Key Leads and Inertia

[Bill Ballard]

At 8:44 AM -0400 6/12/03, Mark Davidson wrote:
>I was referring to the note to note evenness of dimensions
>of all the parts in the action.  Since inertia is a function of
>mass and position, smooth inertia is implied by smooth mass and
>smooth position.

I hear you. I think that once you smooth the SWs, bring in the 
outliers among the 88 leverage ratios, and use David Stanwood's 
technique for graduated lead placement (yes, it does require a clean 
slate, all original leads removed and holes plugged), there won't be 
much room for complaint.

At 3:20 PM +0200 6/12/03, Richard Brekne wrote:
>Springs are always going to be controversial me thinks... have been since the
>beggining of time.

So, just when do they become controversial, the moment you put them 
on a wippen? Or is a matter of degree, like when they start doing 
more than 12-15g or work?

The only difference I see between magnets and springs is that so far 
the magnets are applied to the key and springs, to the wippen. 
Otherwise they are both objects which apply a force different from 
and independent of mass-based gravity (in one case, magnetism and the 
other, deformation of elastic materials), and thus "lighten the load" 
within significantly changing the mass in the system.

At 3:26 PM +0200 6/12/03, Richard Brekne wrote:
>Course this is the real sticker.... keys sticks are going to be 
>different dimensions no matter how you look at it.. which means 
>either they are made of a material which mass is not significant 
>enough in these conexions... or we redesign how they are made 
>dimensionally so that they conform well enough to a standard key.
>
>I kind of think that at the outset that we are looking at the first 
>option to begin with. The variance in key stick mass perhaps can be 
><< overlooked >>... at least in an attempt to arrive at a next step 
>in all this dynamic balancing stuphfe.

Don't forget, if the variation is on the front side of the key, it's 
included in the FW. How much does the back end of the key vary in 
relationship to the load sitting on the capstan. How will It? A 
backcheck a few degrees further in or out than its neighbors, or a 
capstan slightly off the mark?

At 10:01 PM +0200 6/12/03, Richard Brekne wrote:
>Would be fun to see this instrument. The thing about springs and magnets is
>that the farther into the stroke you get the weaker their effect. This is
>supposed to be a bad thing according to some critics.

David has measured the fade in wippen springs: 8% from the beginning 
to end of the stoke. The same test could measure fade in the 
balancing magnets.

>But one consequence of
>this I''ve always thought was kinda interesting is that this very capacity
>could be used to even out some of that initial heaviness in the key stroke....
>or exhasperate it.. Magnets could be used this way real easily.  Depending on
>how you install them, they could effect their strongest pull (or push) on the
>key at either full up or full down.

As I understand it, the magnets are installed on he underside of the 
key below the backcheck wire and on the keyframe back rail. 
Essentially, lifting upwards against gravity. Another pair could be 
installed on the top side of the key in front of the check wire and 
on the underside of the wippen rail. Wire magnetic repulsion at 
either end of the stroke, you could conceivably do away with gravity 
as the basis for UW. (Right now the lower limit on DW is the 
corresponding drop in UW.

At 10:01 PM +0200 6/12/03, Richard Brekne wrote:
>I suppose I have to think about how this differs from the whippen assist
>spring. It also has its max strength at key full up, but its the whippen being
>yanked at ... not the key.

If there is a difference between the performance of these two, that 
would seem to be where it lies. So hows'bout an adjustable key helper 
spring.

Boy it's a shame we don't have a representative of the MBA technology 
here on the list, to answer questions.

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

"No one builds the *perfect* piano, you can only remove the obstacles 
to that perfection during the building."
     ...........LaRoy Edwards, Yamaha International Corp
+++++++++++++++++++++