Aftertouch Question

[Jon Page]

.45" is .05" shy of a half inch.  Ouch!

I don't know the specs for these but .42 would be maximum for me.

I would start with 1 3/4" hammer blow, .390 dip, 5/8" checking,
1/16" letoff and adjust the  repetition lever upstop screw (drop screw)
to engage the lever at the time the jack touches the letoff button.

Set a few trials like this and see how it feels. The dip may need to be
increased.

More importantly is the position of the jack at check-in, it's juxtaposition
to the knuckle will indicate geometry problems. Ideally, the jack should be
just in front of and clear of the knuckle. If it is jammed into the stop felt
at the end of the lever you are possibly a candidate for capstan relocation.

Excessive aftertouch places too much strain on the jack by forcing it apart
from its contact between the L/0 button and the stop felt. The jack should 
still be
able to have forward motion with the hammer in check, not bound-up.

Aftertouch is automatic if the action geometry is set up correctly.

An elementary view of the 3/8" (.375") keystroke is this, broken down into 
three steps.
1st 1/8"        hammer is halfway to the string, damper lifts.
2nd 1/8"        hammer is at L/0 point, escapement begins
3rd 1/8"        action moves thru jack escapement (1/16") leaving 1/16" 
aftertouch.

Action leverage differences will produce different results bit this is a 
generic idea.

My view is that if it doesn't fit these guidelines, there is something amiss.

Happy Hunting,

Jon Page

At 10:02 PM 05/25/2000 -0400, you wrote:
>OK grand regulation techies, here you go! Two related questions about
>checking and aftertouch.
>
>I just did a full regulation on my Boston GP178 (5' 10" grand). I set blow
>dist. @ 1-3/4", let-off as close as possible (about 1/32"), and drop (as
>recommended by Steinway) as short as possible - about 1/16" or maybe a tad
>more - but less than 1/8". I have my checking up nice and high - about 3/8"
>over the treble & up, about 7/16" in tenor, and about 1/2" in bass. Key dip
>is about 0.45".
>
>Out of the piano, all hammers check on even the softest blow (I roughed-up
>the tails a tad). When I put the piano in the instrument, I often get a few
>hammers that will not check on a light blow. And of course, because I have
>the let-off so close and drop so little, the hammer rises up and
>blocks/bobbles on the string when pressing the key through aftertouch.
>
>Question #1: Should ALL hammers ALWAYS go into check, even on a very, very
>LIGHT BLOW?
>
>If answer to Question #1 is yes, then Question #2 is: Why do all hammers
>check out of the piano but not when action is in piano (keep in mind, I am
>talking about very soft blows).
>
>If answer to Question #1 is no, then Question #2 is: If it is normal for
>hammers to occassionally not check on a very soft blow, when let-off and
>drop are real small, is it really feasable to make aftertouch the necessary
>10 thousandths of an inch (or there abouts - perhaps even less). Because if
>aftertouch is any greater, the hammer will simply rise up into the string
>and mute it in a very nasty manner. I like alot of aftertouch - generally in
>the ballpark of 50 thousandths or so. I can't do that unless I am sure that
>all hammers will check every time a key is struck - even when struck VERY
>LIGHTLY.
>
>Any good input for me?
>
>Terry Farrell
>Piano Tuning & Service
>Tampa, Florida
>mfarrel2@tampabay.rr.com

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