[pianotech] Upright Action Bracet Height puzzler

[Joseph Garrett]

Cy said: "Date: Mon, 5 Sep 2011 21:42:56 -0600
From: Cy Shuster <cy at shusterpiano.com>
To: Pianotech <pianotech at ptg.org>
Subject: [pianotech] Upright action bracket height puzzler
Message-ID: <02EBBBE8-76E8-4BF6-80DA-7A54C0B540AE at shusterpiano.com>
Content-Type: text/plain; charset="us-ascii"
 
The patient: Kawai 601M 42" console, 1989 (US-made), clean, and generally
in good shape. Moved several times. Music desk missing; replaced by
woodworker.
 
Symptoms: Chromatic scale from middle C up plays fine. From middle C down,
dip is shallow, even preventing escapement. A2 hammer also hits G#2 string.
 
After opening the case, I notice that all the bass dampers are offset
towards the bass side of the piano by a few mm. The hammers are shifted
left as well. Eventually I discover that the leftmost action bracket is
much lower than the rest (see pictures). Usually the open "U" is wedged
tight against the support bolt coming out horizontally from the plate. This
one is at least five mm below that.
 
At this point, I check for case damage, and don't find any. The action
brackets fit onto adjustable (vertical) bolts screwed into wooden supports,
and there's a horizontal steel U-channel beam supporting them underneath.
Everything appears to be straight. I do wonder about the replaced music
desk, though. The customer says it disappeared during a move (better to
deliver without it, than to show up with a damaged one? The support
brackets are fine.)
 
So, for the first time ever, I adjust the action bracket height by raising
that vertical support bolt. Wow, talk about a hot button! With the
slightest turn, hammer-to-string alignment changes, dampers move around,
and even the amount of damper pressure on the strings changes! Hoo-boy!
 
So at this point, I need advice for finding the right position of the
action relative to the strings. I know that the horizontal (upper) action
support bolts are often bent down to resist the upward forces from playing,
so I measured the distance from the top of each bracket to the edge of the
plate (see pictures). It's 120 mm on the bass bracket, 115 mm on the middle
one, and 112 mm at the top.
 
Key dip: C1=8 mm, C2 = 9.5 mm, C4 = 11 mm, C5 = 10 mm, C6 = 11 mm, C7 = 10
mm. Keys are level. If the action is lower in the bass, wouldn't that raise
the front of the keys, creating more dip?
 
So this is a puzzler that I don't have the answer for. Once I get the
action close, I can regulate to fit, but obviously getting it right to
start with will greatly eliminate the amount of later work. The question,
then, is: how is the height of the lower, vertical action support bolts set
at the factory?
 
--Cy,
My first reaction is someone else has been in there before you. If moving
the Action bracket mounting bolt reduces or increases the damper pressure
on the strings then it has to be bent, imo. The hammers and dampers being
somewhat to the left of where they should be would tell me the action is a
bit too low at that area of the piano. The first thing I'd do would be to
remove the action. Then, check that bass mounting bolt for being
straight/bent. If anything, I'd remove that sucker completely and try to
get everything back in line w/o it. As I removed the action, I'd also check
the bass/tenor break action bracket in regards to it's clearance to the
upper bracket bolt. If it's a bit off too, then someone has moved the bass
one for some reason unbeknown to us.<G> I'd try to get the action up
against the upper bracket bolts, (in the "u"), nice and tight. Then cinch
the Finger Screws nice and snug so it's where is should be (?)(or maybe
not). Something's definately amiss, but I'm as at a loss as you are.
Something happened to move things around and out of line! The big question
is when/by who and who was there before you?
Or....you can wait for our beloved Kawai Guy to chime in and give you all
of the action set-up specs for that model.<G> Don? Are you still lurking on
this forum?<G>
Regards,
Joe


Joe Garrett, R.P.T.
Captain of the Tool Police
Squares R I