Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Why and why not adding lead weight to key

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

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).

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.

\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,

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.

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.

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.

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,

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!

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.

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).

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...

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?

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,

...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?

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.

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.

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.

"...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.