[CAUT] killer half-octave

[Ron Overs]

Hello Don and all,

I have a clue as to ". . . why this happened". After considering the 
structure of these belly rails, I would be very concerned about 
connecting such a tension device. In my workshop, the solution to 
this soundboard-perimeter-support-stiffness problem has been to ditch 
the 'bell' and fit an extra back beam in the treble.

Take a look at the following image of a Hamburg model D from the 
60's, in the process of being rebuilt.

http://overspianos.com.au/stdctoff1.jpg

Notice the belly rail where the back beam connects with the belly 
rail. Now look at the members which are glued together to make up 
this belly rail assembly. The total thickness of the 
full-depth-section of this belly rail is a mere 30 mm wide. The pine 
piece immediately behind the belly rail, with the large knot in it, 
is the filler piece between the belly rail and the laminated piece 
which actually connects with the soundboard. It amazes me why a 
manufacturer, who goes to the trouble of building a rim with a solid 
85 mm overall thickness, would fit only a 30 mm thick belly rail to a 
concert size instrument. It is totally under-engineered. The addition 
of an extra back beam, coupled with the bent bass corner cut-off 
really helps to stiffen these cases to appropriate levels across the 
belly rail in the treble area. The dimensional size of this belly 
rail also goes some way towards explaining why this manufacturer 
chooses to glue the keybed to the belly rail.

Another practice which I find baffling is why some manufacturers 
choose to use weak-and-lossy pine for the connecting strip between 
the belly rail and the soundboard perimeter support strip across the 
belly rail. Quite a few manufacturers do this. It would seem to be a 
wonderful way to cripple the structural integrity of the soundboard's 
perimeter support.

Here's a second image which shows the extra back beam and the bass 
side cut-off, when viewed from the font of the piano.

http://overspianos.com.au/stdctoff2.jpg

Here's an image of our 225 grand piano's belly rail in the treble area.

http://members.optusnet.com.au/ronovers/oversno6.2.jpg

The full depth members of this belly rail assembly is made from two 
pieces of rock maple which are each 30 mm thick, making a total belly 
rail thickness of 60 mm. The piece which connects the full depth 
section of the belly rail to the soundboard-perimeter-support piece 
is also made from rock maple. The back beams are also made from rock 
maple, and there are two of them covering the treble sections. The 
treble is where we need stiffness and structural integrity, not at 
the bass/treble cross where the plate horn collects. The 
'tone-collector' myth is somewhat ironic, since the practice of 
running most of the back beams to the cross between the bass and 
treble makes this area stronger at the expense of the treble 
sections, which are the ones which really need it. If design people 
would pay more attention to structural requirements instead of 
pandering to piano-making myth and folklore, we might get to take 
contemporary piano design somewhere worthwhile while we're above 
ground. Please note that these comments are general in application, 
and not intended to be directed at a single manufacturer.

Ron O.

At 10:18 AM -0400 17/5/07, Donald McKechnie wrote:
>
>Be very careful with the tension resonator. The attached picture 
>tells why. I followed the instructions to the letter but the belly 
>rail was not up to it for some reason. I spoke to Bob Grijalva about 
>the problem and he said it was a first. No clue as to why this 
>happened. The funny thing is it appears to have had no effect for 
>the worse or better. I just left it in and has been there for about 
>a year. This piano is due a new soundboard so the belly rail can be 
>repaired then.
>
>Don
>
>Don McKechnie
>Piano Technician
>Ithaca College
>dmckech at ithaca.edu
>607-274-3908


-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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