Another anniversary clock

[Michael1962]

Ok. So a bit more detailed inspection of the clock today has uncovered this disappointing issue.

The clock has an axial crack on the first 'roll' of the base. It is not bad, but I don't want it to get worse. About 10~12mm long. Who am I kidding? It's crack in a clock base! Of course it's bad.

So I have been sitting here formulating an idea for how to address the crack. Let me know how this sounds please.

1) Strip clock down so just have base on it's own. (obvious)

2) Remove lacquer from base using a paint stripper so as to not introduce scratching to the base brass surfaces.

3) Get a G clamp the will fit across the base diameter and work on a clamping method that can be applied quickly. The reason for quickly will be explained below.

4) Using a Dremel with appropriate bit installed, grind a groove on the underside of the base along the crack.

5) Preheat oven to 190 deg C (melting point of my 60% tin, 40% lead solder) and put base in oven in flat tray.

6) Once the base has heated up, remove from oven, apply solder to fill groove that has previously been made. Use soldering iron as required to assist.

7) Once solder has filled groove an hopefully has entered the crack as well, apply G clamp to pull crack together and inline along the 'roll' onethe base.

8 ) Allow to cool to room temperature. Finish as required.

Reasoning.

Heating with a torch to be able to braze the crack would be too localised and could potentially crack the base more. Even with preheating.

The groove is to give the solder more adhering strength across the crack  for the length of the crack.

I do not believe that something like a cyanoacrylate glue would be a viable option.

The rest of the clock, including everything in the movement is that clean, I think I would add dirt cleaning it.

I would hope that I would be able to end up with a near invisible repair.

If anyone else has any other ideas or proven repair methods, it would be greatly appreciated.

 

Edited August 9, 2024 by Michael1962

[rjenkinsgb]

Soft solder is not very strong & in a crack like that it would be little more than cosmetic.

I would suggest soldering a thin brass "patch" or strip brace across the crack on the underside, to add structural strength.

I would not try clamping the crack closed; that will only introduce further stresses as everything cools. If the crack is at the lower edge and is due to damage (such as someone picking it up by the edge), some very careful tapping with a soft hammer to bring the outer edges down & close the crack may help?

If you use solder paste in the joints and line up the parts carefully before heating, using spring clips to hold the strip or patch on place, you can heat it until the solder flows then allow it to cool slowly again. I think that should add the least stress.

 

 

[watchweasol]

All youngsters,  80 plus medical problems after Covid but still operating.. two French clocks done a Viennese regulator on the bench a barometer to do and a schatz 400 day,   So  quite busy.

I am inclined to agree wirh Rob, I have come across bases repaired the same way and when polished up the crack is almost invisible.

[oldhippy]

Can you photo the part that has the crack. 

[Michael1962]

As requested @oldhippy Crack can just be seen in pretty much the middle of the photo.

I wish I knew how these things happen. I am surprised that the brass cracks and doesn't deform.

Edited August 9, 2024 by Michael1962

[watchweasol]

Hi Michael,  these bases are made from sheet brass spun and formed some are pressed out. Any forming off metal creates tension within the metal, it’s probably a stress crack  and once repaired as suggested should be invisible.  It’s well tarnished and looks like the varnish/ lacquer has aged. Should clean up ok

 

[Michael1962]

That is the only brass that has suffered. The rest of the clock has a lovely goldfish hue to the lacquer. It'll be a bugger to match.

[oldhippy]

I would be inclined to glue it. That will stop it spreading. 

[Michael1962]

Are you suggesting a cyanoacrylate glue @oldhippy?

I will have a look once I get the clock apart to see how difficult it is to get the base circumference in line. That should let me know what will be the best way to repair it to hide the flaw.

[oldhippy]

 Yes I would go for Gorilla Glue Super. It won't hide it but it will stop it from expanding or running. 

[Dell]

That is the trouble with thin spun brass they get stress cracks DON’T try soldering  it will make matters worse, ( ask me how I know ) but as others have said glue a thin brass strip across it , it’s a shame where you are because I probably have one.

Dell

[RichardHarris123]

Brass can be welded, assuming you had the equipment or knew someone with experience, would it be a viable option 

[Dell]

7 hours ago, RichardHarris123 said:

Brass can be welded, assuming you had the equipment or knew someone with experience, would it be a viable option 

Brass can be brazed or silver soldered but being spun and very thin there is a very high risk of distortion .

[rjenkinsgb]

Would low melting point (70'C) solder for white metal be better than glue, to fix a reinforcing strip? That works very well on brass, I've used it quite a bit in modelmaking.

Just be sure to clean everything thoroughly and use acid flux.

 

[ChrisInOz]

If it's a stress crack,  might it be appropriate to simply stop-drill it to prevent it spreading further?  I'm thinking perhaps an 0.5 mm drill bit at the top of the crack to relieve the stress point and prevent the crack increasing in size beyond that point.

[Michael1962]

That's not a bad idea. Then plug the hole like a bushing. Should be able to stop it and hopefully the plug would be next to invisible.

I'll have a think.

[ChrisInOz]

5 hours ago, Michael1962 said:

That's not a bad idea. Then plug the hole like a bushing. Should be able to stop it and hopefully the plug would be next to invisible.

I'll have a think.

At half a millimetre diameter,  I would think even the hole itself might be next to invisible.

[Michael1962]

But I would know the hole is there.