Pianotech

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

The problem is your charting. There is no such thing as a SW "curve". Its an imaginary construct. In reality, hammers are tapered. Once this fact is accepted then the answer becomes self evident.

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I have no idea what you're talking about, but that wouldn't be the first time and I don't want to encourage you. I'll let others weigh in--pun intended. 

The problem is your charting. There is no such thing as a SW "curve". Its an imaginary construct. In reality, hammers are tapered. Once this fact is accepted then the answer becomes self evident.

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

David,

I agree, I don't know what he is talking about. I've used the Stanwood Smart Chart for many years and found it to be very helpful, but I do deviate the top 6 or 8 notes towards a straight line. My reasoning is that the length of the strings in that area change slightly in length equating into a very small mass difference that needs to be activated.

Roger

I have no idea what you're talking about, but that wouldn't be the first time and I don't want to encourage you. I'll let others weigh in--pun intended. 

The problem is your charting. There is no such thing as a SW "curve". Its an imaginary construct. In reality, hammers are tapered. Once this fact is accepted then the answer becomes self evident.

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I'm still new to the world of balancing, so I can't offer much from experience. 

SW charts I've used look similar to your first example, sometimes the top end dropping a little steeper- I tend to like really light top hammers. Normally the bass end kind of gently tilts downhill, so to speak. But I do have a question: I recently adapted a modern prelude composed for a Paulello Op. 102 (102 key piano, C0-F8). There is a very rapid low bass section which is an absolute killer to play on most pianos. There is so much inertia down there most of the time, and fast intricate playing has been difficult across many pianos I've tried. What are your thoughts on keeping a similar SW line, but significantly increasing DW by removing key leads in the lower keyboard? How high DW is too high? 85g? Most of the time each hand toward the center of the piano is playing up to 4 keys (DW x 4), in the low bass usually not more than 2 (DW x 2). It seems like, at least in theory, we could nearly double the DW and the hand would need to exert no more pressure in the low bass as one would need in the midrange, assuming chords are being played in their normal configuration. Faster, intricate work in the low bass would become easier, I think. Of course, this model could become problematic in quieter, more melodic playing. 

Here is the piece I'm referring to on the Paulello piano.

https://youtu.be/wgzjD6UDkDc?si=HK-XM33wy7LWSJsv

If this is too far off topic, please disregard. Thanks!

------------------------------
Tim Foster RPT
New Oxford PA
(470) 231-6074

Original Message:
Sent: 09-11-2025 19:11
From: Roger Gable
Subject: SW Curves

David,

I agree, I don't know what he is talking about. I've used the Stanwood Smart Chart for many years and found it to be very helpful, but I do deviate the top 6 or 8 notes towards a straight line. My reasoning is that the length of the strings in that area change slightly in length equating into a very small mass difference that needs to be activated.

Roger

------------------------------
Roger Gable RPT
Gable Piano
Everett WA
(425) 252-5000

Original Message:
Sent: 09-11-2025 10:23
From: David Love
Subject: SW Curves

I have no idea what you're talking about, but that wouldn't be the first time and I don't want to encourage you. I'll let others weigh in--pun intended. 

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320

Original Message:
Sent: 09-11-2025 10:16
From: Chris Chernobieff
Subject: SW Curves

The problem is your charting. There is no such thing as a SW "curve". Its an imaginary construct. In reality, hammers are tapered. Once this fact is accepted then the answer becomes self evident.

------------------------------
On the page, it looked....nothing.
The beginning, simple, almost comic.
Just a pulse - bassoons, basset horns, like a rusty squeezebox. And then suddenly, high above it..an oboe, hanging there unwavering, until a clarinet sweetened it into a phrase of such delight.
This was no composition by a performing monkey!!

865-986-7720 (text only please)

Original Message:
Sent: 09-11-2025 00:59
From: David Love
Subject: SW Curves

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I'm still new to the world of balancing, so I can't offer much from experience. 

SW charts I've used look similar to your first example, sometimes the top end dropping a little steeper- I tend to like really light top hammers. Normally the bass end kind of gently tilts downhill, so to speak. But I do have a question: I recently adapted a modern prelude composed for a Paulello Op. 102 (102 key piano, C0-F8). There is a very rapid low bass section which is an absolute killer to play on most pianos. There is so much inertia down there most of the time, and fast intricate playing has been difficult across many pianos I've tried. What are your thoughts on keeping a similar SW line, but significantly increasing DW by removing key leads in the lower keyboard? How high DW is too high? 85g? Most of the time each hand toward the center of the piano is playing up to 4 keys (DW x 4), in the low bass usually not more than 2 (DW x 2). It seems like, at least in theory, we could nearly double the DW and the hand would need to exert no more pressure in the low bass as one would need in the midrange, assuming chords are being played in their normal configuration. Faster, intricate work in the low bass would become easier, I think. Of course, this model could become problematic in quieter, more melodic playing. 

Here is the piece I'm referring to on the Paulello piano.

https://youtu.be/wgzjD6UDkDc?si=HK-XM33wy7LWSJsv

If this is too far off topic, please disregard. Thanks!

David,

I agree, I don't know what he is talking about. I've used the Stanwood Smart Chart for many years and found it to be very helpful, but I do deviate the top 6 or 8 notes towards a straight line. My reasoning is that the length of the strings in that area change slightly in length equating into a very small mass difference that needs to be activated.

Roger

I have no idea what you're talking about, but that wouldn't be the first time and I don't want to encourage you. I'll let others weigh in--pun intended. 

The problem is your charting. There is no such thing as a SW "curve". Its an imaginary construct. In reality, hammers are tapered. Once this fact is accepted then the answer becomes self evident.

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I should probably clarify that last statement because we're getting a little bit convoluted here with terms. The primary driver of inertia is mass, in this case, the mass of the hammer mostly, to a lesser degree the mass of the other component parts. mass, or wait as we tend to think of it here, is a static measurement.

What we're concerned with in the piano is the force required to overcome Inertia. So if F = ma, force equals mass times acceleration, and we're wondering how the Action ratio (AR) factors into that the equation, it would look something more like F = ma/MA, where MA Is the mechanical advantage seen in the piano as the AR. Mass times acceleration divided by the mechanical advantage, or in our case, the action ratio. We tend to think of and refer to that resistance to acceleration as inertia.  More accurately, we should be calling it. The force required to overcome inertia.  The factors involved in determining that are, indeed, static measurements

So, In this case, the "inertia", as we tend to think of it, is primarily determined by the mass of the object, The forced to overcome inertia is a function of the mass and the mechanical advantage. There are situations in which there are other factors that contribute to resistance to acceleration. for example, in the case of a soundboard, it's the modulus as well as the mass.

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320

Original Message:
Sent: 09-12-2025 14:04
From: David Love
Subject: SW Curves

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320

Original Message:
Sent: 09-12-2025 13:42
From: Keith Akins
Subject: SW Curves

Original Message:
Sent: 9/11/2025 1:00:00 AM
From: David Love
Subject: SW Curves

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Are we not talking about the difference between static and dynamic friction?  

In the action, there are many contributors to the friction of the assembly.  We have action centers, the sliding of the jack and balancier over the knuckle, movement of the capstan under the wippen heel, the friction in key bushings and so forth.  When these parts are moving, the friction is less than when the key is at rest.  We can measure some factors at rest, like up and down weights of the keys, or weighing components, measuring parts, whatever method you choose, but the feel of the action is different when the parts are in motion which is due to the change from static friction to dynamic friction.  How much force we need to overcome the static friction could somehow be measured, I suppose, though I'm not sure how unless you have the equipment to measure it.  We also know that lubrication to lower friction changes the touch of the action.  What Keith and David and others have differing opinions about I believe is the feel of the action when the static friction is overcome.  Remember that some parts move only during part of the keystroke, and they stop and start moving at different times.  The jack doesn't move until it contacts the letoff button, and even that event has some friction.  The jack tip then slides across the knuckle, then as aftertouch begins the knuckle slides across the balancier.  All of these events are part of the tactile experience of the player, even if hardly perceptible.  For example, unless you play very slowly, letoff is almost undetectable.  Then you have the repetition spring, with its sliding motion under the balancier, the wippen hitting the drop screw, etc.,  and all of it contributes to the dynamic feel of the action.  A heavier hammer will bear more firmly than a lighter one, and thus more friction is going to appear where the hammer is heavier.  We add leads to counter the weight of the heavier hammer, but do we include the additional friction of the jack-to-knuckle in our measurments?  How much extra effort is there to move the jack tip where you have heavier hammers and play hard on that note.  So these factors do influence the touch of the action, over and above the generic measurements of the parts at rest, the action ratios and other considerations.  I think Keith has a good point.

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Are we not talking about the difference between static and dynamic friction?  

In the action, there are many contributors to the friction of the assembly.  We have action centers, the sliding of the jack and balancier over the knuckle, movement of the capstan under the wippen heel, the friction in key bushings and so forth.  When these parts are moving, the friction is less than when the key is at rest.  We can measure some factors at rest, like up and down weights of the keys, or weighing components, measuring parts, whatever method you choose, but the feel of the action is different when the parts are in motion which is due to the change from static friction to dynamic friction.  How much force we need to overcome the static friction could somehow be measured, I suppose, though I'm not sure how unless you have the equipment to measure it.  We also know that lubrication to lower friction changes the touch of the action.  What Keith and David and others have differing opinions about I believe is the feel of the action when the static friction is overcome.  Remember that some parts move only during part of the keystroke, and they stop and start moving at different times.  The jack doesn't move until it contacts the letoff button, and even that event has some friction.  The jack tip then slides across the knuckle, then as aftertouch begins the knuckle slides across the balancier.  All of these events are part of the tactile experience of the player, even if hardly perceptible.  For example, unless you play very slowly, letoff is almost undetectable.  Then you have the repetition spring, with its sliding motion under the balancier, the wippen hitting the drop screw, etc.,  and all of it contributes to the dynamic feel of the action.  A heavier hammer will bear more firmly than a lighter one, and thus more friction is going to appear where the hammer is heavier.  We add leads to counter the weight of the heavier hammer, but do we include the additional friction of the jack-to-knuckle in our measurments?  How much extra effort is there to move the jack tip where you have heavier hammers and play hard on that note.  So these factors do influence the touch of the action, over and above the generic measurements of the parts at rest, the action ratios and other considerations.  I think Keith has a good point.

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Keith Akins wrote:

"It is factual that the current static theories and protocols are inadequate for all situations and in practice do not resolve all playing effort issues. This is not a matter of personal opinion or up for debate. I am aware of a number of reports of people using the currently available protocols with the result of dissatisfied customers."

Of course it doesn't answer every situation or variation in touch and dynamics or answer questions of personal taste.  Who said it did?  But you, and others, seem to be suggesting that dynamic performance can't be derived from static measurements.  That's just flat out wrong.  Is it really necessary to explain why that is (I don't see what tire balancing has to do with it)?  Take any action in which the AR is uniform across the scale.  The bass will have higher "inertia" (as we're using the term--really, it's the "force required to overcome inertia at varying levels of acceleration" to be more accurate) than the treble.  That's directly attributable to more mass in the hammers, and to a lesser degree to more mass in the keys in the form of more lead.  That will be true every time.  A choice of where that SW curve should fall depending on other factors, such as how you want the action to regulate, what kind of tonal response do you want as it relates to hammer mass, is a choice of personal taste that techs make hopefully in conjunction with their playing customers.  No one system will please everyone, of course.  And no one has argued that and if they are and are making claims that their system will always result in a happy customer, they are delusional (but then there is a lot of that going around).  

And you're calling that a customer was "dissatisfied" with a particular outcome, scientific evidence the available protocols are not adequate after arguing that personal taste is a factor.  That makes no sense.  No matter what the protocols, there are choices to be made about the execution. Do you choose a lower or higher AR:SW relationship?  Do you opt for a higher or lower BW?  Did your choice involve a low AR which resulted in excessive key dip for the player?  These choices have nothing to do with protocols.  I use similar protocols every time I do an action but I sometimes make different choices. You can use the same "protocol" to produce a high inertia or low inertia action based solely on the decision you make about AR/SW relationships.  I don't see how that discredits anything.  Plus, you keep saying the velocity is a factor, it is not, it is acceleration--it's getting to your desired velocity that is the issue, not the velocity itself.   

In response to Paul McCloud, this aspect has nothing to do with friction even though friction levels will change with more mass in the hammers.  But that's a separate matter.   

I have no response to Chris C other than, nice promo.  

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Keith Akins wrote:

"It is factual that the current static theories and protocols are inadequate for all situations and in practice do not resolve all playing effort issues. This is not a matter of personal opinion or up for debate. I am aware of a number of reports of people using the currently available protocols with the result of dissatisfied customers."

Of course it doesn't answer every situation or variation in touch and dynamics or answer questions of personal taste.  Who said it did?  But you, and others, seem to be suggesting that dynamic performance can't be derived from static measurements.  That's just flat out wrong.  Is it really necessary to explain why that is (I don't see what tire balancing has to do with it)?  Take any action in which the AR is uniform across the scale.  The bass will have higher "inertia" (as we're using the term--really, it's the "force required to overcome inertia at varying levels of acceleration" to be more accurate) than the treble.  That's directly attributable to more mass in the hammers, and to a lesser degree to more mass in the keys in the form of more lead.  That will be true every time.  A choice of where that SW curve should fall depending on other factors, such as how you want the action to regulate, what kind of tonal response do you want as it relates to hammer mass, is a choice of personal taste that techs make hopefully in conjunction with their playing customers.  No one system will please everyone, of course.  And no one has argued that and if they are and are making claims that their system will always result in a happy customer, they are delusional (but then there is a lot of that going around).  

And you're calling that a customer was "dissatisfied" with a particular outcome, scientific evidence the available protocols are not adequate after arguing that personal taste is a factor.  That makes no sense.  No matter what the protocols, there are choices to be made about the execution. Do you choose a lower or higher AR:SW relationship?  Do you opt for a higher or lower BW?  Did your choice involve a low AR which resulted in excessive key dip for the player?  These choices have nothing to do with protocols.  I use similar protocols every time I do an action but I sometimes make different choices. You can use the same "protocol" to produce a high inertia or low inertia action based solely on the decision you make about AR/SW relationships.  I don't see how that discredits anything.  Plus, you keep saying the velocity is a factor, it is not, it is acceleration--it's getting to your desired velocity that is the issue, not the velocity itself.   

In response to Paul McCloud, this aspect has nothing to do with friction even though friction levels will change with more mass in the hammers.  But that's a separate matter.   

I have no response to Chris C other than, nice promo.  

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Keith Akins wrote:

"It is factual that the current static theories and protocols are inadequate for all situations and in practice do not resolve all playing effort issues. This is not a matter of personal opinion or up for debate. I am aware of a number of reports of people using the currently available protocols with the result of dissatisfied customers."

Of course it doesn't answer every situation or variation in touch and dynamics or answer questions of personal taste.  Who said it did?  But you, and others, seem to be suggesting that dynamic performance can't be derived from static measurements.  That's just flat out wrong.  Is it really necessary to explain why that is (I don't see what tire balancing has to do with it)?  Take any action in which the AR is uniform across the scale.  The bass will have higher "inertia" (as we're using the term--really, it's the "force required to overcome inertia at varying levels of acceleration" to be more accurate) than the treble.  That's directly attributable to more mass in the hammers, and to a lesser degree to more mass in the keys in the form of more lead.  That will be true every time.  A choice of where that SW curve should fall depending on other factors, such as how you want the action to regulate, what kind of tonal response do you want as it relates to hammer mass, is a choice of personal taste that techs make hopefully in conjunction with their playing customers.  No one system will please everyone, of course.  And no one has argued that and if they are and are making claims that their system will always result in a happy customer, they are delusional (but then there is a lot of that going around).  

And you're calling that a customer was "dissatisfied" with a particular outcome, scientific evidence the available protocols are not adequate after arguing that personal taste is a factor.  That makes no sense.  No matter what the protocols, there are choices to be made about the execution. Do you choose a lower or higher AR:SW relationship?  Do you opt for a higher or lower BW?  Did your choice involve a low AR which resulted in excessive key dip for the player?  These choices have nothing to do with protocols.  I use similar protocols every time I do an action but I sometimes make different choices. You can use the same "protocol" to produce a high inertia or low inertia action based solely on the decision you make about AR/SW relationships.  I don't see how that discredits anything.  Plus, you keep saying the velocity is a factor, it is not, it is acceleration--it's getting to your desired velocity that is the issue, not the velocity itself.   

In response to Paul McCloud, this aspect has nothing to do with friction even though friction levels will change with more mass in the hammers.  But that's a separate matter.   

I have no response to Chris C other than, nice promo.  

I disagree with your premise, static measurements are definitely an indication of inertia. Static measurements include the action ratio and they include the mass of the object you're trying to move --since we're only operating on earth we can use weight in place of mass. Those are the two major components of inertia and those are both static measurements.  If you try and slide a refrigerator across the floor, one that is empty versus one that is packed full of soft drinks, the force required to overcome a inertia will be greater for the one that weighs more. Weight is a static measurement.  

Velocity, by the way is not the key component with respect to force required to overcome inertia, its acceleration. A rocket ship traveling of its own momentum, in propelled through space is not overcoming much inertia if any. To get the rocket into space is overcoming a lot--same object.

Nobody is arguing, in fact just the opposite, that balance weight is a dynamic factor. I'm not sure what that's in response to. But the static weight is a factor in perception of touch weight. You can feel the difference between a key that has a balance weight of 50 g and one that has a balance weight of 30 g. While that doesn't necessarily speak directly to the dynamics, it's not a meaningless number.  My response to Tim addresses why that might be.  

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Hi Keith,

Our respected former colleague whose first name you could not remember was the late, great David Andersen. May he rest in peace!

Alan

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------

Original Message:
Sent: 9/12/2025 7:57:00 PM
From: Alan Eder
Subject: RE: SW Curves

Hi Keith,

Our respected former colleague whose first name you could not remember was the late, great David Andersen. May he rest in peace!

Alan

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Alan Eder, RPT
Herb Alpert School of Music
California Institute of the Arts
Valencia, CA
661.904.6483

Original Message:
Sent: 09-12-2025 13:42
From: Keith Akins
Subject: SW Curves

Original Message:
Sent: 9/11/2025 1:00:00 AM
From: David Love
Subject: SW Curves

We are used to seeing SW curves that look something like this (top graph).  This is a 2nd degree polynomial that corresponds to the equation on the chart.  This would be a typical Stanwood style curve, one that is often targeted, though at various values, usually determined by the accompanying AR. 

However, I often see hammer sets that come out of the box more like this (lower graph) which is also a 2nd degree polynomial (equation on chart).  The difference here is the positive value of the first coefficient--note that the curve dips in the middle slightly.  In the graph below pay attention to the small dotted "trendline" which is derived from the larger dots representing samples taken through the set.  (BTW this is the weight curve of a set of Renner Blue Points Gr3)

So the question posed to me by someone I'm helping with this is: What shape should we target?  Is it assumed that the style of curve pictured in the first graph is one should be copied no matter what the set itself suggests? Or should we go with what we are given out of the box and simply smooth the curve in whatever shape the set suggests or conforms to?  Why, and what will be the difference?  

My own practice is to accept what the set gives me mostly because I can't find a compelling reason not to.  Which isn't to say there are no differences.  

One difference is that, all things being equal, i.e. AR and Balance weight target, the lower SW values will always yield lower FWs and lower net inertia (FWs being a consequence, not a factor in that lower inertia).  The reason for that is because the inertia is determined primarily by the AR:SW relationship (as has been discussed).  This is the same principle that will always yield lower inertia in the treble than in the bass.  And given ARs that are equivalent the set with lower SW values will have lower inertia.  In the second graph, then, the midrange of that piano will have lower inertia than the upper graph (again, assuming AR's are equivalent). 

Is there evidence to support that one is preferable to the other?  For the most part, action balancing is very personal thing dependent on the player's taste and, perhaps, skill.  Some will like lower inertia (and BW) some will like it higher.  I make no presumptions about what people will like, all actions I do, I set to a default setting of a specific BW and inertia levels determined by targeted FW specs which combined with AR will yield a predictable level of inertia (yes, you can use static measurements to determine inertia).  But I ultimately let the player decide what they like and if they decide they want it lower or higher inertia or BW, I offer that service.  Many players FWIW, don't know what they like but everyone wants predictability which means uniformity.  Sometimes it takes a player awhile to determine what is ideal for them. 

Anyway, just food for thought, not expecting an answer (because I don't really think there is an answer).  The purpose is more to point out that we often fall into certain habits of working.  Sometimes there is a basis for it, sometimes, it's just that, a habit.  

But wait, what about regulation, you say!?  That's always dependent on AR but is a question for another day.  

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David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
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