Backchecking Height

[Nelson. Gene (PWA)]

You can always shim the keyframe on the work bench so that is mimics the key
bed. Check how the key dip measures at the bass and treble in the piano then
on the bench to get an idea.
Gene Nelson

-----Original Message-----
From: Bradley M. Snook [mailto:bradley@rice.edu]
Sent: Tuesday, May 27, 2003 10:07
To: Pianotech
Subject: Re: Backchecking Height


Stéphane, you have outlined my problem exactly: setting backchecking height
out of the piano often gives substantially different results when the
keyboard is put back in the piano. I too have been using the
chalk-and-blindly-correct method, but I would love to get something that is
more effective. Are there any other ideas out there?

Bradley

P.S. Just so things are clear, I am asking about the height of backchecking,
not backcheck height. ;)


> Stéphane Collin:
> Indeed, I find it very difficult to achieve very even backchecking too.  I
bend the backcheck wires with my fingers with the action on a bench or on my
knees until I am satisfied, but then, when putting the action back into the
piano, nothing is that even anymore (why ? due to minute change of shape of
the action when bedded in it's real bed ? or due to differences in
rebounding force of the hammers against the strings ? who knows ?  I promise
that my blows are quite even, because I practice a lot for that.).
> So I find myself obliged to do a second pass, with action in the piano,
and correcting by eye balling the hammers who check out of line, using the
chalk method (making a pass on all the hammers and marking with chalk on
their key those who are out of line, then pulling out the action and blindly
correcting the offending ones.  Then same again, wiping the marks of those
who are right now.  Then again.  Then having a cup of coffee.  Then back to
step one.)
>
> I am sure that someone has a better understanding of the problem, and a
better solution to solve it.

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