What matters most?

[David Love]

The question may seem absurd to the pianist who doesn't even know the names
of the parts, but it's certainly not absurd if the piano isn't performing
well.  As technicians, we need to be able to quantify cause and effect as
much as possible if we are to have any chance of producing a predictable
action, soundboard, or anything else for that matter.  

With respect to this question, I think what we are likely to find, and have
found (thanks in large part to David Stanwood), is that a certain weight at
the hammer end works best with certain action ratios.  Moreover, with
respect to inertia, how that ratio is achieved will make a difference.  We
can, for example, achieve a 5.6 action ratio with a combination of 16 mm
knuckle mounting and .48 key ratio, say, or 17 mm knuckle mounting and .52
key ratio.  Which one should we choose, given that we have a choice.  The
answer, it seems, would lie in how heavy a hammer we wish to use.  A heavy
hammer, from my experience benefits from a long knuckle mounting and a
light hammer from a shorter mounting.  Though I can't quantify the inertial
relationships (at this time), it would seem that inertia (as well as
friction) would play a role.  The Overs piano that I saw in Reno, for
example, had quite a heavy hammer on it.  Thirteen grams or so in the bass,
if I recall correctly.  But it also had a knuckle mounting of 20 mm.  The
overall ratio (I believe, Ron can correct me on this) was about 5.7.  That
piano certainly did not suffer from any inertia problems (it also had
assist springs BTW).  That may not have been the case had the overall ratio
been achieved with a shorter knuckle mounting and a lower key ratio.  Heavy
hammers, contrary to other thoughts expressed, will not necessarily create
inertia problems given the overall ratio and, moreover, the ratios of the
component levers are a good match. 

At least that's my take on it.  So in answer to the original question: 
None of the above.  High inertia in the top action can feel just as bad as
high inertia at the key.  I'll wait for Birkett's research to try and
quantify that relationship further.  Fortunately, we don't usually have to
make that choice.    In general, I'd say that the hammer weight and knuckle
mounting position should move in the same direction.  Once that number can
be quantified, then all that's left is to establish the key ratio that
gives the desired overall ratio. That ratio (assuming no assist springs or
magnets) will have to consider both the resultant front weight of the key,
or key inertia, and regulation requirements.  

David Love
davidlovepianos@earthlink.net


> [Original Message]
> From: Mark Davidson <mark.davidson@mindspring.com>
> To: Pianotech <pianotech@ptg.org>
> Date: 8/23/2003 1:32:14 PM
> Subject: What matters most?
>
> It's important to realize that from the pianist's point of view, this
> question is a bit absurd.
> The pianist cares about how much weight/muscle it takes to get a sound.
> S/he must accelerate
> the whole mess, along with damper, so it's the total package that matters.
> I recently told a professional pianist that I had moved the capstans
screws
> forward on
> my piano to increase the leverage, to which she replied..."What's a
capstan
> screw?"
> Once the total energy required to play a note reaches some limit, the
piano
> becomes
> unplayable.  The limit varies somewhat for different people, but the range
> isn't really
> that big.  My pinky can only output so much energy in that .1 second.
>
> So the ultimate border condition is the pianist's fingers.
>
> One question a former mentor almost always asked was "what problem are you
> trying to solve?" I would assert that the piano tries to solve the
> following:
>
>     1. Throw the biggest, fastest hammer at the string you can.
>     2. Now do it again, quick!
>     3. And by the way, you only get to use one finger.
>
> Of course the whole problem is that 2 and 3 conflict with 1, so the
problem
> becomes
> one of tradeoffs.
>
> Now I realize that isn't really what you were asking, but good to keep in
> mind when
> looking for your answer.
>
> The solution seems to involve the following:
>
> 1. leverage the hammer.  This allows higher velocity and allows the
>     finger to continue accelerating the hammer all the way through the
>     downstroke of the key (prevents "fly away")
>
> 2. add weight to the hammer until it gets too heavy
>
> 3. add keylead or wippen spring or magnets or...
>
> 4. if you can still play a trill, go to step 2, else stop
>
> -Mark
>
>
> RicB wrote:
>
> >Hi touchweight enthusiasts
> >
> >Conversations with a few folks recently prompt me to put a question to
> >you all relative to the problem of action inertia and touchweight. So...
> >I''ll ask without further ado
> >
> >Whats is more important to the <<heaviness>> of the action, the inertia
> >of the hammer and top action, or that of the key. Or if there exists a
> >kind of border condition where one becomes more important then the other
> >and vice versa.... what is that condition ?
> >
> >Thanks for any thoughts
> >RicB
>
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