin and boot? Yes, you are right, as long as the big difference is between the horizontal positions and the vertical positions. If that is the case here, you can try the following. The first thing is to get the gap between pin and boot parallel and as small as possible without pinching the hairspring. About twice the thickness of the spring will do. This has the biggest effect on positional variation, due to the amplitude drop from the horizontal to vertical positions.

Then ideally you need the spring to be bouncing evenly between the pin and boot, not resting predominantly against one or the other. If your terminal curve is more or less the right shape, you don't need to change it. A very light tweak or two at the stud will be enough.

If the big variations are between different vertical positions, the it's likely to be a poise problem. A bent pivot or weight distribution. Much more difficult to adjust.

Edited April 1, 2022 by Klassiker

[jdm]

  On 4/1/2022 at 3:39 AM, ifibrin said:

I know that the position of the terminal curve between the pin and curb has an effect on the regulation, but I think you have to reshape the terminal curve for this?

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I can only tell you that for best timekeeping an absolutely perfect hairsping is needed. Of course, that is just much easier said than done, and in many cases just impossible to achieve.

 

  On 4/1/2022 at 3:39 AM, ifibrin said:

However, lacking a seconds hand, I’m not sure this movement was ever meant to be regulated…

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Any mechanical movement is to be regulated, that is, basic timing. Adjustment is something else which I also don't think it applies here.

[JohnR725]

  On 3/31/2022 at 1:23 PM, ifibrin said:

After reassembling the Tissot 2700 hairspring into the balance cock, I faced perplexing timegrapher readings. The amplitude looked good visually, but the timegrapher could not get a reading, and showed “snow” in the short instances where it got a reading.

Expand  

Just for future reference when you see basically snow on the graphical display the numbers are usually worthless. Often times people will think the numbers are valid numbers when the graphical display looks like crap and they usually will not be. Which is one of the reasons we always like to see a picture like you gave us because often times people say how wonderful it looks and not show us the graphical display image of how wonderful it does not look. Which doesn't work well if you're trying to troubleshoot and help somebody out so thank you for the picture.

  On 4/1/2022 at 3:39 AM, ifibrin said:

Do you have any literature on how the stud position affects regulation? I know that the position of the terminal curve between the pin and curb has an effect on the regulation, but I think you have to reshape the terminal curve for this?

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I find is sometimes when the pictures don't look right that the website below is nice because usually get a better picture? It's really hard unfortunately with the picture but it looks like your terminal curve isn't quite perfect but I guess it just depends on how perfect you want your watch to be.

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Tissot_2700

The stud position isn't really important at all. What is important is where the hairspring is which is unfortunately attached to the stud. So typically use the stud providing the hairspring hasn't been bent to make sure they hairspring is flat.

The problem with the hairspring that's not flat is no longer floating and it tends to be putting pressure on one pivot or the other. This will often show up in the timing machine As uneven timing between dial-up and dial down depending upon how bad it is. But it's not the only thing that can cause problems of dial-up and dial down.

  On 4/1/2022 at 3:39 AM, ifibrin said:

Would like to know more, but not much mention of this on the forum or elsewhere. I’m getting -20s to +30s positional variation on the tissot 2700 now, which is not very good. The amplitude looks good though, with 290deg in the horizontal positions, and 240deg to 250deg in the various vertical positions. However, lacking a seconds hand, I’m not sure this movement was ever meant to be regulated…

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One of things it's interesting with this movement is supposedly it's an equivalent to an Omega movement? This becomes interesting because if it was the Omega movement it is meant to be regulated.

It looks like the picture of the Omega movement matches your movement so because of that I snipped out the timing specifications for your watch. I also found the parts list for the Omega watch.

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Omega_1100

429_1100_complet_2272.pdfFetching info...

Edited April 2, 2022 by JohnR725

[ifibrin]

  On 4/2/2022 at 10:23 AM, JohnR725 said:

Just for future reference when you see basically snow on the graphical display the numbers are usually worthless. Often times people will think the numbers are valid numbers when the graphical display looks like crap and they usually will not be. Which is one of the reasons we always like to see a picture like you gave us because often times people say how wonderful it looks and not show us the graphical display image of how wonderful it does not look. Which doesn't work well if you're trying to troubleshoot and help somebody out so thank you for the picture.

I find is sometimes when the pictures don't look right that the website below is nice because usually get a better picture? It's really hard unfortunately with the picture but it looks like your terminal curve isn't quite perfect but I guess it just depends on how perfect you want your watch to be.

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Tissot_2700

The stud position isn't really important at all. What is important is where the hairspring is which is unfortunately attached to the stud. So typically use the stud providing the hairspring hasn't been bent to make sure they hairspring is flat.

The problem with the hairspring that's not flat is no longer floating and it tends to be putting pressure on one pivot or the other. This will often show up in the timing machine As uneven timing between dial-up and dial down depending upon how bad it is. But it's not the only thing that can cause problems of dial-up and dial down.

One of things it's interesting with this movement is supposedly it's an equivalent to an Omega movement? This becomes interesting because if it was the Omega movement it is meant to be regulated.

It looks like the picture of the Omega movement matches your movement so because of that I snipped out the timing specifications for your watch. I also found the parts list for the Omega watch.

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Omega_1100

429_1100_complet_2272.pdf 207.56 kB · 0 downloads

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Does that mean the change in rate at different positions is meant to be up to 50s at full wind?

[JohnR725]

  On 4/2/2022 at 12:08 PM, ifibrin said:

Does that mean the change in rate at different positions is meant to be up to 50s at full wind?

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Yes but you need to follow certain specifications on that? And understand I'm going to snip something out like fully wind is not fully wind tight you need to let it run for a little bit of time so you have a window were you doing this. The same as at the end 24 hours and usually the watch companies get more excited about things at 24 hours. We tend to get really obsessed on this group with minimum amplitudes on a fully wound up tight but the watch companies are more concerned with timekeeping and stuff at 24 hours.

[ifibrin]

  On 4/1/2022 at 6:43 AM, Klassiker said:

 A bent pivot or weight distribution. Much more difficult to adjust.

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Assuming the pivot was bent slightly, and not visible at 10x by eye, would this be sufficient to cause a wobble? 

I would imagine that it would not be possible to true the balance wheel using calipers if it was the pivot that was bent slightly? Since the truing calipers hold the balance wheel at the conical part of the pivot.

[ifibrin]

 

[ifibrin]

 

 

[ifibrin]

 

[Klassiker]

  On 4/4/2022 at 4:31 AM, ifibrin said:

Assuming the pivot was bent slightly, and not visible at 10x by eye, would this be sufficient to cause a wobble?

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I don't have enough experience to say for sure either way, sorry. The fact it doesn't occur in the vertical would apparently rule out a bent pivot as the cause though. I would not consider the amount of wobble you are showing in your videos as a problem in itself. Still it's interesting to speculate why it is only occuring dial down. Maybe too much endshake combined with a tapered pivot, or a not perfectly flat cap stone?

I think in my previous post I answered a question you weren't asking, with a description of a very specific set of circumstances which may or may not be present!  From your description of the current performance, and the information John provided on Omega's specifications, your watch seems to be running fine now. If you still have concerns then I'd like to see the timegrapher traces in six positions.

Edited April 4, 2022 by Klassiker

[nickelsilver]

The balance looks fine in the vids. Your positional rates seem to be pretty much in spec from John's document. These little movements can be a bear to get closer than that (some just naturally do have better rates). A big reason is the proportions change so much- there's a limit to how much sideshake you can eliminate and how small you can get the pivots when reducing movement size. Another big thing is the hairspring collet, these are proportionally very large on these little movements, which moves the hairspring center far from the balance center and has a very real effect on timing.

 

Something that will bite you if you are going for a closer positional rate is- the condition of the hairspring! It really has to be perfect, flat and centered at the collet, and definitely flat and centered in general, and definitely centered in the regulating pins. The last one can cause rates that look like a serious out of poise condition or bent pivot. In the verticals, at a lower amplitude and with gravity acting on the spring, if not really perfectly centered in the pins and the pins at the proper size gap (very small), you can have instances where the spring remains in contact with a pin in a certain position, but barely make contact or even no contact with either in others. This will show up as a large rate difference.

 

Another thing on mass produced pieces, especially older ones, is the lock on the escapement can be quite large. This also has a more serious effect on vertical rates (and amplitude). Your vertical amplitude seems good though. Considering what the hairspring has been through I think you should be proud of how well it's running now!

[ifibrin]

I was really staring at the balance for the past few hours, especially in the dial down position, trying to figure out why it was wobbling in only the dial down position.

I guess there’s some tolerance to some wobble? Still very odd that it only wobbles in the dial down position.

  On 4/4/2022 at 10:26 AM, nickelsilver said:

Something that will bite you if you are going for a closer positional rate is- the condition of the hairspring! It really has to be perfect, flat and centered at the collet, and definitely flat and centered in general, and definitely centered in the regulating pins. The last one can cause rates that look like a serious out of poise condition or bent pivot. In the verticals, at a lower amplitude and with gravity acting on the spring, if not really perfectly centered in the pins and the pins at the proper size gap (very small), you can have instances where the spring remains in contact with a pin in a certain position, but barely make contact or even no contact with either in others. This will show up as a large rate difference.

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I’m not sure how many more disassembles and reassembles the hairspring can take before it gets deformed again. The balance wheel is really close to the center wheel, and the hairspring always gets caught on it; you have to push it off the center wheel with a fine Oiler every time I assemble it.