Automatic two piece mainspring - Four ways the bridle can be fitted

[hofnerpres]

Working on an early Omega Bumper  which has needed lots of TLC including a new balance shaft. All the tricky stuff went well so l thought we could retain the bridle and give the old girl an amplitude tonic by using a slightly stronger spring. The usual recommendation of throwing it away and fitting the conventional auto GR 2605 was giving 235 ish DU. The experiment was poor - a bit of thought rendered the realisation that the bridle can be fitted in four different ways. My attempt had the spring force trying to unwind the bridle hoop. Turn it over and the spring force will try and open up  the hoop as it pushes it around the barrel wall thus potentially proving a stronger grip. Anybody out there barrel bridle savvy ?

[hofnerpres]

Well just tried turning the bridle over so that the spring force is trying to expand the thing. Full power now reached but at full wind it does not slip so a real risk of overloading the winding mechanism. I give up and will try the auto spring now the new balance shaft is fitted.

[JohnR725]

7 hours ago, hofnerpres said:

amplitude tonic by using a slightly stronger spring

It really would be preferred to service the watch rather than putting a stronger mainspring in the watch was not designed for. As you introduce other issues.

 

7 hours ago, hofnerpres said:

235 ish DU

Servicing the watch it's amazing what clean the watch with fresh oil properly applied will do for you. Timing procedure dial-up and dial down and at least one crown position Like crown down Is helpful we can really gain a lot of knowledge and pictures of whatever you using so we can see what the display looks like.

7 hours ago, hofnerpres said:

Omega Bumper

I don't suppose it has a number like a model number?

8 hours ago, hofnerpres said:

giving 235 ish DU

Oh and typically the watch companies are only concerned about amplitude either when it's too high or at the end of 24 hours. They are much more concerned about timekeeping than amplitude. Then because typically Omega watches run really well the lowest amplitude it 24 hours depends upon the watch which is why I'd be nice to the model number.

Repairing-Omega-self-winding-watches-bumper.pdf

[hofnerpres]

Excellent - Many thanks John. As is common with old age I went to save the Omega file only to find I downloaded some years ago and forgotten it was there - groan... It shows very clearly the layout I tried first time since it made mechanical sense. - it only gave me a couple of turns before slipping using a tiny amount of 8213 breaking grease. Looks like I should have persevered with different lubrication strategies. Maybe the barrel and bridle gets too polished.

To your other point I apologise for not making it clear that I had already carried out a service and was still struggling with amplitude after all the usual checks. There was a marked disparity with DU and DD amplitudes so this led me to get the balance arbor under the microscope and admire the rather flattened pivot ends - hence the staff replacement.  

I subsequently paid a price for this oversight as the barrel was launched across the room - working tired again. After two full searches and three hours it was found at the back of a draw having flown through the small finger sized opening cutaway. After many years removing springs from barrels they can still catch me napping. I think anchoring it down on a large lump of Rodico before the fun begins might be safer for a clumsy old fool like me. Thanks again for your help. I will wrap up this post once the auto spring is fitted and settled down.

[JohnR725]

28 minutes ago, hofnerpres said:

tiny amount of 8213 breaking grease

Some Where in the group we've already discussed breaking grease and you might try P125 which is what Omega recommends. Then there are pictures in that discussion which show how much are supposed to apply etc. because If you get carried away with it it's really really sticky Also conveniently I can't find it right now but Omega is recommended going to the modern style mainspring versus the older  two-part style. It's a problem at the tech sheet where showing how to do it the old way and yet there might be a much newer reference which says do this instead.

Then yes flying mainspring barrels can be quite interesting as to how far they can fly. I was doing a Hamilton deck watch which is a bigger spring a much bigger and the barrel wanted at a 45° angle to the room bounced off the door and went ricocheting down the hallway. Fortunately it didn't enter into any of the other rooms or it would've never been seen again. Although it could be much worse I had a friend doing a clock he said the barrel got away and it had so much force it fluid hit the wall and actually went up the wall before it ran out of energy. This is why people doing clocks typically wear face protection and very heavy gloves. I always try to remember to use a towel when I'm removing anything related to the mainspring so nothing will go flying away it's all contained in the towel.

Then we didn't get a movement number yet did we? The reason I ask is I will see if I have Omega timing specifications for the movement. Because as I've pointed out before all Omega cares about is timing specifications or if the amplitude is too high and then the minimum amplitude it 24 hours varies between watch to watch the lowest being 160. So while this group is very concerned about amplitude and does not care about timekeeping at all the watch companies are more concerned about does the watch keep time?

 

 

[hofnerpres]

Sorry John - It's an early Omega Bumper 28.10 RA.

[JohnR725]

16 minutes ago, hofnerpres said:

It's an early Omega Bumper 28.10 RA

That's the early numbering system so later today much later today a look on the list and converted to the newer style numbers. That I'll see if we have technical specifications

[hofnerpres]

I suspect that was renamed the 330. Thanks for digging - I'm off to bed. I enjoyed the flying barrel story - perhaps we ought to start a best lost part story thread. It will be lengthy....

[JohnR725]

6 hours ago, hofnerpres said:

Omega Bumper 28.10 RA

I scanned in a page that I have I really prefer PDFs anyway. It's interesting how they do the numbering system so 28.10 is anywhere from 342 to 355.

5 hours ago, hofnerpres said:

I suspect that was renamed the 330.

Looks like a 330 would be a 30.10 But it was curious so I looked up the movement at the link below it looks like basically that the same except diameter size

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Omega_330

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Omega_340

Here's Omega timing specifications.Then the amplitude it 24 hours is in the vertical position none of them can be less than this. Then because this is not a chronometer grade watch This time the only three positions which are dial-up And rather than defined timing by where the crown is a defined by numbers on the dial.Which would be 9 o'clock high and then the 6 o'clock high. Makes it a lot easier to worry about specifications of your little Threes positions.

[hofnerpres]

Excellent thanks John.  The conventional auto spring is reinstalled. Had fun setting the beat error by eyeballing the roller position and moving the balance spring placing - great old school stuff.  l’m delighted to report that the new shaft with shiny rounded ends has done the trick and we should be able to beat those factory specs. Will leave it a couple of days to bed in before final adjustments.

[JohnR725]

Out of curiosity how do you lubricate the escapement?

6 minutes ago, hofnerpres said:

Had fun setting the beat error by eyeballing the roller position

Often times when you look at the older watches like Omega there will be a pinprick on the balance wheel where the stud should be in alignment with. In other words the factory marked where to put things to put it back in beat not that anyone should change that. We once had Omega at work where there's so fiddly on trying to get the beat perfect and I pointed out to my boss see that little mark that's where the stud should be at once you put it there the beat was perfect. Of course that assumes that whoever restaffed the watch but the roller table back where it's supposed to be

 

[hofnerpres]

Hi John. A mark on the balance wheel - I should be so lucky ! Pallets lubricated by my normal application of 941. I used to do this the conventional way with a spot on the jewel stones but did not like the fact that this was pre-assembly. Fiddling around getting the fork into place on these small movements would often expose the danger of getting grease on the wheels etc. After several trials my normal practice is now to dip a pointed and shaved piece of pegwood into the 941 and then gently hold this to the pallet wheel teeth as the wheel is slowly spun. The peg is only damp so a minimal amount is transferred with minimal skill required and also allows the assembly of the pallet for to be done dry. Pre and post amplitude testing shows a consistent gain so I've stayed with this easy method. I have another problem now with a 601 - needs a new thread. These two watches are certainly a battle....

[JohnR725]

2 hours ago, hofnerpres said:

conventional way with a spot on the jewel stones

Was once in a classroom of 12 students and the instructor asked how each of us lubricated the escapement and basically got 12 different variations. There is not a conventional way to lubricate the escapement. I also assume rather than 941 using 9415 which is a grease versus 941 which is an oil.

The only reason I asked was looking at the escapement it looks just a little rough you would think an Omega would look a little bit smoother than that, sometimes lack of lubrication on the escapement can look like this.