Do or Die repair

[Michael]

Zero chance of getting a spare part, so either a new movement or take the power reserve function from the watch. This is an intermediate  wheel assembly from the  power reserve train, which had one of the wheels in the assembly with 3 missing teeth. With nothing to lose,  I have decided to have a stab at a repair. Next stage is to clean up, put the little sub assembly back together and then try it in the watch. I have no idea if it is going to work!!!

BTW, just to explain. The wheel with a section cut out is a doner from my spares bin which had the closet tooth profile. I cut a section of 3 teeth and implanted (soldered) it into the damaged wheel. 

[rodabod]

Looks good. Did you try “topping” the repaired wheel, ie. checking if the new teeth are relatively proud of the original teeth and stoning down?

Must have been a really tricky job at that size!

[oldhippy]

A good try. I have blown the photo up to take a look, the teeth are too high and you have the wrong angle each side, it will be hard for the teeth to mesh when it makes contact with other teeth. I think it will jam up. 

[HSL]

I think @oldhippy is right.
 

From wrestling with hairsprings this is one of the trickiest repairs to do, and when doing it one whish one saved the previous discarded part in the “good to have in the future box”.
When it comes to replacing the teeth the donor piece has to come from a wheel not only with the same diameter but also the same type of teeth and depth on them, this is so you will get the correct amount of freedom for the wheels to rotate in a correct way.

Even small differences like these ones will make the wheels not to run correctly in the length.

 

Another thing to consider is how to put the new piece in place. One should avoid making a rectangular shape to fit with and instead make a “dove tail” shape with a precision triangular file.

Since the teeth on the wheel is subjected to lateral driving pressures a rectangular shape will eventually cause it to wriggle free and fall out, the solder hasn’t a very good mechanical resistance.

This is just some small tips and tricks to think of when repairing wheels.

[Michael]

Thank you very much for your comments. I agree with you all. I am sort of hoping that I might get away with it as all the train has to do is rotate the power reserve hand, and most of the pivot holes are not jeweled. I suspect you are all correct and it will not work.  HSL, you are spot on, as I did not have an exact match of wheel, and then once I got to the soldering stage, when I saw the gaps due to my dodgy workmanship, I wish I had a mini milling cutter (a machine I do not have). I found it hard to be accurate with a file as the 3 teeth are about 0.8mm across, so it was difficult to hold. Over the weekend I should be able to get back to it to see how it fairs

[KarlvonKoln]

@Michael I had been checking in on this project, and was curious to learn how it went.  Did the repaired gear work?  Did it need further altering?  

[Michael]

Hi, it worked absolutely fine first time with no adjustment.  I checked it over a couple of weeks and it never looked like it would cause any problems. The appearance was sub-standard and if I had to do it again I would try and prepare better before soldering to make the appearance better. Thanks for your interest

[nickelsilver]

That's awesome. In non-power delivery gearing, often you can get by with some serious leeway as long as nothing binds. A friend of mine worked at Breguet around 2000, he had an 80s vintage watch come in with two brass pins in the minute wheel where teeth had stripped off. His boss said ,"if it works, leave it", which he did and promptly quit haha (Breguet has massively improved in that time btw).