Kawai heavy action

[Alan McCoy]

Fred,

If you can do all that in a day, my hat is off to you. When I see you I'll
have to bow in the presence of a great one.  :-)

Alan

____________________________________________
Alan McCoy, RPT
Eastern Washington University
509-359-4627
amccoy@mail.ewu.edu 
 

-----Original Message-----
From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org] On Behalf Of
fssturm@unm.edu
Sent: Monday, March 22, 2004 6:22 PM
To: College and University Technicians
Subject: Re: Kawai heavy action

   Today I visited the piano in question. Thought I'd report briefly on what
I found. 
Jim Harvey and Vince Mrkalo get the prize for best diagnosis at a cyber-
distance. 
   The piano is a KG-2, 1984, with wooden, Schwander style wipps, with
carbon jacks (no assist springs). My first diagnostic step was to measure DW
and UW, which were pretty consistent at 70 and 20 (+ or - 2 or so).
Obviously friction problems. Initial thoughts of weight problems as well, as
BW calculates at 45.
   I pulled the action, and checked for key friction. Nothing significant.
Bushings had more play than I like, so were plenty free. Applying side
pressure, there was no noticeable friction against key pins. Balance holes
were pretty good (maybe
1/3 needed easing).
  I pulled up on some hammers. A little working of those flanges revealed a
relatively mild case of the Asian Flange Flu (milder Japanese variety, not
the truly virulent Korean strain). I examined the knuckles. More slop
between leather and core than almost any I'd ever seen. 
   I figured I'd found my main culprits, so I did a little experimentation.
I took three adjacent keys, and
1) Proteked the hammer and wipp flanges, working them side to side (along
the length of the centerpins, not working them as a hinge. This is far more
efficent for getting Protek to do its best).
2) Brushed knuckles and applied powdered teflon.
3) Applied powdered teflon to the wipp cushions for good measure.
   Now I re-measured DW and UW and found 48 (!?!) and 30. IOW, weight and
geometry are just fine, thank you. BW is actually a very workable 39. (If I
should want to reduce it, the hammers are nicely un-tapered, and a gram can
easily be removed by tapering, reducing everything at the front of the key
by 5 gm). 
Interesting how friction can work this way. It's not the first time I've
measured high DW and low UW and predicted not only a friction problem, but a
weight problem as well, only to find that when friction was removed the
weight problem was reduced. Goes to show you shouldn't place too much
credence in formulas. 
Sometimes down friction and up friction are not equal. I think this is also
true often with rubbing parts, but in the opposite direction.
   I then tuned the piano, thinking over what I would propose to do. I ended
up bidding a one to 1 1/2 day job, intending to ream and repin all
hammerflanges (a hammer filing has to go along with this; fortunately the
hammers aren't grooved very deeply); detach one end of each knuckle leather,
stretch and re- glue, apply powdered teflon; do some other incidental
friction removal, like brushing, ironing, applying powdered teflon to wipp
cushions; polish and Mclube capstans; polish and mclube keypins; ease
balance holes as needed. 
And then a fairly rapid regulation, including making damper lift a bit
later. Slam dunk, I think. We'll see if they go for it.
Regards,
Fred Sturm
University of New Mexico
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