It doesn't look great, but the watch will probably run just fine with it. If you want to replace it Generale Ressorts lists it as GR 3698, dimensions 1.40 x 0.11 x 300. With the dimensions you can order from any watch material supplier.

 

MATERIAL CGI UTILITY (julesborel.com)
Regards, BG

 

I would never put that back in a watch...so yes I would replace it without hesitation.

 

Thanks for the suggestion of julesborel.com. I measured 1.5mm by 0.12mm by about 300mm. So the GR3698 is close enough in size that it should work.

I got bored and started reading about heat treating and tempering springs. Obviously I dont have the equipment to do it properly. I figure heating the mainspring to red hot with a propane/MAPP torch will more likely destroy the spring.
But what have I to lose since I will order a new spring anyways.

I decided to stick it in the toaster oven at max temp and see what it would do first. But I chickened out and
ended up baking at about 180C for half an hour followed by a slow cool down. To my surprise, the spring changed from its ¨C¨ shape to a ¨S¨ shape when it came out of the oven. It was also noticeably stiffer and more springy.

If 180C was good, more must be better, so I tried again at high broil for 10mins, followed by 230C (my toaster oven´s max temp) for half an hour, then a slow cool down to 50C at a rate of about 1C per minute. The spring didn´t change shape any further, and retained its S shape when done. I put it back in the barrel and winding it felt a lot more springy, perhaps too springy.

I´ll run it for a day or two to see if the power reserve has improved from its previous 24-30hours. I haven´t put in the dial side minute wheel and the hands so I don´t know if the accuracy is adversely affected by this ¨treatment¨.
But I´m excited since this is my first time stripping down a movement and putting it back together with it running.

 

Thanks for the suggestion of julesborel.com. I measured 1.5mm by 0.12mm by about 300mm. So the GR3698 is close enough in size that it should work.

I got bored and started reading about heat treating and tempering springs. Obviously I dont have the equipment to do it properly. I figure heating the mainspring to red hot with a propane/MAPP torch will more likely destroy the spring.
But what have I to lose since I will order a new spring anyways.

I decided to stick it in the toaster oven at max temp and see what it would do first. But I chickened out and
ended up baking at about 180C for half an hour followed by a slow cool down. To my surprise, the spring changed from its ¨C¨ shape to a ¨S¨ shape when it came out of the oven. It was also noticeably stiffer and more springy.

If 180C was good, more must be better, so I tried again at high broil for 10mins, followed by 230C (my toaster oven´s max temp) for half an hour, then a slow cool down to 50C at a rate of about 1C per minute. The spring didn´t change shape any further, and retained its S shape when done. I put it back in the barrel and winding it felt a lot more springy, perhaps too springy.

I´ll run it for a day or two to see if the power reserve has improved from its previous 24-30hours. I haven´t put in the dial side minute wheel and the hands so I don´t know if the accuracy is adversely affected by this ¨treatment¨.
But I´m excited since this is my first time stripping down a movement and putting it back together with it running.

Quite the Experiment! I wonder what the folks who spec-out the alloys used in rocket engines would think about your oven-based molecular rearrangement ( "OBMR" ) ...bet they'd have a comment or two!

And: do keep in mind that there are basically just two ways to design a watch's power train to deal with a mainspring failure: one is where the force is dissipated before it can get to the train ( many USA watches used a "Safety Pinion" reverse-screwed to the center wheel, that would unwind 'instantly' should the spring fail, and thus prevent the center wheel from transmitting the injurious energy to the rest of the train), while the other--alas!--does NOT protect the train from all that energy.

So: if your watch employs the former design and your spring 'Explodes', well...you're probably OK. If the latter set-up's in place, you are probably Out Of Luck...ouch!

Proceed with caution!

Michael.

 

The mainspring is still powering the watch after about 7 hours. The bad news is that while I was trying to oil the shock absotrber jewel for the balance wheel (dial side), the jewel with the hole for the balance pivot seem to be attracted by the static electricity of my jacket, and disappeared, the dish jewel is still attached to the rodico. After a few hours of searching I am giving up. The watch still runs dial up with be balance resting on one jewel, but I stopped it overnight since I worry it´ll wear out the balance pivot without a jewel.

Now I have to look for a replacement balance wheel jewel. May be it is easier to look for a junk movement instead of
a particular jewel since I don´t know the actual size.

 

I wouldn't be too distraught. At least you got a bit of learning and experimenting out of the watch before you lost that jewel. And who knows, sometimes they show up unexpectedly.

 

To answer your original question...yes. And just in case you’re tempted to find a NOS OEM spring, I’ve had better luck with new GR mainsprings than with those.

 

Power reserve is more often a function of hygiene and condition (ie wear) than of mainspring condition. A weak ms in an otherwise correctly serviced will deliver a lower amplitude...but is still likely to run until there is very little power left on the ms barrel (ie. down to the last 1/4 turn of the ratchet wheel)...so power reserve will not be much affected.
That said. Replace the ms...an in the process didn't you have fun learning from your manipulations?

BTW, what effect did your treatment have on amplitude?
You might have some luck using a masking tape to find your cap jewel. Pat every square inch around your work area...you'll be surprised what you pick up. (the roller tape lint removers work for this as well).

Regards, BG

 

I couldnt find my jewel after couple days on my hands and knees. A friend dropped off a couple of old broken watches for me to steal the incabloc jewel from. While oiling the donor incabloc jewel I promptly lost its cap jewel. Fortunately I still have the cap jewel from the original incabloc and the watch seems to run fine with the donated incabloc.

But it ran only a few hours on my wrist before stopping. I opened it up and it felt like the pallet fork was intermittently stuck. While investigating why the pallet fork was stuck, something fell off the watch.

You guessed it, the original incabloc was inside the watch.

I still need to order a new mainspring. The watch only runs for 24-30 hours before stopping. It runs more than a minute fast per day even though I set it to the slowest rate. My guess is that it is running
a low amplitude. I dont have a way to check the amplitude, but I have a timegrapher ordered and it is stuck in the usps network. I didn´t oil the pallet fork exit jewels (dont have 9415), could that cause a low amplitude? Or a weak mainspring is to blame?

 

You can get a good idea of the amplitude by taking a slo mo video of the balance and eyeing it.

Mike

 

Great idea. I didn't even know my phone can do slow motion video, but unfortunately my slo-mo is not slow enough for me to see the amplitude. May be I can try uploading the video to youtube, and then watch it on youtube at quarter speed.

BTW: the "baked" mainspring now powers the watch for between 38-39 hours after I oiled the pallet stones and the escape wheel pivots. After it ran out of power, I gave the watch repeated shakes to squeeze out the last few ticks until it is absolutely dead, then I wound the watch. It started ticking again after between 3 to 4 revolutions of the crown.

No, it isn't accurate. About +200s/day in all positions except PD, where it is almost -150s/day. I'll learn to do some dynamic poising of the balance wheel next.

 

No, it isn't accurate. About +200s/day in all positions except PD, where it is almost -150s/day. I'll learn to do some dynamic poising of the balance wheel next.

Just a reminder that dynamic poising is very useful, however it should only be done after everything else has been gone over thoroughly, and all other sources of potential variation have been resolved. The watch should be perfect before you start dynamic poising. It is not a shortcut to good positional variation.

Cheers, Al