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A Sicura Automatic Jump Hour Walkthrough


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Boring days passed......

When the Sicura watch and the donor watch arrived, they look like junk.

Yes, I bought a watch with only a mainplate and a rotor and jump hour parts!

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So I can use my Whitney watch that have been in the drawer for few weeks...... It costs me few dollars.

The Sicura shows a BFG 158 31/7 caliber and the Whitney is 158...... They shares the same base movement. Therefore it is possible to combine two calibers into a single jump hour, though it seems strange.

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After servicing, it works like a charm until.......

the jump hour is installed.

Watch stopped?

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It is pretty hard to set the time.

It must be something wrong with the module.

And I noticed that teeth of the date ring is almost missing!

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And the date corrector and yoke......

I browsed the intercharge list on JulesBorel. These also can be found from BFG 582.

But both are rare calibers in Chinese market......

I am searching Internet......

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A day-date BFG 628!

From the technical document on Cousins, parts I need (2566, 2566/1, 2557/1) look like the same.

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So I bought this immediately and I am waiting for 4 days delivery......

Continued

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  • 3 weeks later...


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    • Welcome to the group Stirky. You can search for just about every subject in the craft here. Don't be afraid to ask if you can't find the answer that may have already been covered ( some ad nauseum LOL ). You don't have to buy Bergeon to get good quality. There are many decent mid-range tools available that will last you a lifetime. Cousins would be a good place to start . Cheers from across the pond ! Randy
    • I picked up a similar amount of these jewels some years ago in a watch and clock fair. Every now and then they come in handy. This week I've got a rubbed in bombe jewel in the balance cock that is cracked and needs replacing. Very handy to have a vintage assortment of these type of jewels!
    • Great diagram with the teeth and pinion count. Simple way to reduce the speed of the hour wheel by the 12:1 minute wheel. Genius and yet so simple. Always good to reinforce the principal by what you have done in your drawing. Keep doing that. I had a drawing on my wall for years showing me this which is very similar to the drawing you have done. Here's a formula to work out the beats per hour of a watch movement. The movement's BPH is dictated by the wheel teeth and pinion count and the hairspring being vibrated to the correct BPH by finding the pinning up point on the hairspring using a vibrating tool.  The reason in the formula there is X2 on the top line is because there are two pallet stones.
    • So I just wanted to say "thank you" again.  The angle is the key bit it seems and yes, it did basically just fall, or float, back into position when I got it lined up just right. I had meant to add that now that I see how it goes in, I totally see how it came out in the first place, and that whomever cloned the original movement didn't pay much attention to the fine details around the setting or how it interfaces with the balance cock or the "rings" on the regulator and/or stud carrier arms.
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