Fw: Larudee's mystery - Was: Ditch the tuning pin bushings

[David Skolnik]

Paul & All -

Two things for starters:
1) I agree with Dan Franklin that your industry and perseverance is admirable
2) I find it extremely disappointing that the Delphion web site that Ron 
directed us to will soon    be priced out of reach for (I assume) the 
majority of us.  If anyone knows of a similar but less costly resource, 
please share it.

There are a number of things puzzling me about this, and I doubt I'll get 
them all on the first try.  In no logical order, and with redundancy and 
varying degrees of relevance:
1) I've seen no science or concurring testimonials, as yet, which might 
convince me that the greater surface area contact of pin to block is not an 
equal, or perhaps greater contributor to the loss of refinement in tuning 
than the reduced dimension of the coil portion
2) How might such pins respond to high torque conditions (i.e 120 - 160 
inch pounds) with regard to torsion, flexing, failure, etc.? Neither on the 
previous thread (Ditch) nor on this one, thus far, have we discussed, in 
metallurgical terms, what really takes place in pin torsion and flex 
(flagpolling).  I know they have been written about in the Journal, but do 
not yet possess the search skills to locate such information Torsion 
(twist) would not seem to be an issue until we move into the higher torque 
measurements.  Does a highly torqued pin develop internal torsion?  How 
long does it take the pin to restore equilibrium (?) Would this dissipation 
of energy affect string tension?
3) What is the mathematical relationship between X variation in string 
tension and any measurable movement of that string?  What physical model 
describes the distribution of that movement across the entire string 
(elongation?) ? If, for example, the tuning pin functioned as the front 
termination, thus eliminating the issue of static friction. how much pitch 
variation would occur just by putting the hammer on the pin, or with slight 
pin flex?  If these pin distortions are momentary, the pitch should restore 
immediately.  With the introduction of a separate front termination, so too 
do we introduce friction, a fixed point from which to measure 
elongation.  How much tension differential is required between front 
segment and sounding length (with X amount of force energizing the string) 
in order to allow elongation to overcome friction and return to a stabile 
relationship (may not be equal).

I am imagining that if one  were able to control the amount and consistency 
of torque in a repinned block, using even 4/0's or 5/0's, a good fitting 
tuning tip, and acceptable range of friction across front bearing points, 
you would have little trouble doing a good fine tuning.  One possible 
problem however,  might be the absence of adequate pin flex, that ever 
useful tool in our repertoire of fine tuning techniques.

Then, of course, there are those original pins already against the 
plate.  Don't forget them!!


David Skolnik




At 10:47 PM 05/16/2001 -0500, you wrote:

> >
> > I can think of two good reasons.  Presumably we want tuning pins to be as
> > narrow in diameter as possible because a) the amount of leverage (torque)
> > exerted by the string tension increases with each increase in diameter
> > (radius) and b) the amount of string moved per unit of rotational movement
> > also increases accordingly.
>
>
>
>Yo Dale,
>Wouldn't the torque from string tension relative to the area of pin in contact
>with the block be pretty much the same regardless of pin diameter? With the
>moment arm of the string torque being the radius of pin diameter, and the 
>block
>contact surface area varying with the circumference (pi*D), doesn't this
>proportion scale? Remember that I'm missing the standard math receptors in my
>alleged brain, and am prone to orders of magnitude estimation errors in these
>things. The string movement per degree of pin rotation is shore-nuff smaller
>with a smaller diameter pin. So with the string tension "holding power" being
>more or less equivalent, and the "effect per movement" increment being smaller
>with smaller diameter pins, I'd have to agree that smaller is better - to a
>degree. With bushings, I'd say 1/0 were quite possibly a better choice than
>2/0. Without bushings, I would still consider 2/0 a better choice for the
>flagpoling thing, unless blessed with an open face block.
>
>My take, whatever.
>
>
>Ron N