SW heresy?

[Ray Negron]

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Hi Sarah,

As usual, another thought provoking letter.

It is Sunday morning, not the best time for thinking, and I majored in phys.
ed.(dumb jock), not math, but I will give it a shot.

Hammer felt density increases from bass to treble. In a perfect world, the
density of the wood will be the same from hammer to hammer. However, since
moldings are made from strips of wood glued together, probably from
different trees, this is not the case. This would account for weight
differences from one molding(tree A) to the next(tree B). Different types of
wood are used to make hammer moldings. We use silver maple, sapele, or hard
maple. Other types of woods are used by other manufacturers. Hard maple is
denser than hammer felt, while silver maple is not. Hammer felt gets thinner
from bass to treble, as do hammer moldings, so that, ideally, as you go up
the scale, each hammer will be lighter than the previous hammer. Since it is
not a perfect world, we have you guys to save the day. Hope I gave you some
useful information. Probably should have waited until my brain if
functioning better, but that won't be till ...

Ray Negron
  -----Original Message-----
  From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]On
Behalf Of Sarah Fox
  Sent: Sunday, August 22, 2004 12:31 AM
  To: Pianotech
  Subject: SW heresy?


  Hi all,

  Thanks for the advice about techniques to even out the SW curve!  That
should give me a variety of techniques to use/combine in order to even out
the jags.

  But the question is one of what my target curve should *really* be.
Hmmmm....  My thoughts:

  The unmodified SW curve is obviously very linear.  (Yes, I know what
linear means.  I "minored" in mathematics, sort of -- except that my U.
didn't officially recognize minors).  Stanwood's curves, OTOH, are all
concave downwards.

  I was advised off list that I shouldn't force the hammers to artificially
conform to a standardized Stanwood curve but to simply even out the jags to
make the action smooth from bottom to top.  There's something to be said for
this idea.

  But as I got to thinking about the SW curves, I was wondering, where do
they REALLY come from?  That is, where does the shape come from?  I suspect
the hammer manufacturing people might be able to enlighten me as to this.
(Ray???)  I'm *guessing* that the felt is denser than the molding, and when
the hammer becomes skinnier, it loses more felt than molding, resulting in a
more precipitous dropoff in weight at the higher end.  This would occur with
a constant hammer length and a linear variation in hammer and molding (and
felt) width.  Am I anywhere close on this idea???

  Contrast this function with other functions that might actually relate to
optimal hammer mass:  String length and mass both decrease with the note
number, with a function that is concave upwards.  Note frequency increases
with a function that is concave upwards.  Note period (inverse of frequency)
increases with a function that is concave upwards.  The Stanwood curve seems
rather meaningless with regard to any of these functions.  For instance, it
might be good to match hammer mass to string mass by some proportion.
Right?  As the scale goes up, string length and mass approach an asymptote
of zero.  Therefore, shouldn't hammer mass approach an asymptote of zero?
Instead, the curve starts taking a dive in the treble.  If the scale went up
well past 88, hammer mass would eventually crash to zero.  Because these
curves do not have the same form, the relationship between hammer and string
mass is anything but constant.  That doesn't make sense.

  So is this something that is the way it is just because of tradition --
because the cauls are built that way, and that's what ya' get?

  Now that I look at my linear SW curve (with jags), I'm wondering if this
isn't REALLY a closer match to something meaningful (like string mass) than
the idealized Stanwood curves.  Any thoughts, y'all?

  Peace,
  Sarah



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