Touch Weight

[James Ellis]

I have been reading the numerous "Touch Weight" posts on this list, and I
told myself I was not going to get into this one.  But now I will.  I'll
just mention a few generalities, and I'll suggest that a few of you stop
and think a minute before you haul off and do something you might regret
later.

Touch weight and inertia are NOT the same thing at all.  "Tough weight" is
merely a measure of static force.  "Inertia" is a dynamic quantity.

Inertia is proportional to mass, but it is proportional to the square of
velocity.  That's why putting more leads closer to the center of the keys
will result in less "KEY" inertia.  You will have to use more lead, but the
"key" inertia will be a little bit less.  However, the keys are NOT where
most of the total action inertia comes from.  It comes from the hammer
heads out on the ends of the shanks, because that's where the (mass x
velocity squared) is concentrated.

All I'm saying is that moving the leads closer to the centers of the keys
is not going to buy you very much, because that's not where most of the
total action inertia is coming from in the first place.  What it will do is
weaken the keys, especially if you drill more holes, plug holes, etc.

It will also do something else you might not have considered.  It will
slightly reduce the amount of percussive noise of the key fronts hitting
the front rail punchings, because you will be getting the concentration of
mass in the keys farther away from the key fronts.  Again, this effect will
be slight, at best.  It won't amount to very much.

Those two things are about all it will do for you, other than just making
the keys heavier in the middle.  So, before you haul off and re-do a whole
set of keys, drilling more holes, adding more leads, plugging holes, and
moving all the leads closer to the center, remember:  It won't buy you very
much towarding lowering the overall action inertia, because that's not
where it's coming from, but it will definitely weaken the keys.

Merry Christmas,  Jim Ellis