Expert: Michael Radi - 2/8/2009

Question
I have a Linden mantle clock (made in West Germany) that was given to us in 1974. Up to now, it has been working fine. It now runs slowly and I was wondering if there was an adjustment that would fix this problem. There is a (+ / -) setting on the back of the clock but I am not sure how this will affect the clock.
Thanks.

Answer
I'm guessing that your clock has a movement with the numbers 1040-020 stamped on the back. Let me know if this is not correct.
These clocks have a floating balance rather than a pendulum. Has the clock ever been serviced? I would check a lot of other things before changing the time keeping on the balance. If the clock has been running most of the time you have owned it and it has not been serviced I would bet good money that the movement is worn out. These movements usually last for 15 to 20 years of running. The mainspring barrels and the pivot holes will get worn to the point that the clock can't run properly. In my clock shop we rebuild or replace these movements. It has been a long time since I saw one from the 1970s that did not need major work. Most of them I see are from the late 1980 and after.
If by some chance the clock was lubricated and/or cleaned, or not run for extended periods of time throughout the years there is a possibility that the movement will survive a few more years. If you want to work on the movement yourself, the first thing to do would be to oil the movement. If you can get the movement running better it will most likely get back to good time keeping.
Having said all of that, I will tell you how the timing adjustment works: There are two types of Hermle floating balances. A movement made in 1974 had the older type in it. The balance has a disc that rotates back and forth. When the clock is running good the balance disc will travel about one full turn then change directions. To follow its swing look at the two pins that go through the fork as they pass the back side. The pins are just under the disc and the fork rocks back and forth, changing directions as the pins pass through it. You can see the pins go around and stop as the go toward the front of the movement, then back around again. If the movement is running well they will reach the same point on a left swing as they will on a right swing. If they don't reach at least close to the same point the clock may not keep good time.
On top of the disc there is a fingered spring with its tips pressing down onto the disc. You rotate this spring toward the + for fast or toward the - to make the clock slow down.
I hope this information helps you.
Michael
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