[pianotech] Tuning the duplex sections

[John Delacour]

At 20:25 -0800 12/03/2011, Delwin D Fandrich wrote:


>Yes, I've heard the bit about string longevity once or twice in the 
>past. On first blush it sounds like a good theory until you consider 
>the--what?--millions of vertical pianos out there with sharp and 
>short string deflection angles that are not breaking strings with 
>any great regularity. Nor are they particularly noisy in spite of 
>what are sometimes very rough V-bar surfaces.

There is one over-riding cause of string breakage and that is 
excessive tension.

It's worth mentioning, not for the first time, that friction is a 
function of the "normal force" and the coefficent of friction of the 
two materials involved.  The area of contact makes no difference, so 
whether the surface of a V-bar is rough or smooth, tightly radiused 
or almost flat, has very little effect on the friction.  Change the 
V-var from cast-iron to mild steel and then you will find a 
difference.

JD