Open face vs. closed face pin blocks

[Phillip L Ford]

Del,
     I agree that much of what I have said here seems like theoretical rambling.
In theory I believe that a case could be made for the closed face pinblock
but my personal experience has been, like yours by what I read here, that
I prefer tuning an open face pinblock and I haven't noticed problems with
tuning stability, tone, or power although my experience with these pianos
is not extensive.  Probably there is some lower limit on the amount of
stiffness required to give what we now consider good tone and acceptable
tuning stability and once you are beyond that it doesn't really matter how
you achieve it.  So, an adequate open face design is just as good as an
adequate closed face design and the choice between them comes down
to other matters, such as how you feel about ease or pleasure of tuning,
or how you feel about how closely you need to copy a Steinway design.
At this point I think that if I was building a piano I would lean towards an
open face design.
     I feel that a stronger theoretical case could be made for capo vs.
agraffes but once again my personal experience has been that there
are some fine pianos with agraffes all the way to the top so it's pretty
hard for me to say that the capo design should be better.  It's too
bad that there are so many variables that it's hard to isolate these specific
things so that they can be studied.  It would be nice (in some ways) to
build two pianos that were exactly the same except for the one thing that
you wanted to study. I can add this to my ever expanding wish list.

Phil

---
Phillip Ford
Piano Service & Restoration
1777 Yosemite Ave
San Francisco, CA  94124

On Wed, 15 Aug 2001 09:36:41  
 Delwin D Fandrich wrote:
>
>----- Original Message -----
>From: "Phillip L Ford" <fordpiano@lycos.com>
>To: <pianotech@ptg.org>
>Sent: August 13, 2001 6:04 PM
>Subject: Re: Open face vs. closed face pin blocks
>
>
>>      As I see it, with a closed face pinblock, the plate in the pinblock
>area
>> is acting as a beam - a Z section beam if you will (like an I beam with
>> a couple of pieces of flange missing).  The plate flange against which
>> the pinblock bears is one flange (or cap) of the Z and the upstanding
>> flange at the front end of the plate (along the stretcher) is the other
>> flange (or cap) of the Z with the portion of the plate over the pinblock
>> acting as the web of the Z beam.  The presence of this web allows
>> the entire section to work as one beam.  If this web is not there (as
>> in an open face pinblock) the two flanges work independently as separate
>> beams.  The bending stiffness of these two independent beams is
>> substantially less than the bending stiffness of the entire section
>> working as one beam.  In practice, on an open face pinblock, the
>> flange against which the pinblock bears will be the only flange
>> working (resisting bending) with the front flange in effect doing nothing.
>> So, there should be less deflection of the pinblock in the direction of
>> the string load with a closed face pinblock than with an open face
>> pinblock.
>
>While I agree with your analysis in theory, it doesn't seem to matter all
>that much in practice. Steinway plates are designed with a "horn" to couple
>some of the stress from string tension down to the belly. Baldwin, using a
>similar--though somewhat heavier--plate design, does not. Yes, the Baldwin
>plates deflect a bit as they are pulled to pitch, but it doesn't seem to
>matter much. Once at pitch they are quite stable.
>
>To carry this further we have to go back a bit. Several U.S. grand piano
>builders through the late 1800s and very early 1900s used what we would
>today probably call an "open-face pinblock coupled to a three-quarter
>plate." In other words, the plate butts up to the pinblock but does not
>overlap it. These plates have no front flange and there are no pinblock
>overbars. In general they do have relatively massive pinblock flanges. Even
>here, though, I've seen 'conventional' plates with more iron used through
>the pinblock flange section. We've had several of these pianos in our shop
>and after well over 100 years these arrangements seem to have stood up well.
>There has been little evidence of structural failure in the original
>pinblocks and once remanufactured and tuned to pitch (A=440) they do not
>show any more stress deflection than we would expect to see in a typical
>Baldwin-style plate. Obviously, the designers of these pianos understood
>something about stress loads and about supporting them. Some of these pianos
>have massive wood structures forming what we would probably now call
>stretchers but others do not, the latter being a bit more substantial than
>we would expect today, but not by much.
>
>
>
>> What effect this has on the tone and on tuning stability
>> would probably depend on just how massive the pinblock and plate
>> structure of the open face pinblock in question are.
>
>While I personally don't have enough experience tuning pianos with open-face
>pinblocks to give any kind of definitive answer on their long-term
>stability, I can say that they are certainly easier to tune. They
>pitch-raise easily and stabilize quickly.
>
>
>
>> I can imagine
>> it could have an affect on power, as some of the string energy
>> would be used in flexing the pinblock and plate.
>
>Again, this analysis sounds reasonable in theory and is one I have generally
>subscribed to for some time, but it doesn't seem to hold up in practice. To
>the best of my knowledge there has been only very limited comparison testing
>done to prove this notion. And when the two different types are compared it
>is with instruments that are quite dissimilar in many other areas of their
>design as well. It would be most interesting to be able to compare two
>pianos having identical designs except for this one area.
>
>I will say that my recent experience with several pianos using open-face
>pinblocks and several other pianos with all-agraffe string terminations has
>caused me to rethink much of what I thought I knew about both of these
>designs. We have recently remanufactured pianos of both types in which we
>installed my now-standard scaling and soundboard designs that were most
>satisfactory. I'd have been quite happy with the results regardless of their
>plate configurations. As to whether their open-face pinblock designs or
>their all-agraffe designs made them any better than their more common
>counterparts, I cannot say.
>
>Given this experience and my observations about the performance
>characteristics of both designs, for me, at least, the jury is back out
>reconsidering its earlier verdict. And I am definitely looking forward to
>working with both designs in the future.
>
>Del
>
>


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