Open face vs. closed face pin blocks

[Delwin D Fandrich]

----- Original Message -----
From: "Phillip L Ford" <fordpiano@lycos.com>
To: <pianotech@ptg.org>
Sent: August 16, 2001 10:51 PM
Subject: Re: Open face vs. closed face pin blocks


>      I would like to amend what I said earlier.  I said that if I were
building
> a piano I would lean toward an open face pinblock design.  What I
> think I would prefer to use is an open face pinblock set in a plate
> that is closed beneath the pinblock.  I believe Chickering (and others?)
> used such a system at one time.  It seems to me that you get the tuning
> advantages of the open face design but you get the stiffness of the
> closed face design because you have the full depth beam in the pinblock
> area of the plate.

I've not encountered any grand pianos built this way. Chickering and others
used pinblock inserts that came up from the bottom and were essentially
closed-face blocks with a separate block for each section.

Knabe (I think) and, perhaps, a few others, did make vertical pianos with
the pinblocks installed as you describe.

I'm not sure all that stiffness is really required. I go back to those grand
pianos using what we now call three-quarters plates and open-faced
pinblocks. There was no iron at all much beyond the agraffe/capo d'astro
line.



>      Another topic which I didn't bring up before was plate bushings.  It
> seems in theory that a closed plate design with plate bushings should
> tune like an open face design.  The distance of the string to the plate
> could be the same as the distance from the string to the pinblock in
> an open face design.  However, in my experience pianos with plate
> bushings feel more or less like any other closed face design without
> plate bushings.  Perhaps this is because of the poor quality of the plate
> bushings.

Regardless of how well made the bushings might be, if they are made of wood
there is going to be a problem. The bushing, which is hygroscopic and which
swells and shrinks with changes in ambient relative humidity, is captured
between the iron plate and the steel pins. An arrangement doomed to failure.



> I wonder what would be the result of using bushings of good
> material (say laminated maple) that fit closely to the plate and are glued
> to the surface of the block.  The holes are then drilled through bushing
> and pinblock at the same time so that the bushings essentially become
> part of the pinblock?  I can imagine that it would be a manufacturing
> nightmare.  But it might give a closed face pinblock that tunes like an
> open face pinblock.

Are you familiar with the phenolic bushing used by Knight? At least it was
experimented with by Knight some years ago. I don't know if pianos were ever
produced by them using the device.

I obtained a few from them back in the late 1980s and experimented with them
some but was unable to generate any interest in any kind of full-scale test.
It would have been necessary to obtain one or two plates with the tuning pin
holes drilled somewhat undersize. They seemed like a good idea, but it's
hard to tell what would actually happen in practice without practice.

Del