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Tired mainsprings?

skridlov
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clockboy Distinguished Member

clockboy

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In my opinion when the mainspring is what I call set then the biggest difference is the power reserve reduces and also the amplitude reduces significantly as the spring unwinds. If available and the budget allows I always change the mainspring on vintage watches.

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skridlov WRT Addict

skridlov

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Thanks for you observations which confirm what I'd guessed. Trying to recover quite low value watches (I won't dignify my efforts with "restore" just yet) means that I tend to scrimp and deter myself from spending too much. But I'm getting a bit more confident where the simpler stuff's concerned and mainsprings haven't been too much of a problem - so far. I haven't wrecked anything valuable to date - many not very valuable, but nothing to make me want to quit.

Roy

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anilv Distinguished Member

anilv

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One way to judge if the mainspring should be changed is by taking it out of the barrel and laying it out on a bench. You need to know how a good mainspring looks so if you're new to this you could post a pic here and get some opinions.

Also check if the spring is 'out of flat', ie lying on your table parts of the spring don't contact the table surface.

If the movement is a common one then you should just change the spring as a lot of poor running issues can be solved with a new spring. Without a new spring you may be chasing your tail finding problems actually related to m/spring.

my 2cents!

Anilv

 

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skridlov WRT Addict

skridlov

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Thanks.

This is a general question as I'm dealing with lots of elderly and infirm watches. I suppose that as the mainspring isn't an expensive part, "when in doubt change it" applies.

I'm always a bit puzzled by the mainspring specs on Ranftt - here's a random example:

1.50 x 10.5 x 0.12mm

Where's the overall length? 0.12 is the thickness; 10.5 is the barrel diameter - I assume. But 1.50? Height?

Whilst I'm about it I'm always puzzled by the Ranfft stem (and balance staff) W and U designations since they never seem to relate to the stems I'm sourcing. The Paulson catalogue's another mystery in this respect too.

Roy

praezis Distinguished Member

praezis

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Thanks.

This is a general question as I'm dealing with lots of elderly and infirm watches. I suppose that as the mainspring isn't an expensive part, "when in doubt change it" applies.

I'm always a bit puzzled by the mainspring specs on Ranftt - here's a random example:

1.50 x 10.5 x 0.12mm

Where's the overall length? 0.12 is the thickness; 10.5 is the barrel diameter - I assume. But 1.50? Height?

Whilst I'm about it I'm always puzzled by the Ranfft stem (and balance staff) W and U designations since they never seem to relate to the stems I'm sourcing. The Paulson catalogue's another mystery in this respect too.

Roy

Hi,

yes, 1,50 is the hight of the blade. Length and barrel diameter are alternating measures of the same: the length.

W an U refer to German Flume system and catalogues. W + number for stems, U for balance staffs.

Frank

skridlov WRT Addict

skridlov

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Thanks Frank

I've looked at and tried the mainspring calculator on the NAWCC site and it came up with a figure similar to that which I knew was required for the movement in question at that time. But the sources of mainsprings that I look at always seem to specify length as well as thickness (perhaps because of metallurgical variants?) So if I'm trying to source a mainspring for a WW1 era movement, where I can't just look it up on say, Cousins database, what's the best mechanism for the estimate?

Apologies if this is dense of me.

Roy

clockboy Distinguished Member

clockboy

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With respect Stuart I have never encountered over banking with a new spring. Over banking rarely happens. I have only encountered this once when the spring was way over strength. 

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skridlov WRT Addict

skridlov

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Thanks again. David Boetcher's site is invaluable but I hadn't investigated this yet. It would benefit - or WE would benefit -if it had a search engine.

Still confused about the length issue generally.

Roy

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