How to adjust glocken in Steinway D

[Delwin D Fandrich]

Kazuo Yoshizaki wrote:
> 
> Dear sirs,
> 
> I have posted the following question to rec.music.makers.piano but have
> had no reply. Please e-mail me if someone knows this. Thanks.
> 
> --------------------------------------------------------------------------
> 
> The other day, while I was netsurfing, I happend to find a page by
> Japanese Piano technician.  He has been rebuilding Steinways for years
> but obviously looking for a correct adjustment method for "glocken", the
> peculiar shaped brass part supporting the bell or the plate nosebolt in the
> treble area, which is attached to the rim. He once visited Hamburg factory and
> asked a craftsman there but he says his answer was not quite clear.
> He assumes adujustment is necessary before and after stringing, but doesn't
> exactly know what torque to apply to the screw/bolt.
> Another question is about a wooden bar (1/4in thick) placed inside the corner
> of the rim near the glocken just under the soundboard, of which shape is
> almost the same as the soundboard ribs. What is the purpose of this part?
> 
> yoshi@kobe.hp.com

To Kazuo Yoshizaki

I kept hoping that someone else would respond to these questions, but my
screen is blank. 

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I certainly have no official word from Steinway on either of these two
questions, but I’ll give it a shot to get things started.

I assume that “glocken” is the German nomenclature for what I have
always referred to as the “bell” or “rim-bell.” The book “Piano Parts
and Their Functions” states that this part “...[gives] rigidity to this
part of the piano [rim] which lacks the support of wooden braces normal
to other areas of the rim.” I don’t fully agree with this explanation.
The rims of both the Model B and the Model D Steinway in this area are
quite massive and more than adequately rigid. The material used is sawn,
hard maple veneers, not “select hardwood.”

I have analyzed the motion of a Model B plate in this area with the
coupling bolt both in place and with it removed. Both power and sustain
measurably drop off when the bolt is removed. Tests with an
accelerometer mounted on the plate surface between the bolt hole and the
hitch pins in this area revealed that quite a lot of energy was lost to
the plate with the bolt removed. Replacing the coupling bolt reduced the
amplitude of vibrations in the plate and brought back the power and
sustain back up to their normal levels.

Steinway, in the past, has been less than forthcoming about the proper
method of adjusting this bolt. (I don’t know if this is still the case
or not. I’ve not check for many years.) Rebuilders have pretty much had
to work out their own procedures. My own procedure is based on my
understanding of the function of this part and not on any instruction or
guidance from Steinway. This procedure follows:
    1)  Be certain that the bolt threads are completely clean.
    2)  Substitute a self-locking nut in place of the original. The type
I use has a nylon plug which keeps the nut from loosening up even if the
parts vibrate. A lock washer is neither necessary nor desirable, so...
    3)  Do not use any washer between the nut and the bell.
    4)  Set up a dial gauge to measure the elevation of the plate. The
actual plate elevation is not important, you will be looking for plate
movement. I place mine to read about half-way between the bolt hole and
the hitch pins.
    5)  Install the bolt and nut.
    6)  Tighten the nut until you note a 0.5 to 1.0 mm deflection in the
elevation of the plate. Stop! Don’t touch it again.

Whether or not this is the “right” way to adjust the coupling bolt I
don’t know. I can say that it is consistent and it works. It
accomplishes the intended purpose (as I understand it) of damping the
vibration level in the plate. At least as much as is possible with this
technique.

The wood strap between the rim and the belly rail is there to help
stabilize the belly rail. The downforce on the bridge from the strings
is ultimately transferred to the rim and the belly rail. Mostly the
belly rail since the bridge is located much closer to the belly rail
than it is to the rim. This pressure has a tendency to rotate the belly
rail forward that is counter-acted by this strap. 

The forgoing are the short explanations of what these parts do, but this
is getting fairly long and it’s time for me to shut up and go to work.

Hope this helps.

ddf