[pianotech] key position at rest

[Joe And Penny Goss]

Hi Just a farmers guess. Thre principle of the flywheel if there is one <g>
Once friction is overcome there is not as much an issue of friction 
due to the objects causing friction no longer being in static position.
Now if we were able to measure drag as well ------
Joe Goss RPT
Mother Goose Tools
imatunr at srvinet.com
www.mothergoosetools.com
  ----- Original Message ----- 
  From: William Monroe 
  To: pianotech at ptg.org 
  Sent: Saturday, March 14, 2009 6:45 PM
  Subject: Re: [pianotech] key position at rest


  FWIW, 

  In Feb. of 1999 the Journal published results of an experiment entitled, "What Happens If....?", conducted by our esteemed colleagues: Richard Davenport RPT, Mark Abbott Stern RPT, Kay Forrest, Pam Consoli RPT, (and filmed by Alan Eder, RPT).  In this experiment, the team set up a 1980's vintage Yamaha grand action model to accept a number of geometry changes, one of which was taking a vertical capstan and rotating it to 8 degrees back as well as 15 degrees back, keeping the same contact point between the capstan and wippen heel.  Both changes yielded the same result: a 3g reduction in DW and UW.  Why both changes gave the same result, I'm not sure, but it appears that having some angle on the capstan was "beneficial."

  William R. Monroe



  On Sat, Mar 14, 2009 at 6:33 PM, Richard Brekne <ricb at pianostemmer.no> wrote:

    Hi Paul

    David has it right. The idea of leaning the capstan forward instead of backwards has to do with the friction between the whippen heel and the capstan. You have two parts both moving in arcs, and at half way through the key stroke, these arcs should be touch.  The idea is that this condition yields the least friction between the two parts. So in order for this to happen, the <<point>> of the capstan and the <<point>> of the whippen heel should be exactly parallel and on the same line at half blow. It makes good sense but as to whether or not one can measure a difference ... well I haven't actually measured such things myself... so I wont presume to answer that.

    Why they angled them backwards I'm still unsure of.  I've thought at times they must have thought they were getting more leverage out of the lever.  That doesn't really quite wash when it comes down to it.  You put a vertical force on an angled input to a lever and you get into vectors... and everything is moving anyways.  Like I said to begin with... I don't really understand what they were thinking about when they angled them backwards.  Still, the folks what designed things back then were not exactly idiots.  Might be nice to know.

    Cheers
    RicB



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