[pianotech] Rim Separation

[Wesley Hardman]

Re: [pianotech] Rim SeparationRon,

Thanks for the response.  Your information is going to be very useful.

I have a question:  Do  you have to do anything to the brass drifter so that the adhesive doesn't stick to it? 

Thanks,

Wesley Hardman
  ----- Original Message ----- 
  From: Ron Overs 
  To: pianotech at ptg.org 
  Sent: Friday, March 27, 2009 6:32 PM
  Subject: Re: [pianotech] Rim Separation


  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: Wesley Hardman
      To: 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




-- 
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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