[CAUT] downweight vs. balance weight/capstan move

[David Love]

You can rewrite the formula to isolate any variables you want.  So
recalculate to determine what the maximum SW is for a given BW, R, FW, WW,
etc.  By my calculation, with the data given, at 5.5 R and a target of 38 BW
and a FW at note 1 of 41 (maximum) you can only have a SW of 12.8 at note
#1.  You can look up the curve that corresponds to that on the chart and use
that as a general guide for you other data.  In order to accommodate the SW
at note #1 that you currently have, you would have to lower the R to 5.1.
Probably not doable nor desirable.  In order to achieve the smooth curve
that you want and keep it under FW max (assuming you are not adding an
assist spring), you will have to lower and smooth the strike weights or
raise the target BW (or both) to a point where you can achieve what you
want.  Personally, I would not go lower than 5.5 R nor higher than BW of 40.


BTW, something must be wrong with the data at #64.


David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf Of Bob
Hull
Sent: Wednesday, July 27, 2005 11:59 PM
To: caut@ptg.org
Subject: [CAUT] downweight vs. balance weight/capstan move

I hope everyone's summer is going well.

I'm trying to make improvements to a NY S&S D action 
before it will be time to start on all of the practice
rooms. If you have had some experience with the
Stanwood/pianotek SmartChart, I would entertain your
opinions on the following:

This  70's era D has a new action with NY S&S improved
parts, 17mm knuckle.  (The role of this piano is
definetly that of performance.)  The DW's range from
62 to 49. and several of the bass keys have 6 large
leads.  My goal is to make the action well balanced,
even, and a lighter touchweight without sacrificing
power.  I'd like for it not to feel like you're
playing a Ford F-350. 

In trying to improve some samples I have moved the
capstan 1/16" (1.58mm) forward toward bal.rail.
Lowered the SW on #2 and lowered the FrontW. On #16
the capstan was moved and the frontW brought down to
the maximum.   It helped the DW  some and I was able
to get a little better aftertouch with less keydip. 
(Before I had to barely exceed 13/32 (.406 or 10.3mm.)
I gather from reading David Stanwood's articles that
downweight and upweight are not to be the main
considerations.  

Here are my main questions:
I want to get all of the BW's down to 38 so, if I
lower the FrontW, then the DW will not improve (become
lower). So, do I just seek to get the SW to something
like a #9  or #10 curve and the FrontW to the maximum
(on the FrontW ceiling chart) and let the DW do
whatever it wants to do?  The avg. of these Strike
weight ratios is 5.56, therefore would a 5.6 be a good
target for all?


 Before and after numbers are given on note #2 and
note #16.  On #16 frontW is at the maximum and SW is
equal to the spec for a #10 curve but the touch is so
light with the DW being at 46.  Does this indicate
that the leverage is too strong/high? i.e capstan
shouldn't have been moved? 
* indicates new numbers after capstan move

N     SW    D    U    BW    FrontW     R     WBWAvg.
___________________________________________________
1    13.9  51   21   36      49       5.49    8.56
2    13.6  62   26   44      43.4     5.79    etc.
2*   13.1  55   25   40      40.3     5.47
9    13.2  52   24   38      45.7     5.7    
10   13.3  52   24   38      43.3     5.5  
16   12.4  54   22   38      44.6     5.9
16*  12.4  46   24   35 didn't adjust 5.72
17   12.7  54   24   39.5    43.7     5.8
28   12.7  54   25   39.5    34.4     5.6
29   10.7  49   17   33      37.2     5.7
40   10.7  51   24   37.5    31.6     5.2
41   10.6  54   26   40      27.2     5.4
52    9.9  52   29   40.5    20.7     5.3
53    9.7  53   31   44      21.3     5.8
64   12.8  53   30   41.5    21.3     4.2
65    9.0  55   28   41.5    21.3     5.6
76    8.2  54   29   41.5    11.4     5.4
77    7.7  55   37   46       7.7     5.4
87    7.3  57   34   45.5     7.3     5.4
88    7.0  55   33   44       3.1     5.5


I have already worked on friction some and improved it
before these numbers were taken, but I think there is
still a good amount of variety in hammer flange
centers pinning tightness. But for instance on #2 and
#16 the pinning is not too tight.



Bob Hull








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