Expert: Martin Meyer - 12/28/2009

Question
I have a mechanical 11 jewel Elgin striking ships clock, about 25 years old made in West Germany.  The markings on the back are the above, plus the numbers "81" and 132-071.  

While I was winding it yesterday, the mainspring for the clock mechanism broke. I removed it from its case and checked--the winding ratchet mechanism is intact, but when I turn the key, I can hear the spring tighten up to a certain point,then "let go."

It appears to be a relatively easy replacement (I've done this before with wind-up car clocks)as I don't have to get into the clock/striking mechanism itself, but I need a source for the mainspring.  Suggestions?

TIA

mike

Answer
Hi Mike,

A good source for Hermle mainsprings is Black Forest Imports (www.blackforestimports.com).

The 132-071's that I have seen all have a single mainspring plate on the front main plate. This means that you will have to let down the mainspring which is NOT broken, or it will let go when you remove the plate and could cause serious damage to the movement. I would also make sure that the broken spring is let down, as from what you say it will take somewhat of a wind before letting go. It is almost impossible to let down a mainspring without a letdown key, but you can make one from a regular key and hardwood dowel.

I am not familiar with car clocks, and don't know if their mainsprings are in barrels. If you have not replaced mainsprings in barrels, you will find that this process will be a bit different and more complicated. You must be very careful not to distort the barrel or barrel cap when opening it. It is possible to replace a mainspring without a mainspring winder, but can be quite a bit more difficult, particularly in getting the outer mainspring hole to hook onto the barrel pin. The new mainspring will come wound and bound with a wire, and so should slip into the barrel. If it does not, or is not wound tight enough to fit in the barrel, you can unwind the new mainspring and feed it into the barrel manually. I very strongly recommend using a leather work glove on the hand which is holding the barrel, to avoid injuries. I would note that manually winding the spring in this way will distort (cone) the mainspring. This is not good, but you can usually get away with it with strong springs such as these.  http://www.clockmasteronline.com