Many 30 hour spring driven American antique shelf clock are operating with mainsprings that are WAY too strong! The original springs are often stronger than necessary, but clock repairers have replaced then with springs that are even stronger!
A nice little (17-3/8 inches tall) Seth Thomas I have now (in for adjustment and to have the minute hand properly fitted) has a replacement time mainspring that is feels very strong when it is being wound, at least twice the force that is needed! The clock ticks very loudly! I am going to recommend to the customer that the movement be overhauled and the spring replaced. Or, if he doesn’t want to have that done, I will explain and write on the bill that the mainspring is way too strong, is causing excessive wear, and the clock should not be operated very often.
Job no. 4525
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Thank you