Objective keydip measuring; Hamburg v NY frictions

[Horace Greeley]

Ron,

At 12:25 PM 11/16/1998 -0500, you wrote:
>Two questions:

And, interesting ones, too!

>1. Does anyone know of a tool that measures keydip objectively - ie., you
>don't have to try relying on identical finger pressure for each key (an
>impossibility in my experience!)? I see depth gages, some of which that
>appear to be spring-loaded. Are these accurate and convenient to use? Do
>they work for black keys equally well? It would also be nice to have such
>an instrument for measuring aftertouch - preferably something where the
>spring tension can be varied ever-so-slightly to allow for heavy-touch
>playing or light-touch playing. (Am I getting too esoteric??)

Several thoughts on this, all of which reflect, I admit, some old-fashioned
attitudes and practices.

The first problem with setting up a keybed, especially nowdays, is the
relatively soft felt available.  While harder felts certainly can 
contribute to action noise, they also lend themselves to greater
consistency of compression, both at rest and under load (playing
conditions).

That being said, I prefer to use the thinnest possible (woven) felt
for each rail.  For the back rail, I think that you can still get
some fairly decent dark green action cloth from Charles House.  For
balance rail, thin punchings (I've tried several brands, there does
not seem to be a great deal of difference here).

The front rail is the one most of us find to be problematic, and the
solution I have found is to use the front rail punchings which Renner
supplies for Bose.  These are not only more consistent in density,
but are also less compressable.

Also, just to be really didatic, I use the smallest _number_ of card/
paper punchings; e.g., one thicker rather than several thinner, etc.

Once the basic key height is set, I use a combination of dip blocks,
depending on what the specific piano seems to need.  The one I use
the most often is the old Lucite S&S block, with a blue paper punching
under it, held in place by a strip of plastic tape - hmmm, I suppose
I really should measure just how thick that is...it's not .420", anyway.
Then, doing the naturals first, I check the dip with pressure equal
to a FF blow.  With the naturals done, I set the sharps to stop the
thickness of a nickel above the naturals.  Using the kinds of felt
described above, I do not find this to be particularly hard to keep
even.

I've tried several different jigs for this work, and always wound up
going back to a laminated straight edge for keyheight, having first
set samples (of regulated notes) at the ends of each section in the
keyframe.  Further, even the best jig is not going to really come
close to approximating actual playing conditions.

In terms of aftertouch, I work to set that at between the thicknesses
of a penny and a nickel.  Simply drill a hole in the middle of one
of each, and slip it over the key pin, then depress the key.  With
nominal practice, you can get a very even setting of aftertouch -
FWIW, I greatly prefer to not mess with the dip, per se, when setting
touch.  My preference is to work with fly/balancier placement and
letoff, balancing these against actual key travel.  Again, with a 
little practice, this method works very well.  (I tried using coins
with slots cut instead of holes drilled.  Since I am prone to rather
"slap" the keys when doing this, these fell out of the action often
enough to be truly annoying.)

>2. Has anyone ever heard of different friction specs for Renner centers?
>It always seems like Renner's centers are floppy-loose out of the box. I
>wonder if they pin things loose, anticipating that the centers will
>tighten up after a period of use.

Personally, I don't think much of anything is what can be called "stable".
The wood is cut too young, improperly "aged", kiln dried, machined too
fast to too close a tolerance.  I know, I know - Hornbeam is the greatest
thing since sliced bread.  There are simply too many varibles for some
of the glib statements made about it.

I repin everything before installing it, whatever it is.  Usually, I try
to give myself enough time for the parts to sit in the shop for a month
before doing anything with them.  Everyone's pinning process is different,
but I think that it really makes sense to go through this carefully.
In my experience, those "floppy loose" centers get much like unto a
bear at fly time with even the slightest amount of elevated RH.

Hope the above makes some kind of sense.  It's hard to condense some
of this stuff down to emailable size without getting simplistic.

Anyway, for me, the important part of nay of this is to always think
of the piano as an organic whole.  Thus, whenever possible, I work
directly at the piano.  It's much easier to do this in some
institutional settings than in others, but I think that the results
are worthwhile.

> "Dese are de conditions dat prevail."

Hmmmm - yes, now, where is that recipe for lemonade, anyway?

Best.

Horace


Horace Greeley, CNA, MCP, RPT
Systems Analyst/Engineer
Controller's Office
Stanford University
email: hgreeley@leland.stanford.edu
voice mail: 650.725.9062
fax: 650.725.8014