mainspring strength,length

[joem1964]

good morning everyone
green as can be,,,,can anyone tell me which main spring to use in a seth Thomas 48n movement,,,,i”ved tried the calculator on nacwc …I,m not sure of the results..
(not good at that kind of math )or if theres another way to figure it,,thank you all
joe

[willofiam]

Hey Joe, Not sure if I have worked on a Seth Thomas 48n BUT in a catalog I have from Mile Hi Clock Supplies it does give some mainspring sizes by manufacturer. Just to make sure double check with your numbers on that calculator you found and see if we get anything to match. Let us know what you find, thanks, William
For the time train 3/4 x .012 x 90
For the strike train 3/4 x .016 x 60

[joem1964]

thanks for the come back willofiam
is it unusual to find two different or more springs in a clock

[willofiam]

Hey Joe,
@joem1964 wrote:

is it unusual to find two different or more springs in a clock

no it is not from what I have seen. alot of times the strike train will have the stronger spring. There is actually alot to mainsprings (good subject to really dig into) by no means would I have all the details, One thing to keep in mind would be the strength, for instance a mainspring made 100+ years ago may not have been made with all its potential compared to a mainspring of the same dimensions made today. I have found a thinner mainspring for the average American made clock, (along with a good cleaning and proper pivot/bushing work) will give more than enough strength to run a full 7-8 days. At the same time I struggled with a small desk clock thinking I had the right size mainspring, only to find out I needed one a bit stronger and all my pain went away, (meaning it ran great after that). Have fun, William

[bernie weishapl]

William is right. I have had many a clock come across my bench with a different spring in the strike and time. I have even seen some of the more common kitchen and black mantles that have a 3/4″ X .018 X 96 on the strike side and a 3/4″ X .0165 X 96 on the time side. I came up with the same springs William did in the old S. La Rose catalog. I have found over the last 32 yrs that pivots being polished, bushings done properly is probably the most important thing in the running of a clock. I have run a seth thomas black mantle for 7 1/2 days after going thru all the pivots and polishing to a high shine with a 3/4 X .012 x 72 although for my purpose I went with a 3/4 X .0165 X 96. Just wanted to prove to myself it would run with a shorter, weaker spring if cleaned, repaired and oiled right. Was a fun experiment.

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