Part 3 of the never ending saga

[Klassiker]

11 hours ago, Ammar said:

We do have loads of Ethanol at work I'll get some and start cleaning with it instead of IPA and see the results

Ethanol is an alcohol, just like the propanol (IPA) you've been using. It will not dissolve hydrocarbons (oil and grease). It might remove the plating from your plates and bridges a bit quicker than IPA, and be very careful with it around shellac.

[nevenbekriev]

7 hours ago, VWatchie said:

I always become weary when specific numbers are specified. Amplitude comes to mind. I think the time would vary quite a bit depending on an array of factors such as the weight and diameter of the balance wheel. But "about 100" seconds (I assume you don't mean oscillations) sounds in the ballpark for any common Swiss wristwatch movement. I agree.

It's absolutely mesmerizing to see the balance wheel oscillate for a hundred seconds, but what I usually do is just give the movement a light twist while in the movement holder and then study how the balance stops. If it doesn't come to a stop completely seamlessly there's something that needs attention. Any kind of abrupt stop, even when the oscillation of the balance is minimal, indicates an imperfection.

 

May be this needs some deeper explanation. What I writed is exactly what I mean - 100 oscillations. Yes, the number 100 is dependant on the type and size of the balance. If it was good quality pocket watch balance, the number should be 200-250. But here we have small size wrist watch and the number is about 100.

Why not time, but oscillations? The idea of this whole thing is to determine the Q-factor of a resonant system. The balance is a high quality resonator and it has Q-factor. We don't need here theoretical measurement like Q=3022 for example, but practical way to realize if the balance as resonator is good or has problems. Such simple way to evaluate Q factor is the number of free oscillations as a result of charging the system with measured portion of energy.  That's why I say 180 degr - this is the measured portion of energy we give to the system. Not just puff with air. Specific measured portion of energy, which will be relevant for all sizes and types of balances. Then we count the oscillations. For sure, it wiil be the same effect if we measure the time, but it will be true only if the frequency is always the same. But no, there are alot of different frequencies (different BPH of different movements) For example, If You put some weaker hairspring on the same balance wheel, the Q-factor is not expected to change much, as the main loss of energy in the system is thru the bearings of the balance. If You do the free oscillation thest, You will see almost the same result as oscillations count, but time may be for example twice longer than what it was with the first hairspring, as the frequency is reduced due the weaker hairspring.

[VWatchie]

5 hours ago, nevenbekriev said:

But here we have small size wrist watch and the number is about 100.

Thanks for explaining. I never heard of this so that's why I was sure you meant seconds rather than oscillations.

How can you tell the number of expected oscillations?

6 hours ago, nevenbekriev said:

Then we count the oscillations.

How exactly would you do that?

[caseback]

3 hours ago, VWatchie said:

How exactly would you do that?

If you know the beatrate: measure the elapsed time.

Edited July 13 by caseback

[VWatchie]

59 minutes ago, caseback said:

If you know the beatrate: measure the elapsed time.

Let's say we have a typical 28800 BPH Swiss movement like the Sellita sw200. 

On 7/10/2024 at 2:21 PM, nevenbekriev said:

You must turn the balance to 180 degr. and release it to oscillate till full stop, and count the number of free oscillations. About 100 is expected when balance is OK.

That would mean that if the balance stops after 12.5 seconds (8 oscillations per second) it's OK. If that were to happen to me I would conclude that something is seriously wrong.

The Q theory seems interesting but not very practical.

Why not simply study how the balance comes to a stop? If it doesn't come to a stop completely seamlessly there's something that needs attention. Any kind of abrupt stop, even when the oscillation of the balance is minimal, indicates something isn't right.

[nevenbekriev]

10 hours ago, VWatchie said:

Let's say we have a typical 28800 BPH Swiss movement like the Sellita sw200. 

That would mean that if the balance stops after 12.5 seconds (8 oscillations per second) it's OK. If that were to happen to me I would conclude that something is seriously wrong.

The Q theory seems interesting but not very practical.

Why not simply study how the balance comes to a stop? If it doesn't come to a stop completely seamlessly there's something that needs attention. Any kind of abrupt stop, even when the oscillation of the balance is minimal, indicates something isn't right.

First I must say that 28800 means not 8, but 4 oscillations per second. So it is 25 sec  needed for 100 oscillations. Then, I have never worked on this movement, but as I guess it is not so small. The Q-factor depends mainly on the moment of inertia of balance, on it's mass and on the pivots size.  So, bigger Q-factor is expected than the one of a women's calibre. Then, another thing exists - the 'stronger' the hairspring is, the more energy it accumulates when balance turned to 180 degr. The hi-beat balances have stronger hairsprings. But, on the other hand, the mean speed of balance rotation is bigger, so the losses are bigger. I have not worked much on hi-beat movements (I work on antique watches), so I have not performed the free oscillations thest on Selita SW200. I give the expected ocillations generally based on my practice, and it is mainly with 18000 BPH movements. So please, when oportunity appears, do the test for me, it will be interesting to see the Selita result. I believe that it will only confirm the theory. Don't forget, that balance must be only turned to 180 degr, but not puffed with air as strongly as possible.

Well yes, observing the moment when oscillations stop is verry informative. But it will not help much to evaluate for example a small difference in friction DU/DD.

How to count oscillations... Well, I find this question odd. This is the first time I was asked such question. I didn't think that counting will be problem for somebody. It is not like counting aples and plums, but it is still counting, counting of events. The oscillations happen quite rithmically, so counting with the rythm of oscillatoins is what is needed. Well, 28800 is fast. 18000 doesn't make problem to count, but in the case of 28800, one can count every second, or even every 3rd or 4th oscillation and multipy the result by 2, 3 or 4. Yes, the time method will work too, byt timer will be needed. Not that it is a problem, but counting doesn't need one.

[Neverenoughwatches]

1 hour ago, nevenbekriev said:

First I must say that 28800 means not 8, but 4 oscillations per second. So it is 25 sec  needed

4 oscillations, 8 beats/second. So we are looking for 200 beats of the hairspring or 25 seconds to indicate good low friction of a balance. An 18,000 vibrations / hour movement would last 40 seconds for 200 beats. I often see around 1 minute to dead stop 

[VWatchie]

5 hours ago, nevenbekriev said:

First I must say that 28800 means not 8, but 4 oscillations per second. So it is 25 sec  needed for 100 oscillations.

5 hours ago, nevenbekriev said:

The hi-beat balances have stronger hairsprings. But, on the other hand, the mean speed of balance rotation is bigger, so the losses are bigger.

4 hours ago, Neverenoughwatches said:

4 oscillations, 8 beats/second.

Thanks! You learn something new every day. I wasn't sure about the difference between a beat and an oscillation. So good to know. 2 beats = 1 oscillation. 

5 hours ago, nevenbekriev said:

So please, when oportunity appears, do the test for me, it will be interesting to see the Selita result. I believe that it will only confirm the theory. Don't forget, that balance must be only turned to 180 degr

I sure will. It's going to be interesting. So far I've turned the balance near 300° before letting it go and on a really healthy balance it has been swinging for about 70-90 seconds in the horizontal positions. Anyway, when doing the test, I'll only swing it 180°. I will be surprised to see it swing for only 25 seconds or less, but we shall see.

5 hours ago, nevenbekriev said:

How to count oscillations... Well, I find this question odd.

That could be because I've never tried to count oscillations and only assumed it would be impossible or difficult. Anyway, let's see when I get a chance, hopefully in a month or so as I'm still on vacation and far, very far, from a workbench.

Here's Kalle Slaap doing the kind of test that I do (start at 12:30). An interesting observation is that when Kalle starts the balance towards the end of the video at 14:40, it oscillates for about 50 seconds before the video ends. It is difficult to judge whether the balance swings more than 180° at the start, but it looks like it could be close to 180°.

 

Edited July 14 by VWatchie

[Neverenoughwatches]

9 hours ago, VWatchie said:

Thanks! You learn something new every day. I wasn't sure about the difference between a beat and an oscillation. So good to know. 2 beats = 1 oscillation. 

I sure will. It's going to be interesting. So far I've turned the balance near 300° before letting it go and on a really healthy balance it has been swinging for about 70-90 seconds in the horizontal positions. Anyway, when doing the test, I'll only swing it 180°. I will be surprised to see it swing for only 25 seconds or less, but we shall see.

That could be because I've never tried to count oscillations and only assumed it would be impossible or difficult. Anyway, let's see when I get a chance, hopefully in a month or so as I'm still on vacation and far, very far, from a workbench.

Here's Kalle Slaap doing the kind of test that I do (start at 12:30). An interesting observation is that when Kalle starts the balance towards the end of the video at 14:40, it oscillates for about 50 seconds before the video ends. It is difficult to judge whether the balance swings more than 180° at the start, but it looks like it could be close to 180°.

 

 A benchmark is needed to work from and 180 °appears to be neither too high nor too low and would be close to an amplitude nearing 24 hours of runtime on most watches. If a balance turns freely at this degree of travel and below anything above a start of 180° probably doesn't need to be considered. Trying to count oscillations from 180 ° is hard enough ( for me anyway ) i need all the help i can get by using a drop of tippex on the balance wheel for my eyes to catch sight of

[Mercurial]

2 hours ago, Neverenoughwatches said:

 A benchmark is needed to work from and 180 °appears to be neither too high nor too low and would be close to an amplitude nearing 24 hours of runtime on most watches. If a balance turns freely at this degree of travel and below anything above a start of 180° probably doesn't need to be considered. Trying to count oscillations from 180 ° is hard enough ( for me anyway ) i need all the help i can get by using a drop of tippex on the balance wheel for my eyes to catch sight of

*DISREGARD this post, it’s nonsense, but I leave it in place for continuity*

Don’t forget that when we talk about amplitude, we are talking about half of the full rotation the balance wheel makes in one complete oscillation from its maximum excursion clockwise to its maximum excursion counterclockwise. 

ie If the tippex drop on the balance wheel is moving through 360 degrees and the balance wheel is changing direction of rotation at both extremes of its travel (clockwise and counterclockwise) with the tippex drop in the same place, the total rotation of the balance wheel is 360 degrees, but the amplitude is 180 degrees. 

When nevenbekriev describes releasing the balance wheel after rotating it through 180 degrees, that’s equivalent to the amplitude for the initial swings of the free oscillations test being only 90**(wrong - see below) degrees.

Best Regards,

Mark

EDIT : **this is wrong, as pointed out in the post directly below it should say almost 180 degrees.

Edited July 14 by Mercurial
Correcting a mistake

[Neverenoughwatches]

1 hour ago, Mercurial said:

Don’t forget that when we talk about amplitude, we are talking about half of the full rotation the balance wheel makes in one complete oscillation from its maximum excursion clockwise to its maximum excursion counterclockwise. 

ie If the tippex drop on the balance wheel is moving through 360 degrees and the balance wheel is changing direction of rotation at both extremes of its travel (clockwise and counterclockwise) with the tippex drop in the same place, the total rotation of the balance wheel is 360 degrees, but the amplitude is 180 degrees. 

When nevenbekriev describes releasing the balance wheel after rotating it through 180 degrees, that’s equivalent to the amplitude for the initial swings of the free oscillations test being only 90 degrees.

Best Regards,

Mark

Correct mark we know amplitude is the degree of travel of the balance in one direction from its rest point.  I think you have the last bit wrong though. 

Nev suggests releasing the balance at a point of 180 ° from its rest, equivalent to a balance oscillating with an amplitude of 180°not 90° 

The drop of tippex on the balance wheel  is not to line up with a mark on the plate as you might do with the timing of a car's combustion.  The white dot is merely to make the oscillations more visible. 

33 minutes ago, Neverenoughwatches said:

I think you have the last bit wrong though. 

Or maybe i misunderstand your description Mark. I can't figure out where you have 90 ° in this ??

Edited July 14 by Neverenoughwatches

[VWatchie]

On 7/13/2024 at 8:43 AM, VWatchie said:

Why not simply study how the balance comes to a stop? If it doesn't come to a stop completely seamlessly there's something that needs attention. Any kind of abrupt stop, even when the oscillation of the balance is minimal, indicates something isn't right.

I just recorded this video which demonstrates exactly what I meant. The balance comes to a stop completely seamlessly.