Same Amplitude Wildly different rates?????

[tomprobkins]

Here is my puzzle. I have a watch that I am working on. A Hamilton 987. It has been cleaned and oiled and demagnetized. When I run it on the timing machine the horizontal rates and the pendant down rate are all close and about +/- 4s/day. When I move it to pendant left things get weird. It has the same amplitude but the daily rate goes way off the chart -98s/day or something, also the beat error goes from 0.5ms to 0.0ms.

 

The hairspring is running unobstructed, and he regulator fingers are adjusted correctly.

 

How can this happen? How can a wheel spinning at the same amplitude produce such a wildly different rate? And how does the beat error change with the position change like that? 

 

Thoughts? 

 

Thanks 

Rob 

[clockboy]

Normally when the hairspring touches a part it runs faster not slower. It might be a train wheel issue i.e. binding ion certain positions. You will have to check the end shakes of the wheels & also check the jewels for damage.

[tomprobkins]

I referenced the hairspring not touching to show that it isn't touching in the faster position and "letting loose" when it runs much slower. The Jewels have all been check and are in great shape, not chips on the hole jewels and no pits on the caps. I will check the end and sideshake when I get home. Thank you for the suggestion.

 

 

[rodabod]

Could it be very badly poised? But then I suppose you'd expect it to change performance with respect to horizontal when in crown-right position.

I would have maybe expected an amplitude change if any of the gear train was binding in any way. 

Edited December 23, 2016 by rodabod

[tomprobkins]

Yeah, if the wheel had a heavy spot then it would slow the amplitude drastically at that spot, but the left and right vertical positions are relatively close.