WatchTech

Rainer Nienaber showed me these pictures of a mainspring barrel he had on his workdesk. He said that this seems to happen sometimes, but nobody has an idea why a mainspring would break instantanously not only in one spot, but practically into many fragments.





Has anyone seen something like that before?

Regards,
Marcus

Hi Marcus,

..with the intial breakage flailing around and causing further breaks?

But I have access to information (directly and indirectly) about hundreds of thousands of repairs and I've never heard of such a thing.  Just saying.

Unless someone really did snap the spring into many pieces and then carefully arranged it back into the barrel? Sounds like the infamous tales from the dark (were there any lightones?) days of British Leyland. .. This message has been edited by BDLJ on 2013-09-06 21:42:05

New thing.
I have seen this happen a  number of times over the years  in  both new white steel mainsprings and the old blue steel springs. Regarding the blue springs I feel it had more to do with slight surface surface corrision than anything else. I have fitted new, old stock blue steel springs US, English and Swiss made which looked good with no kinks or rust and have self destructed within a few days of fitting just like the photo's show.
At times it has been at the first winding !
It was certainly not from hand winding the spring into the barrel as a winder was always used.
 I have also seen the modern Swiss mainsprings do exactly the same thing, there was a  replacement spring for a '60's Omega calibre that did the same thing.
I never found any reason for the breakdown, but it seems it must be metal fatigue caused in the rolling process, who knows maybe it is the first or last piece off the roll and is stressed.

I have also seen a few of  the same exploded springs in a clock

David

and was fortunate/unfortunate enough to watch it as it happened. I have never seen this is a watch before but when I was in my first watchmaking school we used to also service clocks. I had this happen on 2-3 mainsprings that has mild surface rust. These were treated with a  mild acid treatment to remove the rust prior to lubricating and installing in the the barrels. In one of the instances it didn't even last long enough to finish preparing the barrel lid before I started hearing the familiar sound of a bowl of Rice Krispies. Upon closer inspection it was clear to see the individual cracks appearing as the pressure of the mainspring seemed to be shattering itself. It was like watching popcorn pop.

I had assumed it was due to the rust removal method causing the steel to become brittle, however further study was not undertaken.

TCP

... without the image of a shattering mainspring in my head!

Regards,
Marcus