Is this a 'hack' ?

[dnhb]

I'm trying to get a balance spring Mantel clock to run to time - even with the regulator set to Slow it's gaining 40mins a day (the balance spring was damaged on receipt so it may be shorter than it should be - can't think why else it should run fast, especially as it is quite dirty & apparently hasn't been working for some time.). Anyway, looking closely at the train I've noticed the pre-escapement wheel is slightly 'dished'. Could this have been done by a previous tinkerer to get around a problem that should have been addressed by e.g. bushing pivot holes?

[watchweasol]

Hi. Sounds like a problem clock, can you post some picture# of the clock and the parts in question please.       Thank you

[nevenbekriev]

Balance-hairspring system is oscillator with big Q-factor. When all in the movement is OK, the rate (frequency) is verry close to the own resonant frequency of the balance-hairspring. But in some cases, the movement (with foult) will force the resonator to work on pritty different frequency, sometimes faster, and sometimes slower. When this happens, the amplitude is always weak.

So, the first thing to ask is what is the amplitude. If it is more than 180 and the hairspring doesn't touch itself and anything else, then for sure it is 'short'.

If the amplitude is weak, then the first thing to do is to understand why and rectify the problem. At this time no point to check timekeeping. But, if one doubts that the hairspring is not correct, then He needs to calcullate the rate of the movement, then to 'vibrate' the balance-hairspring out of the movement and to measure the free oscillations frequency (period) with timer in order to ensure that they comply with the rate.

If we have pictures, then it will be easier to tell something about that wheel.

Edited April 24 by nevenbekriev

[oldhippy]

I need to see photos of the whole movement before I comment. 

[dnhb]

15 hours ago, watchweasol said:

Hi. Sounds like a problem clock, can you post some picture# of the clock and the parts in question please.       Thank you

Showing state of hairspring on receipt, backplate & 'dished' wheel. 

15 hours ago, nevenbekriev said:

Balance-hairspring system is oscillator with big Q-factor. When all in the movement is OK, the rate (frequency) is verry close to the own resonant frequency of the balance-hairspring. But in some cases, the movement (with foult) will force the resonator to work on pritty different frequency, sometimes faster, and sometimes slower. When this happens, the amplitude is always weak.

So, the first thing to ask is what is the amplitude. If it is more than 180 and the hairspring doesn't touch itself and anything else, then for sure it is 'short'.

If the amplitude is weak, then the first thing to do is to understand why and rectify the problem. At this time no point to check timekeeping. But, if one doubts that the hairspring is not correct, then He needs to calcullate the rate of the movement, then to 'vibrate' the balance-hairspring out of the movement and to measure the free oscillations frequency (period) with timer in order to ensure that they comply with the rate.

If we have pictures, then it will be easier to tell something about that wheel.

Thanks, Nev. Amplitude v. weak - balance wheel turns over arc of only ~20deg. Don't know how to calculate movement rate or safely vibrate balance spring! Meantime I have reduced the 'dishing' & clock no longer runs for more than a few minutes except face down which supports my theory that it was 'dished' as a hack to avoid doing a proper repair.

[nevenbekriev]

OK, welcome in the world of alarm clocks...

I guess the 4th wheel is dished because it is from another movement. If it was not dishet, then it would not mesh with the pinion of the escape wheel, am I right? The marks of wear on the 4th wheel pinion doesn't corespond to the 3th wheel table position, at list this is what i see on the picts.

Calculating the rate is easy - there is a formula - BR = T2 x T3 x T4 x T5 x 2 /(P3 x P4 x P5) where T2 - T5 are the counts of the teeth of the wheels tables, and P3 - P5 are the counts of the pinion leaves.

Vibrating the balance is easy - grasp for the hairspring where it should stay in the regulator with tweasers, let the balance hang on the hairspring while the downside staff tip rests on glass surface. Then make the balance oscillate and use timer to measure the time for let say 50 oscillations, or count the oscillations for let say 30 seconds.

You must do the free oscillations test to check the balance staff tips and the cone cup bearings for wear. This kind of staffs wear and need resharpening to restore the normal function of the balance.

[dnhb]

3 hours ago, nevenbekriev said:

The marks of wear on the 4th wheel pinion doesn't corespond to the 3th wheel table position, at list this is what i see on the picts.

That's very observant of you, Nev & that the 4th wheel is from another movement & has been dished to fit does seem a more likely explanation.

Thanks for the education re calculating the rate & spring frequency. In the meantime, spurred by your earlier comnent, I risked a further tinker with the balance spring, cleaning it, fully un-kinking the last few cms (I'd been worried about breaking it first time round) & pinning it at the very end. The clock now seems to be running slow when the regulator is in that position so some progress at last.....Many thanks, once again!

[oldhippy]

These types of hairsprings become weak with age and very fragile. Which I expect it is that giving you trouble, and that wheel is not the correct one, if it were not bent I don't think the movement would run as the teeth are not the correct height. The problem you have is price which depends on you. It can be repaired but is it worth it to you, because there is little value in the clock. A wheel can be made and hairspring replaced. Or hang on to it and keep looking on ebay which is your best bet for replacement parts or even a complete movement but it will be like finding a needle in a haystack. 

[watchweasol]

Hi. In the picture not only does it depict that the wheel is bent but also the plate or is that due to th angle of the picture.  Already received very good advise so I will butt out.

[dnhb]

5 hours ago, watchweasol said:

Hi. In the picture not only does it depict that the wheel is bent but also the plate or is that due to th angle of the picture.

The plate is OK, thanks. It seems the answer to my question is that this is a 'hack' & for me another reminder that in general, one won't be the first person to be tinkering with an old timepiece!. As you day, I've been fortunate to have gotten some good advice and, just as important, encouragement.

6 hours ago, oldhippy said:

These types of hairsprings become weak with age and very fragile. Which I expect it is that giving you trouble, and that wheel is not the correct one, if it were not bent I don't think the movement would run as the teeth are not the correct height. The problem you have is price which depends on you. It can be repaired but is it worth it to you, because there is little value in the clock. A wheel can be made and hairspring replaced. Or hang on to it and keep looking on ebay which is your best bet for replacement parts or even a complete movement but it will be like finding a needle in a haystack. 

I've been lucky then not to have the balance spring break as a result of my novice 'ministrations' - but I did remember to 'stroke' rather than bend per se. The clock is of sentimental value to the owner so I'm relieved to have now got it running to time with the support & encourage of forum members like yourself.

[oldhippy]

So it runs and keeps good time even with that train wheel. You are lucky I would point out to the owner about the wheel, just in case at some point they take it to a different clock maker.