Automatic mainspring in a plain barrel

[Stian]

Hi gurus, 

I have a LeCoultre 481 with a bumper automatic movement where the barrel is plain. There was an automatic mainspring in the barrel, but the amplitude does not reach higher than 160-ish. I took the mainspring out as I assumed it was set but it actually looks fine. So now I wonder if the mainspring is simply slipping too easily. 

Originally this movement would have had a slipping device (a ring coiled along the barrel wall), but now there is only the plain barrel. How would you go about putting an automatic mainspring in without it slipping profusely? Would you simply use a strong braking grease or is it impossible to get the mainspring to stick long enough to build power without the slipping device? 

-- 
Best regards,
Stian

[oldhippy]

Are you sure it is the correct spring? 

[rodabod]

You should be able to replace the original slipping bridle attachment and conventional mainspring (as was the way in the early days) with a standard automatic mainspring. 

I’ve had the opposite problem where the replacement has been too strong, but this could also be due to the change from blue-steel to alloy....

What you need to do is what Omega recommended back in the day for automatic spring adjustment and measure how many turns of the barrel you get before slipping commences. From what I remember, it’s approximately 4.5 to 5 turns. Then you will also need to measure that current spring to confirm it is of the correct “strength”, ie. thickness and also check the length.

Edited February 26, 2019 by rodabod

[clockboy]

Here is a service of the watch. The mainspring should be 1.15 x 0.09 x 260 x 8.5 or the Gr no. is 2797-X

http://watchguy.co.uk/service-jaeger-lecoultre-automatic-calibre-481/

[vinn3]

5 hours ago, Stian said:

Hi gurus, 

I have a LeCoultre 481 with a bumper automatic movement where the barrel is plain. There was an automatic mainspring in the barrel, but the amplitude does not reach higher than 160-ish. I took the mainspring out as I assumed it was set but it actually looks fine. So now I wonder if the mainspring is simply slipping too easily. 

Originally this movement would have had a slipping device (a ring coiled along the barrel wall), but now there is only the plain barrel. How would you go about putting an automatic mainspring in without it slipping profusely? Would you simply use a strong braking grease or is it impossible to get the mainspring to stick long enough to build power without the slipping device? 

-- 
Best regards,
Stian

   a slipping device or a " clutch" is discussed in de Carles book.. was patented by Movoto?  vin

[Stian]

Thanks guys!