I just serviced an E. N. Welch “Arditi” perpetual calendar clock. I disassembled the movement and cleaned it, but the only repair was replacing the click rivets, as the original brass rivets were coming loose.
This clock has a 27 3/8 inch tall walnut case, and was made in the 1880’s. The movement has very old mainsprings which appear to be original. They are thin (0.0153 inches thick for the strike spring and 0.0156 inches thick for the time spring) and do not seem very “springy”. Yet, they provide plenty of power and have no visible damage, and so I kept them in the clock. If a mainspring has lasted for over 120 years, it is likely to keep on working.
The video below shows how well this clock runs, even with the weak mainsprings (and it is run down several days, not fully wound).
Here is a slide show:
Repair job 4880
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