Action Geometry

[Richard Brekne]

Jon Page wrote:

> I'm scratching my head too, I think you're thinking too much. Might I
> suggest that you get an action and start
> playing with the variables to understand their inter-relationship. Then get
> another one, then another. You have
> a lot of theory which needs some practical application. Nothing beats
> hands-on experience.
>

Well, grin.. of course I am getting ready to plunge into one. I have three
likely cases, A large Petrof which has had a hammer replacement job done on it
with the wrong bore length, A Young Chang which has monster hammers and
extremely strong whippen assist springs (very heavy touch), and an August
Forster which is very heavy and sluggish.

That being said, I like to think things over several times before jumping. And
this is a new approach for me so each comment I get to my musings is going to
help me get the most out of my first shot at refigureing the action and
resulting touch weight.

>
> Friction does not affect BW to the degree that it affects UW & DW. Extreme
> friction will contribute to a higher BW

Hmmm... Stanwood gives BW as the quotient of UW + DW divided by 2... seems like
friction could play a significant role here.

> but generally BW is derived by weight and counter-weight. Once BW is
> established, friction establishes UW & DW.

But you can isolate BW using the balance equation which takes friction out of
the equation. If all the parameters fit a real situation then any deviation
between the "theoretical" and the actual situation should be due to friction.
Should actually be possible to calculate friction in this fashion and if the
balance equation truly is dependable it would seem that the calculated friction
values should correspond pretty well with measurements.... ??

>
> Survey some keys, reduce the friction (repin, ease keys) and  resurvey; see
> what happens. Balance Weight is
> centered on these two factors, friction determines their spread and
> 'weight' determines the BW position on the scale.

I am not sure what you mean by this... could you rephase ?

>
> And don't pay such close attention to the Wippen Balance Weight. It is not
> important. Once you get into it up to your
> elbows you will see what the important factors are.

Well, neither variations I have seen talk about in KR or small variations in
WBW are going to impact the result of the equation much, as these two combine
to result in the least significant part of the equation, so that makes sense
enough... still could be fun to be a bit picky one time through..

>
>
> Get busy :-)

grin... I will probably have my first set of measurements on an action I can
actually work with later this week. It will probably be the Petrof as there is
potentially a lot more to gain on this instrument then the other two... I'll
keep you posted

>
>
> Jon Page,   piano technician
> Harwich Port, Cape Cod, Mass.
> mailto:jonpage@mediaone.net
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

--
Richard Brekne
RPT, N.P.T.F.
Bergen, Norway