Please help me identify this pocket watch mainspring of an FEF movement

[Alessio]

Hello

This is my very first watch service, and I need some help identifying the mainspring, and perhap also the movement.

What I know so far is:

BWC pocketwatch

41mm FEF movement, no serial number or any other code I can see in it.

The mainspring is: 1.22mm height, 0.25mm thickness, ~51cm long. The barrel has an internal dimeter of 16.21mm.

I've opened all the FEF documents I could find in the cousinsuk website, but I was unable to get my one.

Can you please help me finding the replacement for the mainspring since the bridle is broken?

I found this one that seems very similar, but I dunno if it would be ok or not considering that the measurements are donw with a caliper

 

Thanks in advance for all the help.

Alessio

[LittleWatchShop]

Go here and scroll down to the FEF movements at the bottom of the list (FEF41B-49H).  They look similar to your movement (if not the same).  The mainspring measurements do not agree with yours precisely but close.  Pick the one that you think is closest and then do a google search on that number.  When I did this, google scans all of bidfun and gives you all the watches using this mainspring.  That may help you find a replacement.

[LittleWatchShop]

A little more poking around.  This looks close.  Search for "22847" on this page.

[JohnR725]

All those nice pictures except the one that we need? It would be really nice to see the backside of the movement so we can see the setting parts. There is a system used to identify watches if we have the movement size and a picture the setting parts we can possibly identify who really made this.

2 hours ago, Alessio said:

The mainspring is: 1.22mm height, 0.25mm thickness, ~51cm long.

It would've but also nice to see a picture of the inside of the barrel just for my curiosity. But since you have the mainsprings size we can go to the mainspring catalog not worry about who made the watch. I snipped out an image even though you measured 1.22 it's probably 1.20 mm. The thickness is problematic it's much better to use a micrometer. So here's spring is that would work.

 

[Alessio]

2 hours ago, LittleWatchShop said:

Go here and scroll down to the FEF movements at the bottom of the list (FEF41B-49H).

Many thanks for your answers, I confirm that pic 1 and 2 from the FEF41B-49H are exactly the one I have.

47 minutes ago, JohnR725 said:

It would've but also nice to see a picture of the inside of the barrel just for my curiosity.

Sorry, I actually had the pic but forgot to add it into the thread, attached this time

Checking the informations present in the ranfft website it seems to me that the watch was probably serviced long time ago and fitted with a compatible spring.
I'll go ahead and search for an original one and if can't find it, will back up to one similar to the the one I have.

Thanks again guys!
Alessio

[JohnR725]

16 minutes ago, Alessio said:

Checking the informations present in the ranfft website it seems to me that the watch was probably serviced long time ago and fitted with a compatible spring.
I'll go ahead and search for an original one and if can't find it, will back up to one similar to the the one I have.

It would be interesting if you put the old mainspring back in and notice if there is a height discrepancy?

Then for future reference if you had the setting parts and the diameter the movement we might get lucky and identify the watch that way. So I snipped out some images see you can see you how that works. It also see there's a height difference in their movements which of course changes the mainspring sizes a little bit.

[Alessio]

I took a pic of the spring installed in the barel, but I dunno if it's enough for you to spot any issues. I haven't noticed anything wrong when I open it, but for sure that was due to my inexperience.
I'll go ahead and order a spring based on the above charts and let you know.

Many thanks for your help
Alessio

[praezis]

Hello Alessio,

it is not really needed to  know the calibre of your watch to find a correct mainspring. An optimal spring can be found by a bit math, based on the inner diameter of the barrel.

From your picture the existing spring thickness is easily found as 0.19 mm.

A spring calculator supplies 0.19 mm for your barrel, too. Optimal length 480 ... 530 mm!
Now you just should check if height 1.20 mm is right.

Frank

 

 

 

[Alessio]

Thanks for the info Frank!

I've ordered a 1.50 x .21 x 440 x 16, I'll see how it goes, if it's too high, I'll order a 1.20mm accordingly

 

Many thanks

Edited December 6, 2021 by Alessio