Ron Nossaman wrote:
> . . . About ten or twelve years ago, I was doing some tuning work for a Baldwin dealer who has since gone on to less
> stressful employment. He had been getting complaints from the floor tuner about the pin torque in a new SD-10 (9'). I took
> my torque wrench over and we went through the piano together taking readings, and making notes. This was in the Summer, and
> the readings ranged from just at 300 in/lb to about 25. All of the low torque readings had pins riding the plate, but not
> all the plate riders had low torque
> readings (just to confuse the issue). We called Baldwin and talked to Alan
> Vincent, who was the "Technical Interface" at the time. He said that they
> carefully checked torque readings at the factory and fixed anything that
> read over 300 in/lb. He didn't mention raising low readings. I don't know at
> what torque the plastic deformation limit is exceeded in a 2/0 tuning pin,
> but I doubt it's an awful lot higher than this. Anybody know? Mr. Vincent
> also staunchly defended and dismissed the absence of plate bushings as
> "traditional" and had a few things to say about the pinblock as well. His
> story was that this block was chosen because of it's dimensional stability
> with humidity changes. In other words, the changes in pin torque between
> Winter and Summer will be minimal. This was to make the tuning easier and
> more stable, and the block should last nearly forever. Admirable intent! He
> also maintained that one couldn't expect any better uniformity of pin torque
> in a production situation because they couldn't take the time to custom fit
> each individual tuning pin as one person could in a small shop. This was
> news to me. I wasn't aware that a one person shop could take the time to
> custom fit each individual pin in a block when rebuilding and still feed the
> employee. Interesting concepts. Not getting any help from the fountainhead,
> we decided to wait and see what Winter brought.
>
> We attacked the piano again in November with my torque wrench and found
> readings from a high of about 225 in/lb to lows below 10. So much for
> dimensional stability. He eventually sold the piano somewhere out of state,
> so I don't know how it fared after that.
>
> So that's what I've got against the Baldwin pinblock. It doesn't leave the
> manufacturer enough margin for error to work well in a production
> environment. With the best of all possible intentions, and lavishing much
> more care than is economically feasible, they couldn't produce a product
> with uniform tuning pin torque, using this block, even with bigger plate
> holes or bushings. Perhaps with tapered pins like the old Vose.
>
> That's also why I use Delignit. There is a greater margin for error so I am
> not required to supply a degree of perfection I'm not capable of. It makes
> me look better than I am.
>
> Are we havin' fun yet?
>
> Ron
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Back in the early eighties I was curious about the material used to make Baldwin pinblocks. So I did some study and asked
some questions. The following is from a paper I wrote at the time about my findings. It was never published (actually, it was
never submitted), but it might be of some interest here.
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THE CONSTRUCTION & CHARACTERISTICS OF
COMPRESSED–IMPREGNATED WOOD PRODUCTS
The process used by Baldwin to make their grand piano pinblocks is a slightly modified version of one developed during the
1940's to make a resin-treated compressed wood product known as "COMPREG" - or "COMressed, imPREGnated wood. A paper written
for the U.S. Dept. of Agriculture by the Forest Products Laboratory in 1951 discussed the development of this process and the
characteristics of wood based products made in this manner. This material was originally developed to form the engine mounts
(stringers) found in wood hulled mine sweepers. Being non-magnetic, it would not trigger the mines that were designed to
detonate in the presence of ferrous metals. It had the advantage of being harder and more reliable than brass in this
application.
Compreg is a treated wood product that is made of wood and resin-forming chemicals (typically phenol- or
resorcinol-formaldehyde) that act as plasticizers for the wood so that it can be compressed under high pressure to a specific
gravity of 1.0 to 1.4. Several different resins were tried while the process was being developed, but the most successful
was, and still is, water-soluble phenol-formaldehyde resin.
In making Compreg, veneers are treated with water-soluble phenol-formaldehyde to a level that will result in a resin content
of 25 to 30 percent based on the ovendry weight of the wood. The resin is allowed to dry without curing at temperatures
below 30º C (approx. 175º F). The resin is cured later during the heating and densification (compression) process. Panels
are made by heating and compressing the veneers to a specific gravity of approximately 1 to 1.4. In the original Compreg
process, temperatures of 150º C (300º F) and pressures of 1,000 to 1,200 lbs/in2 were used.
The Baldwin process varies from this somewhat and uses both lower pressures and lower temperatures, hence, the density of the
Baldwin pinblock is lower than the maximum that the process is capable of, but it is still quite high.
The resulting material is very nearly a fiber-reinforced plastic (FRP) material and has some characteristics that are more
commonly found in FRP products than it does with wood. Indeed, with the exception that kraft paper is used instead of maple
veneer, the process is very similar to that used to make Formica and other such "plastic laminates".
Compreg does have certain characteristics which would seem to make it a good material for piano pinblocks:
1) It is very stable when subjected to humidity and temperature cycles.
2) It resists cracking and splitting.
3) It has high compression strength.
It was probably these characteristics that led Baldwin to use the material in the first place.
Unfortunately, it has several other characteristics that, in my opinion, make it unsuitable for use as a piano pinblock
material:
1) Springback (after compression), or resiliency, is very low.
– A material with low springback will simply deform when compressed.
– When the tuning pin is driven into the pinblock it compresses the wood
and depends on the woods ability to "springback" to hold it tight and
maintain good, consistent tuning pin torque.
2) Hardness is much higher than normal wood, even maple.
3) Impact strength ("toughness") is much higher than that of normal wood, but
it is very susceptible to the variables of manufacture.
– The impact strength of the pinblock material is the quality that prevents
the pinblock from being damaged while the pin is being driven into the
tuning pin hole.
– The reduced impact strength, or toughness, of Compreg allows the
pinblock to be easily damaged as the piano is being strung.
4) Machinability is decreased. It takes on some of the characteristics of metal
and in some cases requires metal working tools for machining operations.
5) It is possible to burnish material to a very smooth, glossy surface.
– This is the characteristic that leads to "jumpy" pins in Baldwin grand
pinblocks after several years in use.
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Remember that this was originally written about 15 years ago. Since then I spent some time working for the company. And,
while I did learn a bit more about the details of how this pinblock material was made, my opinion of the material and its
suitability for use as a pinblock did not change very much for the experience. Now, if I could just get plate bushings made
out of this stuff... Ah, well...
Happy New Year one and all.
Del
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