Action Geometry

[David Porritt]

Were both of these measurements taken when the key was halfway through
its travel?  This line intersection should happen at the halfway point.

David M. Porritt, RPT
SMU - Dallas


On Thu, 22 Jun 1995 Kam544@aol.com wrote:

> Back on Tuesday I (Keith A. McGavern) asked:
> -----------
> "Will someone please re-educate me as to the method of placing a string or
> thread from the hammer flange center to some other action part to determine
> appropiate alignments?"
> -----------
>
> Since that time I have received basically two concepts:
>
> Concept 1) If a straight line were drawn between the wippen flange center pin
> and the bottom of the key at the balance point, the place where the capstan
> and wippen heel cushion contact each other will pass through that straight
> line.
>
> Concept 2) If a straight line were drawn between the wippen flange center pin
> and the hammer flange center pin, the place where the knuckle and the jack
> tip contact each other will pass through that straight line.
>
> Five pianos were used to test these concepts:
> Baldwin Concert Grand, #91497, 1941
> Steinway Grand D, #400653, 1967
> Steinway Grand D, #382123, 1963
> Steinway Grand M, #379569, 1962
> Yamaha Grand C3, #F5333137, 1994
>
> Concept 1) works proves true.
> Concept 2) does not prove true.
>
> Concerning Concept 2): Of the five pianos Yamaha was closest, Baldwin next,
> then Steinway (not even close).  Can someone shed some light on Number 2)
> please?
>
> Keith A. McGavern, RPT
> Oklahoma Chapter