Del,
While I will agree that the explanations given at Steinway are,
frequently, obnoxious sales pitches, and I have posted such here, I don't
think that the explanation given for the "Bell" which I referred to as
possibly having been received as the factory was such, and, after looking
carefully at several nosebolts this week, I believe this explanation very much
makes sense, although I would certainly take with a very large grain of salt
anything said by anyone associated with this factory in particular, and others
as well. As I indicated in the post I don't know for sure where I acquired
this explanation, but, if I, in fact, was given this explanation at the
factory, it would not have been by a sales oriented person but rather by a very
accomplished, widely-known and well-regarded technician who was very forthright
about the problems and virtues of the pianos produced at the moment.
A point in the post above indicates that the nosebolt, if adjusted
correctly, can and does in fact pull the plate down with the intention of
increasing downbearing, even if this is a risky course, and this, I believe, is
how it was intended to work. Obviously, as you say, the risk of breaking the
plate when this is done increases and this is the reason the factory ceased
giving specifications on this adjustment.
I have not seen the patent posted on this subject by Richard Breckne as
the posting came in with no data on my browser. However, I believe this is
pretty much what the patent indicates the device is for, judging from the
subsequent commentary about it. Of course, as the patent application is not
directly a sales pitch, I would take the applicant on his word as to what it
was and what it was intended to do. However, as you say, lets see what it does
actually do.
I believe this "bell" is simply, a strong cantilever, probably of cast
iron, at least originally, which was in a period of very high usuage of
castings, designed to resist an upward pull and it is of a design which
strongly suggests this is the case. This week I have looked at three such
nosebolts, two installed on "A"s from the 1890's and one from a 5 year old B.
These are castings, apparently, of iron, probably of the same material as the
plate, although I don't know this for a fact; perhaps a different mixture was
used, but this seems unlikely at least at the time they were originally
designed. The three differ slightly, with the two from the 1890's being,
characteristically, somewhat larger than the later one.
Four functionally important features can be discerned upon inspection of
the so called "bell". They are: the conical shape or "bell" itself, the
large, 90 degree notch cast into it which is designed to fit the rim, the
number and placement of screws which fasten it to the rim, and the bolt itself.
The conical shape of the casting is plainly, a design feature to
strengthen the cantilever and to help it resist the moment created by the
upward pull of the plate. But this would also be the case were the bell being
driven downward by the bolt and the plate. The distance which the load must be
transferred, roughly, six inches mandates this. However, the fitting of the
base of the "bell" shaped as it is, to fit the rim in two dimensions, and its
method of attachment suggests the former is its intended function. This is
particularly, important, that is, it would be a more efficient design, were the
nut to be tightened and the plate flexed downward, resulting in an upward pull,
something that the assembly was evidently designed to resist as will be
indicated below.
Of course, the cantilever must transfer its load somewhere and how this is
accomplished is most instructive, in my opinion, as to its design purposes. It
is notched where it fastens to the rim. I don't mean to suggest it is worked
this way, but, rather, I believe it was cast this way. One part of the notch
fits the bottom of the rim; the other, much larger surface, fits the interior
side. There are, in all seven screws that attach the nosebolt to the rim in
the two dimensions of the notch. Five large, vertically oriented, screws
pass through the nosebolt and a spacer into the bottom of the rim and secure
this joint. Two more fasten the nosebolt to the interior side of the rim.
A set of critical observations can be made. These arise, principally from
the placement of the two screws that attach the nosebolt to the rim, and, to a
lesser degree, from the placement of the five screws attaching it to the bottom
of the rim and, finally, the shape of the notch itself.
The two that attach the nosebolt to the interior side of the rim are
located just above the lower edge, a location pregnant with implications.
These two screws are, at least on the A's, smaller than the other ones,
indicating, at least to my mind, the designer's expectation that the five
screws on the bottom rim would take the principal load, which they do. These
five are not, however, very effective in resisting a moment experienced by the
bell caused by forces on the bolt as they are a significant distance away from
the bolt. The way in which this moment is dealt with is most instructive.
It is obvious that the designer expected the two bolts attaching to the
side of the rim to resist an upward pull as they are placed very close to the
lower edge of the rim and this in conjunction with the notch itself, of which
the area in contact with the interior side of the rim is most effective. Were
the nosebolt being driven downward then this would be the most ineffective
position conceivable due to the leverage of the cantilever, and the moment
arising from this could, possibly, indeed probably, result in the nosebolt
being torn loose from the bottom of the rim and failing.
The correct placement of the two screws attaching the nosebolt to the
interior side of the rim in the case of a downward force exerted upon the bolt,
would be on the higher side of the nosebolt to effectively resist the moment
associated with such a force, particularly if only two screws are to be used,
and, it is likely more than two would be necessary in this case. As I said,
however, they are placed on the lower edge of the rim, obviously to resist the
moment associated with an upward pull such as would be exerted by the plate
were the nut tightened. The fact, that no more are needed shows an admirable
design efficiency. There are, at least on the pianos I examined, no screws
whatsoever in the upper part of the notch which transfer the load to the
interior side of the rim, as would be expected and are necessary were it
designed to resist a downward force exerted upon it.
Furthermore, the notch itself can only work effectively against an upward
pulling force which it does and the screws are placed to be most effective in
dealing with a moment arising from such a force. By such means, at least in my
opinion, is the functional aspect of this indicated.
On a different but associated subject. It appears to me the factory, upon
redesigning their pianos in the 1870's, discovered, or at least gave some
thought to the possibility of there being an instability, either of the plate,
the bracing, and the rim, or any and all, and took additional, post-design
measures to deal with it. These measures are the small stiffener made of wood
running from the belly rail to the first beam/rim junction and the brace bolted
upon the top side of the plate in the B, C, and D, recently discussed here.
Perhaps, and this is merely speculative, the "bell" nosebolt was also an
attempt to deal with this instability.
Other companies, for example an older Yamaha GE-2 I saw this week also
have a similarly located nosebolt although without the bell whose function
appears to be to hold down the plate. In the Yamaha, this is simply a large
wood screw which passes through the plate and board and is attached directly
into a beam underneath.
As you know, I don't subscribe to the flexural view which you and others
advocate and, hence, would not find the mass-coupling idea, although
interesting, useful or necessary in this context. Although the plate is, no
doubt, vibrating I don't believe it vibrates in such a way to require such
massive damping as the use of the "bell" were such the case, would suggest. .
Regards, Robin Hufford
Delwin D Fandrich wrote: t
> ----- Original Message -----
> From: "Robin Hufford" <hufford1@airmail.net>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: September 17, 2002 12:02 AM
> Subject: Re: [pianotech] Grand Treble Bell
>
> > Richard,
> > I was informed, I think at the factory, or perhaps I read at some
> point in the PT
> > Journal, that the nosebolt at the "Bell" was intended to be an adjustable
> mechanism
> > to preserve downbearing as the board changed after leaving the factory.
> Also,
> > Steinway eventually refused to make recommendations as to how much
> tightening was
> > recommended, apparently understanding the risk of breaking the plate or
> encountering
> > difficulties in this regard.
> > Regards, Robin Hufford
>
> Robin,
>
> Over the past roughly 40 years I've heard Steinway factory representatives
> give three or four different renditions of what the bell does. And, yes,
> this is one of them.
>
> Until someone--anyone--can explain to me just how adjusting this thing will
> have any effect on downbearing other than by bending the plate--a
> problematic and potentially dangerous process at best--I'll stick with my
> own proven theory.
>
> I can only add that none of the rest of their explanations have made any
> more sense than this one does.
>
> Del
>
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