Key Leads and Inertia

[Richard Brekne]

Phillip Ford wrote:

> >Stephen, Bill, John, Phil, and the rest of y'all:
> >
> >Seems from reading the essay posted (below) that there is a direct
> >relationship between how far from the balance rail pin any eventual
> >leads are (perhaps the center of all key mass is better ??) and the
> >occurance of the breakpoint seperating soft/hard zones.
>
> ...As the lead is moved closer to the balance point the slope of the balanced line becomes closer to the unbalanced line, so that the response of the key must become more like an unbalanced key.

Yep... they converge evidently. Except that the unbalanced key will still have to over come more initial force to get started, and that an unbalanced key has a breakpoint that would be different. But the acceleration per unit of increase in input force once the thing is moving would be more similar.

>
> As the lead is moved closer to the balance point the negative consequences of having balancing lead, in terms of force required at high levels of acceleration, becomes smaller.  Or in other words, the level of acceleration that it takes so that the balanced key feels heavier than an unbalanced key is higher.
>
> >Its interesting that the use (or not) of leads changes absolutely
> >nothing relative to the division between hard/soft play.
>
> I don't understand what you mean here.  The charts show that the location of the leads affects the break point, or the level of force required to go from soft play to hard play.

Thats the tradeoff... I worded that sentence poorly I suppose. The amount of lead used at any given point does nothing to the breakpoint... only the placement of the lead. And the amount of lead verses the placement of lead have sort of opposite affects on inertia.


> At a given lead location, the break point is independent of the amount of lead - perhaps that's what you mean.  One thing that I question about the charts is the meaning of the break point between soft and hard play.  Stephen's conjecture is that in the soft play area the action is 'harder to control'.  You'll notice that the break point for the unbalanced key moves with the lead location under discussion, and yet the unbalanced configuration hasn't physically changed at all.  Why should the location of the breakpoint, or transition from the hard to control zone to the easier to control zone be changing for the unbalanced key?

Thats sort of why I wondered if "center of key mass" was a better term to use then "placement of leads" ... But yes.. I am a bit confused on that point as well. And the "harder to control" bit.... hmmm. I gathered tho that it (the breakpoint)  was along the lines of Johns diagram about key leads and inertia...which started off this whole thread.


Otherwise... thanks for the good stuff below (snipped for this reply). I will read through  your observations a bit closer this evening. And thanks for the reply.

Cheers

RicB
--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
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