Mainspring set?

[rgmt79]

The picture attached shows 3 barrel springs removed from a 30 hour Grand Sonnerie movement. The middle spring powers the going train and looks like it might be set, how can I check this?

IMG_0351red.jpg (134.12 KiB) Viewed 4575 times

[willofiam]

Good question, I think the simplest way to answer would be to test how it runs and length of run time. As long as the mainspring is the correct strength and length (this can take some investigating) but if we assume it is.... then at various wound states within its 30 hour run time you can examine the function of the escapement, listen to it, measure pendulum oscillation, ect...looking for any lack of power.

This of course after addressing all issues, cleaning, bushings, pivots and lubricating since friction throughout the train and escapement will even effect the performance of a new mainspring.

For me it sometimes ends up being a "feeling"...if I have any question I replace them though that is because I am dealing with a customers clocks...It is fairly rare that I do replace them though since alot of clocks have mainspring that provide plenty of power.

Some of my own thoughts, maybe someones else will chime in with more ideas. Have fun.

[rgmt79]

Thanks William, I guess I can assemble the movement with just the going train to test the spring in the way you suggest...that way I don't have to assemble the whole movement and then have to take it apart again if the spring doesn't work...being a complicated movement, that would be a right pain in the ****

Richard

[willofiam]

good idea, remember though that lifting levers ect... can use up some power.

[rgmt79]

good point William, I will have to make some allowance for that...

[Bernie Weishapl]

Generally when I see a spring like the middle one it gets replaced. A new spring when the retainer is taken off will spring out at least twice that size or more. My problem is I can't afford to have any come backs out here as most clocks are out quite a distance as my service area covers 125 radius of my location. I have learned after 33 yrs of doing clocks to error on the side of caution. Just my $1.298.

[rgmt79]

Thanks for your input Bernie, I'm not fixing this for a customer and I would agree that, given your circumstances, it makes sense to replace...having said that, I read somewhere that they don't make them like they used to and a new spring is prone to break quite early in it's life. At least I know this one has lasted over 100 years and I guess will last another 100 years provided it has enough power to drive the clock for 30 hours. Apart from all that, I want to keep this movement as original as possible....the pound is running at around $1.34 right now

[Bernie Weishapl]

Not sure about springs not being as good as the original but I have only had 3 new springs break in 30 some years. If it were my own clock I may let it go but most times I still replace unless it is a very unusual clock or a expensive one but that is just me. But no worries give it a go and see what shakes out. LOL