Under lever gram resistance

[Porritt, David]

I have no scientific research to bring to the table here but only
observation.  I believe inertia has a big effect on the feel of an
action.  More, perhaps, than we usually think of when setting one up.
Fortunately the start-up key inertia has been overcome by the time the
key engages the damper lever.  Remember that inertia is the tendency of
a body at rest to stay at rest, and the tendency of a body in motion to
stay in motion.  Once you get the key moving, that moving inertia helps
to start the damper lever.  

In most well designed and regulated actions you don't notice the damper
lever being lifted because the key's motion inertia helps to overcome
the damper levers rest inertial.  If you have key weight of 45 grams and
damper weight of 25 grams at some point in the key travel you increase
the load by over 50%.  Only the inertia of the key overcoming the
inertia of the damper lever could explain your not noticing this
additional load.

dave

David M. Porritt
dporritt@smu.edu

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of V T
Sent: Friday, March 25, 2005 8:04 PM
To: pianotech@ptg.org
Subject: Under lever gram resistance


Hello Dave, List,

>What's the difference whether the effective weight of
>the underlever is due to lead weights or spring 
>tension?

That is a very interesting question.  The main thing
that comes to mind is inertia.  The heavily leaded
damper would in theory take longer to accelerate, and
it would also add some heaviness to the key when
playing fast/loud.  How significant is this in
practice...?  Many of us subscribe to Stanwood's
method of controlling weight within a narrow window,
but I never hear much about the effect of the damper
system.  Has anybody on the list made some interesting
discoveries about the inertia of the damper system?

Vladan

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