Hi Clyde, Plate design has come a long way since the post war years, the average manufacturer has done more with stress analysist. The Schimmel if I recall has what is termed a full perimeter plate. In other words the outer struts or webbing form a box, this prevents trapezium distortion from the in balance of tension due to the cross stringing, but is a cheaper design. A little more cast iron and no back support. now the draw back. The centre of gravity has moved back closer to the rear edge, in a school setting there is a danger that the piano can easily be flipped over. The other disadvantage is that the soundboard liner does not have the same kind of support as in the more conventional method of manufacture. MY gut instinct makes me think long term stability may be an issue. Most of the tension is taken by the plate in all designs, depending on the ductility of the cast, rigidity and placement of plate webs ect. will determine the need for back post, the material used, cross sectional area and placement. Getting back to the liner and back assy. the average piano has to bear 1000-1500lbs of down bearing pressure, the sound board is carrying this load and this is where the liner and back support really comes into play,as it keeps the perimeter of the board more rigid if well designed, therefore reflecting more energy back to the centre of the board, many of the full perimeter plate designs that I have listened to have only so so sustain qualities. This could be overcome with hard maple or beach liners, but is not usually the case. You have opened a real can of worms with this question, so now I will don a flame suit. Roger At 10:54 PM 25/08/98 -0400, you wrote: >Friends: > >As I was tuning a late model Schimmel studio piano today I noticed it >had no back posts, really no back at all that I could see, other than >the soundboard and ribs. > >Which got me to wondering -- how much of the 20 tons of tension is >usually on the back and how much is on the plate? Only once before did >I see a vertical piano without back posts, an old upright. I also >remember about 20 years ago a salesman pointing out the rather thick >back posts on Everett studio pianos as an indication of their high >quality (I knew much less about pianos then than I do now). How >important are those posts really? > >Clyde Hollinger (who is getting tired of adding RPT Lititz PA) > > Roger Jolly Baldwin Yamaha Piano Centre Saskatoon and Regina Saskatchewan, Canada. 306-665-0213 Fax 652-0505
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