AS 984 Replacement Balance

[Paul Raposo]

I have a rebranded Rotary caliber 440 which is an AS 984. I need to replace the balance and found a couple on ebay. NOS balance with staff and hairspring however they are listed as being for the incabloc balance and the movement I have doesn't have incabloc. Can I still use these replacements or would there be a difference in the staff height because of the incabloc shock protection?

 

[Chris Radek]

An incabloc staff has extra shoulders on it near the ends and may not fit in your jewel settings.

 

[Skutt50]

The AS984 came with 4 different types of staffs of various lengths......
Have a look at this page: Ronda Balance Staffs - Pages 1-10 (A - B) - Vintage Watch Parts

 

[Paul Raposo]

Thank you Chris and Skutt50 for your replies and information about this. I knew there were different versions of the 984 movement but had a fleeting hope that this balance would work in my watch.

My next question is; I have dozens of spare movements, if the balance diameter is the same and height of the staff is the same, could I use a balance complete from a different watch or does it have to be specifically an AS 984 balance complete?

 

[Skutt50]

There are more parameters to consider. The roller table must be at the right height and the roller jewel must be of the right dimmensions and mounted at the correct distance from the barrel/pallet fork. Also the pivots should be of the correct diameter/thickness. Then the hairspring stud needs to match the balance cock and the BPH must be the same.

The possibility that you find a balance that will function is extremly small and the watch will be a Franken type watch.......

From a pure technical point of view there is no hinder to instal a different balance wheel (including a hairspring vibrated to match the balance wheel) but from a practical point of view it is much easier to replace the staff as such. (Or is there more damage to the balance?)

 

[Paul Raposo]

From a pure technical point of view there is no hinder to instal a different balance wheel (including a hairspring vibrated to match the balance wheel) but from a practical point of view it is much easier to replace the staff as such. (Or is there more damage to the balance?)

Thank you for this informative reply Skutt. The balance and staff are ok, the hairspring is mangled.

 

[Skutt50]

the hairspring is mangled

Sounds like it is time to learn some new skills.......

Read up on how to manipulate a busted hairspring and get some "simple" tools and a good magnifier......

Personaly I seldom do it on customer movments. Takes too much time, but sometimes if I have time to spare I can play around with busted hairsprings just for practise and to see what I can do.

 

[gmorse]

Hi Paul,

There's a very interesting set of three videos on YouTube by The Selective Luddite. It's really about making balance springs from music wire, (yes, it can be done!), but the second video in the set deals mainly with corrections to distorted springs in an innovative way, using a paper strip instead of the spring to demonstrate techniques. It's one of the clearest explanations I've come across.

Regards,

Graham

 

[Paul Raposo]

Thanks Skutt. I used to be able to manipulate hairsprings but have been having some balance issues--no pun intended--of my own, so my hands aren't too steady right now.

Thank you Graham. I looked up those videos and they were fun to watch. Maybe I'll grab a few parts springs and practice what I saw. I miss doing fine work on watches and want to get back to my old skills.

 

[Paul Raposo]

One more question--could I replace the hairspring of the same diameter onto my watch balance wheel?

 

[gmorse]

Hi Paul,

One more question--could I replace the hairspring of the same diameter onto my watch balance wheel?

It isn't just the diameter of a replacement balance spring that needs to match. The strength has to match the wheel as closely as possible, and the strength of a spring is inversely proportional to its length, proportional to its width, and most importantly, proportional to the cube of its thickness.

In practice, this means that a tiny difference in thickness can have a large effect on the spring's characteristics when trying to match it to the balance wheel, because the natural frequency of a watch balance is determined by the weight of the wheel, (mostly in its rim), in combination with the strength of the spring. The wheel by itself without the spring has no natural frequency, which is why early, pre-balance spring watches were such imprecise timekeepers.

Regards,

Graham

 

[Paul Raposo]

Thank you for the very informative and enlightening reply Graham. I'll keep looking for a correct part for this watch.