Ideal leading pattern: more questions

[David Love]

So this model S I am trying to solve has what appears to be another quirk.  
Admittedly, I don't make this measure of comparison very often but, the 
capstan to balance rail distance varies by about 6 mm from end to end, i.e., 
note #1, the distance is 106 mm, and note #88 is 112mm.  The capstan centers 
underneath the heel at both ends.  It is counterintuitive if this is the 
design.  I operated under the assumption that the balance rail, capstan 
line, front of key line were all parallel.  If this is true (please correct 
me if it isn't)  it would seem that brackets were not squared up with the 
frame and that the capstan line was then drawn at an angle.  Could this 
explain why I seem to need an excess of lead in the upper end of the piano?  
Interestingly enough, though the downweight diminishes 50-47 from 1-88 (and 
the upweight follows inversely), the action actually feels heavier in the 
upper end of the piano.  My sense tells me that with the capstan line moving 
ever farther away from the balance rail as you progress from bass to treble, 
that the action becomes more poorly leveraged and therefore feels heavier in 
spite of the fact that it is getting lighter.  Feedback is appreciated.

David Love


>From: larudee@pacbell.net
>Reply-To: pianotech@ptg.org
>To: pianotech@ptg.org
>Subject: Re: Ideal leading pattern:
>Date: Thu, 29 Mar 2001 19:10:04 -0800
>
>I stand corrected.  By the way, it is part of the principle of the Steinway
>accelerated action design, right?
>
>Paul
>
>Mike and Jane Spalding wrote:
>
> > Paul,
> >
> > I believe you are mistaken regarding the inertia.  (As a former machine
> > design engineer who recently jumped out of the frying pan and into piano
> > tuning, I have some experience with this).  It does indeed vary with the
> > placement of the lead:  Putting less lead further out will result in 
>more
> > inertia than more lead closer in.  Half the weight, twice as far out, 
>same
> > static downweight, but twice the inertia.  (For those of us old enough 
>to
> > remember phonograph records, this is why the counterweight on the tone 
>arm
> > is very large and very close to the pivot point.)  Doesn't change your
> > conclusion:  all other things being equal, keep the lead near the pivot
> > point.
> >
> > Mike Spalding
> >
> > ----- Original Message -----
> > From: <larudee@pacbell.net>
> > To: <pianotech@ptg.org>
> > Sent: Thursday, March 29, 2001 10:15 AM
> > Subject: Re: Ideal leading pattern:
> >
> > > David,
> > >
> > > As a matter of simple physics, it makes no difference whether you put 
>less
> > lead
> > > farther away from the balance rail or closer in, with one stipulation.
> > The
> > > stipulation is that the key is perfectly rigid and has no flexibility.
> > > Otherwise, both the momentum and inertia will be the same either way.
> > >
> > > Of course, we know that the key is not perfectly rigid, so placement 
>of
> > more
> > > lead closer in is probably preferable, all else being equal.  This 
>reduces
> > the
> > > sense of inertia in the key because the part that takes the force of
> > depression
> > > has less mass in it than otherwise, and applies leverage to the part 
>that
> > has
> > > the mass, closer to the balance rail, after some momentum has already 
>been
> > > gained in the key.  Along with the use of cylindrical key bearings, I
> > think this
> > > design is part of what Steinway calls its accelerated action, but I am
> > prepared
> > > to be corrected.
> > >
> > > Paul Larudee
> > >
> > > David Love wrote:
> > >
> > > > I run into this sort of situation frequently and I would like some
> > opinions.
> > > >   Steinway model S ca 1936.  I am replacing hammers and shanks only. 
>  I
> > use
> > > > Steinway hammers full taper, Abel shank 16.5 mm knuckle gives me the
> > best
> > > > combination of regulation/downweight from which to work.  The strike
> > weight
> > > > is medium and consistent throughout.  Key weight ratio is 5.0.  When 
>I
> > > > install the hammers, I will still want to take 2-5 grams off the
> > downweight
> > > > throughout much of the piano (though it is somewhat erratic) to get 
>a
> > 52-48g
> > > > taper.   Doing so does not compromise the upweight.  The present 
>front
> > > > weight of the keys allows me to add lead without exceeding the 
>maximum
> > > > recommended front weight (according to Stanwood charts).  But... the
> > keys
> > > > already have a fair amount of lead grouped mostly toward the balance
> > rail.
> > > > Though the front weight is not excessive, the keys themselves weigh 
>a
> > lot
> > > > because of the amount of lead in them (e.g. C16 = 163g , C40 = 144g, 
>C64
> > =
> > > > 133g).  I have the option of adding a small lead, or removing two or
> > more
> > > > large leads from near the balance rail and replacing them with one 
>large
> > > > lead out toward the front of the key.  The latter will produce a 
>more
> > > > conventional leading pattern--and involves a lot more work.
> > > >
> > > > My questions are:
> > > >
> > > > 1.  Which one will produce a better feel?
> > > > 2.  Will the difference be significant?
> > > > 3.  Do front weight parameters change with the overall length of the
> > key:
> > > > i.e., is the allowable front weight greater for a model D than for a
> > model
> > > > S, or there other factors.
> > > > 4.  What additional information will be helpful in making a 
>quantifiable
> > > > decision?
> > > >
> > > > David Love
> > > > _________________________________________________________________
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> > >
> > >
>

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