Open face vs. closed face pin blocks

[Phillip L Ford]

On Sun, 19 Aug 2001 17:07:07  
 Delwin D Fandrich wrote:
>
>----- 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.

---
I think you're right.  I haven't seen one of these pianos in quite some
time.  I think I've reversed things (inverted things?) in my mind over
the course of time.
---
>
>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.
>

---
Once again, you're probably right.  It may be more an issue of strength
than stiffness.  Given the amount of string load and the spans of any
particular plate design there has to be a certain amount of material to
meet strength requirements.  If that material is there then whatever
stiffness it turns out to be may be enough.  Lesser stiffness may just
mean more tunings to stabilize the piano.  This brings up the topic of
plate struts or braces.  If stiffness is not really an issue, then are they
really necessary if you can design a plate without them that has the
necessary strength.  I have seen Broadwood pianos with their so called
'barless' plate and they have a good sound.  I've only seen small ones.
I've never seen a large one, spent much time with any of them, or tuned
or pitch raised one, so I don't have anything like a definitive judgement
on them.  But it seems a good idea in some ways, since the tone on a
piano with a conventional plate always seems to deteriorate somewhat
near the struts.  It may be that a piano without plate struts would take
more tunings to stabilize, but once stabilized would be just as serviceable
as a piano with a more conventional plate.
---
>
>
>>      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.
>

---
Good point.
---

>
>
>> 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
>
---
No, I'm not familiar with these, but it sounds like a good idea.  I've thought
that perhaps some sort of engineering plastic such as used for bearing
material (say Rulon) might be appropriate for this application.  As you say,
it's hard to say with some empirical data, but I think it might be a worthwhile
topic for exploration.
---

Phil

























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