Capstan Relocation

[Farrell]

>"I would love to hear some explanation as too
> what exactly makes this half-key dip / line of centers / whippen
cushion-capstan
> contact point so essential. care to expound ??"

I think I understand it - now let's see how poorly I explain it. Consider
the forces acting on the capstan and heel cushion as they move. In the ideal
situation quoted above, at start (contact below the line) you have major
vector forces acting directly opposite each other AND a small vector forces
at 90 degrees to the major vector - these smaller forces are wasted. As the
contact crosses the line, the motion is perfectly efficient - only directly
opposite vector forces (one parallel with the capstan stem and the other
opposite, but from the wippen). When motion goes past the line, again a
small vector force appears as a loss.

If the whole motion never crosses the line, a larger loss will occur at the
start (assuming all motion is below the line).

I can picture all this, like, you know, really well. But like, you know, I
think, like, I'm not like, really explaining it very, like, er, a, well.
Like you know what I mean? OR - you could just trust me!  ;-)

I think, basically it is draw your arcs from the action centers and detail
all the vectors from various motions, and you will see.

Terry Farrell
Piano Tuning & Service
Tampa, Florida
mfarrel2@tampabay.rr.com

----- Original Message -----
From: "Richard Brekne" <Richard.Brekne@grieg.uib.no>
To: <pianotech@ptg.org>
Sent: Friday, October 20, 2000 1:12 PM
Subject: Re: Capstan Relocation


> Thanks muchly for this posting...will read it through a couple more times
before
> digesting it all. In the meantime a couple points stuck out and I wanted
to get
> your thoughts on those.
>
> Overs Pianos wrote:
>
> > Bill Ballard touched on the influence of the jack/roller relationship
> > to the line-of-centres in his recent post. His was an excellent
> > point. The location of the jack/roller contact for many actions, is
> > very poorly laid out.
>
> Yet there are seemingly two somewhat opposing friction concerns here...
the
> roller sliding on the repetition lever... vs the rollers contact situation
with
> the jack. I agree Bills point was a good one in as much as it addressed
the
> unobtainability of this line of centers / knuckle consideration.
>
> > While it is important to have the capstan/heel
> > contact pass through the line-of-centres at half key dip, the
> > jack/roller contact position is of equal importance.
>
> This is another point discussed a bit lately... and none of those who seem
active
> in action design parameters who have written about this lately have seemed
to see
> the importance of this.. I frankly do not see how this ends up being an
important
> point (tho I strive to adhere to it) I would love to hear some explanation
as too
> what exactly makes this half-key dip / line of centers / whippen
cushion-capstan
> contact point so essential. care to expound ??
>
> > I find it
> > incredible that almost all piano action designers over the past
> > century have failed to grasp this.
> >
> > Ron Overs
> > --
> >
> > _________________________
> >
> > Website:  http://www.overspianos.com.au
> > Email:      ron@overspianos.com.au
> > _________________________
>
> --
> Richard Brekne
> RPT, N.P.T.F.
> Bergen, Norway
>
>
>