<html>
To: "PTG" <pianotech@ptg.org><br>
Subject: Re: Key Lead Placement<br>
<br>
Since nobody bit on this one I'll chip in with my 47 cents worth.<br>
<br>
I like to place my leads out as far as posible.Tho I have been back and
forth<br>
on this a few times in my life. And I like to use a healthy amount of
lead. I<br>
am not convinced of this low mass approach and dont particularly like the
feel<br>
of such actions as I have run into that were set up such.<br>
<br>
In short.. I like mass levels ranging from around 35-40 graduating down
to 2-4,<br>
and I like to use as little lead as possible to get there.<br>
<br>
RicB<br>
<br>
Farrell wrote:<br>
<br>
>I have read material that suggest placing key lead close to the
center<br>
>rail, and other material that suggest to use a minumum of lead and
place<br>
>it out near the front of the key. For a given balance weight,
what<br>
>guidelines do listy folks use for lead placement?<br>
><br>
>Perhaps just do the 3-2-1-0 arrangement and let them fall where they
will<br>
>placement-wise to get the job done? Any rules like "no closer
than X mm<br>
>from key end.....?<br>
><br>
>Terry Farrell<br>
<br>
<br>
At 02:49 PM <font color="#FF0000">4/1/2001</font> -0500, you wrote:<br>
<blockquote type=cite cite>Ric,<br>
<br>
The short answer is, you're right about isolated weights undergoing the
same<br>
change in motion. But in the case of keyleads, we're interested in
the<br>
reaction force perceived by the pianist at the front rail, when
he/she<br>
applies a force hoping to causes a given acceleration of the key.
So the<br>
effect of the lever arms on both the acceleration of the lead, and on
the<br>
reflection of the reaction force back to the pianist's finger at the
front<br>
rail, must enter into the calculation.<br>
<br>
The long answer is:<br>
<br>
Inertia is the tendency of a body to resist a change in velocity,
otherwise<br>
known as acceleration. The greater the mass, or the greater
the<br>
acceleration, the greater the resisting force. The governing
formula, for<br>
linear motion, is F = m*a. (Force equals Mass times
Acceleration)<br>
<br>
The formula we looked at earlier in this string (I=M*r^2) applies
to<br>
rotating bodies. The rotational formula is T = I*alpha
(Torque equals<br>
Moment of Inertia times angular acceleration). It's neat 'cause it
takes<br>
the lever arm lengths into account within the values for torque, moment
of<br>
inertia, and angular acceleration, but I always get bogged down in the
units<br>
conversions, lb-in^2, radians/second^2, etc. etc., so where possible I
try<br>
to see every problem in the linear model.<br>
<br>
Let's take the key weight example, and we'll round off the numbers to
make<br>
it easier, if not necessarily correct for your specific piano: (You
may<br>
find it makes more sense if you sketch this as you read through)<br>
<br>
The key measures 8" from front rail pin to balance rail pin.
You want to<br>
increase the keyweight by 4 grams, and are considering putting the weight
at<br>
4" (4 grams times 8" divided by 4" = 8 grams required) or
at 2" (4 grams<br>
times 8" divided by 2" = 16 grams required).<br>
<br>
Let's let A equal the acceleration of the key, at the front rail pin, for
a<br>
mezzo-forte blow. The acceleration at 2" would be A times
2" divided by 8",<br>
or A/4. The force at 2" would be M * A/4, or 16*A/4, or
4*A.<br>
<br>
The acceleration at 4" would be A times 4" divided by 8",
or A/2. The force<br>
at 4" would be M * A/2, or 8*A/2, or 4*A.<br>
<br>
So, in both cases, the force AT THE WEIGHT is equal to 4*A. But the
force<br>
felt by the pianist, AT THE FRONT RAIL, is reduced by the leverage:
For the<br>
weight at 4", the force is reduced by 4" divided by 8", so
the pianist feels<br>
2*A. For the weight at 2", the force is reduced by 2"
divided by 8", so the<br>
pianist feels A. Bottom line, the closer the weight can be placed
to the<br>
balance rail, the less inertial resistance the pianist will feel.<br>
<br>
Mike<br>
<br>
<br>
<br>
<br>
----- Original Message -----<br>
From: Richard Moody <remoody@midstatesd.net><br>
To: <pianotech@ptg.org><br>
Sent: Saturday, March 31, 2001 1:46 AM<br>
Subject: Re: Ideal leading pattern:<br>
<br>
<br>
> >Putting less lead further out will result in more<br>
> > inertia than more lead closer in........<br>
><br>
> I thought more mass meant more inertia. Perhaps I lost the
meaning of<br>
> the terms. Inertia is the "force" needed to move (or
change the<br>
> motion of) a body? Momentum is the force of a body
in motion?<br>
> You can balance a lever (Key) with one weight near the end, or with
4<br>
> weights near the fulcrum. Both are in balance but one with 4
times<br>
> the mass. Wouldn't the one with more mass require more
force to move<br>
> it? As piano keys, both would still have the same down weight, but
one<br>
> would feel harder to press. That would be the key with more
mass in<br>
> it, right? ---ric?<br>
><br>
> ----- Original Message -----<br>
> From: Mike and Jane Spalding <mjbkspal@execpc.com><br>
> To: <pianotech@ptg.org><br>
> Sent: Thursday, March 29, 2001 11:47 AM<br>
> Subject: Re: Ideal leading pattern:<br>
><br>
><br>
> > Paul,<br>
> ><br>
> > I believe you are mistaken regarding the inertia. (As a
former<br>
> machine<br>
> > design engineer who recently jumped out of the frying pan and
into<br>
> piano<br>
> > tuning, I have some experience with this). It does indeed
vary with<br>
> the<br>
> > placement of the lead: Putting less lead further out will
result in<br>
> more<br>
> > inertia than more lead closer in. Half the weight, twice
as far<br>
> out, same<br>
> > static downweight, but twice the inertia. (For those of
us old<br>
> enough to<br>
> > remember phonograph records, this is why the counterweight on
the<br>
> tone arm<br>
> > is very large and very close to the pivot point.) Doesn't
change<br>
> your<br>
> > conclusion: all other things being equal, keep the lead
near the<br>
> pivot<br>
> > point.<br>
> ><br>
> > Mike Spalding<br>
> ><br>
> ><br>
> > ----- Original Message -----<br>
> > From: <larudee@pacbell.net><br>
> > To: <pianotech@ptg.org><br>
> > Sent: Thursday, March 29, 2001 10:15 AM<br>
> > Subject: Re: Ideal leading pattern:<br>
> ><br>
> ><br>
> > > David,<br>
> > ><br>
> > > As a matter of simple physics, it makes no difference
whether you<br>
> put less<br>
> > lead<br>
> > > farther away from the balance rail or closer in, with
one<br>
> stipulation.<br>
> > The<br>
> > > stipulation is that the key is perfectly rigid and has
no<br>
> flexibility.<br>
> > > Otherwise, both the momentum and inertia will be the same
either<br>
> way.<br>
> > ><br>
> > > Of course, we know that the key is not perfectly rigid,
so<br>
> placement of<br>
> > more<br>
> > > lead closer in is probably preferable, all else being
equal. This<br>
> reduces<br>
> > the<br>
> > > sense of inertia in the key because the part that takes
the force<br>
> of<br>
> > depression<br>
> > > has less mass in it than otherwise, and applies leverage
to the<br>
> part that<br>
> > has<br>
> > > the mass, closer to the balance rail, after some momentum
has<br>
> already been<br>
> > > gained in the key. Along with the use of cylindrical
key<br>
> bearings, I<br>
> > think this<br>
> > > design is part of what Steinway calls its accelerated
action, but<br>
> I am<br>
> > prepared<br>
> > > to be corrected.<br>
> > ><br>
> > > Paul Larudee<br>
> > ><br>
> > > David Love wrote:<br>
> > ><br>
> > > > I run into this sort of situation frequently and I
would like<br>
> some<br>
> > opinions.<br>
> > > > Steinway model S ca 1936. I am
replacing hammers and shanks<br>
> only. I<br>
> > use<br>
> > > > Steinway hammers full taper, Abel shank 16.5 mm
knuckle gives me<br>
> the<br>
> > best<br>
> > > > combination of regulation/downweight from which to
work. The<br>
> strike<br>
> > weight<br>
> > > > is medium and consistent throughout. Key weight
ratio is 5.0.<br>
> When I<br>
> > > > install the hammers, I will still want to take 2-5
grams off the<br>
> > downweight<br>
> > > > throughout much of the piano (though it is somewhat
erratic) to<br>
> get a<br>
> > 52-48g<br>
> > > > taper. Doing so does not compromise the
upweight. The present<br>
> front<br>
> > > > weight of the keys allows me to add lead without
exceeding the<br>
> maximum<br>
> > > > recommended front weight (according to Stanwood
charts). But...<br>
> the<br>
> > keys<br>
> > > > already have a fair amount of lead grouped mostly
toward the<br>
> balance<br>
> > rail.<br>
> > > > Though the front weight is not excessive, the keys
themselves<br>
> weigh a<br>
> > lot<br>
> > > > because of the amount of lead in them (e.g. C16 =
163g , C40 =<br>
> 144g, C64<br>
> > =<br>
> > > > 133g). I have the option of adding a small
lead, or removing<br>
> two or<br>
> > more<br>
> > > > large leads from near the balance rail and replacing
them with<br>
> one large<br>
> > > > lead out toward the front of the key. The
latter will produce a<br>
> more<br>
> > > > conventional leading pattern--and involves a lot more
work.<br>
> > > ><br>
> > > > My questions are:<br>
> > > ><br>
> > > > 1. Which one will produce a better feel?<br>
> > > > 2. Will the difference be significant?<br>
> > > > 3. Do front weight parameters change with the
overall length of<br>
> the<br>
> > key:<br>
> > > > i.e., is the allowable front weight greater for a
model D than<br>
> for a<br>
> > model<br>
> > > > S, or there other factors.<br>
> > > > 4. What additional information will be helpful
in making a<br>
> quantifiable<br>
> > > > decision?<br>
> > > ><br>
> > > > David Love<br>
> > > ><br>
>
_________________________________________________________________<br>
> > > > Get your FREE download of MSN Explorer at<br>
>
<a href="http://explorer.msn.com/" eudora="autourl">http://explorer.msn.com</a><br>
> > ><br>
> > ><br>
> ><br>
><br>
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