ratio question

[David Love]

In mechanics, the weight and distance ratios are forever interlinked.  A
lever or series of levers that lifts weight at a 6:1 ratio also moves that
object at the same ratio.  There are other factors that might change the
distance relationship such as sliding at various points in the levers.  I
think it is safe to say that a lever or series of levers cannot move an
object a greater distance than is suggested by the weight relationship.  An
action that has a key dip of 10 mm and lifts the hammer a total of 60 mm
(at 6:1) would seem to have plenty of room to compensate.  But when you
factor in let-off and after touch, sliding at the capstan and knuckle, that
additional distance between 45 blow and 60 mm of movement gets used up
fairly quickly.  Assuming you are using the same standard of measuring the
ratios for both weight and distance, and all other things being equal, An
action with a 5.5 ratio cannot regulate the same as an action with a 6.0
ratio.

As far as the question about similar ratios achieved by different means
(15.5 knuckle versus 17 mm knuckle and varying capstan locations);  I think
it is not surprising that there would be a difference in feel.  Friction is
probably different due to more weight bearing on the knuckle in the 15.5
arrangement.  Also, I would assume a different dynamic arrangement between
a 15.5 and 17  mm knuckle (strike weight being equal).  The inertia as
contributed by those two different arrangements would have to be different.
The calculation should not be that complicated to do.  Perhaps Stephen
Birkett can enlighten us with some new data here.  Also, there would be
different amounts of flex in the hammer shank between those two
arrangements, that would contribute to a different feel as well.  

David Love
davidlovepianos@earthlink.net


> [Original Message]
> From: Richard Brekne <Richard.Brekne@grieg.uib.no>
> To: Pianotech <pianotech@ptg.org>
> Date: 7/13/2003 4:03:53 PM
> Subject: Re: ratio question
>
>
>
> A440A@aol.com wrote:
>
> >  Richard asks:
> > << Can a (for the sake of example) 6.0 static weight ratio ala Stanwood
> > result in differing distance ratios ? >>
> >
> >   If you mean, can a 6.0 ratio be found with various keydips or with
various
> > hammer blow distances?  Yes.
>
> Well not exactly...   rather I was asking whether the ratio of  vertical
keydistance
> moved to vertical  hammer movement  can vary while the weight ratio stays
the
> same.... perhaps thats what you meant above.
>
>
> > Which brings up another question that I am not
> > seeing asked.....
> >
> >     Why is there is a distinct difference in feel between two actions
that
> > achieve the same ratio with different knuckle distances?  Ie.  you can
arrive at
> > the same overall action ratio with a 15.5 mm knuckle distance and a
short key
> > ratio as you can with a 17 mm knuckle distance and a longer key ratio,
but
> > the response of these two actions are NOT the same.
> >     I have certain ideas about finding the optimum combination, but I
confess
> > to making many of my final decisions on hard-to-quantify feedback I get
from
> > the piano.
> >
>
> This is a very good question and was more or less where I was going with
my own
> leadin question.. Hard to quantify to be sure, or rather very  time
consuming. I
> look forward to hearing some differeing views
>
>
>
> > Ed Foote RPT
> > www.uk-piano.org/edfoote/
> > www.uk-piano.org/edfoote/well_tempered_piano.html
> >  <A
HREF="http://artists.mp3s.com/artists/399/six_degrees_of_tonality.html">
> > MP3.com: Six Degrees of Tonality</A>
> > _______________________________________________
> > pianotech list info: https://www.moypiano.com/resources/#archives
>
> --
> Richard Brekne
> RPT, N.P.T.F.
> UiB, Bergen, Norway
> mailto:rbrekne@broadpark.no
> http://home.broadpark.no/~rbrekne/ricmain.html
> http://www.hf.uib.no/grieg/personer/cv_RB.html
>
>
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives