Talkin' Torque

[Jim]

Dear Bill:

I have shown several times at conventions a test similar to what you
describe.  I took a complete pinblock to my class where I had top & bot.
piano wire pointers which met out beyond the edge of the pinblock.  There
is a difference which can be seen.  Now a 1 degree difference is probably
more than what we observed, but it still is some difference.  It may
not be as much as one writer described as the marshmallow zone, but it
still is a factor.  While your chapter is doing some testing, it might be
well to also check what is the smallest difference one can measure when
tuning a unison strictly by machine.  I find it extremely difficult to
tune unisons within less than .1 cent by machine or by ear.  How much
twisting of the pin is needed to effect .1 cent?  It will be
interesting to compare out results later.  Let me know what you come
up with.

Jim Coleman, Sr.


On Tue, 3 Sep 1996, Bill Ballard wrote:

> Hey Gang,
> Guess what I did last Sat. I took a piece of pinblock scrap and made a
> device for observing tuning pin torsion (you know, the twist which we
> leave in a tuning pin if we're not careful). Drilled a hole for the
> tuning pin, ran a band-saw kerf over to it, and set a lag bolt across
> that kerf for adjustable torque on the tuning pin, installed a piece of
> music wire leaving the bottom end of the pin which could be visually
> checked against a piece of wire coming out of the becket. At rest, the
> two wires were set parallel.
>
> The results were dumbfounding (actually, it doesn't take much). Even at
> 200 "/# torque (the most I could get from this firstversion of the
> torsion indicator), there was nary a 1 degree lag between the top and
> bottom ends of the pin. and as soon as the bottom stopped moving, and I
> stopped pushing on the top end, the two were in perfect alignment. So
> where's this mythical "twist-in-the-pin" which haunts our dreams? It
> probably has as much effect on the stability of the tuning as the test
> blow, which (as calculated for the string path of C52 on a Steinway B)
> barely musters 3.7 oz.(correct me if I'm wrong, Doug - you've got the
> spreadsheet) of extra string tension in the face of the 20#
> friction barrier presented by the capo bar. (BTW, this is part of the NH
> Chapter's Jr. Science Project.)
>
> Startled? Check it out for yourself.......
>
> Bill Ballard RPT
> NH Chapter
>
> "We mustn't underestimate our power of teamwork." Bob Davis
>