Key Inertia

[John Hartman]

Mark Davidson wrote:
 > John Hartmann wrote:
 >
 >> The points are:
 >
 >> 1) The only force that gets transferred to the string is that
 >> portion of the force applied at the key that works to accelerate
 >> the hammer and
 > shank. Agree.  But note that not all of the hammer's energy is
 > transferred to the string. The hammer bounces off and is still
 > moving, so it still has energy, which is also wasted.  But I think
 > you mean that none of the key or wippen energy makes it to the
 > string, with which I agree.

Mark,

Yes I am aware of the fact that the hammer rebounds from the string,
could hardly miss it since I see it happen every day. The point being
made is that none of the kinetic energy of the moving key or the wippen
gets transferred to the string through the hammer. You seem to have
gotten this but it doesn't hurt to mention it again. I thought it would
be best to leave the issue of elastic interactions and other
complications out of the mix in order to better see how the the various
action parts contribute to action inefficiency due to inertia. I thought
I made this clear in the first paragraph of my original post? There are
many other factors that contribute to the inefficient working of the 
action but now I am looking at just one, how inertia of the action parts 
contribute to inefficiency disregarding friction, bending, compressing, 
bouncing and any other factors that may be there. Maybe you are ready to 
move on to explore other problems like how much energy is wasted by the 
hammer but from reading some of the post here I see that this simple 
matter originally put foreword by Sarah is not easily grasped. Let's 
"get this" before going on to loftier pursuits.

Please remind me again about the hammer bouncing off the string when the
discussion turns to this.


John Hartman RPT

John Hartman Pianos
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Rebuilding Steinway and Mason & Hamlin
Grand Pianos Since 1979

Piano Technicians Journal
Journal Illustrator/Contributing Editor
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