[pianotech] action ratio

[Ron Nossaman]

On 8/27/2012 6:54 AM, Jim Ialeggio wrote:
> Right...The regulation and especially fine regulation by feel are points
> well taken, and are how I proceed in the real world.
>
> My simple brain looked at the initial post, and interpreted it as a
> question: "Are the 2 sides of this equation, mathematically speaking,
> not regulation-ally speaking equivalent?"
>
> My take is no. I think that the formula states terms that are not
> equivalent.
>
> Does it matter...maybe not, especially if the hammers weight is kept
> under control. Its only when the shank is swinging a sledge hammer
> weight that the functionality bandwidth is driven into OCD land anyway.

And this is hardly an isolated incidence. A few years ago when the big 
get lead out of the keys at any cost to lower inertia crusade passed 
through the CAUT world I tried to point out that the keys wouldn't have 
seven leads in them if the action ratio and hammer weight didn't demand 
it for static balance. Inertia is mass times acceleration, but which 
mass? Inertia down is a hammer problem, not a key weight problem because 
the hammer is accelerating at over five times the key's rate. The key is 
not in free fall, so whether it's being depressed faster than free fall 
under earth's gravity is irrelevant as the hammer on the under end of 
the lever train is being lifted against gravity at the same time. As key 
acceleration increases, hammer acceleration also increases at over five 
times that rate. Key inertia becomes a problem on release, when the rep 
spring has to lift the key to reset the jack. So how do we set rep 
spring strength? By hammer rise, which doesn't happen in actual play. So 
shouldn't we be setting rep spring strength with key rise instead? 
Pretty much everything we do in a piano is a workaround, an average, a 
compromise, or a substitute representing the current method giving us a 
result similar to what we think we want, when it's done under certain 
conditions. Sure, we have to start somewhere, but we also have to 
rethink our premise too, just like measuring action ratio. This is a 
first rate resource for doing just that to get observations we might not 
have made ourselves. There are still lots of loose ends but questions 
are still being defined to try to deal with them. Is good.

Ron N