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<DIV><FONT face=Arial size=2>Ron,</FONT></DIV>
<DIV><FONT face=Arial size=2>Wow, this approach of a complete track down both
sides of the bridge has occurred to me but always seemed to complicated. Thanks
for the great photos and description.</FONT></DIV>
<DIV><FONT face=Arial size=2>Fenton</FONT></DIV>
<DIV>----- Original Message ----- </DIV>
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<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=sec@overspianos.com.au href="mailto:sec@overspianos.com.au">Ron
Overs</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">Pianotech List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Cc:</B> <A title=bronwyn@bijl.co.nz
href="mailto:bronwyn@bijl.co.nz">Bronwyn Bijl</A> ; <A
title=canterburybenz@hotmail.com
href="mailto:canterburybenz@hotmail.com">Miles Warner</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Sunday, August 03, 2008 5:53
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Decapping bridges with a
router</DIV>
<DIV><BR></DIV>
<DIV>Hi all,</DIV>
<DIV><BR></DIV>
<DIV>I've been following this thread which David started, and since the
process we use doesn't seem to have been covered by anyone here is an outline,
with image links, of the procedure we use when recapping a bridge without
disturbing the original board (in cases where the board is deemed to be
satisfactory, ie. stiff enough, for wearing out another set of hammers and
wire).</DIV>
<DIV><BR></DIV>
<DIV>We find that most of the time, when fitting new bridge caps, we usually
will want to make some adjustments to the bridge height. After removing the
strings, an assessment of the current bridge heights are made before removing
the plate. If the bridge height needs to be raised, we glue small blocks of an
appropriate thickness to the existing bridge caps. The blocks are made
precisely to the height we wish to raise the bridge at each measurement point.
This will provide a reference height for manufacturing the router guides so
that they conform to the revised bridge height profile. The image link below
shows our most recent rebuild of a 2001 Hamburg Steinway D. Initially, I
thought we were going to need to build a new board for this piano. The board's
strung crown was turned quite inside-out in the high treble string sections at
the rib feathering behind the bridge. But after stripping the piano the board
seemed to recover its crown quite nicely, so a decision was made to keep the
original board and bridge root. The original string scale of this piano had
shorter speaking lengths in the high treble, when compared to model Ds we've
rebuilt in the past. Our previous model D string scale re-designs wouldn't fit
this piano. So I designed a new string scale similar to our previous revised
model-D log scales, to enable the new string scale to fit on the original
bridge root. Take a look at the first image by opening the link below.</DIV>
<DIV><BR></DIV>
<DIV><FONT face="Lucida Grande" color=#000000
size=-4>http://users.tpg.com.au/ronovers/CrstchrchDbd1.jpg</FONT></DIV>
<DIV><BR></DIV>
<DIV>You can see the router guides are finished to the desired height, ready
for routing off the bridge caps. The templates for the new string scale, which
must be determined before routing off the original caps, are sitting on the
iron plate, just to the right of the case. For this job, we decided to retain
the original board finish, since it was still in good condition. First,
masking tape is laid down on the board where the runners will be attached to
the board. The wax surface on the top of the masking tape is removed by wiping
the tape with lacquer thinners. This ensures that the adhesive will stick to
the masking tape. The runners are cut slightly higher than required, with the
bottom surface cut to approximately follow the contour of the board. The
accuracy of the lower contour is not critical, since we fix the runners to the
tape using body filler. Once the filler hardens we plane and scrape the
runners until we arrive at the desired bridge height and profile. Note the
small blocks we have glued to the lower section of the bass bridge and the
lower half-section of the treble bridge. This piano had insufficient
downbearing in the low bass and low end of the long bridge, while there was
quite a bit too much downbearing in the high treble (which was why the board's
crown when strung was turned inside-out in the high treble). The down bearing
can be reduced to the desired angle by packing the rear duplex strips with
hardwood made to an appropriate thickness. While we could have adjusted the
high treble downbearing by reducing the height of the new cap, I didn't want
to do this because this piano had an original bridge height in the high treble
which was only 30 mm. Taking another 1.0 - 1.5 mm off this height would make
what I believe to be an already marginally low bridge height for a concert
grand treble bridge even lower. So we decided a better route for the high
treble in this instance would be to pack up the rear duplex strips.</DIV>
<DIV><BR></DIV>
<DIV>The beauty of using masking tape for board-finish protection, and using
body filler to fix the runners to the tape, is that once the bridge cap has
been routed off, the runners can simply be pulled off the board leaving it
completely undamaged.</DIV>
<DIV><BR></DIV>
<DIV><FONT face="Lucida Grande" color=#000000
size=-4>http://users.tpg.com.au/ronovers/CrstchrchDbd2.jpg</FONT></DIV>
<DIV><BR></DIV>
<DIV>The above image link shows the same piano once the new bridge caps were
fitted, and the notching, sealing and pinning completed. Notice that the new
log string scale results in pin-lines which form uniform curves. Next time you
get your eye under the lid of a standard D, have a look along the pin-lines,
particularly those in the string section shown in the image. They don't look
like this. Instruments equipped with his type of scale will make it easier to
lay a tempered scale, and the tuning stability will be improved as a
consequence of the piano having a smoother percentage of breaking strain
deviation.</DIV>
<DIV><BR></DIV>
<DIV><FONT face="Lucida Grande" color=#000000
size=-4>http://users.tpg.com.au/ronovers/CrstchrchDbd3.jpg</FONT></DIV>
<DIV>(<I>this original image was provided courtesy of Reubin Bijl who took a
series of images at the launch concert in early June)</I></DIV>
<DIV><BR></DIV>
<DIV>The above link shows an image of the finished piano, during its launch
concert at the Music School of Christchurch. The underside of the top lid has
quite a good reflection because we flatten and polish this surface to the same
standard as for the outside of the case. I realise that most manufacturers
don't bother too much with the under side of the lid, including the original
manufacturer of this piano. But this image shows just what a difference
high-polishing the underside of the lid makes. Yes I know its only cosmetic,
but that's also part of the concert experience.</DIV>
<DIV><BR></DIV>
<DIV>Ron Overs</DIV><X-SIGSEP><PRE>--
</PRE></X-SIGSEP>
<DIV><FONT face="Times New Roman" color=#0000ff size=+1><B>OVERS PIANOS -
SYDNEY</B></FONT></DIV>
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color=#0000ff><I>Grand Piano Manufacturers</I></FONT><FONT
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