Phil,
Phillip Ford wrote:
> >>Date: Sun, 28 Apr 2002 02:00:28 -0700
> >>From: Robin Hufford <hufford1@airmail.net>
> >>
> >>> It does not seeming nitpicking to me, of course it is the centripital tension
> resonator. I was thinking of the Yamaha I described in the post and the torsion
> it had undergone and the device magically became a torsion resonator, something
> which I did not notice. I was aware that the patent had issued to Gertz but have
> not seen it.
> >Not to nitpick, but I believe they call it a tension resonator (actually I
> >think M & H refers to it as a centripital tension resonator. Not that the
> >name affects what the thing actually does, but at least it gives an
> >indication of what the inventor thought it was supposed to do. The patent
> >for this thing was given to Emil & Richard Gertz. It is patent number
> >658,985. It's an interesting patent and there are several claims, many of
> >which have to do with various aspects of piano construction and not
> >specifically with the 'tension resonator' (by the way, that name does not
> >appear in the patent, so I'm assuming that it's a M & H creation). Among
> >the claims:
> >
> >1. A symmetrically shaped grand piano.
> >2. Inner and outer rims are separate with a clearance between them and
> >both are connected to a bottom board so that the inner rim 'is isolated
> >from the outer rim and the vibrating capacity of the sounding-board is not
> >in any way interfered with'.
> >3. The tension resonator is attached to the inner rim and the intent was
> >that tension be applied to the rods so that 'every portion of the rim and
> >its corresponding section of sounding-board can be compressed and
> >regulated at will'.
> >
> >There are various other claims as well.
> >
> >I far as I can tell the 'tension resonator' was the only part of this
> >patent that M & H adopted.
This I wholeheartedly agree with. The operation of an actual "centripital tension
resonator" as described in your post of course would induce and maintain crown and
could be most interesting. .
>
>
> >
> >
> >
> >I don't agree with this. If you assume that the rim braces are necessary
> >to supply stiffness to the rim then this device can serve just as well as
> >wooden rim braces. Perhaps better because, as Del has pointed out, it
> >gives more support to the straight side than a conventional wooden rim
> >brace configuration. I don't see that both are necessary. It's like
> >wearing a belt and suspenders. This metal device (or a device made of
> >other high strength material like some sort of composite) also takes up
> >much less room than the equivalent wooden rim braces for the same strength
> >and stiffness. There could be some advantages to this:
> >1. Since a lot of the sound comes from the bottom of the soundboard you
> >wouldn't be blocking as much of its area with the massive wooden braces.
> >2. The framing wouldn't need to be as tall so perhaps the rim could be
> >made less tall which might help the proportions of the piano aesthetically.
> >3. The plane of the centroid of the rim braces could be closer to the
> >soundboard plane so that there is less tendency for the rim to twist due
> >to soundboard input.
> >
I don't think the bracing on the pianos with the resonator are signifcantly less
than on highly quality pianos that don't have the device, which seems, to me, to
weaken the supposition that the resonator as used by M&H could have been a stand-in
for bracing. For example, I took a little time and measured the bracing on an
1893 roundtail Steinway 88 note A with the dog-leg bridge, the piano that is the
prototype for the AA ( This can be a very interesting comparison which I don't
have time to go into, at the moment.) and similar measurements from a 1906 M&H AA.
While the layout of the bracing of the two pianos is substantially different, the
volumes are, in point of fact, quite close one to another. The Steinway, of
course, has the typical quasi-radial set of three beams originating at a cast iron
fixture attached to the frame member in front of the plate wedge at the belly rail;
the M&H AA has two longer, more nearly parallel beams originating from the
homologous frame member at the belly, however both beams proceed to the tail of the
piano and, on the way, cross and are lapped with a smaller transverse beam a little
bit past midway.
Attempting as much accuracy as could be had in a quick desultory effort, the
volume of the beaming, excluding gussets and the transverse framing member at the
belly rail, in the M&H was 1539.32 cubic inches; that of the Steinway, similarly
taken, was 1588.27 cubic inches, a difference of, roughly, three percent. Adding
to these figures the volume of the transverse belly rail framing member one arrives
at a total figure for each of: M&H: 2599.32; Steinway 2411.92. As you can see,
these figures suggest a reasonable equivalence of framing in the context of the
supposition of the tension resonator allowing less bracing and, to me, render this
hypothesis insupportable. Additionally, the BB is very heavily braced, probably
more so than the S&S B and, possibly, such is the case also when the comparison is
of the M&H A to a Steinway M.
>
>
I am not saying I don't like the idea necessarily. In fact, I may: I don't know.
>
> As to its ability to prevent spreading of the rim, surely the plate
> >> is at
> >>least equally efficacious, if not more so in this regard than the resonator.
> >
> >
> >The tension resonator is directly attached to the rim and is more or less
> >centered on the centroid of the inner rim. It should provide substantial
> >support for the rim. The plate is far above the rim. If load were to be
> >transferred from the plate:
> >-At one end the load would have to bend through the pinblock over to the
> >rim and then shear down through the rim to its center.
> >-At the other end the load would have to transfer to bolts fitted in loose
> >fitting holes and then transfer from the plate to the rim through the
> >bolts in bending.
> >
I don't think the holes are that loose fitting, nor in a high quality piano the
bolts flimsy and, particularly, in comparison to the normal loads placed upon the
rim. These, surely, must be of such a magnitude that (stipulating for the moment
to your idea that the transfer of loading is inefficient) relative to the
capabilities of the plate and its fasteners significant strengthening of the rim
occurs, notwithstanding the putative inefficiency of the fastenings.
>
> >Neither of these paths is very efficient, but the bolts would be
> >especially flimsy for this type of loading. In my opinion, the plate is
> >supporting string load, but is doing very little to support or add
> >stiffness to the rim. I would think that the bolts are effective for mass
> >coupling the plate to the rim (or vice versa). They are probably also
> >effective in keeping the plate from bowing up under string load (since the
> >string plane is above the plane of the plate).
> >
> >> In
> >>highly traumatized pianos that have suffered substantial impacts, one can
> >>easily
> >>see the effects of the structural integrity of the inner rim/plate assembly,
> >>operating as a unit, as an opening can frequently be found developing
> >>between
> >>the laminations that comprise the inner rim and those of the outer rim.
> >
> >
> >I would think that this has more to do with the fact that the glue joints
> >between inner rim plies and outer rim plies are stronger than the glue
> >joint between the two because of the nature of rim construction.
>
Properly effected, the joints should have equal strength, regardless of whether the
inner and outer rim is laid up together as at Steinway, or the outer rim
subsequently attached as at Mason & Hamlin, although I will concede that, as a
practical matter, this may, particularly in this day and age, be hard to achieve.
. I still maintain that the frequent developing separation of the inner and outer
rim, whether traumatically induced as I described in the post, or occuring in a
more normal, slower fashion is proof positive of the essential structural integrity
of the strungback, that is the inner rim, plate and pinblock, relative to the outer
rim.
> >
> >> At the time of its development however, the stability associated with a
> >>continuous rim was, as you know, a relatively recent development and I
> >>think a
> >>case can be made that there were many older pianos then in existence which
> >>indeed had unstable rims, a fact which facilitated the commercial utility of
> >>the concept of a remedy, hence the torsion resonator and its development.
> >
> >
> >I think it had more to do with the belief that the soundboard needed to be
> >in compression to function properly.
> >
This belief, although widespread was by no means universal. I can't give the page
number without a lot of reading to find it but I repeat an interesting comment
quoted in "The Steinway Saga" by Forsythe. I read this book, again, recently and
the quote is taken from a letter sent by Theodore Steinway to his brother William
the managing partner in New York. With regard to soundboard compression the book
quotes Theodore as remarking with a simple word: "Humbug". This from the man
considered by many to the hi-tech founding father of the modern piano, a device
which was very hi-tech for the time and particularly with regard to his
contribution to his company's products which have been widely emulated.
Regards, Robin Hufford
>
> >> Once
> >>in use, it seems to me it would be a great sales risk to forego such an
> >>arcane,
> >>obvious emblem of technical superiority, whether actually effective or
> >>not and
> >>so it continues. I, for one, cannot place much stock in a sales pitch
> >>placed on
> >>line by a company whose purpose in doing so, naturally, is not merely
> >>informative.
> >
> >>Regards, Robin Hufford
> >
> >Since when are sales pitches meant to be informative? When was the last
> >time you saw a car ad in which they actually talked about the technical
> >merits of the car?
> >
> >
> >Phil F
>
> Phillip Ford
> Piano Service & Restoration
> 1777 Yosemite Ave - 215
> San Francisco, CA 94124
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