[pianotech] Bouncing Bostons

[Michael Magness]

On Thu, Jul 29, 2010 at 8:19 PM, William Monroe <bill at a440piano.net> wrote:

>   Hi List,
>
> Anyone know of anything chronic in Boston Grands (GP178) that has the
> hammer double striking on a quick/firm staccato blow?  I've got one that
> does.  Anyone have any ideas/solutions?  The piano is finely regulated
> otherwise (just today, in fact).  1 3/4" blow, about .400" Key Travel,
> Checking about 1/2", Rep springs are definitely NOT jumpy.  In all other
> ways, the action plays nicely, controllably.  And that is no mean feat.  I
> took some DW/UW measures today out of curiousity, and they were haywire.  DW
> range from 62g - 46g, UW from 18g to 35g or so.
>
> My thoughts are turning to action pinning (haven't checked yet).  Key
> Bushings and pins are clean and lubed (teflon), but that's as far as we
> got.  Wondering if tight pinning (of any parts) might contribute to this
> rebounding back into the strings - and it is a full rebound.  You can watch
> the hammer appear to bounce off the rest rail, though I'm not convinced that
> is exactly what is happening.  Kind of musing aloud here..............
>  William R. Monroe
>

Hi William,
I believe .400 is too deep for a Boston & may be adding to your problem.
The Bostons I have regulated all were dipped at 10mm +/-.3, with a 47mm
blow.

As Al Guecia suggested, I have also had the backchecks catch on the hammer
felt causing an initial "catch".

Depending on the amount of use the piano has had, the pinning may be suspect
as well but i would suggest changing the dip/blow on some samples first &
see if that helps.

Mike
-- 

It is the mark of an educated mind to be able to entertain a thought without
accepting it.

    Aristotle (384 BC - 322 BC)

Michael Magness
Magness Piano Service
608-786-4404
www.IFixPianos.com
email mike at ifixpianos.com
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