[pianotech] key position at rest

[William Monroe]

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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