Yamaha Jumping Jacks

[Geoff Sykes]

Follow-up to my previous post, (below). Please bear with me.

I had the opportunity to do preps on two new out-of-the-box Yamaha uprights
today, so I did a little experimenting with this double-strike phenomena.
What I think I may have discovered is that it just may be operator error on
us, (or is that we), techs that is causing this. 

What I found was that when pressing the key down slowly I was sort of
unconsciously pausing, just for an extremely minor moment, at the exact
instance that the jack just starts to move out from under the butt. At that
exact moment, when you are moving slowly, there is a very slight, but
noticeable, increase in resistance as the jack starts to rub against the
butt in it's move to escape. What I found myself doing was reacting to that
subtle increase in resistance and almost unconsciously changing the motion
of my finger pushing down on the key. In other words, I believe I was
perhaps actually introducing the phenomena into the system myself. 

What I observed happening was that since the hammer was already in motion,
the slight pause that I was introducing allowed the hammer to continue to
move, leaving the jack and subsequently striking the string and then
bouncing back, at which point I would continue pressing the key allowing the
action to complete it cycle and giving me that second strike.

When I carefully monitored my finger movement, forcing myself to move
smoothly through that subtle point of increased resistance, I could not
reproduce the effect. It only happened again when I stopped thinking about
it. And even though the speed of the key press is within a very narrow
window, it was definitely and easily reproducible, on any key on both
pianos.

My guess is that this may turn out to be a new piano only effect. Once the
piano has been played for a while and "broken in", and the butt leather
smoothes out a little this may be impossible to reproduce at all. And as
long as I'm guessing here, I don't think anyone but a tech could even MAKE
it happen. Certainly not the person at home just playing the piano under
"normal" circumstances. 

I find the combination of piano action physics and our human reactions to
what we see and feel as a result of those physics all very interesting. I'll
shut up now.

-- Geoff Sykes
-- Assoc. Los Angeles




-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf
Of Ric Brekne
Sent: Thursday, November 03, 2005 11:19 AM
To: pianotech
Subject: Yamaha Jumping Jacks


Hi

At just past half blow on the upright piano the jack should already 
sufficiently in motion that by the time the hammer evntually would 
bounce back on a slow (but realistic) keystroke the butt should be able 
to push it out of the way.  If it cant, then there isnt really all that 
much that can be wrong. Either its not out far enough for this to 
happen, ie. a regulation issue, or something is preventing it from 
moving out easily enough... ie. some resistance in the action.

I've run into a few Steinway K's and Z's with this problem and I've 
solved it every time by a good regulation and appropriate spring 
strenghts. 

That said... Crescendo punchings wont really help me thinks in as much 
as one of my earlier attempts was to simply increase key dip 1 mm with 
no real change in the double strike at soft play. I think (not know) 
this is because one really isnt playing with all that great a technique 
in the first place and that the situation is bordeline relative to the 
technique of the pianist.

That said again... there are all kinds of good reasons otherwise for 
useing Crescendos... so buy em :)

Cheers
RicB

-------------
Not to dis the Crescendo punching's, which I hear nothing but good reports
about, but this is not a soft blow problem, it's a slow key movement
problem. My experience with this double-strike phenomena is that the hammer
jumps off the jack about halfway through the keystroke, (in other words long
before the jack actually releases from under the butt), hits the string and
bounces back onto the jack, the keystroke continues through the point of
actual let-off where the jack actually does it's work of throwing the hammer
into the strings, and then the hammer bounces back correctly into the
backcheck. The key then completes it's stroke eventually landing onto the
front rail punching. My point of all this is that the double-strike is not
the result of a soft blow so much as it is the result of an improperly
functioning action during a slow key movement. It happens long before the
front rail punching's are even part of the picture.

-- Geoff Sykes
-- Assoc. Los Angeles _______________________________________________
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