Optimizing repetition (revisited)

[Richard Moody]

----------
> From: Jerry Anderson <jandy@MicroNet.fr>
> To: pianotech@byu.edu
> Subject: Re:Optimizing repetition (revisited)
> Date: Saturday, April 19, 1997 2:56 PM
>
>
> I invite anyone interested, to experiment with changing the
> jack/shank contact angle, and to notice the coincident
> change in the touch, particularly in the critical first millimeter
> of key movement.  I think the value of a perpendicular contact
> will be manifest in most well designed actions.
>
> Jerry
>
>
This  is an interesting concept.  Until now the  consideration for me
was where on the roller the jack sits in order to produce a jack drag
sensation (during let off) that is least and even.  (and this
distance should be the same as after touch distance??)
If your rollers line up like the ones in the picture on page 153 of
the Reblitz book (1st ed). and some are flatter than others,  you can
see why my jack placement might be "all over the place".  Of course
the prime consideration is that
the jacks don't pop out from the rollers before they are supposed to.
 But the realities of grand action regulation often tread the thin
lines of max power, repitition and failure. This should get us into
another thread, how do we test for failure?
	So considering the angle of the jack to the shank.  Ideal by common
sense is 90° to the hammer shank.  Two thoughts occur, one that since
the shank and jack move in arcs, this 90° relationship is fleeting.
Two; then when is the best time for the jack to be at 90°? The first
millimeter, the third, or fourth? Is that even possible?

	The stop motion diagrams on page 30 and 31 of Reblitz if they are to
scale show a picture of the jack angle as it lines up against the
knuckle and shank during the stroke. Probably to determine the true
angle of the jack, a model or an action should be used. But it
appears that the 90° relationship occurs  after the beginning of key
dip but before key contact with the damper lever.
	So back to experience, if the jack is too far off either edge of the
"wood core of the knuckle"  you better beware and test extensively
for failure.
	If I can line up jacks within this "zone" to be at 90° , I for sure
will try it.

Thanks for the suggestion.
Richard Moody