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Lost in the balance staff jungle...again

bsoderling
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bsoderling WRT Addict

bsoderling

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Hi guys,

 

Trying to get an old AS984 to run. Balance staff pivots are gone so I start looking in the usual places (balancestaffs.com, cousins and a few more).

 

My movement is possibly an early version i.e. no inca or other shock protection.

 

What I end up with are way too many staff versions with slightly differing dimensions. Some are indicated as inca but several have no such indication and are still coming in different overall lengths and diameter at the place where the wheel is sitting.

 

I sit here with a list of Ronda no’s that differs ever so slightly in what I guess are the more relevant dimensions and all are somehow related to AS 984.

 

Once I remove the balance wheel I will be able to measure the diameter at the wheel position which may narrow down things a bit, but still frustrating.

 

Curious how the more experienced would go about this problem as trial and error doesn’t seem like a viable option....

 

/bsoderling

 

 

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bsoderling WRT Addict

bsoderling

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Hi,

Yeah, Ranfft is the obvious place for info. But the balance staff info there refers to Flume no’s and the Flume website seem to leave me hanging as most other sources that supply to hobbyists as myself refer to Ronda or DCN systems.

And as Rogart63 is pointing out, this movement comes in a huge variety and ranfft is just a single example. (No complains about ranfft, it’s a brilliant place but can understandably only cover so much)

I can’t help wondering how these issues were handled in the good old pre-internet days? Every watchmaker/repairer must have had a huge bookshelf with printed catalogues that needed frequent updating.



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rogart63 Distinguished Member

rogart63

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1 hour ago, bsoderling said:

Hi,

Yeah, Ranfft is the obvious place for info. But the balance staff info there refers to Flume no’s and the Flume website seem to leave me hanging as most other sources that supply to hobbyists as myself refer to Ronda or DCN systems.

And as Rogart63 is pointing out, this movement comes in a huge variety and ranfft is just a single example. (No complains about ranfft, it’s a brilliant place but can understandably only cover so much)

I can’t help wondering how these issues were handled in the good old pre-internet days? Every watchmaker/repairer must have had a huge bookshelf with printed catalogues that needed frequent updating.



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Like this :) DSC09619.thumb.JPG.4db97e9d5c8d98576d97af0ede6e5902.JPG

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  • 3 weeks later...
bsoderling WRT Addict

bsoderling

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Hi again...

Coming back to this thread as there’s been some development (and more questionmarks).

So I found a balance staff type ”ordinary” i.e. No shock protection at all. Got that riveted into the wheel (getting the hang on that procedure now) and tried the wheel in the movement.

And it gets stuck hard...

After some real close up work with the loupe I realize that the pivot isn’t even prodruding the jewel hole in the balance cock. It goes in a tiny bit and gets stuck.

On the bottom plate there’s no such problem, even though the hole looks a bit worn around the edges.

So how could this thing ever have run?

I then noted that the cock jewel has some burrs around the edges (see photo) i.e. It has probably been swapped out at some point.

So my question is if it can be that the old staff got so worn down (diameter) that the guy who replaced the jewel put in one with a smaller hole that actually better fitted the worn pivot?

And then obviously the pivot broke at some point....

I would be happy to hear your response on my ”theory”.

Bsoderling
IMG_4012.JPGIMG_4014.JPG




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rodabod Distinguished Member

rodabod

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In that second photo, it looks like the jewel hole may be cracked.

I think your investigation work is probably sound. Also look out for punch marks underneath the balance cock, on the main plate. If it were me, I'd replace the balance cock and balance itself, or at least get another to compare to if you a dead set on repairing.

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bsoderling WRT Addict

bsoderling

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Hi Rodabod and thanks for responding.

The base plate jewel is definitely not sound even though I can’t see any major cracks.

It’s a bit frayed around the edges and even appears a bit oval to my eyes. But there’s not huge side shake around the new staff pivot and on the general list of priorities I am pushing it down a bit for now.

In the future I will look a bit closer on the shape of functional balance staff pivots when servicing a movement to see if I can trace any cross section diameter reduction from wear. If I do, I will take that as evidence towards my ”theory” of what happened to my movement.

For now (or maybe later :-) ) I will try to gather enough confidence for a jewel swap in the balance cock, using the Seitz tool I bought on the bay a while ago. The previous owner kindly included a few tubes with jewels that might work.






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bsoderling WRT Addict

bsoderling

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To wrap this up....

There was indeed a jewel with my Seitz tool that seemed to be in the right direction ( 0,9 mm OD & 0,11 hole) so no excuse for not trying.

And it turned out well with the balance wheel fitting nicely and spinning forever when tried without the hairspring.

The hairspring turned out to be a bit of a nightmare. Appearing nice and flat on the wheel still on my table, it tilted heavily once the stud was pushed in. I spent several hours trying trying to grasp the dynamics of that thing and what influences what. Finally a tiny push a few mm’s from the stud levelled the spring to flat and parallell with the wheel.

I suspect there must have been different materials used in hairsprings over the years? This one was really soft as butter and made very little resistance to maintain its shape when applying any kind of ”force”.

After cleaning and oiling it now runs reasonably well with a decent amplitude.

I attached a photo. With the clean and undamaged dial, I guess it’s an ok piece from the period or...?

IMG_0563.JPG


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