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

Weiyan,
One way you can improve repetition and increase touch weight in a vertical is to lighten the front end of the keys by using a Forstner bit to drill holes through the sides just like they do for installing key leads-but leave them empty. Then if you still want a more firm touch add a small lead to the back of the key as close to the end as possible. It is very easy to ruin the touch by having too much weight in the hammers, keys and action parts.

I think what matters the most in the action is that the parts get together so there is minimum loss when the keys are repeated.
The light inertia key can also be very tiring as the pianist have to follow the keys so yes some energy is expected.
I think pianists are use to control the uncontrollable .
There is of course a range of feel more adapted to different way of apprehending the keyboard, ala harpsichord player or ala A. Schnaebel .

Hopefully different pianos still may be pleasing different pianists.
WHen it comes to Steinway they have things at the limit, what they do cannot be done with a Renner action , and only works because an ensemble of parameters put together.

Forget one and the action does not play right (while it have been getting more tolerant now - out of the softer hammers to make a more easy tone to pianists with problems of touch - or to compensate for something else)


Analyzing their action may lend to the impression hammers are too heavy for the global ratio, for instance.

I happen to like the tone of light older hammers with a flat crown that compensates for mass, but the attack is damping partials still, an the tone does not seem to project as much (while I mostly have seen that in private homes)

To put in motion such heavy things as wound strings + bridge plus sounboard, a minimum amount of mass is necessary, the max you can accelerate while using action compression, shank/key stiffness reaction, etc

I am certain a piano with rigid keys (no flex an release) at all would be bad.

The pianist is "keeping balls in the air" predictability is certainly a must there, but due to the necessary process the mind of the pianist automatically maps the instrument in regard of inertia an stiffness, then forget it an concentrates on music.

Me too...almost verbatim.

Ed Foote, let's be honest: we all know the condition of concert pianos out there is generally so poor, that when artists find a 'functioning' piano, they are thrilled beyond belief <---- that's not saying very much. I've been to Carnegie twice in the past few years where a key on the piano simply failed to return at all; luckily, it was not my piano and not my problem. It's all a matter of perspective--I tend to focus more on what the artist is able to say at the piano; that is the only thing that matters to me. I hope you can understand.

Ed McMorrow, RPT, I'll have to go get your book; it sound like a very interesting read! I'll try reading your patent application again; I kind of got side tracked...the patent legalese doesn't necessarily make for an easy/efficient read, especially when I have to also think about the topic at hand and all the implications. ;-)

Paul678,
Yes.

Which falls faster? A wooden ball or a ball made of lead?

It has been proved that they fall at the same time.

The acceleration is the same:

G = 9.81 m/s2

So back weight in the keys does not make them to return faster.

There is a neat demonstration of that by Poletti seeing the piano action as 2 weights balanced a rope

https://drive.google.com/file/d/0B6GjQDkF_AMQQVI5Z3NhS3F4cGc/edit?usp=sharing

he leave aside the catapult an kinetic energy. Just about mass.

I also believe that the flexing and release of the action may add acceleration (at what point ?)


that is at the point the acceleration is more than that where the mass begin to be interesting.

PS on Kg of feather fall more slowly than ....

The mass of the front of the key, by braking the key is helping the finger to take more easily control on key flex and hammer shank flex I think.

Yes it may have changed the way piano is played.

Now I think there should be some relation between mass of the key , mass of the pianists arms, and level of acceleration of the hammer/shank.

Heavy keys and low ratio are horrible.

The breaking of inertia gives some immediate tactile return in the finger that knows at that point what the rest of the resistance will be.

WIthin limits - make sense

I don't have a lack of understanding.
Just the will to try to pass your litmus test.
Ed explained some of it but consider this:
Olec uses a lead weight at front of key to assist acceleration of hammer and it gets him more force at the string from the hammer.
I add weight to the hammer to increase the force at the string of the hammer.
As I and Ed stated - F=MA so that a starting energy accelerates a hammer to some value giving a force at the string. The same starting energy accelerates a slightly more massive hammer to a slightly slower value giving the same force at the string - all things being equal.
The latter will increase up and down weight while the former will decrease down weight and decrease upweight.
In the real world F=MA works but in the piano action maybe not quite.
Parts flex especially the hammer shank.
Action saturation sets limits.
Pianist can vary the starting energy that accelerates the hammer.
All things being equal one would think that Olec's approach and mine would net the same tonal result but not the case. The heavier hammer gives a better tone.
Have I taken a piano action into a physics lab to measure acceleration and force and observe string vibration patterns? No. but I know how my technique effects touch weight, I can redesign touch weight to cope with what I do and the tone and I can make a heavy hammer work within certain limits. Certainly hammer string contact time is a limit and all of the things I have explained are the tools that I use to avoid and work within this limit - I would not know how to provide scientific data to demonstrate hammer felt resiliance or the voicing techniques that I use or the resulting tone that can be produced - sorry.
Moving 5 and 100 pound weights around has no relevance to piano actions.
What more would you like to know?
BTW - I own Ed McMorrow's book and have read it cover to cover more than once. I refer to it frequently - he is a brilliant technician.

No, that is not true, (unless you are dropping them in a vacuum). The 5 lb. ball of lead and the 10 lb. ball of lead will drop the same speed, and two wooden balls of different weights will fall the same, but the density of the lead will have it on the ground before the wooden one, i.e., a 1 lb ball of lead will fall faster than a 100 lb ball of wood.

consider dropping a marble and a marshmallow at the same time. They weigh about the same, but there is a dramatic difference in how fast they fall.
Regards,

That would be true if you dropped the key from the leaning tower of Pisa, but not for a pivot mechanism.
Imagine a see-saw rate of fall with 1) One person slightly heavier than the other 2) One person much heavier than the other.

Kees

If you add lead to a key, you increment weight but you increment mass (inertia) in the same proportion, the result is you left unchanged the falling acceleration.

In the see-saw the same happens! The heavier person applies a greater force but has a higher mass and that results in the same acceleration.

a = f/m

a acceleration
f force
m mass

If you apply a force with no increment in mass, as with a spring, then you have a greater acceleration.

I enjoyed working with the solution MBA brought to the table. Shame, the high cost.

I guess you have never played on one.

Imagine A and B sitting on the see-saw with their feet on the ground and the thing is horizontal. What happens if they lift their feet? 1) A is equal mass to B, nothing happens, acceleration is zero 2) A now downs a big gulp and we repeat. Now the side with A is accelerating very slowly down as he is a bit heavier. 3) Now let A hold a 10kg weight and repeat. I assure you the side A is sitting on will now accelerate much more rapidly.

Kees

If you considere an isolated key (no whippen) you'll see that it is a pendulum, the return of the key to its rest position once it is released is only subject to gravity.


There is no other force acting on the key. So the acceleration is no other than G.

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!

I think you are confusing "force" and "energy". The hammer doesn't really apply any specific "force" to the string, it applies an "impulse". An impulse is a time varying force over a short duration.

Assuming the same force on the key, and the key dip is D, then the energy transferred to the hammer is FD. The kinetic energy of the hammer is .5MV^2 so the strike velocity V is sqrt(2FD/M).

When the hammer, moving at speed V, hits the string it is rapidly decelerated, stops, then accelerating by the string in the opposite direction until the contact is broken. During this process the force on the string looks somewhat like 1/2 period of a cosine, and the total duration of the contact event is proportional to sqrt(M).

So a lighter hammer (smaller M)results in a shorter impact event, which results in more high frequency content, and vice versa.

Of course reality is more complex, but this is the basic physics.

Kees

I am of the opinion that no matter what the mass of the hammer, the string will attempt to bounce it back in 1/f seconds, where f is the frequency of the note. How successful it is at that depends on a number of properties of the hammer, and mass is only one of them.

Sounds like a reasonable approach to refine the physics intuitively. But what is f? The fundamental? The strongest partial?

Long time ago I looked at hitting a bell with a metal hammer. If the hammer impacts, the local surface is propelled away but returns very rapidly to collide again with the hammer; this would correspond to your f being one of the higher partials. After this second collision the process repeats several times, each event involving lower partials and more complex motions of the bell. These multiple impacts (called micro-collisions in the literature) are an essential feature in determining the resulting sound.

For the case at hand it is even more complex, as the hammer itself is not rigid, and the contact area also comes onto play.

Yet the conclusions from the "level 1" approximation, that a lighter hammer excites relatively more higher partials (resulting in a "thin" sound) remains valid I think.

Kees

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.