Touch Weight

[Ed Sutton]

Jim-

Weakening of keys is certainly a consideration.  When I remove leads I'm ususally
removing them from the front of the key where it doesn't matter much, and I don't
use the largest diameter leads near the balance rail. One could argue for Jiffy
leads here.

I think it will be interesting to quantify inertia rather than just trying to add
weights closer to the balance rail.

My intuition (for what that's worth!) is that reduced key inertia can have a
significant effect on the speed with which the key rises, i.e. produce the sense
that "the key stays with the finger."  I don't have any equipment to measure this,
so can only rely on the pianist's response.  (I think I know someone in Tennessee
who has the equipment to test this!)

And I will appreciate any reduction of key thump.

Best wishes,
Ed Sutton


----- Original Message -----
From: "James Ellis" <claviers@nxs.net>
To: <caut@ptg.org>
Sent: Saturday, December 20, 2003 2:31 PM
Subject: Touch Weight


> 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
>
>
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