Movement id ?

[bsoderling]

Hi again...

 

Started to take apart an old (50’s ?) Stowa Sport and found a movement I can’t id. It looks like the pivot coming through the cannon pinion for the seconds hands is broken off. Will most likely be a challenge to find a replacement but to even try that I need some more details on the movement.

 

I ”think” I have seen something similar on the keyless side before but can’t remember...

 

I suspect it might be a PUW movement as I read that Stowa used these and Durowe during these times. But there’s so many PUW’s on Ranfft that I thought I might take a chance and through out the question on the forum.

 

Photos are attached.

 

 

 

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[WatchMaker]

Looks like an Osco 66. 

 

[nlapietr]

Yes does look like the Osco 66.  A little more info can be found here:  http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Osco_66.

[bsoderling]

You are definitely on to something here...

Osco is a new brand name to me, never heard of that one before.

I did see the OS 66 stamp on the movement but had nothing to connect it with.

Thanks a lot, now I have a starting point for furthet investigation!




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[watchweasol]

Hi According to the bestfit book Movement Id pages,    the rocking bar equates with the Osco 66.

[bsoderling]

Osco 66 seems to be the general opinion and I tend to agree.

Just took the movement apart and lucky me, I took some photos of the process. This is not your generic swiss design and I would likely have been lost in the assembly process.

Looks like there are actually parts to have. Cousins are fairly well stocked, at least for the Osco 65 parts that comes up when searching for the 66, so I guess they fit in between these movements.

The movement belongs to a very worn case but the dial is nice with passable yellowish patina, so I’ll try to give the thing a 2nd life.

Thanks again for all help!




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[Rafael]

On 9/3/2020 at 9:54 PM, bsoderling said:

Osco 66 seems to be the general opinion and I tend to agree.

Well, if the movement's name is written on it, I don't see why you won't agree 

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&Osco_66

Edited September 6, 2020 by Rafael

[bsoderling]

So far so good...

Movement is up and running decently with amplitude around 250 and close to zero beat error. Currently off by around +20 sec dial up/down so should be tweakable.

Photo as assembled in cleaned and a bit polished casing with new crystal and re-lumed hands is attached.

I guess I will have to get that centersec-wheel and fit a sec hand before the adventure is over...:-)

I like it when a 2,5 euro investment can be turned around to something decent.





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[bsoderling]

It seems I was too quick to pat myself on the shoulder here..

After a couple of days wearing and winding the watch, the winding started to hack and slip over.

Taking the rocking bar mechanism out, the problem seems to be that the square part of the winding stem that is supposed to fit in the square hole in the winding pinion is worn down or wrong from start and the stem slips over inside the pinion when you turn the stem to wind.

I attached a photo of the stem fitted inside the pinion and find it hard to believe that there should be that difference between hole and stem size.

Measuring the stem, it’s maybe 0,1 mm undersized relative the nominal for the Ronda 382 that’s supposedly the correct one.

Is it the wrong pinion?

If anyone has experience from similar rocking bar designs, I appreciate any feedback.



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[bsoderling]

I ended up using a rounded punch on the edges of the pinion in the staking set to close the hole i tiny bit. This prevents the stem from rotating freely in the hole and winding now works ok.

Probably a bit unorthodox and maybe frowned upon...?

But I’d rather have a wearable working watch than chuckng it back in the drawer with the other hopeless cases. :-)






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[HSL]

Well since the square part of the winding stem almost fits diagonaly in the winding pinion I would lean towards that stem has a error more than 0.1mm. The square hole on the winding pinion looks nice and crisp.
The winding stem is probably not a correct one for this watch, but of course someone can have changed the winding pinion, likely not since it obviously fits in diameter towards the crown wheel on the rocker.

[bsoderling]

That’s the strange part. Checked the stem again with micrometer and it’s more like 0,05 mm off the nominal for the specified stem.

I can visually see that the corners of the stem has been worn down slightly right where it touches the wheel.

If there had been less size diff between stem and wheel from start, this would never have happened.


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