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Need help with mainspring selection

Blubarb

By Blubarb
in Watch Repairs Help & Advice

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Blubarb WRT Addict

Blubarb

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Hi all

I am working on cleaning an inexpensive pocket watch with what I think is some generic name: Anti-Magnetique. I have heard of Anti-Magnetique as a concept but not as a brand. 

I can't determine what movement is in the case as there is no marking to indicate the movement name.

Anyway, I removed the mainspring from the barrel and tried to measure it as best I can and I have also used the formula bYNnWwr.jpg to check the length of the mainspring. Using the formula I get a spring length of 566mm (so I can say 56cm) but when I stretch out the mainspring and allow for the end turn I get 54cm total length. Which method should I defer to - I guess it is possible that a shorter spring was put in last time. 

Can I get your thoughts on how to progress. I am just uncertain how critical this extra cm or two will be in the scheme of the age of the watch and the fact that it's just a project. 

Appreciate any assistance and thank you in advance. 

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wls1971 Distinguished Member

wls1971

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The more important measurements in determining mainspring size are the height and strength of the spring the loss in length of 26 mm would make hardly any difference in the running of the watch other than it would run for a shorter period of time so if the power reserve was 30 hours the difference in length may mean it runs for 28.

 

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Blubarb WRT Addict

Blubarb

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Yes, that makes complete sense. I have come across some interesting reading online and even found a reverse engineering calculator that helps in selecting a mainspring based in the inner diameter of the barrel. 

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Tiktok WRT Addict

Tiktok

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As already said the strength (thickness) is the most important and the height, the length just needs to be as near as what ever is available.

The other thing that can sometimes be a pain to match up by ordering by size rather than calibre is the centre that goes around the arbor, sometimes if the arbor is too small it doesn't hook properly.

Sometimes with older stuff you just have to make do with what you can get and make it fit. 

I would be more concerned about the condition of the escape wheel, hopefully it is just dirt and will clean up.

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Blubarb WRT Addict

Blubarb

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3 hours ago, Tiktok said:

As already said the strength (thickness) is the most important and the height, the length just needs to be as near as what ever is available.

The other thing that can sometimes be a pain to match up by ordering by size rather than calibre is the centre that goes around the arbor, sometimes if the arbor is too small it doesn't hook properly.

Sometimes with older stuff you just have to make do with what you can get and make it fit. 

I would be more concerned about the condition of the escape wheel, hopefully it is just dirt and will clean up.

Yes, that escape wheel is caked ugly with muck, but is beginning to clean up okay. 

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