[pianotech] Best way to change touch on Yamaha Grand

[Joseph Alkana]

Pardon a very simplistic question, but do you mean that "action ratio
reduction" is accomplished by movement of the fulcrum point of a given lever
in question, right?
Another question: At what percentage point "improvement" do we start to see
reduced sliding friction benefits?

Joseph Alkana


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of V T
Sent: Wednesday, January 06, 2010 12:15 PM
To: pianotech at ptg.org
Subject: [pianotech] Best way to change touch on Yamaha Grand

Hi William,

I think the concise explanation is that most of the inertia on the down
stroke does not come from the key stick with its lead. The hammer weight
is the largest single contributor. So, you might as well chip away at
that first. Reducing the action ratio is actually more effective because
of the things Frank said. Rotational inertia is proportional to the
radius squared, but only to hammer mass to the first power.

So, if you reduce hammer weight by 10%, you get an improvement that is 10%
of the original contribution from the hammer. However, if you reduce the
action ratio by 10%, you get 0.9*0.9=0.81 which is a 19% improvement over
what the hammer was contributing before.

As a side benefit, once you reduce the hammer weight and/or action ratio,
you can trim off some lead from the key stick and get a smaller
improvement there too.

Another very simplified way to look at it is like this:

A 10 gram weight on a 30 inch end of a see-saw has much more effect on the
inertia than a 25 gram weight on the end of a 5 inch arm.

Vladan