Evidence of overlacquered hammers

[Bernhard Stopper]

Hello Sarah,
thanks for your interesting post.

Let me refine what you call elasticity. What is going into heat is defined
as damping or resilince and that occurs in the hammers felt as a hysteretic
parameter function that means that the reaction force going into heat is
offset in time compared to the reaction force of the elasticity. The real
elasticity is the springieness that rejects the felt compression.

For everybody who is interested in trying out my scaling software that
includes a hammer/string physical model of both the string and hammer, you
may download a demo of the software at:

http://www.piano-stopper.de/dl/Mensurix_5.0.10.msi

it is possible to play around also in the demo version with hammer
parameters like elasticity and damping, and nice imperssive.

regards,

Bernhard

----- Original Message ----- 
From: "Sarah Fox" <sarah@graphic-fusion.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Saturday, October 02, 2004 4:54 PM
Subject: Re: Evidence of overlacquered hammers


> Hi Bernhard et al.,
>
> Fascinating discussion!
>
> You wrote:
>
> > Yes that´s what i say. As long as you put the same amount of energy into
> > the
> > key, the sound will not be louder. This the principle of conservation of
> > energy.
>
> and then:
>
> >> > The amount of energy imparted to the string which is
> >> > transferred to the soundboard is a function of mass and/or density of
> >> > the object striking the string.
> >
> > Not only. The function includes also the hammer speed and the strings
> > impedance (including mass and tension of the string).  If you put in the
> > same amount of energy into the key, the speed will be lower so the
> > loudness
> > will not change therefore. With a heavier hammer you will get louder
lower
> > partials, but less higher partials. May that´s why you have the
impression
> > of a louder sound. But the overall energy does not change.
> > Yes that´s what i say. As long as you put the same amount of energy into
> > the
> > key, the sound will not be louder. This the principle of conservation of
> > energy.
>
> This is all true, of course, but one also has to consider the efficiency
of
> energy transfer between the hammer and string.  This depends largely on
the
> elasticity of the hammer.  But considering two hammers of similar
> elasticity, I would of course agree.
>
> Having said this, I think there can be huuuuge differences in hammer
> elasticity.  I just finished replacing the hammers on my 9' Wissner.  The
> old hammers were not *too* misshapen, but as a set, they were very
> inconsistent from note to note.  I did put on heavier hammers, but not
> *that* much heavier (about 1 Stanwood level).  The primary difference
> between my old hammers and my new hammers is the felt.  The old felt was
not
> of particularly great quality, and it was highly lacquered.  The new
hammers
> are of unlacquered Wurzen felt.  Overall, the tonal properties of the two
> hammer sets are similar, sort of.  They are of similar
brightness/darkness,
> anyway, although the old ones sound a bit "woody" (for lack of a good
term).
>
> The weaknesses of my old hammer set were most apparent in the mid treble,
> which was rather thready.  The last octave had reasonable sustain,
> considering the age of the SB, but not much strength either.  However, one
> really expects and needs strength in the mid treble, and I didn't have it.
> The bass and tenor, by comparison, were very robust.  At the time I bought
> the piano, I had faith <grin> in the problem deriving from the inferiority
> of the hammer set.
>
> I'm happy to report that the new hammer set gives me well balanced sound
> from bottom to top.  (To be more accurate, the top few notes may indeed
need
> a bit of filing and/or lacquer.)  The problem with the thready treble has
> been eliminated.  More to the point of the discussion, and to paraphrase
> from an earlier post from someone on this list (regarding Wurzen felt),
I've
> got power out the wazoo!  Good lord, if I wanted to, I could now compete
> with the guy across the street with the powerful sound system that
delivers
> crystal-clear music to my bedroom at 4:00 AM, at least if I faced the
piano
> the other way and opened the window.  ;-)
>
> The difference in power is not a perceptual phenomenon with regard to
> emphasis of different partials.  It's quite profound and real (perhaps by
15
> or 20 dB in the mid treble), and I would say it has to do with the
> differences in elasticity between the two hammer sets.  The unlacquered
> Wurzen felt is simply springier than the (over)lacquered felt, and
therefore
> more of the energy reaches the string, instead of burning off in the form
of
> heat.
>
> I frankly don't know whether "good" lacquering would have made my old set
> perform well.  The old hammers were visibly soaked (blue-gray) from the
> shoulders to the 9:00 and 3:00 positions.  I didn't do any strike point
> analysis (e.g. with chalk), and it's quite possible that shaping could
have
> improved them slightly.  Anyway, I offer these observations for all they
are
> worth.  YMMV!!  And no, I have no experience with how these hammers would
> have performed on other scale and SB designs -- only on a 1933 clone of an
> S&S D.
>
> Incidentally, I did try out some Abel samples (both the light and the
> premium), prior to selecting the Wurzens.  They weren't appreciably
> different from the hammers I already had, but I bet they would have
largely
> balanced out my mid treble.
>
> Peace,
> Sarah
>
>
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