Killer Octave & Pitch Raise

[Overs Pianos]

Greetings Arnold,

Nice to see you posting.

At 1:10 PM +0100 13/2/05, Arnold Duin wrote:

>. . . Extra compression along the grain can also 
>be achieved by gluing the long bridge (straight 
>not curved) after the board is glued in.

Are any manufacturers fitting the bridges to the 
panel after the board is glued in? I would be 
worried about achieving good clamping pressure 
between the bridge and the panel in the high 
treble in particular. Furthermore, it would not 
be possible to fit sound board buttons in the 
high treble, should one want to.

We use a sound board button between each rib with 
a clamp at each end of the long bridge, gluing it 
to the panel before fitting the board to the 
case. One manufacturer has a rather elaborate jig 
which holds the panel to the shape of the rim 
perimeter while the bridges are fitted. I think 
this is an excellent idea, if you can afford to 
accommodate a jig for each model in the factory.

I am currently doing a remanufacture of a 200 cm 
(6'8") Kawai KG5. This piano will get the first 
treble bridge we have built with a reduced height 
of the treble bridge extended out, to over the 
inner rim, in the treble corner. Bösendorfer has 
done this for many years, and I am beginning to 
suspect that it might be a good idea. We have 
been making our bridges quite bulky in the treble 
(35 mm wide) to increase mass and stiffness (and 
tapering to thinner at the low end). Running a 
reduced height of the bridge out onto the inner 
rim would seem to be an easy way to pick up extra 
stiffness in the very top for not much effort.

I have noticed that Bösendorfer seem to be 
getting, on average, slightly longer sustain in 
the extreme high treble, and I suspect the little 
bridge extension over the inner rim to be the 
contributing factor. Anyone else got any thoughts 
on this idea?

>Yet another approach is to glue a heavily dried 
>(cooked) bridge on the board first, before 
>gluing the ribs to achieve a crown and add some 
>extra stress.

Fazioli is one who must have fitted the bridges 
before the ribs on some of his instruments. An 
image in his colour brochure shows a model 156 
gluing jig for fitting the ribs, and there is a 
trench for bridge clearance in the bottom of the 
caul. However, when I was at the factory in 1994, 
he was fitting the bridges after the ribs were 
glued to the panel, and before the board was 
fitted to the case.

Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron@overspianos.com.au
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