What matters most?

[Mark Davidson]

>>Bill Ballard wrote:
>> There are two ways to up the inertia of a key, adding weight to one
>> side and adding weight to both sides. The former (normally referred
>> to increasing the FW), if done to excess in an action with a normal
>> Top Action Weight, will quickly render the action unplayable with Up
>> Weights in the 5g range. So in posing this question you must have had
>> in mind adding weight to both sides of the key, which *will* leave BW
>> untouched. But show me the practical situation where there was a
>> normal top action weight sitting on the capstan, and one had reason
>> to increase the weight on both sides of the key, to the point of
>> excess.

Not quite true.  You can change inertia to a degree without adding weights
to
backside.  Keyleads packed in close to balance rail until desired FW is
achieved
will have less moment of inertia than keyleads packed in close to key
front until desired FW is achieved.  And of course a range in between.

Example:

30g at 12.5cm from balance rail, 25cm key front:
30*12.5/25 = 15g DW, inertia = 30/1000 * 12.5^2 = 4.6875 kg cm cm

25g at 15 cm from balance rail:
25*15/25 = 15g DW, inertia = 25/1000 * 15^2 = 5.625 kg cm cm

>Richard Brekne wrote:
>This seems to hint at pianists not being able to sense inertia of the upper
>action except as it is defined as the opposite to FW... which seems to
point
>very much in the direction of a static sensation and not inertial. In
anycase...
>have we really established that same overall inertial levels feel the same
>regardless of the levels of the individual component parts ? Sounds like
you are
>saying the overall action ratio can be seen only in terms of some kind of
>effective key inertia concept.

This was basically my point about the only thing mattering to the pianist is
acceleration.  Total mass being moved is what matters.
Put a 10kg and 20kg weight in wagon, pull it around.  Take them out and put
in an 11kg and 19kg weight.  Feels the same.  That's oversimplified for a
piano, where parts accelerate at different speeds, but it's the same idea.
Not sure why you call it static.  You can't feel the weight if you don't
move it.

I will work on an example that assumes constant wippen, key(excluding lead),
shank and just changes hammer weight, leads and ratio.  Should be able to
do the kinetic energies on all those parts without too much problem.

-Mark