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Automatic mainspring question

Hi,

How is the automatic mainspring build up?
Is the Safety spring just one part (spring slightly smaller then the circumference of the barrel) that alows the mainspring to slip when overwound?

If so is the mainspring then just a normal mainspringspring with a normal (as in hand-wound) bridle?

If've read the Bulova self-winding watch manual but this isn't that clear to me.

Thanks in advance
Regards
 

Reverend Rob's picture
Reverend Rob
Panel Member
Posted November 6, 2019 - 1:51am

Here's a little article on the very thing:

 

https://www.standardtimewatchrepair.com/blog/automatic-watch-mainspring

Reverend Rob's picture
Reverend Rob
Panel Member
Posted November 6, 2019 - 10:50am

For anyone wanting to delve deeply into this or any other watchmaking subject, the WOSTEP textbook 'The Theory of Horology' is an excellent resource, and was what we used in watchmaking school. 

Avolub
Posted November 6, 2019 - 12:10pm

Thanks Rob,

But I was talking Bulova-specific, I thought (as described in the self-winding manual of Bulova) that it was build up different then conventional self-winding mainsprings...

So not really an answer to my question I guess?

Reverend Rob's picture
Reverend Rob
Panel Member
Posted November 6, 2019 - 4:00pm

All automatic mainsprings, including Bulova, are made the same way, with a slipping bridle.