Schiedmeier Pianos and under bridge structure

[John Delacour]

At 6:36 am -0700 6/7/07, David Love wrote:

>The only issue about whether this really contributes to stiffness is that
>the underside bridge structure is tunneled out, as it were, in order to
>allow the ribs to pass through the structure untouched.  While there remains
>a thin piece of wood below the rib at those points, I don't imagine there is
>much stiffness to the overall structure.  I don't know if I'm painting a
>very clear picture.  The piano, btw, has more than adequate power.

Here is a picture of the Grotrian, which is the same.  If you want to 
find out how stiff the structure is in spite of the the tunneling for 
the ribs, cut some tunnels like that in a piece of 1 x 1 and glue 
that to a flexible 1" lath.  You will discover the result is not much 
less stiff than if you had not cut the tunnels, just as square tubing 
and I-beams are stiff without the need for the hollows to be filled. 
An engineer would be able to tell you exactly how much difference it 
makes and the maths that determines it.  If added mass were the 
function of the under-bridge, they would not need to go to the 
trouble to make it like this.

Unfortunately it was the end of a tiring day when I remembered to 
take the pictures and I forgot to measure the heights of the bridge 
below and above the soundboard, but I reckon the total height 
excluding the soundboard must be nearly 55 mm, probably equivalent to 
a standard bridge about 50 mm high.  As I said, the Grotrian bridge 
is also unusually wide.  My feeling about Grotrians of this period 
has always been that they are _too_ stiff.

JD





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