Pallet fork disengages roller jewel eta 2824-2

[Sassman]

Hello,

I'm brand new here and also new to watchmaking.

While servicing a eta 2824-2 movement I have run into the following issue. Dial down everything runs great, but when I turn the movement dial up the pallet fork disengages from the roller jewel on the balance shaft. It's a new balance wheel assembly as I assumed the original was bad and the cause. Pallet fork looks good, pivots are good and the jewels are not crooked. I am guessing the balance wheel has too much end shake (even though it doesn't seem to). It's baffling that it happens on both old and new balance assemblies. I can push down on the end of the balance bridge quite a bit before it slows the wheel.

Any thoughts?

 

[mikepilk]

How much endshake is there on the balance? I like to imagine the correct amount as about the thickness of the pivot. 

I assume the pallet is not bent, and the endshake OK?

[Sassman]

I'll look more closely tonight and tomorrow. My initial look for the balance end shake seemed 'normal', that plus the fact this happened on the previous balance that I replaced makes me think its the pallet fork or the lower balance pivot jewel assembly. I'll report back soon. 

[Knebo]

9 hours ago, Sassman said:

dial up the pallet fork disengages from the roller jewel on the balance shaft.

Are you sure about this diagnosis? Can you show us a picture (I understand that it'll be difficult to take when dial up)? 

Also very useful would be a picture (can be dial down) of the balance exactly from the side (to see if the balance cock is deformed). 

 

8 hours ago, mikepilk said:

How much endshake is there on the balance?

That's definitely the most logical explanation.

 

2 hours ago, Sassman said:

lower balance pivot jewel assembly

Upper (=balance cock), no? 

[Sassman]

Here are some pics, videos from iPad aren’t the right format. There is a lot of slop on the bottom balance pivot. Double checked and both pivots are good. Took both cap jewels out, cleaned and oiled. Rodicoed the settings and reinstalled. The balance bridge seems too high in my humble opinion.

[Knebo]

35 minutes ago, Sassman said:

The balance bridge seems too high in my humble opinion.

It does look like it in your last picture! 

It can be bent down, but better to do so with the balance removed. 

 

 

39 minutes ago, Sassman said:

There is a lot of slop on the bottom balance

As said before, i doubt that the bottom (dial side) is the problem. The slop logically (and visually from your last picture) is at the top side (train side=balance cock) 

[Sassman]

Resolved, sort of. Balance and fork now stay engaged. Yay! Rate is good, beat error good, but a bit low on amplitude. Might have bent the bridge too much.

[clockboy]

Bent the bridge !!!!?  That is not a normal method to say the least.. was the bridge bent during disassembly. 

 

[mikepilk]

17 hours ago, Sassman said:

Resolved, sort of. Balance and fork now stay engaged. Yay! Rate is good, beat error good, but a bit low on amplitude. Might have bent the bridge too much.

The amplitude is fine, don't worry about it. 

Did you bend the bridge? 

How much endshake is there - you just need a touch. As I mentioned, I like to think of it as about the thickness of the pivot

I think the bridge looked OK, but the balance was clearly sitting at a slant. 

There are marks on the lower jewel, has someone fiddled with it and could it be sitting too low?

In which case you should have pushed the jewel mounting up and not bent the bridge. A misplaced jewel is more likely than a bent bridge

Edited March 2 by mikepilk

[Sassman]

The replacement balance assembly is not an ETA part, might be why it didn’t sit right. The other might be like you said, the upper jewel may have needed to be pushed down. (Dial side) As it’s running well and assembled I’m going to leave it be for the moment. Curiosity will pull me in again and I’ll check out the jewel seat.

 

[Knebo]

7 hours ago, mikepilk said:

but the balance was clearly sitting at a slant. 

Can you post an "after" picture just like this? 

 

23 hours ago, Sassman said:

bit low on amplitude. Might have bent the bridge too much

Try to loosen the screw of the balance cock by just 1/2 a turn and see if amplitude increases. 

Was it higher before (dial down) you bent the cock? 

[Sassman]

Here are pre and post service. Definitely an improvement. I serviced the mainspring and reinstalled it, might improve amplitude with a new one. I was using this watch as practice and wanted to try removing, cleaning and reinstalling the mainspring.

 

Edited March 3 by Sassman