Restoration of a Knabe Ampico Reproducing Upright for Carol Drummond
211) 
212) 
213) 
211) The next job is to notch the top of the bridge so that
the strings will clear the bridge on their way to meeting the bridge pins and also to
ensure that the strings hit the wood of the bridge in the same plane as they hit the
bridge pins. This prevents false beats and increases sustain. The first task
in notching out the excess wood is to carefully cut saw kerfs into the wood down to a
pre-marked depth. The mark is made on the sides of the bridge and the saw cuts are
made just to the line. When the chisel removes the excess wood, the saw kerf will
keep the bridge from splitting in places we don't want removed. A round razor cutter
is then driven into the saw kerf to cause it to take a rounded shape near the pin holes.
This will be the shape the chisel will make so it further prevents splitting.
212) The bass bridge has received its new bridge pins. After it is glued to
the piano, a final coat of lacquer will finish dressing up the appearance.
213) Now I carefully notch out the long bridge to match the original. To do
this job right, requires a chisel which is razor sharp. It is necessary, actually,
to resharpen my chisels about three times for each bridge. I use the curved shaped
knife to help me get a clean curved shaped cut. To sharpen these tools, I use a
diamond stone and a special jig. After rough sharpening them on a course stone, I
fine tune them on a very fine stone. Each side of the chisel's cutting edge is
sharpened on the stone until a fine wire edge is drawn up on the opposite side. Then
the chisel is flipped and the other side worked until the wire edge comes up on the
opposite side. Then the chisel is buffed on the polishing wheel to clean off the
excess metal on the edge and point the sharp wire edge toward the cutting direction.
This process is repeated, as I said, three times for each bridge. I wear a
very clean glove on one hand as I work to keep my hand oils from soiling the freshly cut
wood and to protect my hand from the nice clean edge I've created on the corners of the
bridge. After the notches are all cut, I will seal the notched areas with an epoxy
sealer which forms a beautiful finish with just one coat. The rest of the bridge
will be finished solely with lacquer. Then the bridge pins will be driven into place
and the bridge will be ready to glue to the new sound board. A basic cut out is all
that is needed to make the bridge function well. The real important part is that the
notch begin its path down exactly in the center of the bridge pins. This prevents
false beats. Many companies do not give much attention to getting the notches
looking extremely neat and uniform. They just knock off the edges any way that is
convenient and leave it go at that. Even this piano did not have perfectly uniform
notches across the length of the bridge. I give great care to making each notch
resemble all its neighbors as closely as I possibly can. The finished bridge will be
neater looking cosmetically than the original bridge was!
214) 
215) 
216) 
214) Now all the notching is complete. The final
shaping of the bridge has also been completed. This shaping includes the tapering of
the bass of the bridge to match the original. The purpose of tapering the bridge is
to make the surface which glues to the sound board straighter than the bridge is on its
own. The sharp bends are taken out. Also, the treble area is thinned to leave
more sound board area free from being glued to a bridge so that more spruce will be
available for free amplification. This also gets the edges of the treble part of the
bridge farther away from the rastin to keep the bridge from becoming too rigid. Much
rigidity in the upper treble is desirable but too much will reduce the sustain and power
of that section. The accompanying photo here is of all the bridges I've built in the
time I've been working on the bridges for this piano. I have five pieces I was
working on at the same time and all their bridges are now made new and pictured here.
For better tone production, the bridge pins are slightly over-sized compared to
what was used originally. And as a final nicety, I did not have to grind the tops of
the bridge pins down to get them consistent since I took great care to make them come out
even without doing this. The bridge pins are more rounded and the copper plating is
preserved. This ensures that the ends of the bridge pins will not rust if the piano
is asked to live in a moist environment and the final cosmetic look is very slick.
215) The dried sound board has been taken out of the hot box and fitted to the case
of the piano.
216) The old sound board is being used here to set up the sound board press.
Each caul of the press must be aligned with the ribs of the board and with the location of
the long bridge as well. My press is made so that the clamping cauls (green in the
photo) will move in two different directions. This enables me to align them with the
ribs and to move them so that the deepest part of their curve is directly under the long
bridge. By doing this, I repeat the shape I put into the ribs which placed the
highest point of the rib directly under the long bridge. The press will mate with
this by having its lowest point align with the ribs highest point. The juxtaposition
of low to high is caused because the sound board is glued together upside down while it is
in the press.
217) 
218) 
219) 
217) Each rib has had a small hole drilled through it and
into the case. Then a sharp metal bridge pin is driven into the hole. This
will enable me to transfer these index points onto the new sound board. By placing
the board in its exact correct position and then pressing it down hard, the pins leave
prick marks at the point of each pin. These prick marks will enable me to align the
ribs properly when I glue the board and ribs together. There are also index marks in
the rastin which are also transferred to the new board.
218) These second index pins are used to help me do what is pictured in this photo.
The old board and the new board are aligned with each other using the index holes
and prick marks that I have discussed. Once aligned, I can transfer all the
important features of the old board onto the new one. These include the location for
holes for the nose bolts and power cord. I used to use this time to transfer the
index marks for the bridges as well. However, since I'm installing new bridges, I
prefer to locate those in a different way which will be described later.
219) This piano has two dead bars which reduce the overall size of the main
vibrating surface of the sound board. Doing this to the board causes it to be able
to produce a more intense saturation of overtones in the sound of the piano and it also
prolongs the life of the board since the ribs don't have to traverse such a long span.
Because I intend to diaphramize this board (which means to thin the edges of the
speaking area of the board so as to make it more flexible) I have to transfer the
locations of these dead bars onto the top of the board. First I trace the exact
point that the board meets the bar with the board in the piano. Then I use various
techniques to transfer those lines onto the top of the board. Finally, I use a
router to remove wood down the line of the board which is just inside of where it will
glue to the dead bar. The routed lines leave the edge of the board more flexible in
that area while leaving full thickness wood to be glued over the dead bar itself.
220) 
221) 
222) 
220) The edges of the vibrating sections of the board which
are not over a dead bar are thinned using the standard method. An indicator line is
drawn as a guide along the edge of the board. Then a saw kerf is cut in the wood to
help guide me in thinning the board evenly. Finally, planes are used to shave away
the unwanted wood and finally the plane marks are sanded smooth. This photo shows
the saw kerfs in place before the wood removal began.
221) In this photo, the wood is being planed away.
222) This photo is of the finished board that is sanded and ready to be glued to its
ribs. It must spend the night back in the hot box before this can be done since the
board has been out of the box too long to do any more work with it today. It should
be noted that the edges of the board which are near to the high treble section of the long
bridge are not thinned. This area of the board must remain more rigid for maximum
treble tone production.
223) 
224) 
225) 
223) The sound board is now glued up to its ribs inside of
my sound board press. The press is custom designed to impart the correct amount of
curvature to the surface of the board.
224) The glue has dried and the clamping cauls have been removed. The board
must now go back into the drier to shrink back up before any further work is done to it.
225) To ensure accuracy in the placement of the bridges, I chose not to trust to any
index markings I made on the original sound board and bridges to position the treble and
bass bridges. Rather, I waited until I had the ribs glued to the sound board and
then fitted the board tightly into its place in the piano. Then I positioned the
plate in its exact position and put the bridges into place. Using strings and
measuring tools, I positioned the bridges precisely where I wanted them and then made
index marks on the sound board and bridges to show me exactly where they fit together.
These indexes are holes drilled through the board and into the wood of the bridges.
These holes will take pins that will lock the two pieces together while they are in
the gluing press. In this way, they will not drift during gluing and will be exactly
correct for where I want them in the piano after completion.
226) 
227) 
228) 
226) Shaping the ribs to match the original.
227) Gluing the bass bridge into place. Normally I can glue both bridges into
place at the same time. However, the shape of this board made that impractical so I
glued the bass bridge on later.
228) Here you see the sound board being glued into the piano. Due to some
issues of hydroscopic reaction in the wood of this sound board, we chose to help belly the
board by using a special trapeze underneath the long bridge. This helped press the
proper crown into the board as it was glued into place. When the glue was dry, the
crown of the board was perfect. For a while, the way the board was acting after it
was glued up had me considering the possibility of scraping it and making another one.
We managed to solve the problem, however, and the board ended up sounding
fantastic.
229) 
230) 
231) 
229) This is a shot of the board after it had the clamping
assemblies removed and then had received its final coats of epoxy sealer and lacquer.
I went especially heavy on the epoxy sealer on this board to help prevent any
future excessive expansion and/or contraction due to the unusual hydroscopic nature of the
wood of this board. Even after conferring with my suppliers, we really couldn't come
up with a good reason why the wood of this board seems to want to expand and contract more
than is usual. However, the steps I have taken during its construction have set us
up for success even when we were challenged with an unusual circumstance.
230) The main part of the cabinet has been sprayed with lacquer.
231) The plate is now ready to be reguilded. First it must be washed with
acetone and then sanded. Next, the capo bar area is resurfaced to improve its shape
and rid it of excess string marks. Then the plate is cleaned thoroughly with a tack
rag before spraying.
232) 
233) 
234) 
232) New guilding is sprayed onto the plate and then it is
clear coated for durability. Guilding finish has little ability to protect the
surface so a clear coat is used to make it durable. Then the serial numbers are
replaced and all the embossing which was painted black is repainted as original.
233) Now the plate is being installed into the piano. The sound board must be
pressed downward with clamps to simulate the downward stress caused by the strings.
Then the plate can be adjusted into its correct height using the nose bolts and wood
shims.
234) Now the plate is screwed into its final position and all the wooden supports
are in place along with the adjustable support bolts (called nose bolts) are set to their
final correct height. All minor adjustments to the string heights will now be done
with correct stringing felt choices.
235) 
236) 
237) 
235) Another shot of the piano now ready to be strung.
You will also note, in this photo, that the wooden plate bushings have been
installed. On this brand of piano they always install wooden bushings inside the
holes which the tuning pins pass through. This permits a much tighter connection
between the string and the piano because the tuning pin is physically in contact with the
plate through this bushing. Many other makes of piano do not have this connection
through these wooden bushings and, therefore, do not have as solid and stable a connection
between all the stringing components.
236) Making a paper pattern for the bass strings. These patterns allow the
string winder to make a much more accurate and cosmetically appealing set of strings than
they could by simply working off the original set.
237) Now the stringing felt is in place and the piano can now start receiving
strings.
238) 
239) 
240) 
238) The treble wire has now been installed and the pressure
bar put into place to lock the strings down against the capo. The bass strings will
have to wait until they come in from the string winder. While we wait, I'll begin
work on the action.
239) We had originally planned to replace more aspects of this action outright.
However, the manufacturer who makes the parts closed their plant and now we have to
get these parts from Japan. At the time this work was being done, the Japanese were
behind on orders and could not supply us with everything we wanted. Therefore, the
whippens and dampers of this action will get less actual new parts but a great deal of
extra labor on my part. I still want to put this action into brand new condition.
Certain components of the whippens of a player piano cannot be replaced in any
event and the "stickers" are seldom worth replacing since the originals are
always more heavily built than what we can get as replacements. So, to make these
stickers like new, I am performing the following tasks: Replacing the whippen
flanges with new; repinning the place where the sticker fits into the whippen body; and
installing new abstracts onto the stickers. The jacks are perfect on this set as are
the whippen bodies themselves so this work will produce a whippen that will perform like
new.
240) Here is a set of whippens ready to have the restoration process started.
© Copyright 2010 {David Rodgers' Piano Rebuilding}. All Rights Reserved.