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Hmmm, which mainspring?

MuensterMann

Registered User
Mar 23, 2008
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I have a Hamburg American Clock Company mantle clock with both mainsprings broken. The size is 18mm wide (.70 inches) , and about .48mm thick (.018 or .019 inches) and 61 inches long.

Are old German mainsprings overpowered like American ones in clocks around 100 years old? If so, perhaps the clock could tolerate a thinner spring. There is a .016 one that is 61.5 inches long. And there is .0175 one that is 70 inches long. Which one, if any, would work well?
 

Willie X

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Feb 9, 2008
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I would go with the .0175" springs.

Often the strike spring is slightly thicker/stronger than the going spring.

Willie X
 

MuensterMann

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Mar 23, 2008
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I am leaning toward the 70 inch long one as well, but hoping that extra length will fit in the barrel just fine.
 

Uhralt

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Sep 4, 2008
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I am leaning toward the 70 inch long one as well, but hoping that extra length will fit in the barrel just fine.
You can always shorten the spring. 9 inches longer than the original is quite a bit and may reduce the runtime of the clock.

Uhralt
 

Uhralt

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Sep 4, 2008
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Do you believe the .016 inch thickness one would be too weak?
Hard to tell. You probably don't know how much overswing the clock had with the original springs. You could go the risk and try. If it works, fine. If not, you have spent some money and have two springs left that you may or may not use in the future. It's not hard to shorten springs. How to do it has been many times described in the Forum.

Uhralt
 

MuensterMann

Registered User
Mar 23, 2008
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I have another German clock where the lengths are both around 55 inches. One spring is about.016 inches thick and the other is about .018. I imagine the .018 is for the strike and .016 for the time. So, it sounds like these thicknesses were used in German movements. I was trying to figure out if the mainsprings in the HAC were original or not.
 

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