For explaining the contribution of the component parts to inertia and the dynamic performance of the piano action this article is the best single article I have found
http://pianobytes.com/ActionAnalysisinertiaa.htm.
The recent series of articles by Nick Gravagne in the PTJ should be helpful and his program might be helpful as well if you don't have your own spreadsheet. John Hartman wrote several articles on inertia in the piano action in the PTJ some years back as well.
In terms of why the FW and BW give an indication, this relates to David Stanwood's FW maximum ideas. While this doesn't directly address inertia (it's an indirect approach using component relationships) it is an indication that the relationship between the action ratio and the strike weight is not optimal which in turn requires an excessive amount of lead to balance the action at a reasonable balance weight. While the FW itself, the amount of lead and its location, is not a major factor in the action inertia, it does suggests that the relationship between action ratio and strike weight (or hammer mass) is not optimal and tells you that the inertia will be, in this case, too high.
In your action the data is somewhat varied, probably owning to a somewhat inconsistent strikeweight curve, but generally it is on the high side. That means that there is a relatively high FW required to achieve a mostly "highish" balance weight. It suggests that the relationship is not optimal. I generally like to see the FW around 85% of maximum with a BW between 36 and 42g. My personal target is 38 grams BW. If I have a higher BW then I'd prefer a somewhat lower FW. Below is a table of FW maximums as outlined by David Stanwood. While this is not a number written in stone it can be used to help determine if that relationship is poor. BTW the FW can be too light as well which would indicate that there is not enough inertia, the action may feel "fly way" or the pianist will not be able to feel the mass of the hammer well enough to be able to adequately control the throw.
It also tells you that the amount of lead is not so important without knowing the location. While there are quite a few leads in these keys, that they are located closer to the fulcrum shows you how many leads can be used without exceeding maximums if they are located closer to the balance rail.
Curiously, you reported that the complaint was that the action felt too light. That I only attribute to an issue of personal taste with the pianist. I would not call the action "light" and the inertia would be, relatively speaking, on the higher side. But in these numbers there are some notes that are light, 34 BW at F#22 for example. I think what is apparent is that the action is quite uneven, if these numbers are an indication. There's certainly nothing inherently wrong with a 90% or even 100% FW max number but it does indicate higher levels of inertia. That may or may not be desirable.
What you need to determine is how to proceed to optimize this action for this player. Depending on the scope of the work you will undertake that will depend. For the minimum amount of work to get a good result I would:
1. Plot the strikeweights, create a trendline (if you know how to use excel you can do this easily--this would probably be a 2nd degree polynomial) and create a smooth curve, as it appears you have some outliers. Then adjust the strikeweights to match your curve.
2. Determine the desired BW which may well be on the high side (maybe 42 is what the pianist wants), and then either calculate the FW specs which you can do if you know how to manipulate the Stanwood formula which would be FW = (SWR x SW) - BW + (WW x KR) where
FW = Front weight
SWR = Strike weight Ratio aka Action Ratio
SW = Strike weight
BW = Balance Weight
WW = Wippen Weight
KR = Key ratio.
I would l guess your SWR is probably somewhere around 6 but you can figure that out by measurement or plugging in samples to the above formula. If so then a simplified formula using 6 as the SWR and 9 for the term (WW x KR) gives you: FW = (6 x SW) - BW + 9. If you use BW = 42 then you can further simplify to FW = (6 x SW) - 33. If note #1 strikeweight is 12 then the front weight would be 39g. That's under maximums and suggests that with a higher BW, if that's what the player wants, this arrangement could work.
If you don't wish to calculate the FWs then just do a weigh off after you smooth the SWs and adjust the leads accordingly. FW to BW relationhiop is an inverse relationship 1:1. For removal of lead, take it from the front lead first even if it means you are just cutting away some of the lead (rather than removing the lead, plugging and redrilling a new position or inserting a smaller lead. If the leading pattern location transitions from note to note in a consistent way then I would probably do that. If it is very inconsistent (Steinway is usually pretty consistent in the pattern) then you may want to make the pattern more uniform.
Of course if they want to have you rebuild the action then you can do that and consider changing the action ratio. I would at least go to a 17 mm knuckle hanging if this one isn't (if it's original it will be 16 mm probably). That would allow you to achieve a higher BW, or static starting point, but lower the inertia somewhat in the process as well as being able to remove some lead. You'll have to calculate all that out as to what is optimal.
| % FW Max |
Note |
| 100.00% |
|
|
|
| 41.3 |
1 |
| 41.1 |
2 |
| 40.8 |
3 |
| 40.6 |
4 |
| 40.3 |
5 |
| 40.1 |
6 |
| 39.8 |
7 |
| 39.5 |
8 |
| 39.3 |
9 |
| 39.0 |
10 |
| 38.8 |
11 |
| 38.5 |
12 |
| 38.3 |
13 |
| 38.0 |
14 |
| 37.8 |
15 |
| 37.5 |
16 |
| 37.2 |
17 |
| 37.0 |
18 |
| 36.7 |
19 |
| 36.4 |
20 |
| 36.1 |
21 |
| 35.8 |
22 |
| 35.5 |
23 |
| 35.2 |
24 |
| 34.9 |
25 |
| 34.6 |
26 |
| 34.3 |
27 |
| 34.0 |
28 |
| 33.7 |
29 |
| 33.3 |
30 |
| 33.0 |
31 |
| 32.7 |
32 |
| 32.4 |
33 |
| 32.1 |
34 |
| 31.7 |
35 |
| 31.4 |
36 |
| 31.0 |
37 |
| 30.7 |
38 |
| 30.4 |
39 |
| 30.0 |
40 |
| 29.6 |
41 |
| 29.3 |
42 |
| 28.9 |
43 |
| 28.5 |
44 |
| 28.1 |
45 |
| 27.7 |
46 |
| 27.3 |
47 |
| 26.9 |
48 |
| 26.4 |
49 |
| 26.0 |
50 |
| 25.6 |
51 |
| 25.1 |
52 |
| 24.7 |
53 |
| 24.2 |
54 |
| 23.8 |
55 |
| 23.3 |
56 |
| 22.8 |
57 |
| 22.3 |
58 |
| 21.8 |
59 |
| 21.3 |
60 |
| 20.8 |
61 |
| 20.2 |
62 |
| 19.7 |
63 |
| 19.1 |
64 |
| 18.6 |
65 |
| 18.0 |
66 |
| 17.4 |
67 |
| 16.8 |
68 |
| 16.2 |
69 |
| 15.5 |
70 |
| 14.9 |
71 |
| 14.3 |
72 |
| 13.6 |
73 |
| 13.0 |
74 |
| 12.3 |
75 |
| 11.6 |
76 |
| 11.0 |
77 |
| 10.3 |
78 |
| 9.6 |
79 |
| 9.0 |
80 |
| 8.3 |
81 |
| 7.6 |
82 |
| 7.0 |
83 |
| 6.3 |
84 |
| 5.6 |
85 |
| 5.0 |
86 |
| 4.3 |
87 |
| 3.7 |
88 |
------------------------------
David Love RPT
www.davidlovepianos.comdavidlovepianos@comcast.net415 407 8320
------------------------------
Original Message:
Sent: 05-18-2020 11:09
From: John Pope
Subject: 1949 Steinway D with Lots O' Lead
Recall that inertia is mostly based on the relationship between the action ratio and the hammer mass. The FW along with the BW gives a good indication of that relationship.
I need to understand this better. Can someone point me in the right direction?
I have a sense that a higher action ratio means higher inertia and definitely a heavier hammer means more inertia, but what is this relationship between them that is so important? And how do FW and BW tell us something about this relationship?
Send me to a physics textbook if you must.
------------------------------
John Pope
University of Kentucky School of Music
Lexington, KY
Original Message:
Sent: 05-15-2020 19:44
From: David Love
Subject: 1949 Steinway D with Lots O' Lead
It's hard to know if the lead is excessive without knowing the front weight. Since the leads are located mostly toward the balance rail then it's possible to have this many leads and not exceed front weights that would indicate high levels of inertia. Recall that inertia is mostly based on the relationship between the action ratio and the hammer mass. The FW along with the BW gives a good indication of that relationship. To get a better sense, having the FW data along with the BW on some sample notes would allow one to perform a simple analysis.
Otherwise Jon Page's advice is good.
------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
Original Message:
Sent: 05-15-2020 15:19
From: Jon Page
Subject: 1949 Steinway D with Lots O' Lead
If you want to do the least amount of work, reducing the FW (removing lead) to attain approximately 40g BW. With a scale remove the lead that will give that BW. Since you have the BW already, create a new spreadsheet for the Hypothetical BW. The formula would be Desired BW minus Current BW. The result will be the deviation needed to achieve the desired BW. The extremes are higher than 40 and would require the addition of lead but since they are rarely played, they can be left alone. A move of 2 to 3 grams is negligible unless one of the inboard leads are that amount
Have you graduated the SW. If the extreme hammers are too heavy, that would cause the elevated SW.
------------------------------
Regards,
Jon Page
mailto:jonpage@comcast.net
http://www.pianocapecod.com
Original Message:
Sent: 05-15-2020 14:55
From: John Pope
Subject: 1949 Steinway D with Lots O' Lead
------------------------------
John Pope
University of Kentucky School of Music
Lexington, KY
------------------------------