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German Time Bomb springs

Blueboy

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Aug 28, 2021
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I don't think the main spring is supposed to look like this.:(
Bought the clock for parts or repair, so I'm not complaining.
I'm thinking I can cut off the bad two turns and re-drill the hole.

In the pendulum spring pic, is that bend supposed to be in there like that?
The other ones I have, have a different spring like a coil, this one is flat like in a watch.

IMG_0281.jpeg IMG_0285.jpeg
 

shutterbug

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It's in pretty bad shape. I'd cut off the bad part and put a new hole in it. Interestingly, they will run without a hole too .... but it's best to put things back like they were intended.
 

Wayne A

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Sep 24, 2019
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I'd cut the mangled bit of mainspring off and make a new hole for attaching the end. That pendulum hair spring is different style than on my clock which has a helical one, see pic.

20210826_174318.jpg
 

Ibehooved

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Jun 9, 2021
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Since recently dissecting a pocket watch, I have been wondering why 400 day clocks didn’t have pendulum hairsprings, helical or otherwise. I guess they do! What does “GTB” stand for? Gustav Becker? Do clocks with these hairsprings still run at 8 bpm, or are they quicker?
 

Cheezhead

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Dec 30, 2010
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Blueboy, I suggest that the bend in the pendulum spring that you mention and illustrate in your original post is for a final adjustment to center the beat. A brand new helical wound small compression spring, for example must be compressed to solid (set) once or twice before it is measured for strength to see if it meets the design specification. The Haller pendulum spring similarly would need to be flexed to its tolerable extremes unless Haller would use a separate fixture to do that. It might be less work to just assemble the spring into the clock and flex it there and then center the beat as needed. The pendulum timing adjustment can, of course compensate for spring strength and other variables.

I wonder why the pendulum spring was changed from a flat spring to a cylindrical spring. Could it be for ease of assembly? Does anyone have suggestions for the reason for this change?.
 

Blueboy

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Aug 28, 2021
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Blueboy, I suggest that the bend in the pendulum spring that you mention and illustrate in your original post is for a final adjustment to center the beat.
Then it's probably a good thing I didn't try to straighten it. The bend looks to uniform to be an accident.

The main spring on the other hand...

I cut the bad part off, annealed the end and drilled a new hole.
Kinda wondering why the manufacture didn't do it like this. Having the spring wind backwards onto the other hub puts a lot of constant stress on that little screw, which could potentially strip out the threads in the plastic. And you know what happens then. :emoji_bomb:
IMG_0303.jpeg RenderedImage.jpeg


I wonder why the pendulum spring was changed from a flat spring to a cylindrical spring. Could it be for ease of assembly? Does anyone have suggestions for the reason for this change?.
Inquiring minds would like to know... Anyone? Anyone? Anyone?
 

Wayne A

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Sep 24, 2019
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The mainspring force is applied by winding it as you called "backwards", but thats the way this type of spring works. Winding it "forward" stores no energy. By the time you get a few turns on the spring I feel like its going to take most of the upward pull away from the mounting screw. I'd rather mine never to fully unwind to reduce stress on this attachment.

Wayne
 

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