Renner "Turbo Wippens" ?

[Bill Ballard]

At 10:46 PM -0400 10/10/98, A440A@AOL.COM wrote:
>Rich asks:
>> What is the
>>list's opinion on them - looks like for certain pianos it will do the trick.
>
>Greetings,
>   I don't know about the list's opinion, but mine is that the additional
>spring will allow an action to be biased toward a lighter feel, but if they
>are used in an attempt to correct geometry problems, the piano will still feel
>unresponsive.
>Regards,
>Ed Foote

Did my alarm just go off?

To take off from Ed's comment:
I'm not sure what Ed means by "biased toward a lighter feel". Possibly, in
that returning the touchweights (DW,UW, and yes...BW!) to original levels
after the springs have taken over parts of the counterbalancing job from
the front weights (FW), the inertial resistence of the action will drop
with the removal of FW. Or maybe, that the spring balanced action will feel
lighter than a lead (mass) balanced action for the same BW (oops, I mean,
DW/UW.) This is Newton's little fig of wisdom here.

In all this talk of "geometry probleams", it's useful to contemplate Ken
Sloane's experience with the 80's D with an action unplayable until he
swapped the shanks for a set of significantly lower leverage. (PTJ in '93?
where's my directory.) Of course the new set of shanks with the knuckle
core further down the shank meant that his jack-to-knuckle line was
unacceptably bent (at least, to the eye). No gold stars for that straight
line! But the new shanks were exactly what he wanted as far as the
resistence problem.

Let's all make sure we're starting back at the same Square One. The surplus
force of gravity on the back side of the key which we measure with gram
weights is combination of mass of the hammer modulated by the overall
action leverage ratio, plus the force of friction encountered moving that
mass with that leverage. (Yes, the mass should be treated as of each
individual particle of  each action piece modulated by that partical's
distance from the pivot of that piece, combined with the ratio of any
pivoting parts below it. Those of you who use rocket science as a regular
part of your daily piano work, can stand over in that corner.)

We all know the difference between a mass problem and a friction problem.
Each has it's own diagnosis and treatment. Because each is dealt with
separately, we should start thinking of them as separate attributes as
early as we can. If we want to separate mass from friction, by far the most
expedient amd practical way is to infer these two quantities from UW/DW. As
David Stanwood has laid out, BW=(DW+UW)/2 and Friction=(DW-UW)/2. (Are
there any people here who should be over with the rocket scientists, BTW.)

As I mentioned earlier, the rep spring's purpose is to counterbalance
action mass. FWeights are the conventional way to do this. With bad
leverage, the resulting friction can widen the spread between DU and UW,
but your first problem is mass anyway. It doesn't matter whether you are
pushing down high DW resulting from bad leverage or heavy hammers, or
whether you're bringing an UW up above 20g because someone else has
overleaded the keys in repsonse to the same problem. With either FWeights
or helper springs, you're changing the balance of weight between the front
and back halves of the key.

Usually, as soon as the helper springs go on, certain amounts of lead (FW)
are soon removed from the key fronts. The exact amount of counterbalancing
done by the springs can be further adjusted individually, to acheive the
exact amounts we're used to acheiving with leads. (A set screw design
exists for this, BTW.) But the results are no different in an action with
"good or bad geometry": the helper spriongs goes on, the lead comes out.
Certainly, that's the way a Viennese action should feel. But you'll be just
as glad to pull lead out of an action with bad leverage.

To tell the truth, it's less expensive to correct bad leverage and solve
the problem at its source (either by rehanging the hammers on more
favorable shnks, or moving the cap line), than it is to purchase the new
Tarboy Whips (which as we understand change neither the hammer mass nor the
overall leverage). But to do this you need to have a few more measurements
on your worksheet than just DW (or maybe even UW). I am much in awe of the
two primary rebuilders whom Loyd Meyer is relying on for action advice. But
any paper which outlines the use of the spring balancing rep without
advising on its effect on weight and friction as matters separately read
and corrected, is bound to be a little confusing. At least that's what the
Renner sheet on the inbstallation of Turbo Reps was for me.

I would straighten out this confusion by genrealizing: The helper springs
should be used the way lead is, to counterbalaince the back half of the
key. Although the springs may change the feel of and action with bad
leverage or mass, they will not change those aspects of the feel having to
do with bad mass or leverage. Helper springs should  not be chosen because
they can correct bad leverage. They won't. You may be able to use the
change in feel they may offer in a situation of bad leverage, but don't use
them because you think they'll clear up a leverage or hammer weight
problem. They won't.

Bill Ballard, RPT
New Hampshire Chapter, PTG

"Round here we don't talk unless we can improve in the silence."
    Ron Rude, local Public Radio Commentator.