ei8htohms
8555
realistically? probably yes
Sep 05, 2011,07:24 AM
Hi Nick,
This is only a couple hours worth of data, so it's definitely only useful on a per watch basis and even then more for curiosity's sake. If you look at the total amplitude and rate trace over the full run-down of a watch it tells you a little more about the generalized performance of that caliber, but would often be highly variable still, especially on watches with curb pin regulators. I'll try to gather some data sets of this type on a couple different watches that I can share.
A few years ago I put together an Excel based tool to perform Fourier Analysis on this type of data in the interest of identifying sources of variability in the power train that might be causing amplitude and rate fluctuations. For you math geeks, it applies a Fast Fourier Transform to the amplitude and rate data and graphs out what I refer to as the "Periodicity Spectrum" (probably not a strictly correct term). Spikes in the Periodicity Spectrum will indicate the source of periodic fluctuations as well as the amount of the periodic variation (to some extent). Then you compare these spikes to the known periods of the rotations of the wheels and the passing of their teeth and you can see where your greater sources of variability are.
This is the chart derived from the amplitude and rate data I posted previously, indicating periodic amplitude fluctuations at approximately 300 seconds and at approximately 50 seconds. These most likely correspond to the teeth of the barrel engaging with the center wheel pinion and the teeth of the center wheel engaging with the third wheel pinion. The amplitude (size) of the spike itself must be taken with a grain of salt, since the Fourier Transform resolves only for perfect sinusoidal fluctuations which in this case are "best fit" approximations of the real world fluctuations.
It works pretty well for identifying worn teeth, wheels that are out of round or if your second hand is touching the crystal, but not so much for anything else in my experience and the time that it takes and the hassle involved with gathering the data are not usually justified by the utility of the results (especially because these most easily identified conditions can readily be identified by a careful examination of the components themselves in almost all cases). It's still a tool that I'm pretty proud of intellectually, but I lost interest in refining it as much as I probably could (yet) once I realized how limited its use would be.
The resolution of this sort of tool is quite limited by the way the data is collected also. For extended data sets the machine records at larger intervals (every 5 or 7 seconds for example) and there's no way to control this with machines I'm using currently. Clearly for this type of analysis you'd like to record a data set for every single tick of the escapement, but alas this is not possible.
The way a timing machine interpolates amplitude based on the sounds of the escapement is also a pretty rough science and doesn't stand up well to rigorous interrogation of the data in my opinion. You could probably get a lot better results if you used a laser or optical gate on the arms of the balance to collect your amplitude and rate data. Enough fiddling with a Microset 3 could perhaps yield resuilts or of course Witschi makes the Velocimetre SMEV which would probably give you better resolution for this sort of analysis, but the investment in a machine like that is really only justified at the manufacturing level.
_john