David writes:
<< Why wouldn't you want the minimum friction to occur the slowest rising rate
of the key, the beginning of the stroke? The momemtum of the key will
compensate for increasing friction later in the stroke. >>
Two reasons: I think it best to have the least amount of friction and
maximum ratio at the point of finest control, (escapement). The zero friction
at this point assists control at ppp and the higher ratio provides maximum
power at FFF. Reaching the the magic line at let-off provides this.
The difference between maximum friction occuring at the beginning of the
stroke or half way to the magic line is not measurable, but the difference in
ratio is. So, why create a fall-off in the acceleration to avoid an
immeasurable change of friction?
I think friction's effect increases with speed, thus, placing it at the
lowest speed in the event will minimize its effect. At this point, the major
resistance is the inertia of the action parts. If the magic line is reached at
let-off, what we have is friction decreasing and the ratio increasing
throughout the stroke.
Splitting the path on either side of the magic line creates a situation
where friction begins to increase and the ratio decrease as we reach let-off.
This can't be good.
The same concept of steadily increasing ratio can be seen in the
original idea behind Steinway's accelerated action; with the half-round slightly
off-set proximally, the key ratio increased as the key was depressed, due to the
fulcrum effectively moving towards the performer. In later production, the
half-rounds appear to be drilled in the middle, thus negating the effect.
Regards,
Ed Foote RPT
http://www.uk-piano.org/edfoote/index.html
www.uk-piano.org/edfoote/well_tempered_piano.html
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