Wooden action parts and frames

[Delwin D Fandrich]

----- Original Message -----
From: "Phillip Ford" <fordpiano@earthlink.net>
To: <pianotech@ptg.org>
Sent: February 18, 2003 11:57 AM
Subject: Re: Wooden action parts and frames


> >I doubt that your Bechstein representative intended to imply that certain
> >vibrations were essential, or desirable, to the overall sound mix, but
that
> >they were not. Much gets lost in the translation between languages.
>
> Quite likely.  But it did get me to thinking about where the vibrations
that you feel in the key are coming from.  In my opinion, one of the
characteristics that distinguishes a really good piano from a mediocre one
is this ability to transmit vibration to the keys.  On a good piano you have
the sensation that you are feeling the sound as well as hearing it.  This is
an attribute that I value highly, and many pianists do as well.  I'm not
sure what the path for this is.  I had always assumed that the vibration was
coming from the rim, through the keybed, and through the keyframe to the
keys.  The conversation mentioned above made me wonder if some of this
'vibration' wasn't coming from the hammer back through the action rails and
frame and into the keys.
>
> There has been some discussion on the list in the past about whether the
pianist can actually feel the hammer hitting the string.  The transmission
of this impact feel back to the key is probably different for aluminum and
wood rails.  Which would be superior I suppose is an open question.  If it's
aluminum, then it becomes a tradeoff between this feel and the noise
associated with the aluminum rail.
>
> Also, the letoff feel that is detected in the key I assume is coming
through the jack, whippen, capstan, and into the key.  Whatever impact
transmitted through the letoff button, rail, and frame to the key is
insignificant.  If that is the case, I can see that it could be a good idea
to isolate the letoff buttons as much as possible from the brackets and
frame to prevent the noise problem that I encountered on the CF-III.
-----------------------------------

I rather doubt that what you feel at the key would be all that much
different in either case. Anything your fingers are physically capable of
picking up would be pretty low-frequency, high-magnitude stuff which
probably wouldn't be damped much even by the most punky wood. The bothersome
action noise is typically fairly high-frequency stuff that is readily
transmitted by aluminum but tends to be absorbed, or damped, by wood.


>
> >  I once encountered an
> >action key frame resting on three strips of felt--one each for the front,
> >center and back rail nicely set into a machined recess. I don't recall
> >knowing enough about piano function at the time to properly evaluate the
> >system in terms of action efficiency, but it was a quiet action.
>
> I would worry about this dampening the transmission of vibration to the
keys, which I mentioned above.  Were the strips of felt wider than the
action rails?  In other words, was all the weight of the action supported by
the felt strips.  If so, I would also worry about stability of the
regulation.
--------------------------------

I don't recall there being any problems of this kind. If memory serves, the
felt strips (actually woven felt cloth) were about 25 mm wide. One each
under the front rail, center rail and directly under the capstan line, not
the back of the back rail. (I've no idea just how significant that was.)

I expect that any instability would work itself out in the first few months
as the wool fibers settled themselves in. After that I would expect the
setup to be fairly stable.


>
> In my original post I also talked about metal flanges, but you made no
comments on those.  How do you think that these would affect action noise?
What I had in mind was not something like the brass flanges of various sorts
that we have seen in actions.  But rather a direct replacement of a wood
part with a metal part.  As an example, a whippen flange made of aluminum
having the same dimensions as a conventional wooden flange and having a felt
bushing of the same sort as the wooden flange. If these were mounted on a
wooden rail do you think that they would be noisier than a wooden flange
mounted on the same rail?
>
> Phil F

Well, I have no experience with them other than with early Chickerings. And
those were brass which at least has the advantage of mass.

I expect aluminum flanges would be some noisier, especially as the felt
(bushing) takes on compression-set over the years and leaves room for a
slight amount of slop. Wood is inherently a better damper. Though, I suppose
the argument could be made that the transmission path is so short between
the flange tongue and the edge of the rail that there would be no practical
(audible) difference.

On the other hand, how often have you come across hammer flange screws that
were slightly loose. Enough that the flanges had to be moving slightly each
time the note was played. Yet there was little or no audible clacking or
clicking. I expect there would be some of both with an aluminum flange. Of
course, on yet the other hand, without the expanding and contracting wood
fibers the screws might not loosen up in the first place.

Del