Weird behavior at full wind

[Levine98]

Hi,

been working on a Wittnauer c11kas for a while now and have noticed a rather strange behavior, but only at full wind.

at full wind the movement has super crazy timegrapher reading, non-sensical really. However after the watch runs for a little while it comes into perfectly solid readings. 
 

At any other percentage of wind, I get great readings (280 amp, 0 beat error, etc). But spin it up to full wind again and erratic readings return until it runs for a while (then back to normal).

It’s the correct mainspring, so don’t think I’m overpowering the train. Does anyone have any ideas on why this is happening?

 

thanks in advance 

[GPrideaux]

It will help others to help you if you can define what you mean by 'strange behaviour'. Before/after photos from your timegrapher will help.

In the absence of that, I have a couple of thoughts that may be way off (and that you may have already considered).

1. Have you checked end shake and side shake of the arbor in the barrel? If these are excessive, the force of the fully wound mainspring might be moving the barrel sufficiently out of centre that it rubs the bridge or mainplate, or affects the way it interacts with the centre wheel. It could also be an issue with side/end shake anywhere in the train as the increased force of a full wind is transferred down the line.

2. Try winding the mainspring click by click from, say, 90% wind and running well until you see the strange behaviour begin to exhibit and look (and listen) for what changes. Does the errant behaviour kick in suddenly or gradually?

 

[HectorLooi]

Could be overbanking or the hairspring touching something at higher amplitudes.