Touchweight query

[David Love]

Third paragraph below should read ...48 grams DW (38 + 10).

----- Original Message -----
From: "David Love" <davidlovepianos@earthlink.net>
To: <pianotech@ptg.org>
Sent: June 29, 2002 8:12 PM
Subject: Re: Touchweight query


Note 1 has 10 grams of friction ((48 - 28)/2), note 2 has 14 grams of
friction ((57 - 28)/2).  Depending on which notes these one of them could be
either too high or too low.  Double check all friction points again and
check pinning in the hammer flange.

Either way, the balance weight is different between the notes. Note 1 BW =
38 ((48 + 28)/2), note 2 BW = 42 ((56 + 28)/2).

Expect the normal range of friction from bass to treble will be 15 - 10
grams.  (Heavier hammers in the bass will bear more on the knuckle and cause
naturally more friction than in the treble.)  If you want a BW of 38 grams,
then in the bass you should have 53 g of DW (BW + F) and in the treble you
will have 38 g of DW (38 + 10).

Changes in the front weight of the keys will change the balance weight in a
1:1 ratio.  If you want to reduce note #2 to a 38 g BW (and assuming you
don't want to change the weight of the hammer) you will have to add 4 g to
the front weight.  That will make the new DW/UW 52/24 unless you address the
friction.

Changes in the friction will cause the DW to move in the opposite direction
from the UW proportionately.  One gram reduction in friction will cause the
DW to go down by one gram and the UW to go up by one gram (BW remains the
same).  So if, after adjusting the balance weight with the addition of 4g of
lead, you were able to reduce the friction by 4 grams in note 2, you would
end up with 48 DW and 28 UW.

Work first for even balance weight through front weight manipulation (after
insuring that strike weights are where you want them).  Uneveness in DW and
UW between notes will then be a function of friction.  Work next for smooth
transitional friction from section to section corresponding to the change in
hammer weight, and your DW/UW should transition smoothly as well with
adjacent notes being virtually equal.

There can be other complications if the action ratios differ from note to
note, such as when the key ratios between sharps and naturals vary.  But
that is another question.

David Love


----- Original Message -----
From: <kam544@flash.net>
To: <pianotech@ptg.org>
Sent: June 29, 2002 7:30 PM
Subject: Touchweight query


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