Capstan Relocation

[Richard Brekne]

Think you made your explaination pretty good... That picture was more or less
vaugely forming in my mind.. was looking at the arcs both pieces made... trying
to fit that into er... moveing perpendiculars ( or somekind of average ) to the
so called magic line. Could sorta see a friction concern here... but was
reaching for any kind of leverage concern... still had a hunch I should try to
make the thing conform. So on the Duysen I did that.

This is still a bit vague in my mind... but your post is more food for
thought... Golly gee willickers... this is a 100 percent bonified gas..

Thanks also to Clark for his response.. I am sure I will come back at you all
for more in the very near future. I will look closely at Ron Overs posting and
webside and I would like to thank him as well. Great stuff guys.

Farrell wrote:

> >"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
> >
> >
> >

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway