Moment of Inertia of grand action parts.

[Bill Ballard]

Hi, John.

At 11:17 PM -0500 12/28/03, John Hartman wrote:
>From a tonal point of view we also don't want the hammer to deliver 
>all of its energy to the string. It has to have enough energy left 
>to rebound from the string.

It'll will have enough energy to rebound, alright. The energy for 
that rebound is absorbed during the moment of impact in the elastic 
deformation of both the hammer and the string. Each of these are 
springs. The hammer crown squashes and the string gets stretched out 
of the way.

>But I agree with you on the possibility that there may be a 
>relationship between the string scale / strike point design and the 
>mass of the hammer.

I've long felt that the best combination of hammer and string is one 
where both are a well-matched set of springs. For optimal energy 
transfer, each should reach its maximum displacement at the same 
moment. Where the string scale enters in is in the stiffness with 
which the stings greet the hammers' impact. With a hammer too hard, 
it may not still be stopped by the time the string has reached its 
maximum displacement. With a hammer too soft, the string will never 
get properly displaced. With the hammer properly selected (and here, 
weight and hardness can be independent yet complementary factors), 
the action can be set-up (hung as 'twere) so that energy loss inside 
the action due to action saturation can be avoided. (Energy loss due 
to frictional, gravitational and inertial resistance however comes 
with the territory.) In a nutshell, the action set-up starts in the 
string scale AND the board design.

Bill Ballard RPT
NH Chapter, P.T.G.

"No, Please wait, you're all individuals" Brain Cohen, exasperated
"Yes, we're all individuals"  the throng assembled in the street          
                 below his window, in unison
"I'm not..."  Lone dissenter.
     ...........Monty Python's "Life of Brian"
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