Ideal leading pattern:

[Richard Moody]

>Putting less lead further out will result in more
> inertia than more lead closer in........

I thought more mass meant more inertia.  Perhaps I lost the meaning of
the terms.  Inertia is the "force" needed to move (or change the
motion of) a body?   Momentum is the force of a body  in motion?
You can balance a lever (Key) with one weight near the end, or with 4
weights near the fulcrum.  Both are in balance but one with 4 times
the mass.   Wouldn't the one with more mass require more force to move
it? As piano keys, both would still have the same down weight, but one
would feel harder to press.  That would be the key with more mass in
it, right?    ---ric?

----- Original Message -----
From: Mike and Jane Spalding <mjbkspal@execpc.com>
To: <pianotech@ptg.org>
Sent: Thursday, March 29, 2001 11:47 AM
Subject: Re: Ideal leading pattern:


> 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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