Action Geometry

[Jon Page]

Richard,
Like I said, get busy. Theorizing can only go so far.
It reminds me of the difference between theory and practice:

In theory, there is not difference between theory and practice but in 
practice there is.

On the piano with the 'long hammer bore', check the pitch of the hammer,
it might compensate for it; or check the string deflection (angle to the 
keybed).

Balance Weight being the average of Up Weight and Down Weight has a feature
that if you alter the friction, the BW stays the same; it is the UW and DW 
which
converge or expand upon BW  through Friction.  ie:
BW =40,  F = 10
UW =30
DW =50.......alter Friction by +5g: F=15
UW=25
DW=55
BW=40
The only thing changed is the friction.  Balance Weight is controlled by FW 
and SW
and to a lesser degree by leverage which has more to do with geometry.

Reduce Friction first, action prep is paramount.

The actions which you will be tending to soon have unique problems which 
will require
different solutions which may depend solely on the budget of the customer.

Do the best you can, with what you got,

Jon Page

PS  You can talk about this until you're blue in the face but it is not 
until you work
        at this will your understanding take form.  Get busy.

         -   Don't think, DO.  -  Yoda


At 11:26 PM 08/20/2000 +0200, you wrote:


>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
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