[pianotech] Rim Separation

[Ron Overs]

Terry and all,

I have seen enough delaminated rims in pianos with an accompanying 
serious tonal problem to be convinced that it is a serious issue, 
which must be fixed if the piano is to be anything other than a PSO.

We have glued up several inner out rim joints, and back beam inner 
rim joints, which has proven to me beyond doubt that a lossy case 
joint is an energy sucker that we cannot allow.

A couple of years ago we repaired a 6' new grand which was from a 
showroom in another Australian city. The distributor sent the 
instrument to us for an appraisal, since the local-dealer service 
tech' had hung new hammers along with many other procedures in an 
attempt to fix the tonal problem with the particular grand.

We inverted the piano and glued up the inner/outer rim joint, which 
was so de-laminated that a 300 mm steel rule could be pushed through 
the entire height of the joint in many places. The piano was 
transformed when the rims were glued together and it went back onto 
the showroom floor.

However, I believe that the rim must be drilled and doweled along the 
joint-line to achieve a satisfactory repair. The reason is that there 
will be sections of the joint where there is very little gap between 
the inner and outer, which will make it impossible to work the glue 
into the entire 150 mm depth of the joint unless some means of 
physically getting the glue into the joint is provided. We drill 
holes vertically along the joint spaced at approximately 25 mm and 
drill from the bottom to within 30 mm of the inner rim to soundboard 
panel joint. The plate really needs to be out of the piano to 
facilitate clean up because glue goes absolutely everywhere. The 
diameter of the holes are sized so that a 6mm or 1/4" hardwood dowel 
can be glued in after the glue has been forced into the joint. We use 
a polished brass drift for driving the glue into the rim. Each glue 
hole is filled to the top with glue, then the brass drift is used, 
driving it to the bottom of the hole and forcing glue everywhere. The 
drift is removed and a hardwood dowel glued in to fill the void. This 
technique results in a thorough repair. Some will wonder why we don't 
just drive the dowel into the glue-filled hole. This won't work when 
gluing a 6mm diameter dowel of 160 mm long into the hole, because 
friction between the dowel and the side walls will prevent you from 
being able to drive the dowel the full depth of the hole.

Here's a couple of images I found in my archives, which show the work.

http://users.tpg.com.au/ronovers/innr.outer.rep1.jpg
A long series drill, as shown, is necessary for drilling the 
glue-access holes to a sufficient depth.

http://users.tpg.com.au/ronovers/innr.outer.rep2.jpg
The glued up rim, before the black underside finish is repaired, with 
sample hardwood dowel lengths sitting on the rim.

The inner/outer rim joint, belly rail and back beam joints is one of 
the fundamentally serious matters which must be evaluated when 
assessing a shell, such as a Steinway D for re-manufacture. If the 
inner or outer rim laminations are de-laminating, the case should be 
scrapped. The other joints, and the entire internals, soundboard 
action and keyboard can be changed, but the rim must be good or the 
outcome can be nothing but a compromise. Even if the outer/inner rim 
joint has de-laminated I'm not scared off from re-manufacturing it 
provided that the laminates which make up the inner and outer remain 
in good condition.

Ron O.
>----- Original Message -----
>From: <mailto:whardman at scottsboro.org>Wesley Hardman
>To: <mailto:pianotech at ptg.org>Pianotech List
>Sent: Friday, March 27, 2009 8:36 AM
>Subject: [pianotech] Rim Separation
>
>The piano is a 1924 Mason-Hamlin model A.  The inner rim and outer 
>rim have separated.  What is the procedure for making the repair?
>
>Wesley Hardman
>Scottsboro, Alabama


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OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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