Don's "Self tuning piano"

[Don A. Gilmore]

----- Original Message ----- 
From: "Ron Nossaman" <RNossaman@cox.net>
To: "Pianotech" <pianotech@ptg.org>
Sent: Thursday, December 25, 2003 12:03 PM
Subject: Re: Don's "Self tuning piano"


> Hi Don,
> Have you tried a ceramic? Though I have no clear idea how the agraffes
> would work. It's been a while since I read the article, and my memory is
> more selective and less dependable than I'd like, but aren't you using the
> plate and hitches as the electrical common and insulating at the agraffes
> and V bar for individual strings, with the contact at the bottom of each
> tuning pin? If I'm remembering correctly, that tuning pin contact struck
me
> as potentially problematic, though it may not prove to be in practice. I
> thought of possibly an insulated hitch pin, vertical or with ceramic (etc)
> aliquots so the agraffes and V bar could be the common, with ribbon cables
> on the underside of the plate for individual string contacts. That would
> also require individually tied strings, but a standard agraffe and V bar
> could be used unless corrosion problems develop at the contact points.
> Might well be just trading one set of concerns for another.
>
> Ron N


Hi Ron:

I had thought about ceramic, but most ordinary, affordable refractory
materials don't have very good tensile properties and are brittle.  It would
be sort of like having glass agraffes.  Just think if you ever dropped your
tuning hammer on one of them!

I have also thought about making the tuning pin end the common and
energizing the harp end.  But that would require that the hitch pins and
lower string rest bars be individually insulated, which is not much better
than what I've got.  Besides, the fact that the tuning pins are already
mounted into a nice, insulating wooden block is too good to pass up!  I have
found (at least in the S&C Prelude) that the pin bushings must be in good
shape and concentric or they can short through the bushing to the harp and
disable the heating of that string.  Just in this prototype I encountered
eight pins like this.  We will have to either have better quality control on
the bushings or check every pin with an ohmmeter before we string it and
replace bad ones.

Thanks for the input!

Don A. Gilmore
Mechanical Engineer
Kansas City