Key Leads and Inertia

[Bill Ballard]

At 4:17 PM +0200 6/14/03, Richard Brekne wrote:
>But now that we are on the same
>page about whether or not the choice of springs visa vi leads results in a
>significant difference in how the action behaves, I'm sure its also 
>easy to see
>that at least some portion of this is going to necessarilly fall 
>into a more or
>less subjective category which will be hard to quantify in terms of 
>performance
>shortcomings.

I could think of some mechanical studies. At one point I wanted to 
find out if the hammer tail and the backchecks were ever in contact 
during deep and fast repetition. I mean, that's what this kind of 
repetition seems to ask for (among other things). So I fantasied an 
electrical circuit which would be completed by contact between these 
two parts, a brass mesh grid wrapped around the hammer tail and a 
single flattened wire running down the face of the backcheck. Anytime 
the two touch, an indicator bulb would come on. The same set-up could 
monitor decoupling between a capstan and a wippen heel cushion.

To provide mechanized fast repetition, Bill Spurlock once mounted an 
eccentric wheel in the chuck of a 3/8" drill, attached it to a bench 
and set an action model in front of it. The action noise was very 
loud, he said, and the friction from the wheel melted a hole in the 
keytop. I would imagine a solenoid capable of delivering 1kg of 
force, with variable excursion, in continuous cycles of up to 15/sec. 
With knobs to set all of these. The mounting of this in relation to 
the key could include actuating the key, beginning at half stroke. 
(Not just fast but deep repetition, also.)

>Some folks are just plain going to like the feel of lead driven 
>counterbalancing
>compared to springs or magnets.

As we heard of Don Mannino, and as we would expect of many 
generations of pianists raised on pianos with conventional levels of 
inertia.

>Grin... we are going in circles me thinks....

We've been going around in circles for a while. I just don't know 
who's Fred and who's Ginger. <g>

>I dont believe there exists a desirable BW/FW combination that
>cannot be accomplished without the use of assist springs. I also
>dont believe there exists a desirable SW level that cannot
>be comfortably counterbalanced with leads and an appropriate ratio.

Yep, we can leave it at that, with user-defined values such as 
"desirable", "comfortable", and "appropriate". No problem.

>In fact,  Stephen's slopes would seem to be telling us that the adjustment
>of BW should be done from exactly a mass standpoint instead.

What he has said so far is that using mass in the key sick to adjust 
BW should also comply with how that mass is also determining the 
key's moment of inertia. Which is to say that you pick one spot to 
make your mass adjustments (which determines the force on inertia to 
be encountered), and that you vary the size of that mass to determine 
the force of gravity to be encountered. But that's when what you're 
employing to adjust BW is mass, and not say another force, say 
magnetism or deformation of an elastic material.

I think Stephen needs some more cookies.

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

"Talking about music is like dancing about architecture"
     ...........Steve Martin