What's all this I hear about Inertia ?

[Fenton Murray]

> Agreed as far as it goes, tho you do change the key inertia quite a bit... 
> which several have offered opinion on. The only two formal studies I know 
> about the affect of key ratio are Dr. Stephen Birketts treatise on the 
> matter ( http://www.pianostemmer.no/files/key_balance.pdf ) and Bob Hohfs 
> empirical experiments that bark up the exact same tree about half way up 
> and echo Stephens results quite nearly exactly. The effect of key inertia 
> / key mass on dynamic touch is quite interesting. The math in Birketts 
> paper requires a bit of study unless you are adept... but with a bit of 
> work most who have dug through their high school pre calculus and physics 
> stuff should be able to make sense of it easy enough.
>
> Cheers
> RicB

I don't think formulas will give me much here. A while back Nick G. talked 
about
tire shops spinning a mounted tire to balance it, it just works better than 
the old static bubble.
The best test for inertia in the key is to play the piano making note of 
what feels right.
If you play a lot of pianos and take a peek at the leading I think you can 
gain an understanding
of what that lead feels like. Too little lead has a weird fell as well.
Just my opinion at the present time.
Fenton
----- Original Message ----- 
From: "Richard Brekne" <ricb at pianostemmer.no>
To: <pianotech at ptg.org>
Sent: Tuesday, October 07, 2008 2:32 PM
Subject: What's all this I hear about Inertia ?


> Hi Fenton
>
>
>    Ric,
>    With Assist Springs. If the assist springs take 18 grams off the
>    back of the key, that moment value as it relates to key ratio may be
>    removed in lead from the front of the key. Nothing is changed except
>    an amount of lead is replaced with a spring. Now, a before and after
>    comparison can be made of the 'fell' of the action. BW will be the
>    same, perhaps friction will be reduced slightly by less weight on
>    the capstan. All of these experiments on my part were simply my
>    mistakes that required a re-do, best opportunity there is for 
> knowledge.
>    Fenton
>

>
>
>