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Low amplitude - slipping mainspring?


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I have been working on a Felsa 4000 movement - which is described as having 30 jewels on the dial and on the rotor. It has gone from a non runner to one that runs reasonably well in the dial up and dial down position but with terrible amplitude which drops further when you put the watch on its side and then it becomes a bit random!

It is the 2nd time I have found an automatic movement where it has a 2 piece mainspring with a non automatic spring and a short spring that goes around the inside of the barrel wall and can slide when necessary.

I have had a few problems with non automatic mainsprings not latching onto the barrel wall and learned that in some cases just popping the mainspring into that barrel is not good enough and you have to line up the groove in the barrel wall with the end of the mainspring before pushing it into the barrel.

But I have been curious about the automatic springs I have put back into barrels - how can I tell that they are slipping at the right tension and not slipping too early or too late?  I tend to wear them for a day or 2 after I have serviced them and then I take them off and see how long they run for and take anything over 30 hours as acceptable.

Well this watch with the 30 advertised jewels has given me some insight!  The barrel lid is not solid and instead has 20 holes which allows you to see down into the barrel and see the spring while it is in the watch. 9 of the holes have been filled with jewels on this watch. I have seen a similar watch boasting 61 jewels -  I guess on that one all the holes on the barrel lid have been jewelled! 

What I am seeing here is that at some point (and I think is too early) the spring begins to slip around the barrel.

As I said I am experiencing very low amplitude and I expect a large part of that is because I put the old blued steel mainspring back in (while I wait for the replacement I have ordered) but I also believe it is because it may be because the spring is slipping too soon.

On this occasion I removed both of the old springs from the barrel , cleaned the barrel and lid along with the other watch parts and ran a piece of watch paper with some d5 on it along the length with some tweezers.  I then put some breaking grease on the barrel wall before reinstalling the small spring (with my fingers) and then putting the larger spring into the barrel with a mainspring winder.
The large mainspring locks nicely with a little hook on the small spring and it all kind of works. I was a little surprised to see what it looked like when it slipped.  I thought I had read that automatic watches slip around to the next ridge on the barrel wall and I expected the slip to be quite quick.  But this watch, which doesn't have ridges around the barrel, slips slowly and quite far when it does slip.

Is my low amplitude because the spring is slipping too soon?

Have I put too much or too little breaking grease around the barrel wall?

If the barrel lid is not see through how do you check that it is slipping as expected?

It has been about 20 hours since I wound the watch and it is still running - so I therefore assume it isn't as bad as I first thought.  Perhaps the low amplitude is just due to the age of the spring?

Here is a photo - you can clearly see the light reflecting off 2 of the extra jewels - there are 3 sets of 3 set around the outer ring.
9_extra_jewels.thumb.jpg.73cb2adbada4da9a5a5a68b116f97644.jpg

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4 hours ago, ColinC said:

But I have been curious about the automatic springs I have put back into barrels - how can I tell that they are slipping at the right tension and not slipping too early or too late?  I tend to wear them for a day or 2 after I have serviced them and then I take them off and see how long they run for and take anything over 30 hours as acceptable.

what you really should do is replace to peace mainspring with a modern one piece automatic spring. Some service manuals will outline a procedure in other words you wind it up so many turns and then it slips have it slips it's not supposed to slip more then something. So basically they don't do the lubrication right elitist slip way too much or worst-case might not sleep at all which is unlikely

then how long the watch runs is dependent upon the particular watch.

4 hours ago, ColinC said:

Felsa 4000 movement

so according to the specifications found at this website you should get 44 hours

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Felsa_4000

4 hours ago, ColinC said:

As I said I am experiencing very low amplitude and I expect a large part of that is because I put the old blued steel mainspring back in (while I wait for the replacement I have ordered) but I also believe it is because it may be because the spring is slipping too soon.

are you using a timing machine the measure the amplitude and could we see the results maybe we will see something you don't see. Typically with blued steel Springs they can be wound up tight and they will supply adequate power they just typically won't supply it for very long. Which breaking grease are you using?

 

2769_Felsa 4000N.pdf

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Thanks for your input!

I will be replacing the mainspring with a modern one although I am unsure if the barrel is suitable for an automatic mainspring as the barrel walls are smooth. I was thinking of ordering both the automatic and non automatic mainsprings and using the non automatic one with the old small spring if the automatic one didn't work.

However I would still like to be more confident that when I put a spring into a barrel that I have done it right and what I should be looking out for and checking.

I am using the open source tg-timer app with a dedicated microphone.  It is showing a magnitude of around 180º dial up - dropping to 140º with the watch in pedant down position


Screenshot2023-10-27at09_23_27.png.b1a9b040ac8c34389d0cf0745ab21a49.png

The watch eventually stopped about 26 hours after I wound it - so about half of what it should be.

I am using Moebius 8213 as braking  grease 
 

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