Different amplitude dial up and down

[Delgetti]

So I am working on a Valjoux 72 and can‘t really solve the following problem: After a complete disassembly, cleaning and re-assembly with correct lubrication I get the following results on the timegrapher:

Dial down: 320 degree

Dial up: 340 degree, sometimes starting knocking

 

Knocking at such high amplitude is no surprise, but why the high difference between DU and DD? I already checked the balance pivots, both clean and identical in shape. I also checked both incas, no jewel damage, clean and well lubricated (diameter of oil drop identical). The hairspring runs flat and doesn‘t touch anything.

 

So what could it be? Any help welcome. Thanks in advance.

 

[jdm]

How much endplay there is at the pallet and escape wheel? Between DD and DU even a small change in the area the pallet stones present to the escape teeth can introduce variances. 

[Nucejoe]

How about shakes on staff, fork and escape arbours? 

Are there any end stones on escape arbour?

 

[Poljot]

10 hours ago, Delgetti said:

So I am working on a Valjoux 72 and can‘t really solve the following problem: After a complete disassembly, cleaning and re-assembly with correct lubrication I get the following results on the timegrapher:

Dial down: 320 degree

Dial up: 340 degree, sometimes starting knocking

What were your readings before disassembly?

[nickelsilver]

That's a lot of amplitude. I wonder if it has the correct mainspring; the 72 should have a spring 0.14mm thick. I've gotten replacements from suppliers in little packages marked V72 that were 0.15+, and had the watch rebanking.

 

Otherwise, lots of little things can cause a 20 degree difference in amplitude in the horizontal positions. As JDM and Joe say, check your endshakes. If they are excessive you can have things lining up differently enough between the two positions that you get what you're seeing. Another thing that can happen is a microscopic bit of dirt can find its way to the tip of the balance pivot and act like a ball bearing, giving you more amplitude. That is usually a problem with flatter pivots. Then just small variations in pivot shape can have an effect, and cap jewels can look fine until really closely inspected and you find that there is in fact a small bit of wear.

[Delgetti]

Thanks for the replies so far. To give some information: Amplitude before strip down was 270 DD and DU but for the complete watch. The current 320/340 reading is just for the base movement, so I hope the additional friction of the wheels to come ( especially hour wheel with washer) will bring the thing into the non-knocking-area. I didn‘t replace the mainspring ( should do it on a chrono, i know, shame on me).

Hope to find some hours at the bench tomorrow, will check endshakes and the plate side balance bearing. 

[Delgetti]

I finally made it. No endshake issue, but a very tiny piece of dust on the escape wheel jewel. I have to improve cleanliness at the bench I think. Once again thank you for your help.

[jdm]

Good you solved this. Dust is in the air... we had a thread on possible ways to alleviate the problem in a small shop or at home.