Touchweight query

[Richard Brekne]

Hi Keith.

Assuming you have made perfect measurements... and they are probably at least
fairly reflective in the sense that there is a real difference then I would
make the following point.

You have two different Balance weights. The first is 38 and the next is 42. You
are not going to solve your problem  unless these are corrected to be the same.
So looking at friction to begin with is going to take you off on a tangent and
get you nowhere methinks.

You know already that BW can be achieved with different up and down weights.
You could have 48 and 28 for your example below, or 52 and 24... or whatever
adds up to 2 * BW.  The difference between THESE two equal Balance Weights is
friction. So once you get the same BW's THEN you can adjust friction to get Up
and Downweights to correspond.

Changing BW can be done in a number of ways also, and you probably are already
aware of some of these. 

As far as things to look directly for, in addition to what Dave has pointed to
I would look at any slight differences in the angle the knuckle is glued to the
hammer shank... a very small angle difference can mean a lot really...
suprisingly so. Same thing about the capstan. 

Also... do any adjustments in BW with whippen assist springs disconnected if
they are present.

JMTOTM

RicB

 kam544@flash.net wrote:

>List,
>
>I am reviewing some fundamental principles in downweight/upweight 
>[UW/DW] concepts and have come across a minor puzzle in this older 
>vintage grand piano.
>
>Two notes:
>1) one reads 48 grams DW, 28 grams UW
>2) one reads 56 grams DW, 28 grams UW
>
>My interest was to have the 56 gram DW number be closer to the 48 
>gram UW number without adversely affecting the 28 gram UW number.
>
>However, this is where my minor puzzle begins.
>
>Some information:
>Hammer flange pinning is equal on both, wippen flange pinning is 
>equal on both, capstan to wippen heel appears to be satisfactory, 
>knuckle/rep lever appears to be okay. And there is freedom in the key 
>bushings.
>
>Additional information:
>The weights of the hammershank assemblies of both notes respectively 
>are 16.4 grams 16.1 grams.
>
>The weights of the wippens assemblies of both notes respectively are 
>20.1 grams 20.8 grams.
>
>I seem to be unable to accomplish my interest. Any ideas?
>
>At your convenience,
>
>Keith McGavern
>Registered Piano Technician
>Oklahoma Chapter 731
>Piano Technicians Guild
>USA


Richard Brekne
RPT NPTF
Griegakadamiet UiB