Keyframe Bedding

[andre oorebeek]

On Jul 8, 2008, at 8:10 AM, David Skolnik wrote:

> I'm not sure that Andre's tuning fork analogy is operational here.   
> I would need to hear a more thorough explanation.

Hi David, and list,

The principle applied here is the 'transfer of energy', nothing else.
I always use the analogy of the sea saw, used by children :
two children on a sea saw and they go up and down fast...
One child goes down. The sea saw hits the ground (the consistency of  
the ground is important ... remember the endless pro's and con's about  
white conical front punching ? brrrr....)  and the shock of hitting  
the ground is transferred along the sea saw to the end of the sea saw  
and, to the other child going up.
The shock, and thus the transfer of energy, causes the other child to  
hop up a little into the air.
The energy is transferred along the balancier (the lever) of the sea  
saw, but also into the post that supports the lever.
The combined weight of the sea saw lever, the children, and the shock  
of impact of the lever hitting the ground is supported by the post  
that supports the lever, the balancier.
The heavier the weight of the lever and the heavier the weight of the  
children, the more energy is transferred into the post, and thus into  
the 'ground'.

This is my explanation of what happens to keys and an action, resting  
on a key frame, which rests on the key bed.

The keys (the balancier) and the action (the children sitting on the  
sea saw) represent the combined weight of the balancier and the  
children.
The key frame, supported in the middle by posts, the glide bolts,  
carries the weight and automatically transfers the energy onto the key  
bed, which is a part of the 'basic' construction of the 'basis' of the  
instrument.

The heavier the weight of the lever(s) and action, the more energy is  
transferred into the ground, the structure of the piano.
More energy input will cause the structure to respond (re-sound).

So, if the contact between the glide bolts and the key bed is so so...  
the transfer of energy is 'so so' as well.
If however the contact is firm, so will the transfer of energy be,  
resulting in a louder tone.

If you put energy into a tuning fork by hitting it on a solid object  
and you then bring it into contact with a 'sounding board', the energy  
of the vibrating tuning fork will be transferred into the board.
The quality of the board of course determines the transfer, but the  
final output it is also determined by the weight (down bearing) of the  
'sea saw and the children'.

In other words :
More wieght/pressure results in this case in a louder tone.


We find analogies everywhere. A good example is the shock absorber of,  
for instance, a car, and, of course, a piano hammer head, or anything  
that transfers/absorbs energy.


friendly greetings
from
André Oorebeek

Antoni van Leeuwenhoekweg 15
1401 VW Bussum
the Netherlands

tel :   0031 - 35 6975840
gsm : 0031 - 652388008

concertpianoservice at planet.nl
www.concertpianoservice.nl

"where music is,
no harm can be"