[pianotech] double-striking hammers on Chinese uprights

[Gerald Groot]

Years ago I ran into this on tons of Yamaha P202 models.  I fooled around
with different things until I finally tried to re-bend the back checks to
check in a little different position to catch the hammer butt instead of
allowing it to bounce off like it was doing.  Maybe this same thing might
help on this model.  

I bent the back checks towards me first by hand and then holding the middle
of the back check wire with my index finger, I rebent the back check forward
again.  This did the trick by enabling it to check better thus eliminating
the bobbling.

-----Original Message----- 
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Paul McCloud 
Sent: Wednesday, August 19, 2009 8:27 PM 
To: pianotech at ptg.org 
Subject: Re: [pianotech] double-striking hammers on Chinese uprights 

With the Schwander type of hammer spring, the letoff distance can be 
increased because of the weaker spring rate.  There's plenty of momentum to 
allow the hammer to get to the string, and making the adjustment will help 
the backcheck do its job.  I had a shipment of pianos which had a very 
pronounced bobbling problem.  Making the letoff at about 1/4" made most of 
the problems go away.  YMMV. 
        Paul McCloud 
        San Diego 


-----Original Message----- 
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf

Of Jim Busby 
Sent: Wednesday, August 19, 2009 4:53 PM 
To: pianotech at ptg.org 
Subject: Re: [pianotech] double-striking hammers on Chinese uprights 

All, 

Can I throw something else into the mix? Last year I posted a similar 
problem on CAUT and got a lot of the same advice. Lot's of good advice, 
great advice, for the "normal" or typical resolution of double striking. 
However, nothing solved it completely. 

It was the same make as Britney's piano, and I tried everything. The real 
problem seemed to be in the design, or at least the implementation of it, 
whether right or wrong. (i.e. The design may have been good but the 
gorrillas in the factory missed it.) If the hammer assembly doesn't tend to 
"lean" (for lack of a better word) back so that the center of gravity favors

a return, it sometimes ends up double bouncing more. The Chinese pianos use 
the Schwander type return spring, which is considerably less strong than the

American spring. The weaker spring can't overcome too much of this gravity 
thing. If the hammer isn't raked enough, and/or if the hammer 
assembly/action (balance) set up is not favoring a return this problem seems

to be exacerbated. On my piano strengthening the return spring helped, but 
there was something else. 

With my piano I experimented by physically leaning the piano forward (toward

the player, slightly) and the problem went away. So... what I ended up doing

is "Turbocharging" the piano a la Jack Wyatt. I won't post this exact 
procedure here since Jack might not like that, but maybe it's been posted 
before. It consists of tilting the action forward (out, spacer washers) then

reregulating blow, etc. 

FWIW, that's what did it in my case.. 

Jim Busby= 
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