tooling up for soundboard replacement

[Overs Pianos]

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At 9:10 PM -0500 6/12/03, Erwinspiano@aol.com wrote:
>
>    Hi Ron
>   Beautiful plate and soundboard shot on the url. WOW!!!
>   How are you turning the bolt in full depth without a head on it?

Sorry Dale if I didn't explain it properly. Before fitting the 
dome-nuts-fitted-to-booker-rod into the iron plate, we use a piece of 
threaded booker rod with a nut welded to the top. This piece of 
booker has a section of its diameter ground away where it first 
enters the inner rim, so as to cut a slightly tight thread into the 
inner rim. This makes inserting the dome nuts and booker a lot easier 
so as to avoid damaging the chrome finish on the dome nuts.

>  & Would you mind clarifying this procedure?

In the case of our 225 piano, the pin block is first fitted to the 
plate (which has a flange on either side of the pin block). The plate 
and pin block are bolted together when the plate is fitted to the 
case. The plate and pin block is secured to the inner rim using long 
coach screws which pass through both the plate and pin block. We 
don't glue the pin block to the inner rim so that, if necessary, the 
plate and pin block can be removed from the piano as a unit when 
overhauling the piano at a later date. We adjust the height of the 
plate in the piano by shimming up or letting in the pin block ends, 
relative to the inner rim. The shims are tapered to ensure that the 
orientation of the pin block agrees with the final angle of the plate 
inside the rim. At the back of the piano a cap screw (a bolt with a 
hexagon wrench recess in the head) is fitted through the sound board 
panel and into the inner rim. This cap screw is responsible for 
setting the height of the plate behind the bass bridge. The cap screw 
is adjusted via the access hole which is drilled in the plate (this 
hole is visible in the large image of piano no. 3 at 
http://overspianos.com.au/bkcl.html ). All setting of the plate 
height in the case is done with the set bolts wound down sufficiently 
to avoid contact with the plate. So the plate is adjusted using only 
three support points (each end of the pin block and the cap screw at 
the back) until all hitch pin fields are at a height which enables 
the down bearing to be fine tuned with various heights of rear 
aliquot blocks manufactured for the purpose (in 0.5 mm steps from 4 
mm to 7.5 mm). Once the correct height for the plate has been 
established, proper tapered hardwood shims are manufactured for each 
end of the pin block contact with the inner rim. The thread holes 
(around the plate perimeter) are then 'tapped' into the inner rim 
before fitting the dome nuts. After locking down the dome nuts, the 
set bolts are raised just until they meet the underside of the iron 
plate (a dial gauge on a magnetic base is used for determining the 
exact point of the set bolt meeting the plate).

>  I"d might be interested in adapting this perhaps on certain 
>rebuilds.The plate holes on S&S & others are a bit big so I'm not 
>sure how retrofits would work out.

The S&S D plate looks as if a Baldwin style plate mount conversion 
would work with 1/2" bolts. I've just pulled down a 1962 Hamburg D 
for a rebuild. After pulling the plate we found that the board has 
collapsed in the second last treble section. There's plenty of crown 
out the back of the bridge, but the board is inside out between the 
bridge and the belly rail (would anyone like to see an image?). I 
will be discussing a proposal, with the concert hall's house 
technician, of building one of our new sound boards into the piano, 
along with a curved bass corner cutoff, a back beam & set bolt in 
place of the bell (which in this case had the drop bolt bent into a 
25 mm offset to accommodate what appears to be an incorrectly drilled 
hole in the plate). I designed my own log style scale for Ds back in 
1990. I'll certainly use it if the clients are OK with it, since the 
tuning stability and tune-ability has proven to be better than the 
OEM version (I have re-bridged three Ds with this scale to date). I'm 
also considering a sound board cut-off out the back of the top treble 
section to rid the piano of a few acres of unnecessary panel out the 
back of the treble bridge. As has been our previous practice, we will 
be placing text in the piano to state exactly what we have modified, 
just to keep the dollar signs out of the legal-eagle eyes. Wouldn't 
want anyone to allege that we were 'Passing off' would we?

>. . . Also how do you cut that relief channel in the board so beautifully?

We use an air driven die grinder which is mounted in a custom made 
mini-router style attachment. The die grinder is mounted directly 
over a corner of the base plate so that it can be used right in close 
to a vertical surface. I turned up a number of different diameter 
steel 'tyres' which fit over a ball bearing mounted above the half 
round cutter. The bulk of the material is removed by taking passes 
with the required diameter guide wheels, before hand blending the 
profile.

By the way folks, I am pleased to be able to tell you that our piano 
no. 4 will be playing by this coming Saturday. We are having an open 
day for local technicians to try it out against no. 3. Wal just got 
the last strings on today (Sunday) and I chipped it up to pitch this 
afternoon. Details of the new sound board design (the first is fitted 
into no. 4) can be released from Saturday December 13.

Best,
Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:info@overspianos.com.au
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