Key Inertia

[Richard Brekne]

Here's a nice problem to work out... if it is workable.... I think it more or
less goes to the point Sarah's making, and I think you are trying to
illustrate.....

What force comprised of what amount of mass and velocity is exactly enough to
accelerate the key stick to 1 m/s while having no left over energy to force the
key stick into the cushion...

That being impossible... what (force)  yields the least possible amount of
wasted energy while achieving that same 1 m/s key velocity ?

Cheers
RicB



John Hartman wrote:

> The points are:
>
> 1) The only force that gets transferred to the string is that portion of
> the force applied at the key that works to accelerate the hammer and shank.
>
> 2) The portion of the force applied to the key used to accelerate the
> key and wippen do not go into into the string but are wasted.
>
> 3) Removing mass from the key and wippen will make the action more
> efficient.
>
> 4) Given our ideal action with no bending and friction losses changing
> the hammer mass does not effect the efficiency of the action.
>
> Note:
>
> Efficiency is not the whole story. The action needs to be designed to
> work within the range of force that is comfortable to the player. The
> force applied by the hammer to the string needs also to be controllable
> by the player so that dynamic shading is possible.  Furthermore,
> changing the efficiency could adversely effect the tactile feed back the
> player gets from the front rail. I can envision an action that is very
> efficient, that plays loudly with ease but the player is hindered by a
> lack of control and confused by unexpected tactile feed back.
>
> John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
> Rebuilding Steinway and Mason & Hamlin
> Grand Pianos Since 1979
>
> Piano Technicians Journal
> Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]
>
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives

--
Richard Brekne
RPT, N.P.T.F.
UiB, Bergen, Norway
mailto:rbrekne@broadpark.no
http://home.broadpark.no/~rbrekne/ricmain.html
http://www.hf.uib.no/grieg/personer/cv_RB.html