[pianotech] Whistlin' Wixey

jimialeggio jimialeggio at gmail.com
Thu Aug 12 06:33:11 MDT 2010


  On 8/12/2010 6:08 AM, William Truitt wrote:
>
> Hi Jim:
>
> Thanks for the thoroughness of your reply.  Well, ain't I the numby 
> dummy!   I didn't take note of the arrows, and assumed that if the 
> reading was negative, there would be a minus sign in front of the 
> number value.  (That assuming can sure get me in a lot of trouble).  
> In my own feeble defense, there is nothing in the directions indicate 
> what the arrows mean, at least not the ones I got.  So chuck my 
> readings out the window for now.  I was wondering why I had no 
> negative readings, particularly on that old B board
>

the arrows tricked me the first time I used it too.

> Regarding the composite angle you describe, I assume from what you 
> write that the only thing you are measuring is the difference, 
> positive or negative, between the front and rear bearing.  Yes?
>

yes
>
> I have long read that the bearing angle should be between  about .5 
> degree and 1.5 degrees, depending on where you are in the piano.  I 
> don't want to assume anything again, so I will ask the question -- 
> does the value you record using this method correspond directly to the 
> values just given (and which I believe are a component reading)?
>

yes
>
>
> To get the composite reading, don't you simply add the front and rear 
> angles and divide by two to average and get the proper value for the 
> bearing angles?
>

ugh...no...now I see why you were trying to find some reliable reference 
to work off of...this will just complicate your life immeasurably, help 
you to make mistakes, and give a reading that has no practical value, ie 
doesn't mean anything.  The way I described using it uses the device as 
an indicator to determine composite angle by simply noting the 
difference between front and back angles.
>
> The up and down arrows as described in your list (thanks) have meaning 
> only in relation to the zero point, and are not in and of themselves 
> an indicator of positive and negative bearing.
>

thats right

As a side note on downbearing, as an experimenting belly designer myself 
(getting better too, I must say, yay), you might find it useful to 
intellectually chuck everything you knew, or thought you knew about 
downbearing and start fresh in your thinking, especially in an rc&s 
design (if that's where you are going).  Reading through trad approached 
to determining and setting downbearing will just take you down confusing 
dead ends, as rc&s vs cc behavior is not apples to apples in this 
regard.  The composite angle gives you (individual string lbs bearing= 
sine of composite angle x individual string tension) a way to
determine how much load the board has to carry...thats all thats of 
practical use...at least thats the way I'm using this measurement.

For example, I really don't know what practical value the measurements 
you are taking on the old B have, other than to maybe help you decide 
the elevation of the plate or something.  Seems like it would be useful 
to see in a very general sense where the board failed, but past that, it 
would get you thinking apples to oranges and just confuse your new 
design thought right from the beginning...no?


Jim I



-- 
Jim Ialeggio
grandpianosolutions.com
978- 425-9026
Shirley, MA

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