Bridge pin spacing

[John Delacour]

At 4:15 am -0500 13/8/06, Conrad Hoffsommer wrote:

>Looks like a Baldwin SF10.  If it is, you'll also finds that the 
>string sizes drop back across that break. (The size on the treble 
>side is larger than the size on the bass side.)  Both bridge pin 
>spacing and string sizes are scaling solutions to having a bridge 
>which doesn't deflect from a straight line when going under a strut. 
>(methinks)

Supposing that the curve of the bridge is continuous under the bar as 
you say, which seems likely, then I would guess that at the point in 
the middle of the picture where the front pins are moved back there 
is an increase in wire gauge.  The picture does not show what happens 
to the bass side of bar, and I've never seen a Baldwin, but almost 
certainly the front pins are again moved forward and the wire gauge 
remains the same on the notes each side of the bar.

If you consider a "standard" piano with the usual dogleg in the 
bridge under the bar, each time you increase the wire gauge going 
down the scale the tension drops, to rise gradually towards the next 
gauge change.  By increasing the speaking length as the wire gauge is 
increased, as happens here, the tension is increased to a value 
closer to the tension on the upper note strung with the finer wire.

The increasing of the speaking length at the point shown in the 
picture is a preparation for the second tension adjustment that must 
take place as the bar is crossed.

JD