Landeron 39 - Running slow

[Khan]

Hi

I recently serviced a chronograph from late 40s/early 50s as it was dry for decades and balance stopped occasionally. But after service, it looses at least 10 min per day. I recognized that the watch stopped when tilted and I solved the issue by polishing the pallet bridge screw.  One watchmaker says it can be a slightly worn staff or wing but the balance runs good by sight, another says that the spiral is too long and the staff is alright. What do you think it is? Let me know if different images required for inspection. All answers appreciated. 

Edited October 22, 2020 by Khan

[Khan]

[rodabod]

Are you achieving good amplitude? The video suggests you probably are.

Does it still significantly lose time if left dial-up like it is in your video?

Was the pallet screw fouling the balance previously? Are you absolutely sure that this issue is now corrected?

Have you check the balance end-shake / side-shake?

[Khan]

Yes, amplitude above 270. It keeps the time like 20 percent better when dial up. I also measures the timing while removing pallet bridge screw but still the same. How do I check end and side shake? I know that the balance wing is a bit shaky when checking the vertical movement by tweezer holding edge of balance wing. And when shaking the watch, there is a rattling sound coming from the balance and can stop occasionally by that. 

[rodabod]

It's a non-antishock jewel setting, so be careful, but you can gently grab the edge of the balance wheel and lift it up and down. Try to see if you can see excessive side shake. If you are not confident doing this then lift the edge of the balance wheel with a fine oiler.

[Khan]

Yes, I grapped the Edge with tweezers and there is a Visual vertical movement of the wheel by maybe 0.2 mm and feels abnormal. But no horizontal shifting by feeling. 

Edited October 23, 2020 by Khan

[rodabod]

So, it's hard to describe in words, but basically it should be able to lift and drop by a small amount (end shake) but when you lift it, it should not tilt much at all (side shake). I'm not sure if there are any videos online demonstrating this.

[Khan]

I have been reading this material:

https://nobswatchmaker.com/blog/simplifying-the-art-of-endshake-in-watchmaking

It doesn't tilt at all when lifting the wheel. But in my opinion, there seem to be too much "tolerance" in end-shake, it lifts more than usual. I guess I need a Horia tool for lowering the upper balance jewel? If so, any alternative to Horia to be used? 

[rodabod]

It's a tricky question, because if you are adjusting the positions of the jewels then that assumes that they are currently incorrect. But it's more common to experience a worn or broken staff. It's worth repeating the end-shake test while observing the position of the roller and impulse jewel relative to the lever fork (while the balance is at rest) to see if the parts interface correctly.

As an experiment, you can reduce the end-shake very slightly by placing a thin dial washer behind the balance cock screw hole (on the outside edge of the movement) to tilt the balance cock down ever so slightly. You need to be careful when doing this in case you reduce the end-shake too far and damage the pivots.

[nickelsilver]

0.2mm is way too much shake. 1/10 of that is good.

 

Your pivots appear ok. It looks to me like the hairspring is tilted down opposite the stud and is possibly touching the balance arms when running.

 

What lift angle are you using? Landeron is typically 42. If you have it at 52 you'll have a false high reading, and if the hairspring is touching the arms it would be normal for the amplitude to be low and have a losing rate.

[Nucejoe]

1 hour ago, nickelsilver said:

0.2mm is way too much shake. 1/10 of that is good.

 

Hi, Perhaps a typo there and 0.02mm was meant, .  I presume you are talking axial staff play, which I reffer to as end shake. How about side shake? I havn't seen a number given for it, I just go by the feel. putting the two end+side shake together, if pivot stays put ie; doesn't jump out of jewel hole as one side of balance rim is lifted, shakes will not stop the oscilator.     

I avoid lifting balance wheel, however gentle, I fear it might knock the rim out of true.

TIA

Regards joe.

 

[Khan]

[Khan]

The hairspring doesn't look to tilt in opposite side of stud. 

[Khan]

The hairspring is very close to the arms on the second picture. Is that the issue?

[rodabod]

It's sometimes hard to judge where the hairspring is sitting as the weight of the stud moves the spring. Holding it vertically (or resting the edge of the wheel on rodico) may give you a better idea.

I'm still wondering about when you said that you had to polish the pallet bridge screw. Unless the screw has been swapped, this doesn't sound correct to me. In your most recent video, at the very beginning, the balance rim looks quite close to the balance cock. Are they ever able to come in contact?

[rodabod]

With the watch running (and not running as well), I would check that the hairspring is always clearing the balance arms as NS suggests and that the rim is always clearing the pallet cock by observing the gaps highlighted in the photo attached. 

[Nucejoe]

On 10/23/2020 at 4:32 AM, Khan said:

 How do I check end and side shake? 

Observe the roller table from the side view as you( gently) raise the balance wheel with a clean oiler or tooth pick, etc, the frèe play on the roller or anywhere else on the staff is your axial free play which we call end shake. 

Side shake is the lateral frèe play on staff, so you ( gently) pull or push on the side of any part of the balance as you keep an eye on the staff in jewel hole, any free side play that you can notice is called  side shake and eats amplitude.

Did you remove the end stone plate on both side to clean and check jewel holes under high magnification? if the hole wears out you get excess side shake.

You can check balance pivots under high magnification for signs of wear or scratches and if thinned and pivot-endstone interface for wear. 

Mere Excess end shake can cause positional variations in the range you are seeing. 

[Khan]

I removed the hairspring and put it back together to ensure a gap between hairspring the balance arms. This still doesn't work and I believe there is too much end shake. There is a remarkable vertical movement when lifting the balance wheel while installed. 

[rodabod]

Are there any punch marks underneath where the balance cock sits?

[Nucejoe]

Positional variations will improve as you reduce that excessive end shake, I shim the cock to lower the jewel.

I presume all data you give is without the chrono load.

"Spiral too long"  is begining to sound correct.

[CMW]

I have noticed that there are two variants of the balance staff for the Landeron 39, the Shockproof and the Super Shock Resistant.

I don't know the difference between them, do you have the right one in the movement?

 

/Carl