Barrel Size And Spring Length

[bacgoff57]

Hello Folks
My question for today is. If the barrel size of the mainspring and the strike spring are exactly the same, and the arbors are the same would the springs be the same size? The two springs that i have are two different sizes, but i don’t know if either were replaced at some time or other. I have looked at the formulas for spring length. Is there a range or are the lengths exact?
Thanks Ben
P.S. The clock is German, same size barrel and arbor for each spring mainspring 64in strike 77in.

[pkamargo]

As much as I know it depends on what clock are you talking about.
It would be a nice idea to calculate how many turns each barrel turn on a week and see if there is much difference. This is very common on quarter chime clocks – the quarter train runs almost the double turns than the strike train, so the spring will be longer.
Many german T&S clocks need more power to drive the strike train than to drive the motion train, so the strike mainspring will be thicker. If the spring is thicker, it will take more space inside the barrel and will be shorter to fit. In this case care is needed not to invert the barrels when reassembling the movement.

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