Action Geometry Correction

[David ilvedson]

I have a customer with a Steinway B, teflon etc. and 6 leads 
in the bass keys progressing up to 5 leads in the treble keys.  
David Stanwood said the problem is the capstan line.  I have 
moved capstans a few times but I want it to look like factory 
work.  I find the 2 to 1 ratio spot on the key and change one 
capstan.  Unfortunately the wippen/capstan point of contact is 
right on the edge of the wippen cushion and moving the capstan 
closer to the balance pin will be very woody sounding.  So do I 
find a Renner wippen from my kit that extends farther?  Are 
there add ons for wippen cushions?  Once I have the right wippen 
and have tested a few with happy results, i.e removing lots of 
lead do I snap a line with the keys on the keyframe?  Or should 
I line them up to a straight edge on the bench before snapping a 
line?  Is there a bit type tool for insert the captans using my 
drill press?  Lots of questions indeed...

Thanks in advance?

David ilvedson, RPT
Pacifica, CA


> Date:          Thu, 29 Oct 1998 19:07:38 -0500
> To:            pianotech@ptg.org
> From:          Jon Page <jpage@capecod.net>
> Subject:       Re: Action Geometry Correction
> Reply-to:      pianotech@ptg.org

> I'll give this a shot:
> Formula for action leverage  (Baldassin/Robinson) :
> 
> (Blow Distance - Let-off / Key Dip - After Touch) =
> (Key Out / Key In) (Wippen Out / Wippen In) (Shank Out / Shank In)
> 
> In English: (BD minus L/O divided by KD minus AT) = (KO divided by KI)
> times . . .
> 
> cp		contact point (my abbrev.)
> All measurements are taken with key at half dip.
> 
> Key Out	Bottom of keystick, center of balance rail hole to cp capstan/wippen
> Key In		Bottom of keystick front to center of balance rail hole
> Wippen Out	Center pin to knuckle/wippen cp
> Wippen in 	Capstan/wippen cp to center pin
> Shank Out	Center pin to strike point
> Shank In	Center pin to knuckle/wippen cp (just forwards of core)
> 
> I haven't gotten to play with this yet, it seems to me to be a lot of
> measurements
> to take with great precision for the equation to balance. I would think it
> is helpful
> with decisions on knuckle radius, capstan placement and action spread. Or for
> just chosing a Blow Distance and Key Dip.
> TINTM     This is new to me  :-)   But I will investigate.
> 
> At 02:53 PM 10/29/98 -0500, you wrote:
> >Should someone else have the formula (and a scanner) I would be most
> >appreciative of receiving this.  I wasn't able to attend Providence but hope
> >to show my funny face in Kansas City.   Action spread is usually around 4
> >13/32" right?  David Stanwood has mentioned in previous classes that
> >generally the spread isn't as big an issue when calculating overall
> >leverage....I guess the next question would follow (maybe Jon and others can
> >answer):  If the spread is greater, say 4 1/2", exactly how will this affect
> >the Strike Weight Ratio?...or would the differences exist...still
> >thinking....in whip ratio?...Trying to sort this out.  Can we make a
> >significant difference in the leveraged system as a whole by altering the
> >spread?  (There, got that out of my system).
> 
> Action spread is another area which I have misgivings. I do know that by
> increasing
> the spread, the capstan moves away from the fulcrum the same as the knuckle
> does, so in essence maybe one cancels the other. I'm not sure. Except I know
> the touch weight does not significantly change. I have utilized the spread to
> better regulate actions, ei: dorp screw too high, L/O button too high:
> expand the
> spread and these will lower.
> 
> I would say that 4.5" is max on spread. The parts are not designed for
> alignment 
> beyond that.
> 
> This is where the "formula" would come in handy.
> 
> >
> >Thanks for reading,
> >
> >Blubbering hammer head
> >Dave Swartz, RPT
> >dms2000@majesticpiano.com
> >
> >At 01:35 PM 10/29/98 -0500, you wrote:
> >>In cleaning out the pile of papers on my desk I found another
> >>pile underneath it. Amongst them was the hand-out from the
> >>Providence Convention about "Action Geometry: Truth And
> >>Consequences" by Rick Baldassin & Chris Robinson.
> >>
> >>Previously I mentioned, that with the key half depressed  
> >>the knuckle/wippen contact point fell on the action spread line;
> >>as recalled to the best of my knowledge from their class.
> >>I obviously did not recall the information correctly.   The lines
> >>they drew on the action parts (pictured indivually, not on the stack)
> >>are between the center pins and their respective contact points,
> >>but no mention at all about proximity of said contact point to action
> >>spread line. Which Don M. pointed out on mIRC one night that the
> >>contact point_is_ below the spread line at halftime. I tested and
> >>found that to be true, I could not find the hand-out and refresh my
> >>memory on the class, but now I have. It is an interesting forumla
> >>but unfortunately I do not have a scanner.
> >>
> >>I know you all were waiting for me to find it and clear that up.
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>Jon Page
> >>Harwich Port, Cape Cod, Mass. (jpage@capecod.net)
> >>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >>
> >>
> >
> >
> 
> Jon Page
> Harwich Port, Cape Cod, Mass. (jpage@capecod.net)
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> 
David Ilvedson, RPT
Pacifica, CA
ilvey@jps.net