FHF 3 13 ligne 27mm? Correct mainspring?

[karlmansson]

Hello!

I'm ordering a new mainspring for a 1930s Ulysse Nardin wristwatch with a movement made by FHF. It's marked "FHF 3". Ranfft lists this movement (the setting lever spring matches the images as well as the bridge layout) at 13 lignes which should be 29mm. I'm measuring mine at 27mm at the dial diameter. Which should make it about 12 ligne.

Am I missing something here? As a matter of fact, Ranfft has no 12 ligne FHF movements listed on his site. Not sure how to interpret it. The ligne system seems to have a very high degree of resolution so allowance in the system seems unlikely.

bidfun-db Archive: Watch Movements: FHF 3, 13'''

www.ranfft.de

Not that it matters that much anyways, I just realized there's no mainspring listed for it. I'll have to order by size.

Thanks for any help figuring this out!
Regards
Karl

 

[karlmansson]

Does anyone know the correct mainspring for this movement? I strongly suspect that the one in the watch is not the proper one. It's 270mm long and 0.08mm thick. Seems far too short and weak for this size watch. Height is 1,57 which seems more appropriate at least.

Tissot specs a heftier mainspring for a slightly smaller movement at 12 lignes with the same type barrel. Slightly dissimilar movements of different year of manufacture though but it's the only, roughly same sized one that I could find that specified the mainspring barrel diameter of 10,5mm.

bidfun-db Archive: Watch Movements: Tissot 27-T

www.ranfft.de

 

[gmorse]

Hi Karl,

Use David Boettcher's calculators.

Regards,

Graham

 

[karlmansson]

Taking more measurements from the barrel the closest bet is this

1.80 x .11 x 360 x 10.5 Non-Automatic

The barrel is unusually high for it's diameter at an internal height of 1,9mm. I'm thinking I should bias the spring to the thinner side (the alternative was 0,12mm) because of that. The Tissot spring I mentioned earlier is only 1,3mm high. I know the majority of the spring strength comes from the thickness but still.

If anyone has a listing that specifies the dimension for the FHF 3 13"' I would be very happy to know. Worst case I'll get two springs but they are surprisingly expensive I have to say.

Regards
Karl

 

[roughbarked]

From Dr Ranfftt: FHF 1 to FHF 16 designate movement groups containing calibres of different dimensions; individual designations start with FHF 22.

This is the mainspring for FHF 26 ~ 1.70 x 11.0 x 0.11 x 390mm
Which is the base model for all the 12''' FHF that Dr Ranfft lists.

 

[karlmansson]

From Dr Ranfftt: FHF 1 to FHF 16 designate movement groups containing calibres of different dimensions; individual designations start with FHF 22.

This is the mainspring for FHF 26 ~ 1.70 x 11.0 x 0.11 x 390mm
Which is the base model for all the 12''' FHF that Dr Ranfft lists.

Dang, I don't know how I overlooked that... Thanks for pointing that out roughbarked! Much appreciated.

Although, the 26 is much more recent, made in the 1950s. And the barrel is 11mm instead of 10.5. Not sure how the 26 can be the base for a movement that was made in 1935?

 

[roughbarked]

It isn't. This was meant as a demonstration.

As Graham pointed out, do the calculations. Otherwise order your mainspring with your barrel dimensions.

 

[karlmansson]

I had too many unknown variables to be able to use the calculators successfully I think. Unknown spring thickness and I’m not sure how many turns I should consider necessary.

 

[gmorse]

Hi Karl,

Unknown spring thickness and I’m not sure how many turns I should consider necessary.

Start with 6 turns and see what the Reverse Engineering calculator suggests from just the barrel ID.

Regards,

Graham