Strange behavior in old movement

[bsoderling]

Hi again,

 

Working on an old (as usual) movement from one ofthe tank style watches mentioned in another topic.

 

Had to fit a new ms but otherwise it all seems pretty ok after a cleanup.

 

And the thing runs but with a strange bahavior on the timegrapher app. Screen shot attached.

 

The beat error switches between a decent 1 ms to around 6 ms and during these periods the curves slope heavily, indicating a drastic and immediate slow down. The behavior is periodic and switches several times per minute in a regular fashion.

 

I suspected over banking and tried a weaker ms that gave a lower amplitude. No change.

 

I also shifted the hs to check if the beat setting influenced. No change with a different beat setting (even though the beat error changed a lot).

 

All pivots appear nice and straight to the eye.

 

My assumption is that this problem should be located close to the escapement, considering how the error repeats...?

 

Any advice or experience is appreciated.

 

 

 

 

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[Nucejoe]

Hi there:    The got no pic you talk of. anyway

How about amplitute in various positions, face up/ down , side and oblique.

wobling escape wheel? .... fork arbor qnd staff  end shake, .slight push down on balance staff jewels too see if it stops balance wheel.

Regards joe.

 

[rduckwor]

Bent or otherwise damaged wheel?

 

Good luck,

RMD

[Nucejoe]

No need to remove any part to produce the aforementioed data. 

Next.

1. Loosen the escape cab screw if any. 

If no change. One drop of lighter fluid on staff ,escape and fork arbor jewels

If no change, try removal of cabs to see the jewels, broken....etc

If none observed, remove balance cock and fork bridge. Oil jewels and wind manually for several seconds. Observe.

While at it check pallet alignment as well.

Timegraph dose not diagnose.

Velocity fluctuation as you describe is common and expectedly from escape wheel.

Regards joe

[watchweasol]

Hi Rduckwor  what Joe says makes sense, with the balance and fork removed take a close look at the escape wheel for poise and its shape check all the teeth as the trace is quite regular.

[bsoderling]

Hi guys and thanks for feedback.

Was working through the balance and escapement along your advice when one of those things not supposed to happen... well, happened... Had a Major flip of the balance cock while holding the wheel and ending up with a h/s all twisted and mangled. Unless I can find a part, I guess I will never know what was causing the problem.

I have attached a photo of the marking on the movement which is unknown to me. If anyone knows of this I’m grateful for feedback to start a search for parts.



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[clockboy]

At a guess I would say the fault is the escape wheel. Looking at the readings there is a regular levelling off after approx 17 beats. Check its pivots and check for bent teeth, check it's jewels. 

[StuartBaker104]

The bottom part of the marking tells you the manufacturer is an Ebauches Trust group member. I don’t recognise the A symbol, but will represent one of those companies such as Arogno. More pictures of the movement and any other marks might help

[bsoderling]

Hi,

Not giving up on this one yet....

Here are a couple of photos that hopefully can help to id this movement.

The key-less part is in my experience somewhat unusual as the yoke and spring are on separate sides of the winding stem. I usually see the spring sitting right beside the yoke. Maybe this ”feature” can be of guidance....?






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[bsoderling]

Hi,

Thanks to Watchmaker and WLS1971, two excellent watch sleuths, two out of three ongoing identification questions have been resolved. 

A Derby 33 and a Bifora 102, no common movements on my list. Had never heard of the brands before. But amazingly enough some parts are available and I have some incoming. 

But this headache remains...

I just noted a small imprint on the balance cock (a "V" it looks like) and was wondering if that perhaps rings a bell somewhere...?

A close up photo is attached.