Unusual rib structure?

[Ron Overs]

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Sarah and all,

>Thanks for the feedback.  Rib crowned?  Interesting.  What 
>characteristics suggest that?

=46rom the image, it looked as if the rib depth increased some towards 
the centre. However your measurements discount this. When the ribs 
are crowned the desired radius is machined into the top surface of 
the rib. This will result in a rib which is deeper in the center and 
shallower at the ends.

>  I gather that rib crowning is a more recent development in piano technolo=
gy?

I don't know whether any of us can definitively say when rib crowning 
was first practised, but certainly it is more widely, though by no 
means universally practised today. Del is probably the best to 
comment on this, but you can be sure that not all piano makers will 
have divulged all of their manufacturing processes. The piano you 
have demonstrates that there are many different approaches out there. 
No one company or individual has a monopoly on good ideas - contrary 
to what some may claim.

>Is there some place I could read a brief history?

The list archives is probably the best source. The two have most 
discussed the procedure on this list would be Del and Ron N.

>  I measured the ribs for you.  I wasn't perfectly exact in my 
>measurements (didn't have the time), but if you want more exact 
>measurements, I'll get them for you later. 

Thank you for your trouble. The measurements you provided are more 
than adequate.

>Aside from the tapered ends, the dimensions are constant throughout 
>the length of each rib. 

This would lead me to conclude that the ribs were not crowned. It is 
possible that they may have planed the ribs to achieve a uniform 
thickness after assembly, but it would nonetheless be unlikely.

>The bottom of each rib is rounded slightly 

This is normal.

>  I didn't measure the lengths of the tapers.  The height and width 
>of the ribs (in mm) are as follows (in order from treble to bass):
>
>rib    h    w
>1    difficult access
>2    19    19
>3    21    21
>4    21    23
>5    25    24
>6    25    25
>7    26    26
>8    ?    26 (difficult access)
>9    28    26
>10    28    26
>11    28    26
>12    27    26
>13    27    26
>14    26    26
>15    26    26
>16    26    26
>17   difficult access
>18   difficult access

So the middle order ribs are quite deep, even for modern piano making 
standards. Its interesting that they have gone the B=F6sendorfer 
Imperial route, by chosing to make the longer ribs wider than they 
are high (actually 28 w by 26 h is very similar to the Imperial - not 
a good idea). This will yield a significant mass increase for only 
moderate gains in rib strength. They would have done better with a 
height of 28 and width of 26. But so often, piano makers are 
frightened to step off the beaten path into new territory.

>
>You are correct that the bass is rather dark.  Of course I like it that way=
=2E

Indeed. I find dark toned low basses more interesting than usual fare 
we get from the current crop of concert grand makers.

Ron O.
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_______________________

OVERS PIANOS - SYDNEY
Grand Piano Manufacturers

Web: http://overspianos.com.au
mailto:info@overspianos.com.au
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