Measuring center pin resistance

[Richard Brekne]

I addition it might be a good idea to put into perspective the relative 
importance of friction variances when comparisons are made like the ones 
made against SW variances. Friction weight variances in the degrees 
mentioned largely disapear as soon as a part is set in motion. In the 
case of a hammer flange,  tho you may find a 5 order difference of 
torque needed to get the part moving,  it will represent perhaps only a 
couple grams at best difference in static DW, and no difference in BW.  
BW is a useable indicator of dynamic touchweight.  Tho I respect Phils 
science quite a bit, I think it fair to say his post rather paints an 
overstated picture the difference between friction levels really 
represents.  Another point worth mentioning here is that friction levels 
are by no means the most stable thing we deal with.... at least not with 
in the ranges discussed.

The swing test and the Steinway tap test are indeed subject to the kinds 
of variances Phil describes... but on the other hand these have been 
used for a very very long time indeed successfully enough to be employed 
in some of the most even playing instruments ever produced. Dont get me 
wrong.... I dont mean one shouldnt strive for as much evenness as one 
can build into an action or piano. But personally, I feel there is more 
to gain by spending extra time and effort on other issues.

A side point.... Phils point about  how so and so many swings can result 
is differing static friction levels.  The flip side of that is that 
idendical static friction levels can equally result in similar variances 
in swing tests.  This is really the main reason I've never used the 
gauge, and prefer the swing test over the Steinway tap test. The swing 
test best describes the friction as it plays into the part in motion.

Cheers
RicB

Stéphane Collin wrote:

> Hi Phil.
>
> I liked this post.
> Precision of measurements is a great concern.  Even better would be 
> defining clearly (and in my opinion this only can be done by empirical 
> tries) how precise you need to be to be pertinent in what you are 
> doing.  Every measurement you do in a piano should be accompanied by a 
> relative error of measurement discussion (which should be easy) and an 
> evaluation of which precision of measurement is still pertinent in 
> relation to the goal you reach (which would need a lifetime careful 
> observations).
>
> Best regards
> (and admiration for your scientific abilities)
>