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#2295582 - 06/26/14 11:42 PM Re: Why and why not adding lead weight to key [Re: Gadzar]
DoelKees Offline
1000 Post Club Member

Registered: 05/01/10
Posts: 1761
Loc: Vancouver, Canada
Originally Posted By: Gadzar
You all are confusing force with acceleration. By adding weight you increment force but no acceleration.

When you add lead, you add force and mass in exactly the same proportion and thus acceleration is left unchanged!

You are ignoring the weight of the front part of the key.

The lead weight experiences the sum of two forces: 1) gravity = Mg (M=mass of weight, g = 9.8m/s^2) , and 2) the pivot force F from the front part of the key, acting in opposite direction.

So total force on weight is F_tot = MG-F and acceleration is
a = F_tot/M_effective where M_effective is the effective mass taking into account the whole key including weight.

If you now increase the weight M and do some basic calculation you will find that F_tot will increase more than M_effective, hence a faster return.

There is a limit however; beyond a certain value of M the process becomes dominated by the weight and the front key weight becomes irrelevant. At this stage you are right, but as far as I understand this is not where piano parameters are.

Please correct me if I'm wrong.

Kees

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#2295605 - 06/27/14 01:42 AM Re: Why and why not adding lead weight to key [Re: Weiyan]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
The piano's action geometry cannot accelerate unlimited mass to unlimited speeds.

Consider: how fast might one be able to accelerate a 10 lbs hammer affixed to the end of the shank? You only have a 10 mm key dip to get it going. Do you think you could even get it up to the string?!? Maybe--it depends on the action geometry--regardless, it is probably not going to be moving very fast at the point of contact--even though it's very heavy--AND more importantly: the resultant sound is not going to be very loud. The mass is overloading the system. <---that is the problem with most modern pianos, and what most limits their overall functionality.

The action geometry determines the limits of the system. In terms of the hammer's maximum acceleration potential, distance is a major limiting factor (i.e., there is only 10mm to accelerate the mass). But, as the aforementioned scenario illustrates, mass is also a limiting factor in the system. How much the system can lift, before it begins to affect the speed of the hammer (i.e., reducing the maximum acceleration potential), is a function of the action geometry. So, the main question is: at what weight does the mass begin to reduce the maximum potential speed the hammer can travel? When does the system start overloading?

The system starts slowing down around 5g (i.e., strike weight), depending on the action geometry. Consider/remember: the original action designs were never intended to lift such heavy modern hammers; modern makers have increased hammer weight beyond what the system was intended to support. Hence why most modern pianos never really get an opportunity to reach their maximum acceleration potentials. A reduction in speed equates to a reduction in sound output, among other issues...and it only gets worse with additional weight.

Anyone can test this concept: take a spare hammer from the capo/melodic section, and install it in the tenor section. <---notice the immediate and dramatic increase in dynamics available. Because the hammer is now being accelerated at faster velocities, the change in condition necessitates a proportionally softer hammer (i.e., you will need to 'over voice' it). Another proportional relationship exists between the hammer weight and the shape of the hammer, when determining the tonal characteristics of the hammer; if you want a thicker tone with more attack, you are going to also have to file the hammer (i.e., the hammer will need to be flatter than you will have experienced with heavier hammers).
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295652 - 06/27/14 04:43 AM Re: Why and why not adding lead weight to key [Re: DoelKees]
Gadzar Offline
1000 Post Club Member

Registered: 12/15/06
Posts: 1910
Loc: Mexico City
Originally Posted By: DoelKees
Originally Posted By: Gadzar
You all are confusing force with acceleration. By adding weight you increment force but no acceleration.

When you add lead, you add force and mass in exactly the same proportion and thus acceleration is left unchanged!

You are ignoring the weight of the front part of the key.

The lead weight experiences the sum of two forces: 1) gravity = Mg (M=mass of weight, g = 9.8m/s^2) , and 2) the pivot force F from the front part of the key, acting in opposite direction.

So total force on weight is F_tot = MG-F and acceleration is
a = F_tot/M_effective where M_effective is the effective mass taking into account the whole key including weight.

If you now increase the weight M and do some basic calculation you will find that F_tot will increase more than M_effective, hence a faster return.

There is a limit however; beyond a certain value of M the process becomes dominated by the weight and the front key weight becomes irrelevant. At this stage you are right, but as far as I understand this is not where piano parameters are.

Please correct me if I'm wrong.

Kees


Kees, as I see it, when the key is depressed it pushes up the whippen. Then the hammer checks and the system locks, it is at rest. The whippen is pushing down on the capstan, by its own weight and mainly by the push of the repetition spring. When the key is released it returns by the means of two forces: the weight of the key and the push of the whippen. IMO, the push of the repetition spring is greater than the weight of both the whippen and the key. The higher the mass of the key, the slower the returning.
_________________________
Rafael Melo
Piano Technician
rafaelmelo@afinacionpianos.com.mx

Serving Mexico City and suburbs.

http://www.afinacionpianos.com.mx

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#2295712 - 06/27/14 09:52 AM Re: Why and why not adding lead weight to key [Re: A454.7]
Ed Foote Offline
1000 Post Club Member

Registered: 05/03/03
Posts: 1228
Loc: Tennessee
Originally Posted By: A443


The action geometry determines the limits of the system. .


\Greetings,
In an ideal world, perhaps, but this statement ignores the limiting effect of compliance, which determines the saturation point of the system. Heavier hammers lower that point, regardless of the weight of the key.
Regards,

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#2295747 - 06/27/14 11:40 AM Re: Why and why not adding lead weight to key [Re: Ed Foote]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Originally Posted By: Ed Foote
[...] this statement ignores the limiting effect of compliance, which determines the saturation point of the system. Heavier hammers lower that point, regardless of the weight of the key.
Ed Foote, I am interested in better understanding your compliance concept and how that relates to the piano. Would you mind please explaining this further?

You seem to be contradicting my statement: the action geometry determines the limits of the system. Let me reinforce my point, with regards to the hammer mass and not yet factoring in any conditions at the key. If we were to increase the action geometry from c.5:1 to 10:1, it would be necessary to dramatically decrease the hammer weight in order for the system to function (i.e., if not, the keys would too heavy to accelerate for musical use); the inverse is also true: if the action geometry is decreased from c.5:1 to 2:1, the system could accommodate a heavier hammer mass without becoming saturated.

That is a very important consideration, ignored by most modern technicians/rebuilders/manufactures, which has significant impacts on how the action feels to the pianists. If they choose to exceed the maximum weight that the action geometry can accelerate, the maximum hammer speed and the controllability of softer dynamics will be effected; the more these limits are exceeded, the greater detriment to playability and performance of the piano.
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295764 - 06/27/14 12:12 PM Re: Why and why not adding lead weight to key [Re: Gadzar]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Originally Posted By: Gadzar
[...]when the key is depressed it pushes up the whippen. Then the hammer checks and the system locks, it is at rest. The whippen is pushing down on the capstan, by its own weight and mainly by the push of the repetition spring. When the key is released it returns by the means of two forces: the weight of the key and the push of the whippen. IMO, the push of the repetition spring is greater than the weight of both the whippen and the key. The higher the mass of the key, the slower the returning.
Gadzar, I would like to ask you et al. to please go to a piano and test your theory; the theory is easy to prove incorrect.

Hold the key to the point immediately prior to escapement (i.e., so that the repetition spring playings no role in your observations, since it is not engaged in the system). Then temporally place a few leads near the capstan (i.e., loosely on top the key) and notice the change in return speed of the key. Compare it to surrounding notes. You should be able to observe a noticeable increase in speed with your eyes, without any special measuring equipment.

Now transfer the leads to the opposite side of the fulcrum, but this time go through escapement and into check (i.e., so the repetition spring is engaged). From this dead stop, you should now notice the key return speed is significantly slower, and the spring is, in fact, not enough to properly return the key to the starting position--most likely, the key will fail to fully return to the original starting position.

This should be enough evidence to confirm that your theory does not apply to the piano's system as you've described. If you would like do further testing, to confirm these results, I'd be happy to provide you with other methodologies.
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295773 - 06/27/14 12:30 PM Re: Why and why not adding lead weight to key [Re: BDB]
prout Offline
500 Post Club Member

Registered: 11/14/13
Posts: 850
Originally Posted By: BDB
Unless the string is vibrating in another mode, the frequency is the fundamental. There is only one string. There are no other strings vibrating at any other frequencies.


As always, BDB, you have an interesting view on how a string vibrates.

You say, if I interpret you correctly, that, because there is only one string, there is only one frequency. Yet, you use the term fundamental for that frequency, implying that the string has other frequencies at which it vibrates. Would it not be better to say that the string vibrates at its 'proper frequency' and avoid the confusion of 'fundamental'?

Also, you and Kees corrected me some time ago when I spoke of the periodic motion of a piano string. You state that a piano string does not exhibit periodic motion, therefore you cannot use the term 'fundamental frequency' to describe the motion of a piano string. If it is not periodic, it has no definable frequency.

I believe that it is practically useful to think of a string as exhibiting many simultaneous approximately definable frequencies, which allows me then to shape the tone of a played note through velocity, strike line, hammer shaping, string quality, etcetera.

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#2295782 - 06/27/14 12:56 PM Re: Why and why not adding lead weight to key [Re: A454.7]
Ed Foote Offline
1000 Post Club Member

Registered: 05/03/03
Posts: 1228
Loc: Tennessee
Originally Posted By: A443
Originally Posted By: Ed Foote
[...] this statement ignores the limiting effect of compliance, which determines the saturation point of the system. Heavier hammers lower that point, regardless of the weight of the key.
Ed Foote, I am interested in better understanding your compliance concept and how that relates to the piano. Would you mind please explaining this further?
<snip>
That is a very important consideration, ignored by most modern technicians/rebuilders/manufactures, which has significant impacts on how the action feels to the pianists. If they choose to exceed the maximum weight that the action geometry can accelerate, the maximum hammer speed and the controllability of softer dynamics will be effected; the more these limits are exceeded, the greater detriment to playability and performance of the piano.


I suppose we should first define a term before using it. What are you calling "limits"? My contention here is that geometry doesn't set "limits", rather, it creates parameters. Flex creates action saturation, which is a limit and the weight of the key has little to do with that. Compliance is the determinant of saturation. It can be measured by how far the key moves before the hammer begins to move. Heavier hammers increase the compliance, and since the flex of the key is a component of compliance, adding weight to the key increases flex of the key.

Gravity is fast, but not as fast as a spring. And gravity doesn't accelerate a heavy object any faster than a lighter one unless there is resistance to overcome. Since the only forces acting on the key when it is released are gravity and spring, and gravity doesn't care what something weighs, adding weight increases the mass ( and inertial resistance). The spring must accelerate this mass in order to reset the jack. Any additional speed that could come from additional mass falling unimpeded is counteracted by the additional work the spring must do to accelerate it. If there is some impediment, like excessive friction, then the additional weight has value, otherwise, my experience is that it is of limited use and often counterproductive. Thus my original statement that if more weight on the back of the key speeds up the repetition, there is something else wrong.
Regards,

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#2295817 - 06/27/14 02:12 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Ed Foote, I can tell--by your writings and your reasonings--that you are a concert piano technician with experience using increased repetition spring tension in an attempt to overcome repetition problems with a specific manufacture's piano.

Having had similar observations and experiences, I can confirm: in a limited manner and under specific circumstances, one can slightly cheat the system and increase repetition. However, the affect is also dependant upon on the amount of drop and the backcheck height.

Increasing the drop, increases the effect--but, that also affects the distance the key must travel before the jack can reset, which then decreases the ability of the pianist to execute very small deep in-the-key repetition movements. It also affects the 'smoochy' feeling of the moments involved around the escapement--which may, or may not, be detectable by the pianist during play.

Decreasing the backcheck height (i.e., a larger distance from the string), increases the effect--but, that also affects the distance the key needs to travel before the jack can reset, which then decreases the ability of the pianist to execute very small deep in-the-key repetition movements (i.e., a decreased backcheck height engages the spring tension for more of the key's return, so it can help, but at the detriment of deep in-the-key repetition). It also makes the keys feel sloppy to the pianist as the the impact timing is perceivably later at the back of the key.

Your observations are valid: a higher than normal spring tension, and the possible compensation of other regulation adjustments, can assist a badly assembled and functioning action by slightly increasing the overall key return. However, not only are there detrimental consequences of 'overclocking' to the intended of function of a 'double-repetion' action--essentially rendering its functionality nearly useless--but the observations that you describe are not actually part of the physics involved: the adjustment can slightly overcome physical limitations of the builder's lack of attention to detail, but can only do so with dire consequences to the intended functionally of the action's design.

The same is true for tension hammers. A tension hammer can assist with the problems of a heavy hammer hitting the string (i.e., the longer a heavy hammer stays in contact with the string, and the multiple string oscillations come in contact with the hammer, the more it will also functions like a damper). If you have a lot of experiences with voicing different kinds of hammers, you will undoubtably know that this hammer 'spring' can be helpful in assisting with the problems of heavier hammers and faster frequencies, but it is not a requirement for solving the problem and creating an excellent/superior tone (i.e., lacquered hammers can be made to sound tonally equivalent, if not better, than tension hammer). <----scandalous...I know; but it's true!
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295842 - 06/27/14 03:51 PM Re: Why and why not adding lead weight to key [Re: Ed Foote]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Originally Posted By: Ed Foote
My contention here is that geometry doesn't set "limits", rather, it creates parameters. Flex creates action saturation, which is a limit and the weight of the key has little to do with that. Compliance is the determinant of saturation. It can be measured by how far the key moves before the hammer begins to move. Heavier hammers increase the compliance, and since the flex of the key is a component of compliance, adding weight to the key increases flex of the key.
OK, so you are saying that compliance = action saturation? If so, I would rather use the term action saturation then.

Yes: in, general, adding weight to the key will increase the flex, which contributes to action saturation. Action saturation, in essence, is wasted or misdirect energy.

Caution: I am not recommending or advocating the addition of mass in the keys. You are probably familiar with the effects of adding more lead to the keys, because that well-know company with repetition issues, at one point in their history, chose to add excessive amounts of mass to their keys. So, your observations are correct: too much mass in the keys produces unnecessary action saturation. However, the increased moments of inertia also gave pianists an additional tactile sensation of where the action started to max-out tonally (i.e., in the upper registers, not the bass). My concern is the health of the pianist, and I don't think that this is a healthy approach. But, is it not completely without merit: the amount of weight in the key is a variable as it relates to the moments of inertia (i.e., the difference in the static feeling of weight between a ppp and fff as perceived by the pianist). Either way, this weight/mass needs to be scaled in to the design of a properly balanced and functioning action. We can't avoid it completely: the mass between the naturals and sharps are different--naturally one would want the moments of inertia scaled consistently through out the action (i.e., even though this detail is usually completely neglected).

What I was referring to previously with regards to lead, was in terms of how out-of-balanced the system should be--regardless of whether one adds lead to the back of the system, or removes leads in the front of the system. What is important is the balance weight [aka down weight](i.e., yes, it is technically the upweight which matters for repetition, but for purposes of this discussion--since we are talking about the perception of weight--I will use the term balance weight): great repetition requires more than a 50g balance weight. So, where are the upper limits of repetition based on the limitations of balance weight? Well, it depends on what your kind of action feel and tonal requirements the pianist desires, but repetition rates will continue to significantly increase up to at least 90g--naturally, with corresponding changes to the rest of the geometry. One can go more than 90g, but increased results seem to start diminishing around 70-80g, and the action really starts to push back at the pianist. Some playing style, however, can take advantage of these opportunities.


Edited by A443 (06/27/14 06:20 PM)
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295850 - 06/27/14 04:14 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
James Carney Offline
Full Member

Registered: 07/30/10
Posts: 440
Loc: new york city
70-80 grams BW? Isn't anything above 40 on the high side?
_________________________
Keyboardist & Composer, Piano Technician
www.jamescarney.net
http://jamescarneypianotuning.wordpress.com/

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#2295853 - 06/27/14 04:22 PM Re: Why and why not adding lead weight to key [Re: James Carney]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Originally Posted By: James Carney
70-80 grams BW? Isn't anything above 40 on the high side?
48g-52g is a pretty normal balance weight (aka down weight) for modern hammers.

It has been awhile such I've checked, but I remember a Japanese manufacture, with slightly lighter hammers, setting their 'down weight' around 60g.

The lighter the hammers, the more down weight one can employ without feeling 'heavy,' and in return, get more return with the key (i.e., faster repetition).


Edited by A443 (06/27/14 05:36 PM)
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295872 - 06/27/14 05:13 PM Re: Why and why not adding lead weight to key [Re: A454.7]
James Carney Offline
Full Member

Registered: 07/30/10
Posts: 440
Loc: new york city
Originally Posted By: A443
Originally Posted By: James Carney
70-80 grams BW? Isn't anything above 40 on the high side?
48g-52g is a pretty normal BW for modern hammers.

It has been awhile such I've checked, but I remember a Japanese manufacture, with slightly lighter hammers, setting their BW around 60g.

The lighter the hammers, the more BW one can employ without feeling 'heavy,' and in return, get more return with the key (i.e., faster repetition).


48-52 grams is a normal downweight (DW) found on a new quality piano. A typical upweight might be 24g on that same new piano. (Assuming all pinning and key bushings are in the zone.)

DW + UW /2 = BW.

Using that equation, the numbers I gave above would give a BW of 36-38. That BW would satisfy the majority of professional pianists.

I cannot imagine how a piano with a BW in the 60s or 70s would feel...
_________________________
Keyboardist & Composer, Piano Technician
www.jamescarney.net
http://jamescarneypianotuning.wordpress.com/

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#2295877 - 06/27/14 05:34 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
OIC...I was using the term "balance weight" more literally, as in, how much out-of-blance the system is set.

It looks like someone else may have coined the term Balance Weight to mean something slight different. But I am curious: why is the average between the the DW and UW of any significance [DW + UW /2 = BW]? What does that number tell us?

Up-weight is important for increased key return (i.e., repetition).
Down-weight is one of the heaviness feelings a pianist can perceive.
The difference between the two is a function of friction.

But, why would we need to know a 'Balance Weight' number?
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295882 - 06/27/14 05:51 PM Re: Why and why not adding lead weight to key [Re: A454.7]
Ed Foote Offline
1000 Post Club Member

Registered: 05/03/03
Posts: 1228
Loc: Tennessee
Originally Posted By: A443
OIC...I was using the term "balance weight" more literally, as in, how much out-of-blance the system is set.

It looks like someone else may have coined the term Balance Weight to mean something slight different. But I am curious: why is the average between the the DW and UW of any significance [DW + UW /2 = BW]? What does that number tell us?
But, why would we need to know a 'Balance Weight' number?


Greetings.,
David Stanwood's work on action measurement, which many of us have found useful, uses specific terms which, as far as I know, most action specialists take into consideration. I do, though I don't use David's exact formula for applying them. They include, UW,DW, BW, SW,KW, FW, and a bunch of ratios. These values are able to be plugged into his metrology system to arrive at whatever target the tech is aiming for.

Regards,

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#2295886 - 06/27/14 06:01 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
...I'm reading through Stanwood's information now.

I guess, I still don't understand how the average of those two measurements has any meaningful significance. One needs to know what the down-weight and upweight measurements are, and indeed the difference between them (i.e, the friction), but why the average?

Perhaps it is just a different way of looking at the same information...unless I am missing something. Is any new information or insight gained from this number, or is this simply the basis of a patentable process?
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295898 - 06/27/14 06:30 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
acortot Offline
Full Member

Registered: 06/28/07
Posts: 484
Loc: Italy
I think this answer said it all:

"IMHO, this is complete and utter nonsense--I place the original blame directly with S&S. There was a period of time where they increased hammer weight so dramatically, and in turn needed to balance out that weight with extra mass by installing crazy amount of leads into the keys, that the pianos became impossibly heavy and difficult to deal with. Pianists got used to this heaviness, piano technique was modified to fit the approach, and other companies followed-the-leader. They have since backed off of the excessive hammer weight, but since pianists became accustomed to that kind of feel, it is difficult to go all the way back to the way that it is supposed to be." -443


Heavy hammers for more volume.. and since volume seems to be be-all and end-all to piano sound, if we are to observe the development of the piano over the last 200 years, here is the reason.

like a balance that is made of steel and weighs a ton, if perfectly balanced and without friction, it is possible to tip the scale with a few grams but the heavier the action, like on a pendulum, the lower the resonant frequency, the slower the possible speed that the action can acquire.

also CHANGES in speed become impossible, so that if a pianist naturally presses the key slowly halfway and then accelerates to escapement or vice-versa, with a heavy key, the inertia is such that the movement is always smoothed-over

heavy weights also ruin technique, not only because you are essentially playing against a 'neutreal' element, which is dead weight, but because all it takes to get a key to play sometimes is to hit it briefly, using the inertia of the key to follow-through, without having good finger-control.

basically, pianists who play on heavy actions tend to play with weight to the extent that finger-action (which becomes very difficult if not impossible) is sacrificed.

Early piano technique, as used by the composers of the classical repertoire, required a light action and focus was on feeling the hammer through the key, which today is next to impossible.


Edited by acortot (06/27/14 06:32 PM)
_________________________
rhythm must be inborn - Alfred Cortot

An Article on the unusual makeup of original Pleyel hammers, during Chopin's lifetime:

http://acortot.blogspot.it/2012/07/pleyel-hammers-in-chopin-era-i-martelli.html

Max DiMario

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#2295900 - 06/27/14 06:32 PM Re: Why and why not adding lead weight to key [Re: A454.7]
Olek Offline
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Registered: 03/14/08
Posts: 7904
Loc: France
Originally Posted By: A443
Originally Posted By: Ed Foote
[...] this statement ignores the limiting effect of compliance, which determines the saturation point of the system. Heavier hammers lower that point, regardless of the weight of the key.
Ed Foote, I am interested in better understanding your compliance concept and how that relates to the piano. Would you mind please explaining this further?

You seem to be contradicting my statement: the action geometry determines the limits of the system. Let me reinforce my point, with regards to the hammer mass and not yet factoring in any conditions at the key. If we were to increase the action geometry from c.5:1 to 10:1, it would be necessary to dramatically decrease the hammer weight in order for the system to function (i.e., if not, the keys would too heavy to accelerate for musical use); the inverse is also true: if the action geometry is decreased from c.5:1 to 2:1, the system could accommodate a heavier hammer mass without becoming saturated.

That is a very important consideration, ignored by most modern technicians/rebuilders/manufactures, which has significant impacts on how the action feels to the pianists. If they choose to exceed the maximum weight that the action geometry can accelerate, the maximum hammer speed and the controllability of softer dynamics will be effected; the more these limits are exceeded, the greater detriment to playability and performance of the piano.


if the pianist cannot feel the action going near saturation then let it release the accumulated energy while accompanying the motion, some type of playing cannot be envisaged.
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#2295906 - 06/27/14 06:40 PM Re: Why and why not adding lead weight to key [Re: A454.7]
Olek Offline
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Registered: 03/14/08
Posts: 7904
Loc: France
Originally Posted By: A443
...I'm reading through Stanwood's information now.

I guess, I still don't understand how the average of those two measurements has any meaningful significance. One needs to know what the down-weight and upweight measurements are, and indeed the difference between them (i.e, the friction), but why the average?

Perhaps it is just a different way of looking at the same information...unless I am missing something. Is any new information or insight gained from this number, or is this simply the basis of a patentable process?


it have the advantage of taking in account the slightly different ratio at the end and at the start, creates a mean .

it is a try to have a number that relates a bit with inertia.
the numbers provide a reference scale that seem to be useable.
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#2295932 - 06/27/14 08:20 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
bkw58 Offline

Silver Supporter until December 19, 2014


Registered: 03/14/09
Posts: 1819
Loc: Conway, AR USA
"...feeling the hammer through the key, which today is next to impossible."

Steinway is still one of the very few grand pianos capable of "feeling the hammer through the key" via a tech who knows how to properly regulate one. Moreover, such is more likely achievable with a real S&S, not a gutted hybrid. To disembowel a S&S and insert non-S&S technology - well intentioned as it may be - is a mistake.
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#2295937 - 06/27/14 08:40 PM Re: Why and why not adding lead weight to key [Re: A454.7]
Gadzar Offline
1000 Post Club Member

Registered: 12/15/06
Posts: 1910
Loc: Mexico City
Originally Posted By: A443
Originally Posted By: Gadzar
[...]when the key is depressed it pushes up the whippen. Then the hammer checks and the system locks, it is at rest. The whippen is pushing down on the capstan, by its own weight and mainly by the push of the repetition spring. When the key is released it returns by the means of two forces: the weight of the key and the push of the whippen. IMO, the push of the repetition spring is greater than the weight of both the whippen and the key. The higher the mass of the key, the slower the returning.
Gadzar, I would like to ask you et al. to please go to a piano and test your theory; the theory is easy to prove incorrect.

Hold the key to the point immediately prior to escapement (i.e., so that the repetition spring playings no role in your observations, since it is not engaged in the system). Then temporally place a few leads near the capstan (i.e., loosely on top the key) and notice the change in return speed of the key. Compare it to surrounding notes. You should be able to observe a noticeable increase in speed with your eyes, without any special measuring equipment.

Now transfer the leads to the opposite side of the fulcrum, but this time go through escapement and into check (i.e., so the repetition spring is engaged). From this dead stop, you should now notice the key return speed is significantly slower, and the spring is, in fact, not enough to properly return the key to the starting position--most likely, the key will fail to fully return to the original starting position.

This should be enough evidence to confirm that your theory does not apply to the piano's system as you've described. If you would like do further testing, to confirm these results, I'd be happy to provide you with other methodologies.


Maybe you are right. But, for what I know, lead in keys is used to regulate the weight of the keys to at the desired value, say 52 gr., and then the repetition spring is used to adjust the resetting of the escapement lever.

If you use the lead in the keys to adjust repetition speed, aren't you disturbing the weight of the keys?
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#2295943 - 06/27/14 09:07 PM Re: Why and why not adding lead weight to key [Re: Gadzar]
A454.7 Offline
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Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Originally Posted By: Gadzar
But, for what I know, lead in keys is used to regulate the weight of the keys to at the desired value, say 52 gr., and then the repetition spring is used to adjust the resetting of the escapement lever.
Kind of, but not exactly. Lead in the keys has always been used to balance out the weight of the hammers in the system: the heavier the hammers, the more lead in the keys--assuming everything else stays the same.

Originally Posted By: Gadzar
If you use the lead in the keys to adjust repetition speed, aren't you disturbing the weight of the keys?
Yes: absolutely. There are other variables that you would need to change. If you simply add more weight to the back of the keys (i.e., increasing the down weight), the keys will start to feel impossibly heavy. The objective it to get the keys to return faster, without the whole system going beyond its limits.
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
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#2295946 - 06/27/14 09:12 PM Re: Why and why not adding lead weight to key [Re: bkw58]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
Originally Posted By: bkw58
Steinway is still one of the very few grand pianos capable of "feeling the hammer through the key" via a tech who knows how to properly regulate one. Moreover, such is more likely achievable with a real S&S, not a gutted hybrid. To disembowel a S&S and insert non-S&S technology - well intentioned as it may be - is a mistake.
Are you suggesting that S&S is the only company with a significant action problem? Or are you saying that S&S is the only action that shouldn't, for some random reason, be corrected? Either way, no one has so far been talking about using non-S&S parts. Would you like to start that discussion? Or should we maybe leave that for another thread?
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295951 - 06/27/14 09:44 PM Re: Why and why not adding lead weight to key [Re: BDB]
Gadzar Offline
1000 Post Club Member

Registered: 12/15/06
Posts: 1910
Loc: Mexico City
Originally Posted By: BDB
Unless the string is vibrating in another mode, the frequency is the fundamental. There is only one string. There are no other strings vibrating at any other frequencies.


Here you go BDB!

Once again you say partials are not present in the one-tone we hear when a piano string vibrates.

Yes, one single string vibrates with several different frequencies at the same time. They are known as harmonics and in piano strings with iH they are called Partials.

Beats are the proof of the existence of partials.

Tuning forks are made to have a strong fundamental and almost no harmonics or partials at all. So you can make the following experiment to check the existence of partials in a piano note and the absence of those same partials in the tone produced by the tuning fork:

Play the major third F4-A4, you'll hear beats. Those beats come from the 5th partial of F4 and the 4th partial of A4. The rate of these beats is the difference of the frequencies of these two partials. Now play the F4 in the piano and sound an A 440 fork, you will hear no beats. Why? Because the tuning fork produces no 4th partial.

Now play the M10th F3-A4 at the piano, you hear beats again. The 5th partial of F3 is beating with the 2nd partial of F4. But if you play F3 and sound the A 440 fork you'll hear no beats, because the 2nd partial of the fork is way too weak to be heared.

Now play the M17th F2-A4, you hear beats, the 5th partial of F2 is beating with the fundamental, first partial, of A4. Now play F2 and sound the A 440 tuning fork. This time you do hear beats, the 5th partial of F2 is beating with the 1st partial or fundamental of the tuning fork.

This proves the presence of partials 2 and 4 in the piano note A4 and also the presence of the 5th partial in the piano notes F2, F3 and F4.

Ghosting tones will also prove the exitence and presence of several partials in all piano notes.

But I know that this will not convince you. So I will show you the following high speed video of a vibrating piano string.

In this video we can see how the string vibrates simultaneously in all its length, at half the length, and at 1/3rd of its length, etc... all at the same time, and we can appreciate the different frequencies of each vibration.

So you will see, with your eyes, all the partials and their corresponding different frequencies in action. I hope with this you won't deny their existence anymore.

Enjoy it.





Edited by Gadzar (06/27/14 10:59 PM)
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Rafael Melo
Piano Technician
rafaelmelo@afinacionpianos.com.mx

Serving Mexico City and suburbs.

http://www.afinacionpianos.com.mx

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#2295958 - 06/27/14 10:15 PM Re: Why and why not adding lead weight to key [Re: Weiyan]
A454.7 Offline
1000 Post Club Member

Registered: 04/28/12
Posts: 1577
Loc: Manywheres
"the video is private"
_________________________
Masters degree in piano technology, +factory(s) training, etc., blah, blah, yada, yada, yada...[uncensored break-out in song]..."it don't mean a thing, if you aint got that swing."
--Klavierbaukuenstler des Erwachens--
Email: klavierbaukuenstler@gmail.com

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#2295961 - 06/27/14 10:22 PM Re: Why and why not adding lead weight to key [Re: bkw58]
Ed Foote Offline
1000 Post Club Member

Registered: 05/03/03
Posts: 1228
Loc: Tennessee
Originally Posted By: bkw58
"...feeling the hammer through the key, which today is next to impossible."

Steinway is still one of the very few grand pianos capable of "feeling the hammer through the key" via a tech who knows how to properly regulate one. Moreover, such is more likely achievable with a real S&S, not a gutted hybrid. To disembowel a S&S and insert non-S&S technology - well intentioned as it may be - is a mistake.


Greetings,
This should be another thread but I would challenge you to make a Steinway with original parts as responsive and sensitive as I, and my clientele, are finding is possible with WNG parts. I cannot find any comparison between the two. If you want to play golf, or ski, or play tennis, or snowboard with wooden equipment, understand that your performance will not compare with those that are using carbon fiber. There are no pros in any of these fields that use the original wooden stuff. If you want to build an action out of unstable material for the sake of tradition, understand that when it comes to immediate or long-time performance, you will be left behind. Regulation is no better than the pinning, and the consistency of factory pinning I have seen is nonexistent.

Maybe if they could get control of their pinning, and machining, and consistency, they could compete with the modern materials, but as it is, I think they are trading on their reputation. It is hard to make the case for quality with 88 hammershanks containing various knuckle placements. It is also hard to make the case for pinning that is either floppy or tight, wood that twists and warps, and flanges that constantly move around in response to humidity.
Regards,


Edited by Ed Foote (06/27/14 10:25 PM)

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#2295964 - 06/27/14 10:29 PM Re: Why and why not adding lead weight to key [Re: A454.7]
Gadzar Offline
1000 Post Club Member

Registered: 12/15/06
Posts: 1910
Loc: Mexico City
Originally Posted By: A443
"the video is private"


Sorry, I thought private videos were accessible to people with the link.

I've made it public.
_________________________
Rafael Melo
Piano Technician
rafaelmelo@afinacionpianos.com.mx

Serving Mexico City and suburbs.

http://www.afinacionpianos.com.mx

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#2296050 - 06/28/14 04:29 AM Re: Why and why not adding lead weight to key [Re: A454.7]
Del Offline
5000 Post Club Member

Registered: 09/04/03
Posts: 5317
Loc: Olympia, Washington
Originally Posted By: A443
OK, so you are saying that compliance = action saturation? If so, I would rather use the term action saturation then.

Yes: in, general, adding weight to the key will increase the flex, which contributes to action saturation. Action saturation, in essence, is wasted or misdirect energy.

Action saturation is simply that point at which the key bottoms out against the front rail punching before the hammer starts to move.

In the real world there is always a delay between the time the key is struck and the time the hammer begins to move. This is due to a number of factors including, but not limited to:
— The compliance of all of the various bits of felt and leather.
— The flexibility of all of the different components of the action (the key being the most significant culprit).
— The mass of the hammer.

With a soft blow—pianissimo—the movement of a light hammer and a heavy hammer relative to the motion of the front of the key is approximately the same. Here there is a fairly direct relationship between the velocity of the front of the key and the velocity of the hammer. In other words, if the overall action ratio is, say, 5.5 : 1 the velocity of the hammer will be &#8776; 5.5 times that of the key.

This changes as the speed, or acceleration, at the front of the key increases. At faster key velocities the velocity of the velocity of the hammer will no longer be in a direct relationship to that of the front of the key; it will be somewhat less. Nor will its initial motion be tied directly to that of the key: the hammer will start moving somewhat after the front of the key begins it movement. There is a time lag between the motion of the key and the motion of the hammer. How much of a time lag will be a function of the bending and the compression of the various action parts.

As well, the velocity of the hammer will no longer be a direct multiple of the velocity of the front of the key. It will be somewhat less. How much less will be primarily dependent on the mass of the hammer. As others have pointed out, F = MA. Or, A = F/M. With the added complexity that the force applied to set the hammer in motion is not directly proportional to the force applied to the front of the key.

But—almost none of this has much bearing on the original question about the practice of back-loading the keys of vertical piano actions.

This practice got started because pianists complained that the “touch weight” of vertical actions was so much “lighter” than that of grand pianos. They wanted the vertical action to “feel” more like that of the grand action. The simple solution was to place leads at the back of the keys making the static down weight roughly similar to that of grands. It did little, if anything, to improve—or alter in any way—either the repetition speed or the reliability of the vertical action but this was never the intent of the modification. (Unless, of course, there was something amiss with the geometry or function—friction, etc.—of the action.)

Repetition in a vertical action is a function of many different factors several of which have not been discussed here. Some of these are:
— The angle of the action in relationship with the string plane.
— The strength of the hammer butt spring.
— The strength of the damper lever spring.
— The relationship of the hammer’s center of gravity in relation to the action center of the hammer butt.
— The relationship of the rotating mass of the wippen in relation to that of the key.

We use the terms “light hammers” and “heavy hammers” rather loosely in these discussions; five pound and 100 pound lead balls are freely tossed around. In real terms—in real piano hammers—there is not all that much difference between the two extremes. In modern piano construction practice a “light” A-1 upright hammer might have a mass of somewhere around 8 or 9 grams. A heavy A-1 upright hammer might run up to 11 or 12 grams (though this would, I think, be unusual). At C-88 the range will be somewhere between 3.5 and 5 grams. (There may be some that come in under or above these numbers but I’ve not been able to actually weigh them.)

These differences may not seem to be all that great but they do have a significant impact (no pun intended) on piano tone. Generally—very generally—on a given piano lighter hammers can be somewhat less dense to give satisfactory performance while heavier hammers will need to be somewhat denser. (Note: density and mass are not the same thing. Both might be the same size but one will have more or less mass than the other.) The lighter hammer will rebound away from the string slightly—very slightly—faster. The differences will be subtle but, of course, when creating piano tone subtleties can make a considerable difference.

Again getting back to the original question—it is generally a good practice to have the back of the keys weighted enough such that the back end of each key will rest lightly against the back rail felt without depending on the weight of the wippen to push them down. This is normally done by adding one or more lead weights to the back of the keys. It could also be done by making the front of the key lighter—per Ed’s suggestion—but I’ve never seen this in production. It is also good practice to have the hammer’s center of gravity forward (i.e., toward the front of the keys) of the hammer butt action centers. If anything is to be weighted it should be—but never is—the wippen lever itself.

Since the vertical action is dependent on both a spring return (the hammer butt spring) and gravity (the hammer butt, the wippen and, to a lesser extent, the hammer if the action installation geometry is done well) its repetition speed and reliability will be dependent on how well the individual piano maker blends all of these different elements of the action together in the final product.

ddf
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#2296056 - 06/28/14 04:59 AM Re: Why and why not adding lead weight to key [Re: Weiyan]
Olek Offline
7000 Post Club Member

Registered: 03/14/08
Posts: 7904
Loc: France
;;; edited


Edited by Olek (06/28/14 05:18 AM)
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#2296057 - 06/28/14 05:06 AM Re: Why and why not adding lead weight to key [Re: Ed Foote]
Mark R. Offline
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Registered: 07/31/09
Posts: 2069
Loc: Pretoria, South Africa
Originally Posted By: Ed Foote
Gravity is fast, but not as fast as a spring. And gravity doesn't accelerate a heavy object any faster than a lighter one unless there is resistance to overcome. Since the only forces acting on the key when it is released are gravity and spring, and gravity doesn't care what something weighs, adding weight increases the mass ( and inertial resistance). The spring must accelerate this mass in order to reset the jack. Any additional speed that could come from additional mass falling unimpeded is counteracted by the additional work the spring must do to accelerate it. If there is some impediment, like excessive friction, then the additional weight has value, otherwise, my experience is that it is of limited use and often counterproductive. Thus my original statement that if more weight on the back of the key speeds up the repetition, there is something else wrong.


Ed, if I may,

You make use of the argument that all objects are accelerated equally by gravity. While this is true for objects in friction-less free fall, it does not apply to more or less balanced levers. Free fall would be applicable to a keystick only if the keystick consisted of just the distal part (and nothing in front of the balance rail pin). Then, indeed, gravity wouldn't care how light or heavy that keystick is. And yes, your subsequent argumentation would then also hold true: that the repetition spring would accelerate a lighter keystick more strongly, because it has less mass/inertia than a heavier one. Such a rear-half keystick would therefore return faster if one decreased its mass. One might word this as you did: "gravity is fast, but not as fast as a spring."

But your argumentation seems to overlook that the keystick has a proximal part. This means that the acceleration of the distal lever arm, under gravity, is not determined by free fall, but by the distribution of mass between the proximal and distal lever arms. In fact, if the proximal and distal lever arms are balanced, the distal part won't fall under gravity at all! Once you start adding mass to the distal part, it will fall, and the more mass you add, the faster it will accelerate. The higher the ratio between distal mass and proximal mass becomes, the closer the acceleration of the distal arm will approach g (9.8 m/s²), i.e. "free fall".

Looking at the effect of the rep. spring vs. total keystick mass: if you compare a perfectly balanced heavy keystick (both ends have identical, high mass) to a perfectly balanced light keystick (both ends have identical but low mass), then I do agree that the repetition spring will accelerate the lighter keystick more, because it has less inertia.

But in a real piano, the keystick is out of balance, hence the acceleration of the distal end is related to two factors:
1) the ratio between distal and proximal mass
2) the ratio between the rep. spring force and the inertia of the keystick.

Adding mass to the distal end of the keystick increases ratio (1), aiding repetition, but decreases ratio (2), hindering repetition. Which of the two opposing effects will win out, I cannot say. Your experience seems to point to effect (2), while that of A443 (if I read him correctly) seems to point to effect (1).

I gladly stand corrected, but to my best understanding, this is a more realistic picture of the physics surrounding the keystick.
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