[CAUT] Birkett videos online

[Ed Sutton]

I believe if you will look up Jim Ellis's Fall 1982 Journal articles, you will find that they go far toward predicting and explaining what you see here. Jim didn't have the video equipment in 1982, but with other lab equipment he gathered remarkable data, including some that doesn't quite agree with Weinreich.

Jim's articles offer clear explanations and descriptions of unison behavior that technicians will understand.

Ed Sutton
  ----- Original Message ----- 
  From: Fred Sturm 
  To: caut at ptg.org 
  Sent: Friday, February 12, 2010 10:19 AM
  Subject: Re: [CAUT] Birkett videos online




  On Feb 11, 2010, at 1:08 PM, Adkins, Richard wrote:


    Is it me, or does that left string of  trichord  get out of phase as
    the clip progresses in this clip?

    http://real.uwaterloo.ca/~sbirkett/videos/c64%20bridge.avi



  To my eye, it looks like a beat. We see the three strings synchronized, then going out of phase, until their phases are opposing at which point we sometimes seem to see a missing vibration at the pins (the strings seem to stop for a moment, about equal in time to one of the regular up and downs - this "pause" becomes pronounced late-ish in the video), then a repeat of the cycle. But it is pretty puzzling, especially as it seems the two bass side strings often alternate with the single treble side string. That is, the single string seems to stop while the two strings move, and vice versa. 
  I think the C64 damper clip was done simultaneously, so there you can see the strings out farther, where they have more amplitude. It would be nice to be able to see them simultaneously and watch how movements by the damper relate to movements by the bridge. Birkett was able to do that, but I don't think MPlayer can do two at once. If someone knows how, please let me know.
  As always, things like this lead to more questions than they answer. Why is that one string so out of phase with the others? Is it tuning? Is it mating? Something else? Then you get to wanting to see what would happen if you set up the experiment to show, specifically, tuning or mating. And with the dampers, to show the difference between bass dampers where the wire bears lightly on the bushing compared to being set in the middle (as they are in D6 and A14 damper clips).
  In any case, they are fascinating, providing hours of entertainment <G>. I think he should get an Oscar.

  Regards,
  Fred Sturm
  University of New Mexico
  fssturm at unm.edu









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