Seating strings

[Ron Nossaman]

> If the force parallel to the pin is higher than the friction generated by 
> the normal force then the string will want to move down the pin.  If the 
> friction force is higher than the force parallel to the pin then the string 
> will want to stay where it is (even if it's above the bridge cap).

And when you throw in vibration from play, and the movements from 
thermal effects, the forces will overcome friction and the string 
will stay with the bridge cap. We know that over time, strings will 
render across the bridge, which takes overcoming friction  at the 
pins. That ought to work vertically at least as well as, probably 
better than, horizontally.


> On a practical note I have to agree with David I that my experience in 
> prepping new pianos is that on tapping the strings down (and I'm talking 
> about a light tap) I often see a noticeable downward movement of the string 
> and will often hear a noticeable improvement in the tone.  I don't have an 
> explanation for why strings on newly strung pianos would end up some 
> distance off the bridge cap, but my perception is that they do.  

There are two possibilities that I can think of, given positive 
front and overall bearing. Either the string isn't touching the cap 
at all, in which case a feeler gage should slide between the string 
and bridge cap in the middle of the section between the pin rows, or 
the notch edge is already crushed to where it is just barely 
touching the string at the pin. It is my opinion that the second 
condition, and a less than solid pin, accounts for this fuzzy tone. 
The string is contacting the notch edge too much to let the pin 
flagpole enough to beat, but not enough to prevent pin flagpoling 
altogether, which is why seating the string "clears" it up. If you 
take a string off of a new piano, you'll almost certainly see a 
groove in the bridge cap. It will be wider (and deeper) at the notch 
edge than in the middle.


>I don't do 
> too much prepping of new pianos these days, but I'll be happy to try to 
> stick a feeler gage or piece of paper under some strings the next time I'm 
> around an unprepped new piano.  I'll report back.
> 
> Phil Ford

Thanks, I'm interested.
Ron N