Reassembly: Sea-Gull ST7

After my slightly traumatic experience with this Sea-Gull ST7, I’m having an attempt at fixing the watch.
As you may remember, I broke the pinion of the minute wheel when trying to tighten it as it was slipping. Torsten and I tried to find a replacement wheel, but nothing fits. I even contacted a 3D printer, but they said that something that thin (0.2mm) will just break. We did find one that was a bit smaller, and I will attempt to fit it. The one on the left is the original wheel, with the broken pinion, and the one on the right is a slightly smaller wheel from another watch.

With a small punch in the staking set, I punch a circle of dots around the wheel to make it a bit larger.

Then, with a larger punch, I flatten the wheel again as it warped a bit in the first step (as you would expect).


Not a thing of immense beauty, but the wheel now has the right diameter. I have also drilled the centre hole to 0.6mm, as it was a bit too small.

The dots on the wheel are irregular, as I was trying to correct to the same diameter all around. This whole operation took over an hour, but well worth while.

Now I can mount the cover plate with the day/date changer.

The day wheel goes in – note that it has 14 days – 2 x the same 7.

The dial gets a final brush before the hands are mounted.

The hands get a quick polish.

Hands are back on.

The case needs a good clean.

Movement back in the case – the only thing that’s missing is the auto winder.

I put in the wheels for the auto-winder. The two little wheels in the centre tilt left or right depending on the direction of rotation of the rotor, so that the main spring is wound no matter what direction the rotor turns.

Movement complete with the rotor mounted. There is an odd jewel at 2 o’clock from the center – quite a big one with a big hole. No function whatsoever. But it adds to the jewel count!

An epic journey comes to an end… I’m probably something like 15 hours down the line at this point. From having to re-glue the pallet jewels to making another minute wheel fit, this watch has given me its share of grief.

A great watch, beating at 8 bps/28800 bph, which is about as fast as it gets for a mechanical watch with a balance wheel (yes, I know, there are faster ones, but this speed has proven to be the maximum that still adds accuracy to a watch – and yes, my Bulova Accutron does 360 swings per second). You can tell in a fair amount of places that this is a prototype and that it would have needed improvements in some areas. The date / day changer doesn’t work great and sometimes moves two days at a time, the manual day/date change sometimes gets stuck, and the watch is over-complex. But all this makes it even more desirable as a collector’s piece.


9 thoughts on “Reassembly: Sea-Gull ST7

  1. I think your double wheel “locked” by the cannon pinion is actually a device to eliminate slack from the seconds hand drive, much like the friction spring of other indirectly-driven seconds hands. There might even be a spring between the two wheels (hard to check now…). And that odd jewel is probably not functionless, but acts as axial guide of the changer pinions.

  2. Pingback: Teardown Sea-Gull ST7

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