Action Balancing/Leverage Quagmire

[David Love]

I have to disagree with this reasoning and think you are asking for more of
the same problem if you don't go to 17 mm (of course it's up to you).  If
it's true that a change to 16.5 lowers the R to 6.2, then medium high SW's
will be too much.  A 6.2 R will require much lighter hammers.  For that zone
you will definitely need to be under 6, preferably down in the 5.75 area.
Even at 5.9 that you achieve with the 17 mm knuckle, medium high zone will
be pressing the limit, if not over it for acceptable FWs.   The resulting
"too light touch" with the 17 mm knuckle on the samples is because there is
too much lead in the keys.  With FW's at ceiling or "up to 4 grams over" you
will have plenty of lead to remove and get the BW up around 37 and still be
at 80 - 90% of FW maximum.  Remember, FW "ceilings" are not a goal. 

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf
Of Ric Brekne
Sent: Friday, August 05, 2005 3:18 PM
To: pianotech
Subject: Action Balancing/Leverage Quagmire

Hi Terry

I think that your answer is to gto with 16.5 knuckle to centerpin 
distance... which I believe will require a change in whippens as well 
assuming you have the kind with the non adustable jack position, and 
releading the keys. As you noticed, simple change in knuckle distance 
will result in to light a touch. I gather you are comfortable with 
medium high SW's and wish to leave those. You could also bring in the 
capstans a bit if you want to bring down your front weights extra much. 
2 mm will actually go a long way along with a knuckle move.

BW being inconsistant is because of variances key to key in the overall 
ratio. (assuming you have measured all accurately)  Lots of variance in 
friction can easily cause your measurements to be a bit inconsistant. 
But remember that friction is essentially independent of BW.  An old 
instrument... worn action parts... inconsistant BW all go hand in hand.  
New parts and carefull installation will aliviate much of that.

Count on releading completely.  Perhaps it might be best to simply have 
a new set of unleaded keys made to start with ??? Just a thought

Cheers
RicB



For anyone interested in a painful experience, I will send you my =
spreadsheet with all the data upon request. For those others more =
sensible, but still reading this, I will summarize below:

DW ranged from 49 to 63. UW ranged from 18 to 28, friction (F) ranged =
from 12 to 19.5 balance weight (BW) ranged from 34 to 45.5,=20

What would make the BW so inconsistent?

FWs are from at Stanwood's Front Weight Ceilings to about 4g over, KR is =
.55 for naturals and .53 for sharps, average WW is 16.5, SW ranged from =
heavy-medium in the treble to just into the light zone in the bass, =
action ratio (R) ranged from 6.7 to 7.5 and averaged 7.1.

Clearly, the leverage of this action is horrible - too high. We =
experimented with a 17mm and 16.5mm knuckle-to-centerpin distance =
knuckles/shanks. They seemed to function very well - you could regulate =
the notes quite well (we tried the 17mm on one note and the 16.5 on four =
notes). However, the improved leverage dropped all the DWs to around 41 =
and all the UW to about 16 or 18g.=20

Looking for a bit of input here - this is too light, yes? Too light DW =
and the low UW will produce poor repetition, yes?=20

Friction on the high friction notes dropped to 12 or so and BW dropped =
to 28 to 30. Calculated R goes from and average of 7.1 to 6.2 with the =
16.5mm knuckles - likely down to about 6.0 with the 17mm knuckles.

Using the Overs action ratio method (we did not do actual measurements =
with the 16.5mm knuckles) I estimate that the knuckle change would drop =
the action ratio down from the original average of 6.4 to 5.9

BUT, these keys have a whole bunch of lead in them. We are thinking =
that, at a minimum, this action needs the knuckles placed out at 17mm =
from the flange center pins to improve leverage. Then, that will allow =
one or two leads to be removed from each key - remove enough lead to =
make the DWs in the 50 gram range and the upweights will gain a similar =
amount - around 10 grams or so and end up with about 27g UW.

Ultimately, I think, this piano needs a complete releading (setting =
gradational FWs) new hammers, shanks, knuckles and flanges and =
gradational SWs (on some nice SW curve).


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