ETA 2452 balance staff replacement

[HectorLooi]

This is the latest Mumbai special that I have been working on. It's a Titoni Airmaster 25 jewels Rotomatic.

It was supposed to be fully serviced, fully working and inspected just before shipment. But sadly, it wasn't working when it reached me.

It couldn't wind automatically and winding it manually causes the rotor to spin.

I have disassemble and recleaned everything. The winding and helicopter effect problem have been resolved. Now the only problem left is the balance staff. There is an endshake of 0.11mm on the balance wheel. 

I've checked Ranfft's website and there are supposed to be 2 versions of the 2452, a balance wheel with screws and a smooth balance wheel. And so there are 2 versions of balance staffs. The one I require is supposed to be a U3136. Is this a Ranfft numbering code?

Cousin's has 2 versions of balance staffs for the 2452. 

https://www.cousinsuk.com/category/filter/eta-movement-parts

Which would be the correct version for my watch?

TIA

[ifibrin]

Are the balance pivots broken? Why are you changing the balance staff? You can change the balance endshake by moving the mainplate balance jewel slightly further in.

[jdm]

17 minutes ago, HectorLooi said:

.There is an endshake of 0.11mm on the balance wheel.

I would be custom know how you have measure endshake with an approximation of 0.01mm

 

17 minutes ago, HectorLooi said:

.The one I require is supposed to be a U3136. Is this a Ranfft numbering code?

No. Codes on Ranfft's are Flume (a large German materials house part numbers.

 

2 minutes ago, ifibrin said:

Are the balance pivots broken? Why are you changing the balance staff? You can change the balance endshake by moving the mainplate balance jewel slightly further in.

Correct. And even before doing that it has to be demonstrated on the timegrapher and on the wrist performances that endhsake needs adjustment.

[HectorLooi]

I measured the endshake by inserting feeler gauges between the pallet bridge and the rim of the balance wheel.

I've already checked the bottom plate for a way to adjust the endshake but this is a very strange Incabloc setting. The jewel is set in a chaton held by a screw. There is no way to press it in. 

The pivots are not broken but seem very short. If you look at photo 3, the balance wheel is almost touching the pallet bridge.

The timegrapher trace is very erratic. Amplitude fluctuates, beat and rate changes with every position. The hairspring stud is stuck in the hole, so I can't tell if the hairspring is centered properly. 

I'll fabricate something to press out the stud tomorrow then I can measure the length of the staff properly.

[ifibrin]

11 minutes ago, HectorLooi said:

I measured the endshake by inserting feeler gauges between the pallet bridge and the rim of the balance wheel.

I've already checked the bottom plate for a way to adjust the endshake but this is a very strange Incabloc setting. The jewel is set in a chaton held by a screw. There is no way to press it in. 

The pivots are not broken but seem very short. If you look at photo 3, the balance wheel is almost touching the pallet bridge.

The timegrapher trace is very erratic. Amplitude fluctuates, beat and rate changes with every position. The hairspring stud is stuck in the hole, so I can't tell if the hairspring is centered properly. 

I'll fabricate something to press out the stud tomorrow then I can measure the length of the staff properly.

Could you take a picture of the chaton? I’ve never seen in incabloc movement like that.

[ifibrin]

29 minutes ago, HectorLooi said:

 

I'll fabricate something to press out the stud tomorrow then I can measure the length of the staff properly.

The hairspring studs in these balance cocks without a stud screw are held by friction very tightly in the stud carrier. It’s almost impossible to press out safely unless you can find a way to support the underside of the stud carrier, but the balance wheel is in the way.

I looked at the Jules database and there’s quite a number of balance staffs listed there for the 2452, with multiple incabloc ones with different pivot sizes? http://cgi.julesborel.com/cgi-bin/matcgi2?ref=ETA_2452

[Nucejoe]

 If it keeps running in FU and FD positions then pivot shoulder seats are not rubbing on hole jewels, so unless you like to renew the staff, this one still has another decade of life left.     

I don't think this approach of mine got approval from OH , he once said just put everything back right( he was reffering to my advice I think), but here is what I do and it works.

Flip cap jewel over, so its domed side faces the pivot, this will reduce end shake.

Oil will stay on top of the dome specially if you epilame treat it. 

You might need to adjust shock springs to press on cap stones( push on them and bend a tiny bit)  so not to have the jewels loose inside housing of the setting. 

Both lower and upper end stones can be flipped over if needed.

Its a lot easier than staff renewal, poise ....

Good luck Doc.

 

[HectorLooi]

8 hours ago, ifibrin said:

Could you take a picture of the chaton? I’ve never seen in incabloc movement like that.

Here you are.

The 2452 has several strange designs that I've not seen in other ETAs. Like the date detent. It uses a roller instead of the usual "V" shaped end on the lever.

And the crown wheel is screwed to a short lever that allows the crown wheel to disengage from the ratchet wheel.

8 hours ago, ifibrin said:

The hairspring studs in these balance cocks without a stud screw are held by friction very tightly in the stud carrier. It’s almost impossible to press out safely unless you can find a way to support the underside of the stud carrier, but the balance wheel is in the way.

The balance stud actually has a screw but it was missing. I suspect the seller put superglue or Loctite into the stud hole to fix it. I'm thinking of modifying a tweezer to fix a pin on one jaw to press on the stud above and cut a slot in the other jaw to allow the bottom of the stud to protrude through.

Once I can remove the balance wheel, then I can decide on what to do next.

[HectorLooi]

This is exactly the kind of "Mumbai Special" test that my mentor prescribes.

When I tell him about all the problems I find in the watch, he'll say, "Good! Now go and fix it". 

[ifibrin]

2 hours ago, HectorLooi said:

The balance stud actually has a screw but it was missing. I suspect the seller put superglue or Loctite into the stud hole to fix it. 

I think the balance stud came without a screw from the factory. I used to have a peseux 7001 that was the same; it had a stud carrier with a screw hole but no screw. The balance stud was secured very tightly in the stud carrier by friction. I think at some point to cut cost ETA stopped using a screw to secure the balance stud, relying instead on friction. ETA left the screw hole on the stud carrier probably because it would cost more to retool the machine.

Interestingly, balance staffs .com has two measurements for balance staffs for the 2452, with one 0.10mm longer than the other.

Edited April 18, 2022 by ifibrin

[ifibrin]

1 hour ago, HectorLooi said:

This is exactly the kind of "Mumbai Special" test that my mentor prescribes.

When I tell him about all the problems I find in the watch, he'll say, "Good! Now go and fix it". 

How will you change the balance staff even assuming you get the correct one? Do you have a lathe or a platax tool? Some of these balance wheels have a fixed hairspring collet which can’t be removed without distorting the balance wheel.

[HectorLooi]

Hmm.... 0.11mm... Interesting number.

[ifibrin]

3 minutes ago, HectorLooi said:

Hmm.... 0.11mm... Interesting number.

Take a look at this: 

maybe someone replaced it with the wrong balance complete or balance wheel?

[HectorLooi]

I have a lathe, a K&D balance staff remover, staking set, etc...

My mentor has been bugging me to do a staff replacement and cutting a staff from scratch. I've done some practice staffs but not an actual one yet.

Probably when I have my lathe permanently setup with a microscope overhead, then I'll do more lathe work.

[ifibrin]

16 minutes ago, HectorLooi said:

I have a lathe, a K&D balance staff remover, staking set, etc..

Would you be able to show the lathe setup that you have? The lathes I’ve been looking at on e bay look enormous, and are fairly expensive as well.

[Nucejoe]

I would shim the balance cock , in case you don't like flipping end stones over.  

I just see no point in fixing this a staff if it ain't broke. 

 

[HectorLooi]

3 hours ago, ifibrin said:

Would you be able to show the lathe setup that you have? The lathes I’ve been looking at on e bay look enormous, and are fairly expensive as well.

I have nothing to show at the moment. It's stowed away in a drawer.

This was when I just fixed the brushless sewing machine motor to the lathe bed. I'm only using for odd jobs and practice at the moment.

[HectorLooi]

2 hours ago, Nucejoe said:

I would shim the balance cock , in case you don't like flipping end stones over.  

I just see no point in fixing this a staff if it ain't broke. 

 

Ok, thanks @Nucejoe. I'll try flipping over the stones tonight  and see how it goes.

[HectorLooi]

I welded a 0.7mm stainless steel wire to the jaws of an eyebrow tweezers. Hopefully it'll be strong enough to push out the hairspring stud.

[HectorLooi]

Last night I tried getting the hairspring stud out of the hole again but it was really tight. I didn't want to risk damaging anything in case I the tool slipped, so I aborted the mission. I'll try again tonight after applying some acetone and WD40 to loosen things up.

I don't think the stud is friction fitted, as a large gap is visible around it. Also, there is a groove in the stud for the retaining screw.

I tried @Nucejoe suggestion of flipping the endstone. It definitely works. So I'll leave it for the moment  until my skill level catches up with the problem.

[ifibrin]

@HectorLooiyou can try flipping the balance cock over and press the stud down a bit to loosen the stud with a jeweling tool and a flat punch. You would need a staking block with small holes as the “anvil”. You can then press it out again from the reverse direction if it’s loosened.

[HectorLooi]

2 hours ago, ifibrin said:

@HectorLooiyou can try flipping the balance cock over and press the stud down a bit to loosen the stud with a jeweling tool and a flat punch. You would need a staking block with small holes as the “anvil”. You can then press it out again from the reverse direction if it’s loosened.

Thanks. But I don't think it will work because the stud has a flange.