[pianotech] Reducing tuning time (was Re: frustrated)

[Ron Nossaman]

On 1/21/2013 9:39 PM, Jim Ialeggio wrote:
> Will,
>
> I glad you posted this.  Faced with a couple of challenging recalcitrant
> poorly rendering grands in the last couple weeks, I came up with a
> movement similar to what you describe...Lower the pitch by moving the
> pin move the pin much more than I normally do, then slowly come up to,
> but not over the pitch.  If  I overshot, do it all again, but coming
> down was way too chancy and I avoided it except for tiny nudges south.
> With these poorly rendering items, they just would not tolerate any
> significant downward pin and pitch motion.
>
> Didn't make sense to me at first, but the stability was greatly improved.

But it does make sense. Rendering problems between the speaking length 
and pin are evidenced by moving the pin without hearing the pitch 
change. So the usual pull it slightly sharp and torque the pin back to 
balance against string tension doesn't work because the string tension 
won't immediately pull the string back over the friction point. It will 
eventually, but it's too late by then. So you have no way to directly 
read and judge the tension and back torque balance necessary to leave 
the string relatively stable. Consider, if that 160+ lbs of tension 
won't pull the string through until you lower the tension opposite the 
friction point to WELL below that, how much tension has to be on the 
tuning pin segment to force the pitch higher? WELL above that, I'd say. 
Now, since tuning a functional piano involves pulling the pitch slightly 
sharp and settling pin torque back ending up in balance against tension, 
you're putting more tension into the tuning pin segment than is in the 
speaking length to pull the pitch sharp, and taking it back down with 
the pin back torque. You have to do the same thing with badly rendering 
strings, only not the same way. Pulling slowly up to pitch, you are 
loading the tuning pin segment with a bunch of extra tension to overcome 
rendering friction, so when you reach pitch, stop, and torque the pin 
back slightly, there is no pitch change, but you have cancelled the 
excess tension in the tuning pin segment and come close to balancing 
tension against torque, like in a real piano, only you have to guess. 
This only works because the high friction loads so MUCH tension into the 
tuning pin segment that it's nearly a match for the pin back torque when 
you let go. It's not as good as being able to hear pitch changes with a 
functional piano, but it's the best we have.

Coming back to one of these untunable pianos a year later, I find the 
tunings much more ragged than my usual work with functional pianos, but 
surprisingly uniform considering that the final settling of each pin and 
string is what amounts to a wild guess.
Ron N