A not so boring, boring dilemma

[David Love]

Jon:

Thanks for the input.  I ended up short boring everything by 1/8" for each
section to create uniform hammer/shank angle throughout.  Fortunately, I did
have the piano so finding the strike point (which varied from section to
section) did not require any running around.  As you suggested, I did not
retrofit the action with new wippens but kept the old rocker arm type which
work fine after a lot of cleaning and replacement of the bushing cloth which
connects to the key.

I am curious what you did about the "Viennese" style of weighting the keys.
The original BW's were quite high due to very sparse leading and very low
front weights throughout.  Though somewhat uneven, the low inertia seemed to
compensate for the high BW as the action did not feel particularly heavy.
After putting on a heavier hammer (I used an Abel concert grand hammer and
set the SW curve from just under 12 g down to about 6), I modified the
weigh-off to contemporary standard.  Since the action had relatively low
friction, I set the BW at 38 to keep the DW in the 51-47 range.

Whenever you get around to checking the new sheet I sent, let me know what
you think.  It's basically a simplified "Smart Chart", allowing you to
create a SW maximum curve by inputting the average SWR in a particular
system with the existing KR, FW maximum at various levels, and a targeted
BW.  I created a HW column to give me specific weights to shoot for when
boring, tapering and tailing the hammers (SW - 1.8 for Renner shanks, and
SW - 1.6 for Abel shanks).  The actual SW's can be modified later to smooth
out the curve in the manner you've described already.

I can see now why David S. aims for uniform SWR.  If you could manufacture
everything precisely enough to give uniform SWR's, you could then preset the
FW's and when replacing hammers, say, just match a precalculated SW curve.
Fortunately for us, manufacturing has a long way to go for that kind of
precision.  More games to make the job a bit more fun.

David
----- Original Message -----
From: "Jon Page" <jonpage2001@attbi.com>
To: <pianotech@ptg.org>
Sent: April 09, 2002 6:28 AM
Subject: Re: A not so boring, boring dilemma


> At 07:11 AM 4/9/2002 -0400, you wrote:
> >One effect of changing a bore distance is the differences in
> >regulation.  Shortening the bore will raise the let-off, the drop and
> >change the capstan location.  I should suggest boring several hammers of
> >different sizes at the angles you suggest and try the regulation and see
> >how it feels.
> >
> >Feel is the ultimate criteria.
> >
> >                 Newton
>
> Last year I installed a set on and old Bechstein. I encountered the same
> measurements in regards to the hammer
> length and angle. Resign yourself to the fact that you will not achieve a
> 90 degree pitch and length close to
> 'hammer flange center to string' difference.
>
> Calculate the longest hammer length attainable by considering what length
> will allow the action to slide in under the
> pin block and have the shanks off the rail.  The angle will have to be
wide
> to get the hammers to hit the strings squarely.
> here's what I have recorded for hammer length between the sections:
> 2 1/4 , 2 1/4  \  2 1/16, 2 1/8  \  2 1/8, 2 1/16  \  2, 2
>
> The only angle I have recorded is for the top section which is 3 degrees
to
> 2 degrees.  The rest were greater than 8 degrees
> as I recall.  Bore a few samples to your calculations and fit them on the
> shanks, the ends of each section.  Lift the hammer to the
> strings and check it's attitude with a square.  Once this is ascertained,
> check strike point.  Angle the hammer back just a
> little more to allow for hammer wear because as the hammer becomes
shorter,
> the angle decreases.  Install your trials and
> check strike point and regulation.
>
> Don't make the tenor/treble hammers longer than what would be proportional
> to the bass section, regulation difficulties will develop.
> So fit the bass hammers to the strings/pinblock allowance and bore the
> treble hammers a proportional distance, that is the difference
> between the bass string height and tenor string height and their
respective
> sections.
>
> Fortunately the piano was also being relocated at the time and it went to
> my shop, which saved a lot of running back and forth for these fittings.
>
> The action played fine and has been functioning without complaints. BTW,
> the friction on these rocker arm, sticker actions is lower
> than the modern configuration.
>
> Regards,
>
> Jon Page,   piano technician
> Harwich Port, Cape Cod, Mass.
> mailto:jonpage@attbi.com
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>