Ideal leading pattern:

[Mike and Jane Spalding]

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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>